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Chile reveals persistent PDO (Pacific Decadal Oscillation) impact
Journal Pre-proof A new 20th century lake sedimentary record from the Atacama Desert/Chile reveals persistent PDO (Pacific Decadal Oscillation) impact Mauricio Cerda, Heitor Evangelista, Jorge Valdés, Abdelfettah Siffedine, Hugues Boucher, Juliana Nogueira, Aguinaldo Nepomuceno, Luc Ortlieb PII:
S0895-9811(19)30361-X
DOI:
https://doi.org/10.1016/j.jsames.2019.102302
Reference:
SAMES 102302
To appear in:
Journal of South American Earth Sciences
Received Date: 14 July 2019 Revised Date:
1 August 2019
Accepted Date: 1 August 2019
Please cite this article as: Cerda, M., Evangelista, H., Valdés, J., Siffedine, A., Boucher, H., Nogueira, J., Nepomuceno, A., Ortlieb, L., A new 20th century lake sedimentary record from the Atacama Desert/ Chile reveals persistent PDO (Pacific Decadal Oscillation) impact, Journal of South American Earth Sciences (2019), doi: https://doi.org/10.1016/j.jsames.2019.102302. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
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A new 20th century lake sedimentary record from the Atacama Desert/Chile reveals persistent PDO (Pacific Decadal Oscillation) impact
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MAURICIO CERDA1,2,3*, HEITOR EVANGELISTA4,7, JORGE VALDÉS3,5, ABDELFETTAH SIFFEDINE5,6, HUGUES BOUCHER6, JULIANA NOGUEIRA4,5,7, AGUINALDO NEPOMUCENO1& LUC ORTLIEB6
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Abstract
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The Atacama Desert lakes located at high altitudes with very low anthropogenic impacts preserve great potential to recover regional climate changes and environmental processes at a decadal to centennial time scales. Herein, we present a high-resolution analysis of the stratigraphy and metal composition of Inka Coya Lake sediment core, in order to clarify the main forcings acting on sedimentation rates and both eolian and precipitation patterns at Atacama Desert environment. The results suggest that terrigenous inputs can be mainly related to the PDO (Pacific Decadal Oscillation), while laminations preserve a direct association with El Nino-Southern Oscillation – ENSO (4.2 to 5.3 yr. cyclicity). Additionally, the Cu mining activities in Chile are recorded in the lake. The sedimentation rates and precipitation patterns were associated with ENSO, highlighting the relation between La Niña and wetter periods at Atacama. Finally, high-resolution analyses of the geochemical composition provided additional criteria to identify the erosion processes at the basin, suggesting different sources of sediments, which fluxes into the lake covariated with PDO at a decadal scale, especially during the 20th century.
Programa de Biologia Marinha e Ambientes Costeiros Universidade Federal Fluminense (PBMAC-UFF) Outeiro de São João Batista s/n, Centro Niterói Brazil. 2 Centro de Investigación e Innovación para el Cambio Climático (CiiCC), Facultad de Ciencias Universidad Santo Tomás Santiago Chile 3 Laboratorio de Sedimentología y Paleoambientes, Instituto Alexander von Humboldt. Facultad de Ciencias del mar y de recursos biológicos, Universidad de Antofagasta, Casilla 170, Antofagasta, Chile 4 LARAMG/IBRAG/UERJ, Pavilhão Haroldo L. da Cunha, Subsolo, Rua São Francisco Xavier 524, Maracanã, Rio de Janeiro, 20550-013, Brazil 5 LMI PALEOTRACES, IRD-UFF-UANTOF-UPCH. 6 LOCEAN - IPSL UMR 7159, IRD-Sorbonne Universités (Université P. et M. Curie, Paris 06)CNRS/UPMC/IRD, IRD France-Nord 32, av. Henri Varagnat,FR-93143 BONDY cedex 7 Programa de Pós-graduação em Geoquímica, Universidade Federal Fluminense/Instituto de Química/Departamento de Geoquímica/Outeiro de São João Batista s/n, Centro, Niterói, Brazil.
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∗ Corresponding author
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E-mail addresses: *[email protected]
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Keywords: Atacama, PDO, lake sedimentology, elemental composition, Copper record
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1.
Introduction
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The Andes plateau at Northern Chile created by the subduction of the Nazca Plate beneath
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the South America Plate houses a series of lakes (Risacher et al. 2003). They are believed
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to provide conditions for reconstructing the regional past climatic changes and the past
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aridity conditions (Anderson et al., 2011; Ritter et al., 2018). The aridity of the Atacama
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desert may have started in the Eocene (from ~ 55 to 36 million years) and evolved into the
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current aridity since the mid-Miocene (from 23 to 5.3 million years) (Clarke, 2006). The
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extreme aridity observed today is due to a combination of factors that includes the influence
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of the Subtropical High-pressure belt, the Ecuador-advection, the Humboldt coastal cold
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marine current, and the orographic aspects of the Andes Cordillera around. According to
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Schwalb (2003), and considering the above aspects, the Altiplano is a region very sensitive
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to changes in the moisture advection, evaporation and precipitation dynamics. Precipitation
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at Atacama Desert is mainly controlled by two climatic mechanisms: the northern monsoon
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(Bolivian Winter) and the southern frontal systems. Precipitation is minimum within the
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area that corresponds to the boundary between both mechanisms, 18-28°S, where their
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effects are minimized. It is believed that the El Niño–Southern Oscillation (ENSO), may
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regionally influence the surface winds as a result of the sea surface temperatures over the
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Pacific Ocean. Its two related phases (El Niño and La Niña) control the longitudinal
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intensity of the Walker circulation that ultimately may bring more or less ocean influence
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towards the inland. According to literature, ENSO events have contrasted effects on
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precipitation regimes at the Andean region with intense summer rain at the Western side
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and droughts at the Eastern side (Lavado-Casimiro and Espinoza, 2014).
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Sediment cores from lacustrine environments are widely used to reconstruct temporal
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variability of natural and anthropogenic processes (e.g.: von Gunten et al., 2009). In this
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context, many authors use joint analysis of sediment geochemical composition and their
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laminated structures to provide insights into runoff processes associated with precipitation
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and dust deposition of chemical species. For Atacama Desert, although the impact of ENSO
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on the regional climate is well documented, we explore its impact over the sedimentary
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record measured from dated lacustrine sediment deposits, sedimentary stratigraphy and
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metal contents using high-resolution XRF analysis. As a complementary aspect, we have
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also investigated if an imprint of the major regional anthropogenic activity, represented by
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the Cu mining and tailing does exist. Over the last hundred years, mining and related
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activities caused a significant reduction in the major watersheds (Romero et al., 2012) and
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several pieces of evidence indicate that their resuspended materials were potential sources
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of contamination (Gregor and Gummer, 1989; Rapaport et al., 1985; Swackhamer and
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Armstrong, 1986).
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Herein we present high-resolution elemental composition variability from a sediment core
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retrieved at the high-altitude Inka Coya Lake, Northern Atacama Desert. This lake is
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characterized by having a relatively low human direct impact and no significant land-use
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change around it during the last century. The analysis on its 20th century lacustrine
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sedimentary record sector allowed us to investigate the impact of the PDO (Pacific Decadal
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Oscillation) over its geochemical and physical characteristics.
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2.
Methods
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2.1. Study site
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The Inka Coya Lake (San Francisco de Chiu-Chiu/Antofagasta; 22° 20.300’ S; 068°35.981’
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W) is located in the Northern Atacama Desert region at an altitude of 2516.4 m a.s.l (Fig.1).
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It is approximately 48 km away from the city of Calama. It has an asymmetric oval shape
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and an area of 1.52 km2. The Inka Coya Lake has an average volume of 1.6x106 m3 and is
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surrounded by a varied xerophytic fauna (Gantz et al., 2009). The local terrain is stony like,
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with salt lakes (salares), sand and felsic lava. The extreme aridity conditions of the region
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are mostly due to the cool north-flowing Humboldt ocean current, and the presence of the
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strong Pacific anticyclone. The lake is situated on the limit among the central valley and the
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cordillera zone, between two mountain ranges - the Andes and the Chilean Coastal Zone.
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This orography protects the site against intense moisture advection from either the Pacific
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or the Amazon basin, contributing to the maintenance of hyper aridity conditions over the
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Atacama Desert. Geological evidence suggests that the study site is composed mostly of
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moderately consolidated sedimentary rock from Pliocene-Pleistocene, while its
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surroundings can be related to old sediments from the late Miocene-Pliocene transition
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period and sediments as recent as the Pleistocene-Holocene (Fig. 2) (Jordan et al., 2015).
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103 104 105 106 107 108 109 110 111 112 113 114 115
Figure 1 – The study site: (a) total view of the Inka Coya Lake (b) bathymetry of the Inka Coya Lake showing a central depression and the sediment core sampling point (T1= XLCHT1); (c) Inka Coya Lake location in the context of South America and Northern Atacama orography.
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Figure 2 – Map of the Inka-Coya site main geological facies. Based on Chilean geological map from the National Geology and Mining Service of Chile.
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2.2. Regional climate characterization
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The small annual precipitation amount that falls on the Atacama is a result of the northeast
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summer monsoon, southwest frontal precipitation, fog deposition below 800 m a.s.l and
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also occasional winter rains at coastal areas below 1,000 m. Occasional winter rains (May-
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October) on Andean slopes South of 25ºS, and summer storms (November-March) that
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cross the Altiplano, spill over the Andes, and rain out on the Pacific slope north of 25°S
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(Latorre et al., 2003). According to Köppen climate classification, the predominant climate
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domain at Chiu-Chiu region is “BWk” – cold desert climate – characterized by dry
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summers with marked seasonal thermal amplitude. During winter, air temperature reaches
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an average of 22 ºC, during the day, and 4ºC by night. Clear sky condition occurs almost
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through all the year, due to a high-pressure system that is generally located over the region
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20-30°S during the summer and early fall. This system acts as a barrier associated with the
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low-pressure systems southwards. During summer, temperature reaches 27 ºC, during the
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day, and 16 ºC by night (with some occasional rain).
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2.3. Sediment coring and samples preparation
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Two sediment cores, of approximately 50 cm in length, were retrieved from the maximum
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lake depth (22° 20.300’ S; 068°35.981’ W) in July 2013 (Fig 1b) using a 5 cm diameter
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gravity core (Wildco, K-B Corer 20’’). Geochemical analysis and dating were employed to
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one of them, measuring 47 cm, identified as X-LCHT1 (Fig 4a-b). The sediment core was
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transported to the laboratory in polyethylene tube, longitudinally sectioned and stored at 4
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°C until analysis. One half was kept closed, without physical or chemical processing, for
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geochemical analysis at the Institut de recherche pour le développement (IRD)-France
145
laboratory; and the other half was sliced into thin sections of approximately 0.5 cm. These
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slices were dried, powdered and sealed in plastic flasks for radiometric analysis and dating
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(non-destructive analyses) at LARAMG Laboratory/Rio de Janeiro State University-Brazil.
