- Email: [email protected]
Continental shelves, including contributions from the 17th INQUA Congress, Cairns
Quaternary International 206 (2009) 1–2
Contents lists available at ScienceDirect
Quaternary International journal homepage: www.elsevier.com/locate/quaint
Editorial
Continental shelves, including contributions from the 17th INQUA Congress, Cairns
During the 17th INQUA Congress in Cairns, Australia in 2007 a session on continental shelves – sea-levels, environments and carbon budgets – was held. The main aim of this session was to enable researchers working on this important yet much neglected part of the Earth’s system to present their latest findings. Five out of 13 papers included in this special issue were presented during this session. This volume is a contribution by the Sub-commission on Continental Shelves, INQUA Commission on Coastal and Marine Processes, and International Geoscience Programme Project No. 526 ‘Risk, resources, and record of the past on the continental shelf’. Korsakova identified three Late Pleistocene marine units in the coastal areas of the Kola Peninsula using a combination of field and laboratory evidences including electron spin resonance and optically stimulated luminescence dating. The oldest marine unit containing thermophilic fauna and diatoms is attributed to the Boreal transgression of MIS 5e–5c age. The next oldest is the marine unit of the Belomorian transgression of Early Weischselian age with lower salinity and temperature either similar or cooler than the present day. The youngest marine unit of Middle Weichselian age was deposited in a regressing shallow cooler and less saline sea than the present day. The development of the Baltic Ice Lake in the eastern Baltic is discussed by Rosentau et al., using a shoreline database containing more than 1000 sites from Finland, NW Russia, Estonia, and Latvia with a modern digital terrain model. The Baltic Ice Lake occupied five different levels, represented by 492 shoreline features. It extended to the ice-free areas of Latvia, Estonia and NW Russia ca. 13.3 ka BP. The Baltic Ice Lake initially had the same water level as glacial lakes Peipsi and Vo˜rtsja¨rv, as these water bodies were connected via strait systems in central Estonia. These strait systems were closed at about 12.8–11.7 cal. ka BP prior to the final drainage of the Baltic Ice Lake due to isostatic uplift. Shaw et al. investigated submerged early-Holocene coastal and terrestrial landforms on the inner shelves of Atlantic Canada. Although coastal and terrestrial landforms formed under lowered relative sea-levels during the early postglacial period and were submerged during the Holocene transgression, these landforms are seldom seen on sea-floor imagery. Factors that contribute to their destruction include the brevity of sea-level low stands and high wave energy on shallow modern shelves. Preservation is enhanced beneath large coastal lakes that existed before being inundated by mid-Holocene rising sea-level, including Bedford Basin, near Halifax, and the Bras d’Or Lakes in Cape Breton. The preservation of shore platforms, barrier beaches and spits, and 1040-6182/$ – see front matter Ó 2009 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2009.03.006
fluvial systems was due to the rapid onset of the transgression and the relatively low marine wave energy. The well-preserved early-Holocene coastlines are highly favourable targets in the search for evidence of early- to mid-Holocene human occupation. Zong et al. presented detailed litho-, bio- and chronostratigraphic evidence for the two phases of marine transgression which took place in the Pearl River mouth region during the Late Quaternary. Their records suggest that the nature and geographic extent of the two marine sedimentary units are very similar, resulted from two sea-level highstands. Based on the data presented, the changing sedimentary dynamics in the area during the two periods of rapid rising sea-level before and soon after w8.2 cal. ka BP can be identified. The spatial and temporal variation of organic carbon in the Pearl River estuary and adjacent northern South China Sea over the last 100 years was studied by Hu et al. The stratigraphic profiles of organic carbon concentration, TOC/TN ratios and d13Corg indicate that terrestrial organic matter decreased from 68.3% to 27.4% of the TOC in the Pearl River estuary, while Dapeng Bay (east of Hong Kong) apparently had little terrestrial organic matter input. The highest deposited organic carbon concentration occurs at the Humen river mouth. Increased concentrations could be caused by high precipitation of land-derived organic matter and the high input of terrestrial organic matter, perhaps related to the rapid urbanization and industrial development in the Pearl River Delta since the 1970s. Algal-derived OC concentration inferred from the d13Corg values increased from 1980 to 2000 in the outer Pearl River estuary and Dapeng Bay, presumably caused by enhanced primary marine productivity supported by higher anthropogenic nutrient inputs. Mahiques et al. present a high-resolution Holocene record from the Southern Brazilian shelf. The core covers a time interval of about 7650 years, with sedimentation rates varying from 0.025 cm a1 to 0.250 cm a1, which represent time intervals of between 8 and 80 a per sample. Textural, geochemical, and magnetic susceptibility results indicate the occurrence of conspicuous changes between 5.2 and 5.0 cal. ka BP, as well as between 3.0 and 2.8 cal. ka BP. The later Holocene sedimentary changes may be correlated with the onset of modern climatic conditions in South America, and especially, with the onset of the Plata Water Plume, a water mass that carries cold, less saline waters towards the north. Minor changes observed at ca. 1500 cal. ka BP are correlated with an increase in atmospheric humidity. Time-series analysis indicated the occurrence of sub-Milankovitch cycles.