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After that, the granulometry aspect of these samples was analyzed using a standard sieve
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and Cilas®1180 Laser Particle Analyzer (Ziervogel and Bohling, 2003) at the Coastal
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Environments and Marine Biology Program Laboratory (PBMAC-UFF). For grain size
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analysis, samples were dried, homogenized, and carbonates and organic matter were
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extracted by adding aliquotes of HClconc and H2O2 solution (30 %), respectively, until stop
153
reactions (Smith, 2000). Dispersion was performed with Sodium Hexametaphosphate (40 g
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L-1) followed by sonication (35 W for 2 min). Cilas®’s analysis was performed on 0.2 g of
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samples and particle size range spanned from 0.04 to 2500 µm. For the other half of the
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core, we first performed the X-ray (X-LCHT1) image acquisition, with a voltage of 50 kV
157
(Axelsson, 1983). At the Central medical facility in Antofagasta-Chile (Fig 4b), the image
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allowed the reconnaissance of internal stratigraphy of the core and processes related to
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bioturbation. Over the X-ray image of the sediment core we have drawn three continuous
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longitudinal parallel lines from the top to the bottom of the image to obtain the average
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grey scale variability along the depth of the core using the Image-J software (Fig 4c). This
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spatial database was converted to temporal scale based on the sedimentation rate obtained
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by the 210Pb dating method (item 2.5). From these data we have applied FFT (Fast Fourier
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Transformation) to search for core lamination structure periodicities (24 – 47 cm).
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167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192
Figure 3- The meteorological database for Calama Station (22° 29.734’ S; 68°54.350 W; https://climatologia.meteochile.gob.cl); (a) Seasonal precipitation at Chiu-Chiu; (b) local wind direction; (c) MEI index from www.esrl.noaa.gov/psd/enso/mei/ spanning the period 1976-2010. MEI index is the multivariated ENSO Index, defined based on six main observed variables over the tropical Pacific: sea-level pressure, zonal wind (U). Meridional wind (V), sea surface temperature, surface air temperature and total cloudiness fraction of the sky (d) wind intensity variability for the three main wind component directions. Arrows point more intense NIÑO events in the above period.
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2.4. Elemental composition analysis
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Insights of the natural environmental changes and anthropogenic impacts recorded in the
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sediment layers of Inka Coya lake were investigated by the high-resolution X-ray
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fluorescence (XRF) technique (ARTAX® device from the Bruker™). This scanning
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technology allows high-resolution, non-destructive elemental analysis at sub-millimeter
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scales (Croudace et al., 2006; Francus et al., 2009). Elemental compositions analysis here
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corresponded to the dated section of the core, that is, the top 24 cm from the total 47 cm-
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long sequence. The XRF analysis performed at the ALYSES platform (IRD/Bondy/France)
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provides geochemical area mapping of surfaces up to 100cm x 5cm. This technique has the
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potential to correspond to both short-duration events and the long-term variability.
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Measurements were made using a Chromium (Cr) X-Ray tube with the electrical
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parameters: 35 kV and 1142 µA. A spatial resolution of 1mm was used for both X (core
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length) and Y (core width) axes, using a counting time of 30 s per measured point.
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Elemental area mapping results of nearly 50cm x 4cm were then cumulated along the Y-
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axis in order to obtain line scans along the X-axis. This technique was used to characterize
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the geochemical variability of main terrigenous elements as Titanium (Ti), Iron (Fe),
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Potassium (K), Rubidium (Rb), Silicon (Si), Zinc (Zn), Zirconium (Zr), Calcium (Ca),
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Phosphorus (P), Ytterbium (Yb), Arsenic (As), Strontium (Sr), Aluminum (Al), Manganese
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(Mn), Sulfur (S), Chlorine (Cl) and Cooper (Cu). XRF analysis values are expressed in
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counts that refer to the specific peak area of each element.
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2.5. Dating of the sediment core
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Dating method employed in this work used the radionuclides 210Pb and 226Ra from the 238U
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natural series. The core from Inka Coya Lake was analyzed radiometrically by a high-
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resolution gamma spectrometry making use of an extended energy range co-axial
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hyperpure germanium (HPGe) detector (model GX5021 – Canberra). Equipment relative
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efficiency is 50% and resolution of 2.1 keV (FWHM) at the 60Co (1.33 MeV) energy peak.
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This detector was installed inside a very low background lead shielding of an average
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thickness of 15 cm, internally coated with pure Cu. Detector efficiency curve for the
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sediment samples was performed using a liquid solution containing a cocktail of
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radionuclides - NIST (serial number HV951). The cocktail used in this study included the
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radionuclides 133Ba, 57Co, 139Ce, 85Sr, 137Cs, 54Mn, 88Y, and 65Zn, which enclose the energy
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range of interest. The total counting time for each sample was 24 h.
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The geochronological model used in this work was the Constant Rate of Supply (CRS). In
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CRS model, the initial 210Pb concentration in the sediment is constant and the influx rate of
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sediment is variable (Goldberg 1963; Appleby and Oldfield, 1978). The model itself
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considers that no post-depositional mixing occurs. Therefore, bioturbation process is a
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source of error in the sedimentation rates estimates through the time. Another assumption is
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that the transport parameterization is independent of the sedimentation rate. Chronology is
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based on the unsupported fraction of the total 210Pb in each strata as 210Pbunsuported = 210Pbtotal
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–
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but also from dust storms (in the case of a desert site) in which it is assumed to be in
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equilibrium with 226Ra. In this model, the mass sediment accumulation rates are a measure
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of sedimentation that changes with depth. Sedimentation rates are determined by plotting
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the log of the excess
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calculating the sedimentation rates over intervals of constant slope. According to Appleby
238
and Oldfieldz (1983), the age of sediment layers can be obtained as equation 1.
210
Pbsupported. Where
210
Pbsupported is delivered from lake borders due to erosion from rain,
210
Pb activities against cumulative dry sediment weights and
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t= 240
1 AO ln λ A X
(1)
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where A0 is the total unsupported 210Pb activity in the sediment column and Ax is the total
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unsupported 210Pb activity in the sediment column beneath depth x and λ is the radioactive
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decay constant of 210Pb, this is, 0.03114 year-1.
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2.6 Statistical analysis
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We have established 95 and 99 confidence intervals for FFT-Fast Fourier Transform to
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detect statistically significant periodicities at visible lamination structures (rhythmites) in
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the sediment core X-ray image. Power function was obtained with PAST Software.
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Principal Components Analysis (PCA) was employed as an attempt to infer factors that
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may control the core geochemistry variability. To improve the detection of non-linear
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relationships, cubic-root or log (x + 1) transformations were applied to the data (Legendre
252
and Legendre, 1998). The total number of samples was 44, and 20 variables were included
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in the analysis (Ti, Fe, K, Rb, Si, Zn, Zr, Ca, P, Yb, As, Sr, Al, Mn, Cu, Clay, Silte, Sand
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and particle diameter). The results of the PCA are presented in the form of a plot diagram.
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The quantitative environmental variables are indicated by arrows. This analysis was
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performed by PAST software Hammer Ø (Hammer et al., 2001).
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3.
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Results of the time series analysis of wind speed direction for 43 years (Calama
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meterological station) (Fig 3b) revealed the influence of a large-scale atmospheric system
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and local to regional effects in Andean plateau of the Atacama Desert determine the
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circulation of the predominant SW-W-E winds during the whole year, with stronger
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intensity during the spring and summer season. As one may observe from Fig 3c, surface
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winds coming from the Pacific Sector, W-SW, were affected by the two strongest El Niño
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Events during the 1980s and 1990s decades, while the Eastern component, coming from the
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Andean Cordillera sector, did the episodes of 82/83 and 97/98 wind intensities changed
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from a typical values around 6 m/s to 8 m/s, suggesting a higher probability for local dust
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resuspension during strong ENSO phases. On the other hand, the analysis of the temporal
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series of precipitation and wind speed direction (Calama meteorological station) revealed
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three distinct patterns seasonal precipitation: (1) a wet season during May-June-July with
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median of 34 mm, (2) a prolonged dry season from August to December with median of 2.3
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mm and; (3) an intermediate season from January to August with median of 9 mm. No rain
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was observed in this period for November and December (Fig 3a).
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Results and Discussion
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3.1. Sediment core stratigraphy, geochronology and relation with ENSO
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In this study of the stratigraphic record, the X-LCHT1 technique exhibited no obvious signs
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of physical or biological mixture and some redistribution of 210Pb may have occurred only
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on the uppermost part of the core as revealed by the radionuclide vertical behavior. 210Pbexc
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data showed a general tendency to decline with depth (Fig 3d). However, the profile had
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some fluctuations that superimpose to the exponential trend of decay. The chronology for
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the Inka-Coya Lake record, by using the
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sampling) to approximately 1886 AD, which corresponded to the top 24 cm from the 47 cm
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collected. Our estimate for the mean sedimentation rate in this interval is 0.19 cm/yr.
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The sedimentation rate along the 20th century increased steadily from the 1970s decade,
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reaching a maximum at the beginning of the 1990s following a decrease until the year 2000
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(Fig 4d). In general, the behavior of the sedimentation rate follows approximately the trend
293
of the accumulated Southern Oscillation Index (SOI) within a lagged response. SOI is an
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index related to the intensity of El Niño (negative SOI) and La Niña (positive SOI) events,
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here calculated from the year 1876 to 2010. This suggests a potential relationship of ENSO
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phenomena and the sedimentary regime at the Northern Chilean desert environment, at
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least over the last approximately 150 years. Like the cumulative SOI, the sedimentation rate
298
was quite stable up to approximately 1945 and then it increases until the 80’s decade, a
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period dominated by La Niña events, then decreases until the 90’s when El Niño was
300
dominant. Between 23 and 25 cm, we found a layer characterized by a very low
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sedimentation rate, of blackish texture that marked a transition between a well-defined
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laminated phase (rythmites) and a non-laminated phase. Herein we will concentrate our
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efforts on analyzing the well-dated sector correspondent with the non-laminated phase of
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the core.
305 306 307 308 309
210
Pb dating, spanned a period of 2013 (year of
310
311 312 313 314
Figure 4 - (a) Sediment core of Lake Inka-Coya (b) corresponding X-ray image; (c) profile of gray values; (d) profile of 210Pbexc in the core; and (e) sedimentation rates inferred from CRS model.
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We have investigated the nature of these laminations by the periodicity they occur. For that
317
we employed the greyscale variability along the longitudinal length of the core. From the
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top to the bottom of the core we have arranged a total of 400 pixels, each one having
319
distinct greyscale intensity. Over the greyscale time series, we have applied an FFT
320
technique to search for periodicities (cyclic patterns) within statistically significant levels of
321
95% and 99%. This allowed obtaining values of significant frequency bands as depicted in
322
Fig 5. Periods were obtained as P=1/f. Periodicities of pixels were converted to thicknesses
323
of the light and dark layers considering that the total of 400 pixels is equivalent to the total
324
core length of 47 cm. Then by using the average sedimentation rate value of 0.19 cm/year
325
we converted to period. From this approach, we obtained two sets of periodicities; (1)
326
4.2yr, 4.7yr and 5.3yr which are near the periodicity band of ENSO (~ 4-7yr) and (2) 8.4yr
327
and 10.5yr that is close to Schwalbe solar cycle of 11 yr. The sunspot cycle has been
328
already recognized in laminated lake sediments from many regions although the scientific
329
climate basis is not completely described (Muñoz et al., 2002). To better understand the
330
impact of solar activity in the desert environment, we compared the sunspot number with
331
precipitation data of the closest meteorological station. Lacustrine varve layers can be of
332
annually resolved or produced in resolutions associated with longer hydrological cycles
333
(Hernández et al., 2010). A varve layer can be produced when particles are washed into the
334
sedimentary basin because the strengthened water flow can carry coarser material, followed
335
by a finer material deposition occurring during the subsequent phase when energy for
336
transporting materials diminishes. It is probable that salts from the Atacama Desert
337
contribute to coagulate the clay into coarse grains. This process may form a rhythmites
338
structure of corse-fine texture, more visible at x-Ray image. From Fig 3a and Fig 5b it is
339
clear that the events of higher precipitation during the austral winter are mostly followed by
340
the driest period at Atacama. Our comparison between solar activity and precipitation
341
shows a coherent variability between these two parameters since the 1960s decade that
342
corresponds to our longer regional database. Smoothed precipitation pattern shown at Fig
343
5b varied at the same phase of solar activity and therefore the decadal varved signal could
344
be related to changes in solar output energy. During the same period, ENSO variability
345
changed at frequencies between 3 and 7 years while the PDO (Pacific Decadal Oscillation)
346
varied in frequencies much higher than the ~a variability (Valdés-Pineda et al., 2018). The
347
total extent on ENSO control upon precipitation patterns hence the hydro-climatology at
348
Atacama Desert is an issue not fully portrayed (Vuille and Keimig, 2004). Nevertheless,
349
early evidence suggests that El Niño may induce droughts in the Altiplano during both
350
summer and winter seasons (Houston, 2006).
351
352 353 354 355 356
Figure 5- (a) Periodicities detected by FFT (Fourier Fast Transformation) based on greyscale series of Inka-Coya Lake sediment core. Confidence curves are depicted; (b) sunspot number (smoothed time series) corresponding to precipitate database.
357 358
3.2. Sediment core elemental composition and grain size variability
359
Total elemental composition of Inka Coya sediment core record is displayed in Fig 6. From
360
all detected elements we identified 3 distinct groups: (a) Ti, Fe, K, Rb, Si, Mn and S named
361
hereafter as Group 1 (G1) (Fig 6 – upper part); (b) P, Sr, Yb, Cl, Ca, As and Al named
362
hereafter as Group 2 (G2) (Fig 6 – lower part); (c) and Cu (whose time series will be
363
presented later in view of the mining process present in the region). G1 group presented
364
decreases in concentrations during the periods 1908-1968 and 1994-2013 while increases
365
occurred during 1886-1908 and 1968-1994. The inverse behavior is reported for the G2
366
group. This suggests two allochthonous terrigenous sources that may control the total input
367
of lithological material into the lake and that may be associated with the light and dark
368
pattern observed. This is especially evident for Ca and Sr, which are commonly associated
369
with authigenic carbonate minerals or biogenic calcium carbonates from super-arid and
370
limestone/carbonate environments. Also for the Atacama Desert, Stivaletta et al. (2012),
371
have reported a common abundance of fossil deposits of halite (NaCl) as part of the
372
composition from the Salar Grande salt. This deposit presents accessory amounts of
373
gypsum (CaSO4. 2H2O) and glauberite (Na2Ca(SO4)2), which explain the association of Cl
374
and Ca in the same elemental group. Elements in G2 suggest a possible composite mixture
375
of both marine spray and eolian salar materials as sulfate salt sources based on Sr and Cl.
376
On the other hand, the G1 group is characterized by typical lithological material that could
377
be provided by erosion from Andes Cordillera.
378 379 380 381 382
Figure 6- Elemental composition along Inca-Coya sediment core as revealed by XRF analysis. Upper part, the set of elements that defined the group 1 (G1) due to their covariability; and lower part, the same for group 2 (G2). Dotted lines separate major changes in geochemistry.
383
The distinction of the aforementioned groups of elements was clarified by the Principal
384
Component Analysis (PCA) (Fig 7), with Component 1 and Component 2, accounting for
385
57.6% and 19.2% of the total variance, respectively. PCA evidenced an association of G1
386
elements (the terrigenous, or crustal component) with the silt (0.05 – 0.002 mm) and clay
387
(< 0.002 mm) content, that represents the finer fraction of the sediment while G2 elements
388
to sand (0.05 – 2.0 mm), the coarse fraction. This means that group G1 represents the fine
389
mineral dust material being transported and deposited into the lacustrine system, probably
390
through eolic erosion. Pre-cordillera and Coastal Cordillera, where Inka-Coya is located,
391
are Pre-Mesozoic basement with scattered metamorphic outcrops of Precambrian age where
392
surface rock geochemistry contains Fe, Mn, and Zn, besides Co, Cr and V (Tapia et al.,
393
2018). These elements reflect the geochemistry of volcanic and intrusive rocks, soils,
394
regoliths and sediments while Fe–Ti oxides depict the importance of the Andean
395
magmatism. Group G2 may represent a multi-elemental source, since As points to the
396
influence of its potential natural sources as volcanic rocks, hot-springs and mineral deposits
397
(Bull et al., 2016). On the other hand, Ca may derive from the abundant carbonates and
398
gypsum (a sulfate mineral composed of calcium sulfate dihydrate), that are major
399
components in marginal mudflat, ephemeral-stream and alluvia-fan of the Salar de Atacama
400
basin (Boschetti et al., 2007). These materials occur associated with the course mode of the
401
sediment core being associated with the sand fraction. The PCA also depicts the Cu as
402
probably derived from an independent emission source. We attribute that to the extensive
403
open-pit copper mining at the vicinity region of Antofagasta. With respect the P, it is
404
associated with deposits of phosphatic guano that typically contain up to 20% of P2O3, with
405
several occurrences at the northern coast of Chile and associated with Ca when occurring at
406
vein phosphate rocks (Tapia et al., 2019).
407 408 409
Figure 7- Components of the Principal Component Analysis (PCA) for sediment core elemental composition and grain size distribution.
410 411
Based on the anti-phase behavior of the two metal sets in Figure 6, we have defined an
412
index of variability for G1 and G2. To perform that, we have standardized each element
413
database using a Gaussian variable [z=(value-mean)/standard deviation] and averaged the
414
z-values of all elements in the same period. Also considering that the core chronology
415
spans nearly a century we have compared the G1 and G2 values with the Pacific Decadal
416
Oscillation (PDO). PDO is defined as the leading pattern of sea surface temperature
417
anomalies in the North Pacific basin (Zhou et al., 2015). PDO resembles the ENSO
418
spatial/temporal pattern where the largest distinction is the timescales, since ENSO is
419
primarily an interannual phenomenon; the PDO is decadal in scale. Positive PDO values are
420
associated with periods of predominantly El Niño events, while negative PDO values are
421
associated with La Niña events (Hoyos et al., 2013). Our comparisons in Figure 8 show the
422
anti-phase pattern between G1 and G2 and that PDO covariates satisfactorily with G1clay
423
and silt. During El Niño phases an increase on the wind intensity is detected, therefore
424
sustaining mobilization of soil particles under the effect of surface wind stress. This
425
indicates that G1 elements apportionment in the lake could be related to regional aeolian
426
dust deposition from close sources areas such as soils from the Pliocene-Pleistocene (PPl1l)
427
formations that surround the lake. This formation type is associated with sedimentary
428
lacustrine sequences, displaying silts and clays with intercalations of calcareous levels,
429
conglomerates or pyroclastic material. Likewise, G2 elements which are related to the sand
430
component – sediment coarse fraction with diameters larger than 0.06 mm up to 2 mm –
431
could be associated with a regional upper Miocene-Pliocene formation (MP1l),
432
characterized by lacustrine sedimentary sequences, partly fluvial and alluvial limestones
433
and volcanic ash. The G2 elements occurrence can be linked with precipitation events
434
during La Niña associated dry conditions on the coast of Chile, and wet conditions in the
435
Altiplano (Williams et al., 2008).
436 437 438
Figure 8 - (a) PDO time series from 1900 and 2013 and running average; (b) silt and clay data; (c) normalized G1 data; (d) sand data; and (e) normalized G2 data.
439 440
3.3. The anthropogenic signal in the Inka-Coya record
441 442
Copper mining in Chile started initially at scale before the 20th century. By the 1910s,
443
Chile was already one of the main copper mining countries of the World, together with
444
Spain and the USA. Nevertheless, only after the First World War mining and associated
445
industry have developed in Chile. The first significant mining production occurred from
446
1914 to 1918 (Collier, 2018) and increased through the 1920s and the 1930s decades. The
447
Great Depression of 1929 in the USA has affected prominently the Copper production in
448
Chile and a decrease occurred until 1933. Copper production and industry were recovered
449
by the 1940s and 1960s decades and due to the nationalization of copper mines in Chile,
450
Copper production has increased again by mid-1970s (Schwanck et al., 2016). Investments
451
in mineral exploration in Chile reached a maximum in 1997 and declined from there on to
452
2003. After this period, Copper production in Chile presented a wider variability, following
453
the World’s demand. Figure 9a shows historical Copper variability at Inca-Koya sediment
454
core and comparison with mining production and percent of Chilean production with
455
respect to the World’s market (Fig 9c-d). In general Cu variability in the sediment core
456
represents the mining history activities consistently along the 20th century in Northern
457
Chile, depicting the initial phase of Cu mining development until the end of 1920 decade
458
and main shifts in the World’s demand. One point to raise here in that Cu variability in the
459
lake does not covariate with the production data after the 70’s decade, which has exhibited
460
a steady increase. This pattern depicts a higher similarity to the Illimani copper record
461
retrieved from the ice core at 16°37’S, 067° 46’W, in Bolivia at the very high altitude of
462
6350 m a.s.l. (Fig 9b). We attribute the discrepancy between the sedimentary and
463
glaciological record to the fact that Ilimani data capture a regional-to-global emission from
464
the observation of both curves “b” and “d” from Figure 9. On the other hand, the Inka-Coya
465
sediment core records the local production. Cu values in Figure 8a, are not consistent with
466
the mining production amount along the 20th century since maximum values observed
467
during the 1930s decade are comparable to modern concentrations after the 1990s. We
468
attribute that to the different mining emission factors since during the early stage of the
469
mining process almost no control in the dust release to the environment existed. During the
470
last decades, although larger Cu ore volumes are remobilized at the open-pit mines, actions
471
of dust emissions mitigation have caused a decrease of aeolian Cu deposition.
472 473 474 475 476 477
Figure 9 - (a) Copper variability in the Inka-Coya sediment core by XRF technique; (b) Chilean copper production (%) in the world market from 1890 to 2008 (modified from; COCHILCO, 2015); and (c) Chilean production in kilotons from 1900 to 2008 (d) Illimani and Inka-Coya copper. (Source: USGS, 2014; COCHILCO, 2015). See that scale is interrupted for better observation.
478 479
4. Conclusion
480
The high resolved elemental composition provided by the XRF scanning technique over a
481
sediment core of the Inka-Coya Lake at Andes plateau/Northern Chile together with grain
482
size analysis allowed recognizing different sedimentation patterns related to PDO
483
variability. Among several elements analyzed, three groups were identified: one composed
484
by Ti, Fe, K, Rb, Si, Zn, Zr, Mn and S, a second by P, Sr, Yb, Cl, Ca, As and Al, and Cu
485
presenting an independent pattern. The first two groups varied in opposite phase,
486
suggesting different sources of sediments apportioning the lake. These changes, together
487
with the grain size variability, showed a clear influence of the PDO at the decadal scale.
488
Cooper variability reflected the evolution of the regional mining activity along the 20th
489
century.
490 491
Acknowledgements
492 493
This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de
494
Nível Superior - Brasil (CAPES) - Finance Code 001. We would like to thank Universidad
495
de Antofagasta for the initiation scholarship for young Researchers granted to the
496
corresponding author (Vice-rectory UA 2015), to Laboratory of Sedimentology and
497
Paleoenvironments (LASPAL-UA), Laboratory Radioecology and Climatic Changes
498
(LARAMG- UERJ) and Laboratory of Oceanographic and Climate (LOCEAN-IRD) for
499
respectively XRF analysis. Dr. Jorge Valdés was favored with a stay project in Spain, by
500
the DFI program of the Ministry of Education, Chile. Thanks are also due to Dr. Marcos
501
Guiñez and Dr. Alexis Castillo for assistance in the field work. In Memorian Luc Ortlieb
502
(1948-2016).
503 504
References
505 506
Anderson, D.G., Maasch, K., Sandweiss, D.H., 2011. Climate Change and Cultural Dynamics: A Global Perspective on Mid-Holocene Transitions. Elsevier Science.
507 508
Appleby, P.G., Oldfieldz, F., 1983. The assessment of 210Pb data from sites with varying sediment accumulation rates. Hydrobiologia 103, 29-35.
509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525
Axelsson, V., 1983. The use of X-ray radiographic methods in studying sedimentary properties and rates of sediment accumulation. Hydrobiologia 103, 65-69. Clarke, J.D.A., 2006. Antiquity of aridity in the Chilean Atacama Desert. Geomorphology 73, 101-114. Boschetti, T., Cortecci, G., Barbieri, M., Mussi, M., 2007. New and past geochemical data on fresh to brine waters of the Salar de Atacama and Andean Altiplano, northern Chile. Geofluids 7, 33-50. Bull, A.T., Asenjo, J.A., Goodfellow, M., Gómez-Silva, B., 2016. The Atacama Desert: Technical Resources and the Growing Importance of Novel Microbial Diversity. Annual Review of Microbiology 70, 215-234. Croudace, I.W., Rindby, A., Rothwell, R.G., 2006. ITRAX: description and evaluation of a new multi-function X-ray core scanner. Geological Society, London, Special Publications 267, 51-63.
526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572
Francus, P., Lamb, H., Nakagawa, T., Brown, E., 2009. The potential of high-resolution Xray fluorescence core scanning: Applications in paleolimnology. Collier, S., 2018. Historia de Chile : 1808-1994 / Simon Collier, William F. Sater. SERBIULA (sistema Libr. 2.0). Gantz, A., Rau, J., Couve, E., 2009. Ensambles de aves en el desierto de Atacama, norte grande de Chile. Gayana (Concepción) 73, 172-179. Gregor, D.J., Gummer, W.D., 1989. Evidence of atmospheric transport and deposition of organochlorine pesticides and polychlorinated biphenyls in Canadian Arctic snow. Environmental Science & Technology 23, 561-565. Hakanson, L., 1980. An ecological risk index for aquatic pollution control.a sedimentological approach. Water Research 14, 975-1001. Hammer, O., Harper, D., Ryan, P., 2001. PAST: Paleontological Statistics Software Package for Education and Data Analysis. Hernández, A., Giralt, S., Bao, R., Sáez, A., Leng, M.J., Barker, P.A., 2010. ENSO and solar activity signals from oxygen isotopes in diatom silica during late glacial-Holocene transition in Central Andes (18°S). Journal of Paleolimnology 44, 413-429. Houston, J., 2006. Evaporation in the Atacama Desert: An empirical study of spatiotemporal variations and their causes. Journal of Hydrology 330, 402-412. Hoyos, N., Escobar, J., Restrepo, J.C., Arango, A.M., Ortiz, J.C., 2013. Impact of the 2010–2011 La Niña phenomenon in Colombia, South America: The human toll of an extreme weather event. Applied Geography 39, 16-25. Jordan, T., Lameli, C.H., Kirk-Lawlor, N., Godfrey, L., 2015. Architecture of the aquifers of the Calama Basin, Loa catchment basin, northern Chile. Geosphere 11, 1438-1474. Latorre, C., Betancourt, J.L., Rylander, K.A., Quade, J., Matthei, O., 2003. A vegetation history from the arid prepuna of northern Chile (22–23°S) over the last 13 500 years. Palaeogeography, Palaeoclimatology, Palaeoecology 194, 223-246. Lavado-Casimiro, W., Espinoza, J.C., 2014. Impactos de El Niño y La Niña en las lluvias del Perú (1965-2007). Revista Brasileira de Meteorologia 29, 171-182. Legendre, P., Legendre, L., 1998. Preface, In: Pierre, L., Louis, L. (Eds.), Developments in Environmental Modelling. Elsevier, pp. xi-xv. Muñoz, A., Ojeda, J., Sánchez-Valverde, B., 2002. Sunspot-like and ENSO/NAO-like periodicities in lacustrinelaminated sediments of the Pliocene Villarroya Basin (La Rioja, Spain). Journal of Paleolimnology 27, 453-463.
573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617
Rapaport, R.A., Urban, N.R., Capel, P.D., Baker, J.E., Looney, B.B., Eisenreich, S.J., Gorham, E., 1985. “New” DDT inputs to North America: Atmospheric deposition. Chemosphere 14, 1167-1173. Risacher, F., Alonso, H., Salazar, C., 2003. The origin of brines and salts in Chilean salars: a hydrochemical review. Earth-Science Reviews 63, 249-293. Ritter, B., Binnie, S.A., Stuart, F.M., Wennrich, V., Dunai, T.J., 2018. Evidence for multiple Plio-Pleistocene lake episodes in the hyperarid Atacama Desert. Quaternary Geochronology 44, 1-12. Romero, H., Méndez, M., Smith, P., 2012. Mining Development and Environmental Injustice in the Atacama Desert of Northern Chile. Environmental Justice 5, 70-76. Schwalb, A., 2003. Lacustrine ostracodes as stable isotope recorders of late-glacial and Holocene environmental dynamics and climate. Journal of Paleolimnology 29, 265-351. Schwanck, F., Simões, J.C., Handley, M., Mayewski, P.A., Bernardo, R.T., Aquino, F.E., 2016. Anomalously high arsenic concentration in a West Antarctic ice core and its relationship to copper mining in Chile. Atmospheric Environment 125, 257-264. Smith, K.A., 2000. Soil and Environmental Analysis: Physical Methods, Revised, and Expanded. Taylor & Francis. Stivaletta, N., Barbieri, R., Billi, D., 2012. Microbial Colonization of the Salt Deposits in the Driest Place of the Atacama Desert (Chile). Origins of Life and Evolution of Biospheres 42, 187-200. Swackhamer, D.L., Armstrong, D.E., 1986. Estimation of the atmospheric and nonatmospheric contributions and losses of polychlorinated biphenyls to Lake Michigan on the basis of sediment records of remote lakes. Environmental Science & Technology 20, 879-883. Tapia, J., González, R., Townley, B., Oliveros, V., Álvarez, F., Aguilar, G., Menzies, A., Calderón, M., 2018. Geology and geochemistry of the Atacama Desert. Antonie van Leeuwenhoek 111, 1273-1291. Tapia, J., Murray, J., Ormachea, M., Tirado, N., Nordstrom, D.K., 2019. Origin, distribution, and geochemistry of arsenic in the Altiplano-Puna plateau of Argentina, Bolivia, Chile, and Perú. Science of The Total Environment 678, 309-325. Valdés-Pineda, R., Cañón, J., Valdés, J.B., 2018. Multi-decadal 40- to 60-year cycles of precipitation variability in Chile (South America) and their relationship to the AMO and PDO signals. Journal of Hydrology 556, 1153-1170.
618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636
von Gunten, L., Grosjean, M., Beer, J., Grob, P., Morales, A., Urrutia, R., 2009. Age modeling of young non-varved lake sediments: methods and limits. Examples from two lakes in Central Chile. Journal of Paleolimnology 42, 401-412. Vuille, M., Keimig, F., 2004. Interannual Variability of Summertime Convective Cloudiness and Precipitation in the Central Andes Derived from ISCCP-B3 Data. Journal of Climate 17, 3334-3348. Williams, A., Santoro, C.M., Smith, M.A., Latorre, C., 2008. The impact of ENSO in the Atacama Desert and Australian arid zone: exploratory time-series analysis of archaeological records. Chungará (Arica) 40, 245-259. Zhou, X., Sun, Y., Huang, W., Smol, J.P., Tang, Q., Sun, L., 2015. The Pacific decadal oscillation and changes in anchovy populations in the Northwest Pacific. Journal of Asian Earth Sciences 114, 504-511. Ziervogel, K., Bohling, B., 2003. Sedimentological parameters and erosion behaviour of submarine coastal sediments in the south-western Baltic Sea. Geo-Marine Letters 23, 4352.
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Figure captions:
641 642 643 644
Figure 1 – The study site: (a) total view of the Inka Coya Lake (b) bathymetry of the Inka Coya Lake showing a central depression and the sediment core sampling point (T1= XLCHT1); (c) Inka Coya Lake location in the context of South America and Northern Atacama orography.
645 646
Figure 2 – Map of the Inka-Coya site main geological facies. Based on Chilean geological map from the National Geology and Mining Service of Chile.
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Figure 3- The meteorological database for Calama Station (22° 29.734’ S; 68°54.350 W; https://climatologia.meteochile.gob.cl); (a) Seasonal precipitation at Chiu-Chiu; (b) local wind direction; (c) MEI index from www.esrl.noaa.gov/psd/enso/mei/ spanning the period 1976-2010. MEI index is the multivariated ENSO Index, defined based on six main observed variables over the tropical Pacific: sea-level pressure, zonal wind (U). Meridional wind (V), sea surface temperature, surface air temperature and total cloudiness fraction of the sky (d) wind intensity variability for the three main wind component directions. Arrows point more intense NIÑO events in the above period.
655 656 657
Figure 4 - (a) Sediment core of Lake Inka-Coya (b) corresponding X-ray image; (c) profile of gray values; (d) profile of 210Pbexc in the core; and (e) sedimentation rates inferred from CRS model.
658 659 660
Figure 5- (a) Periodicities detected by FFT (Fourier Fast Transformation) based on greyscale series of Inka-Coya Lake sediment core. Confidence curves are depicted; (b) sunspot number (smoothed time series) corresponding to precipitate database.
661 662 663 664
Figure 6- Elemental composition along Inca-Coya sediment core as revealed by XRF analysis. Upper part, the set of elements that defined the group 1 (G1) due to their covariability; and lower part, the same for group 2 (G2). Dotted lines separate major changes in geochemistry.
665 666
Figure 7- Components of the Principal Component Analysis (PCA) for sediment core elemental composition and grain size distribution.
667 668
Figure 8 - (a) PDO time series from 1900 and 2013 and running average; (b) silt and clay data; (c) normalized G1 data; (d) sand data; and (e) normalized G2 data.
669 670 671 672 673
Figure 9 - (a) Copper variability in the Inka-Coya sediment core by XRF technique; (b) Chilean copper production (%) in the world market from 1890 to 2008 (modified from; COCHILCO, 2015); and (c) Chilean production in kilotons from 1900 to 2008 (d) Illimani and Inka-Coya copper. (Source: USGS, 2014; COCHILCO, 2015). See that scale is interrupted for better observation.
674 675 676 677 678 679 680 681 682
S0895-9811(19)30361-X
DOI:
https://doi.org/10.1016/j.jsames.2019.102302
Reference:
SAMES 102302
To appear in:
Journal of South American Earth Sciences
Received Date: 14 July 2019 Revised Date:
1 August 2019
Accepted Date: 1 August 2019
Please cite this article as: Cerda, M., Evangelista, H., Valdés, J., Siffedine, A., Boucher, H., Nogueira, J., Nepomuceno, A., Ortlieb, L., A new 20th century lake sedimentary record from the Atacama Desert/ Chile reveals persistent PDO (Pacific Decadal Oscillation) impact, Journal of South American Earth Sciences (2019), doi: https://doi.org/10.1016/j.jsames.2019.102302. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
1 2
A new 20th century lake sedimentary record from the Atacama Desert/Chile reveals persistent PDO (Pacific Decadal Oscillation) impact
3 4 5
MAURICIO CERDA1,2,3*, HEITOR EVANGELISTA4,7, JORGE VALDÉS3,5, ABDELFETTAH SIFFEDINE5,6, HUGUES BOUCHER6, JULIANA NOGUEIRA4,5,7, AGUINALDO NEPOMUCENO1& LUC ORTLIEB6
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
1
21
Abstract
22 23 24 25 26 27 28 29 30 31 32 33 34 35
The Atacama Desert lakes located at high altitudes with very low anthropogenic impacts preserve great potential to recover regional climate changes and environmental processes at a decadal to centennial time scales. Herein, we present a high-resolution analysis of the stratigraphy and metal composition of Inka Coya Lake sediment core, in order to clarify the main forcings acting on sedimentation rates and both eolian and precipitation patterns at Atacama Desert environment. The results suggest that terrigenous inputs can be mainly related to the PDO (Pacific Decadal Oscillation), while laminations preserve a direct association with El Nino-Southern Oscillation – ENSO (4.2 to 5.3 yr. cyclicity). Additionally, the Cu mining activities in Chile are recorded in the lake. The sedimentation rates and precipitation patterns were associated with ENSO, highlighting the relation between La Niña and wetter periods at Atacama. Finally, high-resolution analyses of the geochemical composition provided additional criteria to identify the erosion processes at the basin, suggesting different sources of sediments, which fluxes into the lake covariated with PDO at a decadal scale, especially during the 20th century.
Programa de Biologia Marinha e Ambientes Costeiros Universidade Federal Fluminense (PBMAC-UFF) Outeiro de São João Batista s/n, Centro Niterói Brazil. 2 Centro de Investigación e Innovación para el Cambio Climático (CiiCC), Facultad de Ciencias Universidad Santo Tomás Santiago Chile 3 Laboratorio de Sedimentología y Paleoambientes, Instituto Alexander von Humboldt. Facultad de Ciencias del mar y de recursos biológicos, Universidad de Antofagasta, Casilla 170, Antofagasta, Chile 4 LARAMG/IBRAG/UERJ, Pavilhão Haroldo L. da Cunha, Subsolo, Rua São Francisco Xavier 524, Maracanã, Rio de Janeiro, 20550-013, Brazil 5 LMI PALEOTRACES, IRD-UFF-UANTOF-UPCH. 6 LOCEAN - IPSL UMR 7159, IRD-Sorbonne Universités (Université P. et M. Curie, Paris 06)CNRS/UPMC/IRD, IRD France-Nord 32, av. Henri Varagnat,FR-93143 BONDY cedex 7 Programa de Pós-graduação em Geoquímica, Universidade Federal Fluminense/Instituto de Química/Departamento de Geoquímica/Outeiro de São João Batista s/n, Centro, Niterói, Brazil.
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∗ Corresponding author
38
E-mail addresses: *[email protected]
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Keywords: Atacama, PDO, lake sedimentology, elemental composition, Copper record
42
1.
Introduction
43
The Andes plateau at Northern Chile created by the subduction of the Nazca Plate beneath
44
the South America Plate houses a series of lakes (Risacher et al. 2003). They are believed
45
to provide conditions for reconstructing the regional past climatic changes and the past
46
aridity conditions (Anderson et al., 2011; Ritter et al., 2018). The aridity of the Atacama
47
desert may have started in the Eocene (from ~ 55 to 36 million years) and evolved into the
48
current aridity since the mid-Miocene (from 23 to 5.3 million years) (Clarke, 2006). The
49
extreme aridity observed today is due to a combination of factors that includes the influence
50
of the Subtropical High-pressure belt, the Ecuador-advection, the Humboldt coastal cold
51
marine current, and the orographic aspects of the Andes Cordillera around. According to
52
Schwalb (2003), and considering the above aspects, the Altiplano is a region very sensitive
53
to changes in the moisture advection, evaporation and precipitation dynamics. Precipitation
54
at Atacama Desert is mainly controlled by two climatic mechanisms: the northern monsoon
55
(Bolivian Winter) and the southern frontal systems. Precipitation is minimum within the
56
area that corresponds to the boundary between both mechanisms, 18-28°S, where their
57
effects are minimized. It is believed that the El Niño–Southern Oscillation (ENSO), may
58
regionally influence the surface winds as a result of the sea surface temperatures over the
59
Pacific Ocean. Its two related phases (El Niño and La Niña) control the longitudinal
60
intensity of the Walker circulation that ultimately may bring more or less ocean influence
61
towards the inland. According to literature, ENSO events have contrasted effects on
62
precipitation regimes at the Andean region with intense summer rain at the Western side
63
and droughts at the Eastern side (Lavado-Casimiro and Espinoza, 2014).
64
Sediment cores from lacustrine environments are widely used to reconstruct temporal
65
variability of natural and anthropogenic processes (e.g.: von Gunten et al., 2009). In this
66
context, many authors use joint analysis of sediment geochemical composition and their
67
laminated structures to provide insights into runoff processes associated with precipitation
68
and dust deposition of chemical species. For Atacama Desert, although the impact of ENSO
69
on the regional climate is well documented, we explore its impact over the sedimentary
70
record measured from dated lacustrine sediment deposits, sedimentary stratigraphy and
71
metal contents using high-resolution XRF analysis. As a complementary aspect, we have
72
also investigated if an imprint of the major regional anthropogenic activity, represented by
73
the Cu mining and tailing does exist. Over the last hundred years, mining and related
74
activities caused a significant reduction in the major watersheds (Romero et al., 2012) and
75
several pieces of evidence indicate that their resuspended materials were potential sources
76
of contamination (Gregor and Gummer, 1989; Rapaport et al., 1985; Swackhamer and
77
Armstrong, 1986).
78
Herein we present high-resolution elemental composition variability from a sediment core
79
retrieved at the high-altitude Inka Coya Lake, Northern Atacama Desert. This lake is
80
characterized by having a relatively low human direct impact and no significant land-use
81
change around it during the last century. The analysis on its 20th century lacustrine
82
sedimentary record sector allowed us to investigate the impact of the PDO (Pacific Decadal
83
Oscillation) over its geochemical and physical characteristics.
84 85
2.
Methods
86
2.1. Study site
87
The Inka Coya Lake (San Francisco de Chiu-Chiu/Antofagasta; 22° 20.300’ S; 068°35.981’
88
W) is located in the Northern Atacama Desert region at an altitude of 2516.4 m a.s.l (Fig.1).
89
It is approximately 48 km away from the city of Calama. It has an asymmetric oval shape
90
and an area of 1.52 km2. The Inka Coya Lake has an average volume of 1.6x106 m3 and is
91
surrounded by a varied xerophytic fauna (Gantz et al., 2009). The local terrain is stony like,
92
with salt lakes (salares), sand and felsic lava. The extreme aridity conditions of the region
93
are mostly due to the cool north-flowing Humboldt ocean current, and the presence of the
94
strong Pacific anticyclone. The lake is situated on the limit among the central valley and the
95
cordillera zone, between two mountain ranges - the Andes and the Chilean Coastal Zone.
96
This orography protects the site against intense moisture advection from either the Pacific
97
or the Amazon basin, contributing to the maintenance of hyper aridity conditions over the
98
Atacama Desert. Geological evidence suggests that the study site is composed mostly of
99
moderately consolidated sedimentary rock from Pliocene-Pleistocene, while its
100
surroundings can be related to old sediments from the late Miocene-Pliocene transition
101
period and sediments as recent as the Pleistocene-Holocene (Fig. 2) (Jordan et al., 2015).
102
103 104 105 106 107 108 109 110 111 112 113 114 115
Figure 1 – The study site: (a) total view of the Inka Coya Lake (b) bathymetry of the Inka Coya Lake showing a central depression and the sediment core sampling point (T1= XLCHT1); (c) Inka Coya Lake location in the context of South America and Northern Atacama orography.
116 117 118 119 120
Figure 2 – Map of the Inka-Coya site main geological facies. Based on Chilean geological map from the National Geology and Mining Service of Chile.
121 122
2.2. Regional climate characterization
123
The small annual precipitation amount that falls on the Atacama is a result of the northeast
124
summer monsoon, southwest frontal precipitation, fog deposition below 800 m a.s.l and
125
also occasional winter rains at coastal areas below 1,000 m. Occasional winter rains (May-
126
October) on Andean slopes South of 25ºS, and summer storms (November-March) that
127
cross the Altiplano, spill over the Andes, and rain out on the Pacific slope north of 25°S
128
(Latorre et al., 2003). According to Köppen climate classification, the predominant climate
129
domain at Chiu-Chiu region is “BWk” – cold desert climate – characterized by dry
130
summers with marked seasonal thermal amplitude. During winter, air temperature reaches
131
an average of 22 ºC, during the day, and 4ºC by night. Clear sky condition occurs almost
132
through all the year, due to a high-pressure system that is generally located over the region
133
20-30°S during the summer and early fall. This system acts as a barrier associated with the
134
low-pressure systems southwards. During summer, temperature reaches 27 ºC, during the
135
day, and 16 ºC by night (with some occasional rain).
136 137
2.3. Sediment coring and samples preparation
138
Two sediment cores, of approximately 50 cm in length, were retrieved from the maximum
139
lake depth (22° 20.300’ S; 068°35.981’ W) in July 2013 (Fig 1b) using a 5 cm diameter
140
gravity core (Wildco, K-B Corer 20’’). Geochemical analysis and dating were employed to
141
one of them, measuring 47 cm, identified as X-LCHT1 (Fig 4a-b). The sediment core was
142
transported to the laboratory in polyethylene tube, longitudinally sectioned and stored at 4
143
°C until analysis. One half was kept closed, without physical or chemical processing, for
144
geochemical analysis at the Institut de recherche pour le développement (IRD)-France
145
laboratory; and the other half was sliced into thin sections of approximately 0.5 cm. These
146
slices were dried, powdered and sealed in plastic flasks for radiometric analysis and dating
147
(non-destructive analyses) at LARAMG Laboratory/Rio de Janeiro State University-Brazil.
148
After that, the granulometry aspect of these samples was analyzed using a standard sieve
149
and Cilas®1180 Laser Particle Analyzer (Ziervogel and Bohling, 2003) at the Coastal
150
Environments and Marine Biology Program Laboratory (PBMAC-UFF). For grain size
151
analysis, samples were dried, homogenized, and carbonates and organic matter were
152
extracted by adding aliquotes of HClconc and H2O2 solution (30 %), respectively, until stop
153
reactions (Smith, 2000). Dispersion was performed with Sodium Hexametaphosphate (40 g
154
L-1) followed by sonication (35 W for 2 min). Cilas®’s analysis was performed on 0.2 g of
155
samples and particle size range spanned from 0.04 to 2500 µm. For the other half of the
156
core, we first performed the X-ray (X-LCHT1) image acquisition, with a voltage of 50 kV
157
(Axelsson, 1983). At the Central medical facility in Antofagasta-Chile (Fig 4b), the image
158
allowed the reconnaissance of internal stratigraphy of the core and processes related to
159
bioturbation. Over the X-ray image of the sediment core we have drawn three continuous
160
longitudinal parallel lines from the top to the bottom of the image to obtain the average
161
grey scale variability along the depth of the core using the Image-J software (Fig 4c). This
162
spatial database was converted to temporal scale based on the sedimentation rate obtained
163
by the 210Pb dating method (item 2.5). From these data we have applied FFT (Fast Fourier
164
Transformation) to search for core lamination structure periodicities (24 – 47 cm).
165 166
167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192
Figure 3- The meteorological database for Calama Station (22° 29.734’ S; 68°54.350 W; https://climatologia.meteochile.gob.cl); (a) Seasonal precipitation at Chiu-Chiu; (b) local wind direction; (c) MEI index from www.esrl.noaa.gov/psd/enso/mei/ spanning the period 1976-2010. MEI index is the multivariated ENSO Index, defined based on six main observed variables over the tropical Pacific: sea-level pressure, zonal wind (U). Meridional wind (V), sea surface temperature, surface air temperature and total cloudiness fraction of the sky (d) wind intensity variability for the three main wind component directions. Arrows point more intense NIÑO events in the above period.
193
2.4. Elemental composition analysis
194
Insights of the natural environmental changes and anthropogenic impacts recorded in the
195
sediment layers of Inka Coya lake were investigated by the high-resolution X-ray
196
fluorescence (XRF) technique (ARTAX® device from the Bruker™). This scanning
197
technology allows high-resolution, non-destructive elemental analysis at sub-millimeter
198
scales (Croudace et al., 2006; Francus et al., 2009). Elemental compositions analysis here
199
corresponded to the dated section of the core, that is, the top 24 cm from the total 47 cm-
200
long sequence. The XRF analysis performed at the ALYSES platform (IRD/Bondy/France)
201
provides geochemical area mapping of surfaces up to 100cm x 5cm. This technique has the
202
potential to correspond to both short-duration events and the long-term variability.
203
Measurements were made using a Chromium (Cr) X-Ray tube with the electrical
204
parameters: 35 kV and 1142 µA. A spatial resolution of 1mm was used for both X (core
205
length) and Y (core width) axes, using a counting time of 30 s per measured point.
206
Elemental area mapping results of nearly 50cm x 4cm were then cumulated along the Y-
207
axis in order to obtain line scans along the X-axis. This technique was used to characterize
208
the geochemical variability of main terrigenous elements as Titanium (Ti), Iron (Fe),
209
Potassium (K), Rubidium (Rb), Silicon (Si), Zinc (Zn), Zirconium (Zr), Calcium (Ca),
210
Phosphorus (P), Ytterbium (Yb), Arsenic (As), Strontium (Sr), Aluminum (Al), Manganese
211
(Mn), Sulfur (S), Chlorine (Cl) and Cooper (Cu). XRF analysis values are expressed in
212
counts that refer to the specific peak area of each element.
213
2.5. Dating of the sediment core
214
Dating method employed in this work used the radionuclides 210Pb and 226Ra from the 238U
215
natural series. The core from Inka Coya Lake was analyzed radiometrically by a high-
216
resolution gamma spectrometry making use of an extended energy range co-axial
217
hyperpure germanium (HPGe) detector (model GX5021 – Canberra). Equipment relative
218
efficiency is 50% and resolution of 2.1 keV (FWHM) at the 60Co (1.33 MeV) energy peak.
219
This detector was installed inside a very low background lead shielding of an average
220
thickness of 15 cm, internally coated with pure Cu. Detector efficiency curve for the
221
sediment samples was performed using a liquid solution containing a cocktail of
222
radionuclides - NIST (serial number HV951). The cocktail used in this study included the
223
radionuclides 133Ba, 57Co, 139Ce, 85Sr, 137Cs, 54Mn, 88Y, and 65Zn, which enclose the energy
224
range of interest. The total counting time for each sample was 24 h.
225
The geochronological model used in this work was the Constant Rate of Supply (CRS). In
226
CRS model, the initial 210Pb concentration in the sediment is constant and the influx rate of
227
sediment is variable (Goldberg 1963; Appleby and Oldfield, 1978). The model itself
228
considers that no post-depositional mixing occurs. Therefore, bioturbation process is a
229
source of error in the sedimentation rates estimates through the time. Another assumption is
230
that the transport parameterization is independent of the sedimentation rate. Chronology is
231
based on the unsupported fraction of the total 210Pb in each strata as 210Pbunsuported = 210Pbtotal
232
–
233
but also from dust storms (in the case of a desert site) in which it is assumed to be in
234
equilibrium with 226Ra. In this model, the mass sediment accumulation rates are a measure
235
of sedimentation that changes with depth. Sedimentation rates are determined by plotting
236
the log of the excess
237
calculating the sedimentation rates over intervals of constant slope. According to Appleby
238
and Oldfieldz (1983), the age of sediment layers can be obtained as equation 1.
210
Pbsupported. Where
210
Pbsupported is delivered from lake borders due to erosion from rain,
210
Pb activities against cumulative dry sediment weights and
239
t= 240
1 AO ln λ A X
(1)
241 242
where A0 is the total unsupported 210Pb activity in the sediment column and Ax is the total
243
unsupported 210Pb activity in the sediment column beneath depth x and λ is the radioactive
244
decay constant of 210Pb, this is, 0.03114 year-1.
245
2.6 Statistical analysis
246
We have established 95 and 99 confidence intervals for FFT-Fast Fourier Transform to
247
detect statistically significant periodicities at visible lamination structures (rhythmites) in
248
the sediment core X-ray image. Power function was obtained with PAST Software.
249
Principal Components Analysis (PCA) was employed as an attempt to infer factors that
250
may control the core geochemistry variability. To improve the detection of non-linear
251
relationships, cubic-root or log (x + 1) transformations were applied to the data (Legendre
252
and Legendre, 1998). The total number of samples was 44, and 20 variables were included
253
in the analysis (Ti, Fe, K, Rb, Si, Zn, Zr, Ca, P, Yb, As, Sr, Al, Mn, Cu, Clay, Silte, Sand
254
and particle diameter). The results of the PCA are presented in the form of a plot diagram.
255
The quantitative environmental variables are indicated by arrows. This analysis was
256
performed by PAST software Hammer Ø (Hammer et al., 2001).
257 258
3.
259
Results of the time series analysis of wind speed direction for 43 years (Calama
260
meterological station) (Fig 3b) revealed the influence of a large-scale atmospheric system
261
and local to regional effects in Andean plateau of the Atacama Desert determine the
262
circulation of the predominant SW-W-E winds during the whole year, with stronger
263
intensity during the spring and summer season. As one may observe from Fig 3c, surface
264
winds coming from the Pacific Sector, W-SW, were affected by the two strongest El Niño
265
Events during the 1980s and 1990s decades, while the Eastern component, coming from the
266
Andean Cordillera sector, did the episodes of 82/83 and 97/98 wind intensities changed
267
from a typical values around 6 m/s to 8 m/s, suggesting a higher probability for local dust
268
resuspension during strong ENSO phases. On the other hand, the analysis of the temporal
269
series of precipitation and wind speed direction (Calama meteorological station) revealed
270
three distinct patterns seasonal precipitation: (1) a wet season during May-June-July with
271
median of 34 mm, (2) a prolonged dry season from August to December with median of 2.3
272
mm and; (3) an intermediate season from January to August with median of 9 mm. No rain
273
was observed in this period for November and December (Fig 3a).
274 275 276 277 278 279 280
Results and Discussion
281
3.1. Sediment core stratigraphy, geochronology and relation with ENSO
282
In this study of the stratigraphic record, the X-LCHT1 technique exhibited no obvious signs
283
of physical or biological mixture and some redistribution of 210Pb may have occurred only
284
on the uppermost part of the core as revealed by the radionuclide vertical behavior. 210Pbexc
285
data showed a general tendency to decline with depth (Fig 3d). However, the profile had
286
some fluctuations that superimpose to the exponential trend of decay. The chronology for
287
the Inka-Coya Lake record, by using the
288
sampling) to approximately 1886 AD, which corresponded to the top 24 cm from the 47 cm
289
collected. Our estimate for the mean sedimentation rate in this interval is 0.19 cm/yr.
290
The sedimentation rate along the 20th century increased steadily from the 1970s decade,
291
reaching a maximum at the beginning of the 1990s following a decrease until the year 2000
292
(Fig 4d). In general, the behavior of the sedimentation rate follows approximately the trend
293
of the accumulated Southern Oscillation Index (SOI) within a lagged response. SOI is an
294
index related to the intensity of El Niño (negative SOI) and La Niña (positive SOI) events,
295
here calculated from the year 1876 to 2010. This suggests a potential relationship of ENSO
296
phenomena and the sedimentary regime at the Northern Chilean desert environment, at
297
least over the last approximately 150 years. Like the cumulative SOI, the sedimentation rate
298
was quite stable up to approximately 1945 and then it increases until the 80’s decade, a
299
period dominated by La Niña events, then decreases until the 90’s when El Niño was
300
dominant. Between 23 and 25 cm, we found a layer characterized by a very low
301
sedimentation rate, of blackish texture that marked a transition between a well-defined
302
laminated phase (rythmites) and a non-laminated phase. Herein we will concentrate our
303
efforts on analyzing the well-dated sector correspondent with the non-laminated phase of
304
the core.
305 306 307 308 309
210
Pb dating, spanned a period of 2013 (year of
310
311 312 313 314
Figure 4 - (a) Sediment core of Lake Inka-Coya (b) corresponding X-ray image; (c) profile of gray values; (d) profile of 210Pbexc in the core; and (e) sedimentation rates inferred from CRS model.
315 316
We have investigated the nature of these laminations by the periodicity they occur. For that
317
we employed the greyscale variability along the longitudinal length of the core. From the
318
top to the bottom of the core we have arranged a total of 400 pixels, each one having
319
distinct greyscale intensity. Over the greyscale time series, we have applied an FFT
320
technique to search for periodicities (cyclic patterns) within statistically significant levels of
321
95% and 99%. This allowed obtaining values of significant frequency bands as depicted in
322
Fig 5. Periods were obtained as P=1/f. Periodicities of pixels were converted to thicknesses
323
of the light and dark layers considering that the total of 400 pixels is equivalent to the total
324
core length of 47 cm. Then by using the average sedimentation rate value of 0.19 cm/year
325
we converted to period. From this approach, we obtained two sets of periodicities; (1)
326
4.2yr, 4.7yr and 5.3yr which are near the periodicity band of ENSO (~ 4-7yr) and (2) 8.4yr
327
and 10.5yr that is close to Schwalbe solar cycle of 11 yr. The sunspot cycle has been
328
already recognized in laminated lake sediments from many regions although the scientific
329
climate basis is not completely described (Muñoz et al., 2002). To better understand the
330
impact of solar activity in the desert environment, we compared the sunspot number with
331
precipitation data of the closest meteorological station. Lacustrine varve layers can be of
332
annually resolved or produced in resolutions associated with longer hydrological cycles
333
(Hernández et al., 2010). A varve layer can be produced when particles are washed into the
334
sedimentary basin because the strengthened water flow can carry coarser material, followed
335
by a finer material deposition occurring during the subsequent phase when energy for
336
transporting materials diminishes. It is probable that salts from the Atacama Desert
337
contribute to coagulate the clay into coarse grains. This process may form a rhythmites
338
structure of corse-fine texture, more visible at x-Ray image. From Fig 3a and Fig 5b it is
339
clear that the events of higher precipitation during the austral winter are mostly followed by
340
the driest period at Atacama. Our comparison between solar activity and precipitation
341
shows a coherent variability between these two parameters since the 1960s decade that
342
corresponds to our longer regional database. Smoothed precipitation pattern shown at Fig
343
5b varied at the same phase of solar activity and therefore the decadal varved signal could
344
be related to changes in solar output energy. During the same period, ENSO variability
345
changed at frequencies between 3 and 7 years while the PDO (Pacific Decadal Oscillation)
346
varied in frequencies much higher than the ~a variability (Valdés-Pineda et al., 2018). The
347
total extent on ENSO control upon precipitation patterns hence the hydro-climatology at
348
Atacama Desert is an issue not fully portrayed (Vuille and Keimig, 2004). Nevertheless,
349
early evidence suggests that El Niño may induce droughts in the Altiplano during both
350
summer and winter seasons (Houston, 2006).
351
352 353 354 355 356
Figure 5- (a) Periodicities detected by FFT (Fourier Fast Transformation) based on greyscale series of Inka-Coya Lake sediment core. Confidence curves are depicted; (b) sunspot number (smoothed time series) corresponding to precipitate database.
357 358
3.2. Sediment core elemental composition and grain size variability
359
Total elemental composition of Inka Coya sediment core record is displayed in Fig 6. From
360
all detected elements we identified 3 distinct groups: (a) Ti, Fe, K, Rb, Si, Mn and S named
361
hereafter as Group 1 (G1) (Fig 6 – upper part); (b) P, Sr, Yb, Cl, Ca, As and Al named
362
hereafter as Group 2 (G2) (Fig 6 – lower part); (c) and Cu (whose time series will be
363
presented later in view of the mining process present in the region). G1 group presented
364
decreases in concentrations during the periods 1908-1968 and 1994-2013 while increases
365
occurred during 1886-1908 and 1968-1994. The inverse behavior is reported for the G2
366
group. This suggests two allochthonous terrigenous sources that may control the total input
367
of lithological material into the lake and that may be associated with the light and dark
368
pattern observed. This is especially evident for Ca and Sr, which are commonly associated
369
with authigenic carbonate minerals or biogenic calcium carbonates from super-arid and
370
limestone/carbonate environments. Also for the Atacama Desert, Stivaletta et al. (2012),
371
have reported a common abundance of fossil deposits of halite (NaCl) as part of the
372
composition from the Salar Grande salt. This deposit presents accessory amounts of
373
gypsum (CaSO4. 2H2O) and glauberite (Na2Ca(SO4)2), which explain the association of Cl
374
and Ca in the same elemental group. Elements in G2 suggest a possible composite mixture
375
of both marine spray and eolian salar materials as sulfate salt sources based on Sr and Cl.
376
On the other hand, the G1 group is characterized by typical lithological material that could
377
be provided by erosion from Andes Cordillera.
378 379 380 381 382
Figure 6- Elemental composition along Inca-Coya sediment core as revealed by XRF analysis. Upper part, the set of elements that defined the group 1 (G1) due to their covariability; and lower part, the same for group 2 (G2). Dotted lines separate major changes in geochemistry.
383
The distinction of the aforementioned groups of elements was clarified by the Principal
384
Component Analysis (PCA) (Fig 7), with Component 1 and Component 2, accounting for
385
57.6% and 19.2% of the total variance, respectively. PCA evidenced an association of G1
386
elements (the terrigenous, or crustal component) with the silt (0.05 – 0.002 mm) and clay
387
(< 0.002 mm) content, that represents the finer fraction of the sediment while G2 elements
388
to sand (0.05 – 2.0 mm), the coarse fraction. This means that group G1 represents the fine
389
mineral dust material being transported and deposited into the lacustrine system, probably
390
through eolic erosion. Pre-cordillera and Coastal Cordillera, where Inka-Coya is located,
391
are Pre-Mesozoic basement with scattered metamorphic outcrops of Precambrian age where
392
surface rock geochemistry contains Fe, Mn, and Zn, besides Co, Cr and V (Tapia et al.,
393
2018). These elements reflect the geochemistry of volcanic and intrusive rocks, soils,
394
regoliths and sediments while Fe–Ti oxides depict the importance of the Andean
395
magmatism. Group G2 may represent a multi-elemental source, since As points to the
396
influence of its potential natural sources as volcanic rocks, hot-springs and mineral deposits
397
(Bull et al., 2016). On the other hand, Ca may derive from the abundant carbonates and
398
gypsum (a sulfate mineral composed of calcium sulfate dihydrate), that are major
399
components in marginal mudflat, ephemeral-stream and alluvia-fan of the Salar de Atacama
400
basin (Boschetti et al., 2007). These materials occur associated with the course mode of the
401
sediment core being associated with the sand fraction. The PCA also depicts the Cu as
402
probably derived from an independent emission source. We attribute that to the extensive
403
open-pit copper mining at the vicinity region of Antofagasta. With respect the P, it is
404
associated with deposits of phosphatic guano that typically contain up to 20% of P2O3, with
405
several occurrences at the northern coast of Chile and associated with Ca when occurring at
406
vein phosphate rocks (Tapia et al., 2019).
407 408 409
Figure 7- Components of the Principal Component Analysis (PCA) for sediment core elemental composition and grain size distribution.
410 411
Based on the anti-phase behavior of the two metal sets in Figure 6, we have defined an
412
index of variability for G1 and G2. To perform that, we have standardized each element
413
database using a Gaussian variable [z=(value-mean)/standard deviation] and averaged the
414
z-values of all elements in the same period. Also considering that the core chronology
415
spans nearly a century we have compared the G1 and G2 values with the Pacific Decadal
416
Oscillation (PDO). PDO is defined as the leading pattern of sea surface temperature
417
anomalies in the North Pacific basin (Zhou et al., 2015). PDO resembles the ENSO
418
spatial/temporal pattern where the largest distinction is the timescales, since ENSO is
419
primarily an interannual phenomenon; the PDO is decadal in scale. Positive PDO values are
420
associated with periods of predominantly El Niño events, while negative PDO values are
421
associated with La Niña events (Hoyos et al., 2013). Our comparisons in Figure 8 show the
422
anti-phase pattern between G1 and G2 and that PDO covariates satisfactorily with G1clay
423
and silt. During El Niño phases an increase on the wind intensity is detected, therefore
424
sustaining mobilization of soil particles under the effect of surface wind stress. This
425
indicates that G1 elements apportionment in the lake could be related to regional aeolian
426
dust deposition from close sources areas such as soils from the Pliocene-Pleistocene (PPl1l)
427
formations that surround the lake. This formation type is associated with sedimentary
428
lacustrine sequences, displaying silts and clays with intercalations of calcareous levels,
429
conglomerates or pyroclastic material. Likewise, G2 elements which are related to the sand
430
component – sediment coarse fraction with diameters larger than 0.06 mm up to 2 mm –
431
could be associated with a regional upper Miocene-Pliocene formation (MP1l),
432
characterized by lacustrine sedimentary sequences, partly fluvial and alluvial limestones
433
and volcanic ash. The G2 elements occurrence can be linked with precipitation events
434
during La Niña associated dry conditions on the coast of Chile, and wet conditions in the
435
Altiplano (Williams et al., 2008).
436 437 438
Figure 8 - (a) PDO time series from 1900 and 2013 and running average; (b) silt and clay data; (c) normalized G1 data; (d) sand data; and (e) normalized G2 data.
439 440
3.3. The anthropogenic signal in the Inka-Coya record
441 442
Copper mining in Chile started initially at scale before the 20th century. By the 1910s,
443
Chile was already one of the main copper mining countries of the World, together with
444
Spain and the USA. Nevertheless, only after the First World War mining and associated
445
industry have developed in Chile. The first significant mining production occurred from
446
1914 to 1918 (Collier, 2018) and increased through the 1920s and the 1930s decades. The
447
Great Depression of 1929 in the USA has affected prominently the Copper production in
448
Chile and a decrease occurred until 1933. Copper production and industry were recovered
449
by the 1940s and 1960s decades and due to the nationalization of copper mines in Chile,
450
Copper production has increased again by mid-1970s (Schwanck et al., 2016). Investments
451
in mineral exploration in Chile reached a maximum in 1997 and declined from there on to
452
2003. After this period, Copper production in Chile presented a wider variability, following
453
the World’s demand. Figure 9a shows historical Copper variability at Inca-Koya sediment
454
core and comparison with mining production and percent of Chilean production with
455
respect to the World’s market (Fig 9c-d). In general Cu variability in the sediment core
456
represents the mining history activities consistently along the 20th century in Northern
457
Chile, depicting the initial phase of Cu mining development until the end of 1920 decade
458
and main shifts in the World’s demand. One point to raise here in that Cu variability in the
459
lake does not covariate with the production data after the 70’s decade, which has exhibited
460
a steady increase. This pattern depicts a higher similarity to the Illimani copper record
461
retrieved from the ice core at 16°37’S, 067° 46’W, in Bolivia at the very high altitude of
462
6350 m a.s.l. (Fig 9b). We attribute the discrepancy between the sedimentary and
463
glaciological record to the fact that Ilimani data capture a regional-to-global emission from
464
the observation of both curves “b” and “d” from Figure 9. On the other hand, the Inka-Coya
465
sediment core records the local production. Cu values in Figure 8a, are not consistent with
466
the mining production amount along the 20th century since maximum values observed
467
during the 1930s decade are comparable to modern concentrations after the 1990s. We
468
attribute that to the different mining emission factors since during the early stage of the
469
mining process almost no control in the dust release to the environment existed. During the
470
last decades, although larger Cu ore volumes are remobilized at the open-pit mines, actions
471
of dust emissions mitigation have caused a decrease of aeolian Cu deposition.
472 473 474 475 476 477
Figure 9 - (a) Copper variability in the Inka-Coya sediment core by XRF technique; (b) Chilean copper production (%) in the world market from 1890 to 2008 (modified from; COCHILCO, 2015); and (c) Chilean production in kilotons from 1900 to 2008 (d) Illimani and Inka-Coya copper. (Source: USGS, 2014; COCHILCO, 2015). See that scale is interrupted for better observation.
478 479
4. Conclusion
480
The high resolved elemental composition provided by the XRF scanning technique over a
481
sediment core of the Inka-Coya Lake at Andes plateau/Northern Chile together with grain
482
size analysis allowed recognizing different sedimentation patterns related to PDO
483
variability. Among several elements analyzed, three groups were identified: one composed
484
by Ti, Fe, K, Rb, Si, Zn, Zr, Mn and S, a second by P, Sr, Yb, Cl, Ca, As and Al, and Cu
485
presenting an independent pattern. The first two groups varied in opposite phase,
486
suggesting different sources of sediments apportioning the lake. These changes, together
487
with the grain size variability, showed a clear influence of the PDO at the decadal scale.
488
Cooper variability reflected the evolution of the regional mining activity along the 20th
489
century.
490 491
Acknowledgements
492 493
This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de
494
Nível Superior - Brasil (CAPES) - Finance Code 001. We would like to thank Universidad
495
de Antofagasta for the initiation scholarship for young Researchers granted to the
496
corresponding author (Vice-rectory UA 2015), to Laboratory of Sedimentology and
497
Paleoenvironments (LASPAL-UA), Laboratory Radioecology and Climatic Changes
498
(LARAMG- UERJ) and Laboratory of Oceanographic and Climate (LOCEAN-IRD) for
499
respectively XRF analysis. Dr. Jorge Valdés was favored with a stay project in Spain, by
500
the DFI program of the Ministry of Education, Chile. Thanks are also due to Dr. Marcos
501
Guiñez and Dr. Alexis Castillo for assistance in the field work. In Memorian Luc Ortlieb
502
(1948-2016).
503 504
References
505 506
Anderson, D.G., Maasch, K., Sandweiss, D.H., 2011. Climate Change and Cultural Dynamics: A Global Perspective on Mid-Holocene Transitions. Elsevier Science.
507 508
Appleby, P.G., Oldfieldz, F., 1983. The assessment of 210Pb data from sites with varying sediment accumulation rates. Hydrobiologia 103, 29-35.
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Axelsson, V., 1983. The use of X-ray radiographic methods in studying sedimentary properties and rates of sediment accumulation. Hydrobiologia 103, 65-69. Clarke, J.D.A., 2006. Antiquity of aridity in the Chilean Atacama Desert. Geomorphology 73, 101-114. Boschetti, T., Cortecci, G., Barbieri, M., Mussi, M., 2007. New and past geochemical data on fresh to brine waters of the Salar de Atacama and Andean Altiplano, northern Chile. Geofluids 7, 33-50. Bull, A.T., Asenjo, J.A., Goodfellow, M., Gómez-Silva, B., 2016. The Atacama Desert: Technical Resources and the Growing Importance of Novel Microbial Diversity. Annual Review of Microbiology 70, 215-234. Croudace, I.W., Rindby, A., Rothwell, R.G., 2006. ITRAX: description and evaluation of a new multi-function X-ray core scanner. Geological Society, London, Special Publications 267, 51-63.
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Francus, P., Lamb, H., Nakagawa, T., Brown, E., 2009. The potential of high-resolution Xray fluorescence core scanning: Applications in paleolimnology. Collier, S., 2018. Historia de Chile : 1808-1994 / Simon Collier, William F. Sater. SERBIULA (sistema Libr. 2.0). Gantz, A., Rau, J., Couve, E., 2009. Ensambles de aves en el desierto de Atacama, norte grande de Chile. Gayana (Concepción) 73, 172-179. Gregor, D.J., Gummer, W.D., 1989. Evidence of atmospheric transport and deposition of organochlorine pesticides and polychlorinated biphenyls in Canadian Arctic snow. Environmental Science & Technology 23, 561-565. Hakanson, L., 1980. An ecological risk index for aquatic pollution control.a sedimentological approach. Water Research 14, 975-1001. Hammer, O., Harper, D., Ryan, P., 2001. PAST: Paleontological Statistics Software Package for Education and Data Analysis. Hernández, A., Giralt, S., Bao, R., Sáez, A., Leng, M.J., Barker, P.A., 2010. ENSO and solar activity signals from oxygen isotopes in diatom silica during late glacial-Holocene transition in Central Andes (18°S). Journal of Paleolimnology 44, 413-429. Houston, J., 2006. Evaporation in the Atacama Desert: An empirical study of spatiotemporal variations and their causes. Journal of Hydrology 330, 402-412. Hoyos, N., Escobar, J., Restrepo, J.C., Arango, A.M., Ortiz, J.C., 2013. Impact of the 2010–2011 La Niña phenomenon in Colombia, South America: The human toll of an extreme weather event. Applied Geography 39, 16-25. Jordan, T., Lameli, C.H., Kirk-Lawlor, N., Godfrey, L., 2015. Architecture of the aquifers of the Calama Basin, Loa catchment basin, northern Chile. Geosphere 11, 1438-1474. Latorre, C., Betancourt, J.L., Rylander, K.A., Quade, J., Matthei, O., 2003. A vegetation history from the arid prepuna of northern Chile (22–23°S) over the last 13 500 years. Palaeogeography, Palaeoclimatology, Palaeoecology 194, 223-246. Lavado-Casimiro, W., Espinoza, J.C., 2014. Impactos de El Niño y La Niña en las lluvias del Perú (1965-2007). Revista Brasileira de Meteorologia 29, 171-182. Legendre, P., Legendre, L., 1998. Preface, In: Pierre, L., Louis, L. (Eds.), Developments in Environmental Modelling. Elsevier, pp. xi-xv. Muñoz, A., Ojeda, J., Sánchez-Valverde, B., 2002. Sunspot-like and ENSO/NAO-like periodicities in lacustrinelaminated sediments of the Pliocene Villarroya Basin (La Rioja, Spain). Journal of Paleolimnology 27, 453-463.
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Rapaport, R.A., Urban, N.R., Capel, P.D., Baker, J.E., Looney, B.B., Eisenreich, S.J., Gorham, E., 1985. “New” DDT inputs to North America: Atmospheric deposition. Chemosphere 14, 1167-1173. Risacher, F., Alonso, H., Salazar, C., 2003. The origin of brines and salts in Chilean salars: a hydrochemical review. Earth-Science Reviews 63, 249-293. Ritter, B., Binnie, S.A., Stuart, F.M., Wennrich, V., Dunai, T.J., 2018. Evidence for multiple Plio-Pleistocene lake episodes in the hyperarid Atacama Desert. Quaternary Geochronology 44, 1-12. Romero, H., Méndez, M., Smith, P., 2012. Mining Development and Environmental Injustice in the Atacama Desert of Northern Chile. Environmental Justice 5, 70-76. Schwalb, A., 2003. Lacustrine ostracodes as stable isotope recorders of late-glacial and Holocene environmental dynamics and climate. Journal of Paleolimnology 29, 265-351. Schwanck, F., Simões, J.C., Handley, M., Mayewski, P.A., Bernardo, R.T., Aquino, F.E., 2016. Anomalously high arsenic concentration in a West Antarctic ice core and its relationship to copper mining in Chile. Atmospheric Environment 125, 257-264. Smith, K.A., 2000. Soil and Environmental Analysis: Physical Methods, Revised, and Expanded. Taylor & Francis. Stivaletta, N., Barbieri, R., Billi, D., 2012. Microbial Colonization of the Salt Deposits in the Driest Place of the Atacama Desert (Chile). Origins of Life and Evolution of Biospheres 42, 187-200. Swackhamer, D.L., Armstrong, D.E., 1986. Estimation of the atmospheric and nonatmospheric contributions and losses of polychlorinated biphenyls to Lake Michigan on the basis of sediment records of remote lakes. Environmental Science & Technology 20, 879-883. Tapia, J., González, R., Townley, B., Oliveros, V., Álvarez, F., Aguilar, G., Menzies, A., Calderón, M., 2018. Geology and geochemistry of the Atacama Desert. Antonie van Leeuwenhoek 111, 1273-1291. Tapia, J., Murray, J., Ormachea, M., Tirado, N., Nordstrom, D.K., 2019. Origin, distribution, and geochemistry of arsenic in the Altiplano-Puna plateau of Argentina, Bolivia, Chile, and Perú. Science of The Total Environment 678, 309-325. Valdés-Pineda, R., Cañón, J., Valdés, J.B., 2018. Multi-decadal 40- to 60-year cycles of precipitation variability in Chile (South America) and their relationship to the AMO and PDO signals. Journal of Hydrology 556, 1153-1170.
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von Gunten, L., Grosjean, M., Beer, J., Grob, P., Morales, A., Urrutia, R., 2009. Age modeling of young non-varved lake sediments: methods and limits. Examples from two lakes in Central Chile. Journal of Paleolimnology 42, 401-412. Vuille, M., Keimig, F., 2004. Interannual Variability of Summertime Convective Cloudiness and Precipitation in the Central Andes Derived from ISCCP-B3 Data. Journal of Climate 17, 3334-3348. Williams, A., Santoro, C.M., Smith, M.A., Latorre, C., 2008. The impact of ENSO in the Atacama Desert and Australian arid zone: exploratory time-series analysis of archaeological records. Chungará (Arica) 40, 245-259. Zhou, X., Sun, Y., Huang, W., Smol, J.P., Tang, Q., Sun, L., 2015. The Pacific decadal oscillation and changes in anchovy populations in the Northwest Pacific. Journal of Asian Earth Sciences 114, 504-511. Ziervogel, K., Bohling, B., 2003. Sedimentological parameters and erosion behaviour of submarine coastal sediments in the south-western Baltic Sea. Geo-Marine Letters 23, 4352.
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Figure captions:
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Figure 1 – The study site: (a) total view of the Inka Coya Lake (b) bathymetry of the Inka Coya Lake showing a central depression and the sediment core sampling point (T1= XLCHT1); (c) Inka Coya Lake location in the context of South America and Northern Atacama orography.
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Figure 2 – Map of the Inka-Coya site main geological facies. Based on Chilean geological map from the National Geology and Mining Service of Chile.
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Figure 3- The meteorological database for Calama Station (22° 29.734’ S; 68°54.350 W; https://climatologia.meteochile.gob.cl); (a) Seasonal precipitation at Chiu-Chiu; (b) local wind direction; (c) MEI index from www.esrl.noaa.gov/psd/enso/mei/ spanning the period 1976-2010. MEI index is the multivariated ENSO Index, defined based on six main observed variables over the tropical Pacific: sea-level pressure, zonal wind (U). Meridional wind (V), sea surface temperature, surface air temperature and total cloudiness fraction of the sky (d) wind intensity variability for the three main wind component directions. Arrows point more intense NIÑO events in the above period.
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Figure 4 - (a) Sediment core of Lake Inka-Coya (b) corresponding X-ray image; (c) profile of gray values; (d) profile of 210Pbexc in the core; and (e) sedimentation rates inferred from CRS model.
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Figure 5- (a) Periodicities detected by FFT (Fourier Fast Transformation) based on greyscale series of Inka-Coya Lake sediment core. Confidence curves are depicted; (b) sunspot number (smoothed time series) corresponding to precipitate database.
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Figure 6- Elemental composition along Inca-Coya sediment core as revealed by XRF analysis. Upper part, the set of elements that defined the group 1 (G1) due to their covariability; and lower part, the same for group 2 (G2). Dotted lines separate major changes in geochemistry.
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Figure 7- Components of the Principal Component Analysis (PCA) for sediment core elemental composition and grain size distribution.
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Figure 8 - (a) PDO time series from 1900 and 2013 and running average; (b) silt and clay data; (c) normalized G1 data; (d) sand data; and (e) normalized G2 data.
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Figure 9 - (a) Copper variability in the Inka-Coya sediment core by XRF technique; (b) Chilean copper production (%) in the world market from 1890 to 2008 (modified from; COCHILCO, 2015); and (c) Chilean production in kilotons from 1900 to 2008 (d) Illimani and Inka-Coya copper. (Source: USGS, 2014; COCHILCO, 2015). See that scale is interrupted for better observation.
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