2
Editorial / Quaternary International 206 (2009) 1–2
Nagai et al. carried out sedimentological and foraminiferal analyses on a core from near the mid-shelf of Cabo Frio, southeastern Brazilian continental margin. They identified changes in the hydrodynamic and productivity regimes related to sea-level fluctuations and/or climatic changes during the last 9.4 ka cal BP. Prior to 7.0 ka cal BP the hydrodynamic and productivity regime was less intense followed by increases in intensities between 7.0 and 5.0 ka cal BP. From 5.0 to 3.0 kyr cal BP, bottom currents weakened and input of nutrients increased while from 3.0 ka cal BP to the present, the increase in both hydrodynamic and productivity regimes was attributed to upwelling resulting from the combined action of NE winds and the intensification of the meandering pattern of the Brazil Current. Oceanographic changes over the past 20 ka in the southeastern Arabian Sea are assessed by Narayana et al., through analysis of calcium carbonate, organic carbon, aluminum, and titanium. During MIS 2, low calcium carbonate and high metal concentrations suggest terrigenous influx. In contrast, higher values of calcium carbonate during the Holocene indicate reduced influx from the continent. The changes in organic carbon values over the Late Glacial/Holocene transition show inconsistencies between the cores analyzed. The distribution of organic carbon in the eastern Arabian Sea is controlled by organic matter from the water column, sediment texture, and dilution of sediment components. Santoro et al. conducted a study of uplifted marine terraces dating back to some 400 ka on the east coast of northern Calabria. Eleven terraces up to w480 m a.s.l. and a raised Holocene beach were mapped. Electron spin resonance and radiocarbon dating of shells were made to provide a chronological framework and corrections were made for the uncertainty of measurements, erosion and the bathymetric depth range of the markers. The highest terrace is estimated to be of MIS 11 age (w400 ka) while terraces T4, T3, T2 and T1 are estimated to be of MIS 5.5 (w124 ka), MIS 5.3 (w100 ka), MIS 5.1 (w80 ka) and MIS 3 (w60 ka) ages, respectively. An average rate of uplift of 1 mm a1 is estimated since 400 ka, but at times the rate may range from a low of w0.5 mm a1 to a high of w3.5 mm a1. Antonioli et al. investigate Holocene relative sea-level changes and vertical movements from 105 locations along the Italian and Istrian coasts using geomorphological and archaeological markers. In order to assess tectonic activity, data were compared with predicted sea-level curves for the Mediterranean Sea. Tectonic rates of sea-level change varied from 4.85 mm a1 to 5 mm a1. New MIS 5.5 data, supported by improved dating, indicates a mean subsidence of 0.62 mm a1 in the Venice area. For assessment of more recent change, tide gauge data and repeated levelling measurements from the NE Adriatic and Sicily allow consideration of longer time-spans, up to 100 years, than do altimetric and GPS measurements. The greater time-span allows for more stable differential rate estimates. The plain east of Mestre is subsiding, to 4 mm a1. The Messina tidal gauge demonstrates total subsidence of 77 cm, associated with the event of 1906. Raised coastal terraces along the Ionian Sea coast of northern Calabria, Italy, suggest space and time variability of tectonic uplift rates. The use of archaeology as indicators of sea-levels in the Mediterranean Sea was reviewed by Auriemma and Solinas. The occurrence
of submerged coastal structures including harbours, fishponds and dwellings are particularly valuable. For the evaluation of relative sea-level variations, archaeological interpretation must initially establish the maritime nature of the site, determine the type of usage, and analyze the elevation in relation to sea-level as well as identification of the timing of abandonment/destruction/ obliteration. Bini et al. investigated the mysterious disappearance of Luni Harbour of Roman age located on the central Tyrrhenian coast of Italy. Based on the study of boreholes, radiocarbon dating and archaeological evidence, the main environmental changes in the Luni coastal plain over the past 3000 years can be reconstructed. The coastline shifted south and west, isolating the ruins of the ancient Roman coastal settlement of Luni which was founded in 177 BC from the sea by means of a new coastal plain. The changes can be explained by a prograding complex of swamps, marshes, dune ridges and fluvial sand bars at the river mouth region of the coastline. De Guidi and Monaco studied the rapid uplift of the volcanic island, Pantelleria, located in the Sicily Channel of Italy. A survey of morphological and biological indicators was carried out resulting in the identification of raised palaeo-shorelines at three elevation ranges: 2.5–4.2 m a.s.l. (highest), 1.5–2.7 m a.s.l. (intermediate) and 0.4–1.0 m a.s.l. (lowest). Radiocarbon dating of corals and vermetids indicated that the uplift was centred on Cala del Gadir with tilting of the island towards the southwest from w900 years BP. The uplift rate of up to 5 mm a1 found was attributed to inflation processes related to magmatic intrusion along feeding fissures. In addition to all our anonymous referees, the following referees are thanked for their assistance: Gladys Bernal, Helmut Brueckner, John Cann, Eugenio Carminati, Andrea Dutton, Evan Edinger, Stefano Furlani, Andrew Heap, Stephen Kershaw, Angela Jayco, Barbara Mauz, Philip Myers, Sathy Naidu and Szymon Uscinowicz. Norm R. Catto* Department of Geography, Memorial University of Newfoundland, St. John’s, Newfoundland, Canada A1B 3X9 Corresponding author. Tel.: þ1 709 737 8413; fax: þ1 709 737 3119. E-mail address: [email protected] (N.R. Catto) Wyss W.-S. Yim Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China Fabrizio Antonioli ENEA, Special Project Global Change, via Anguillarese 301, 00060 S. Maria di Galeria, Roma, Italy Yusuke Yokoyama Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan Available online 2 April 2009
Contents lists available at ScienceDirect
Quaternary International journal homepage: www.elsevier.com/locate/quaint
Editorial
Continental shelves, including contributions from the 17th INQUA Congress, Cairns
During the 17th INQUA Congress in Cairns, Australia in 2007 a session on continental shelves – sea-levels, environments and carbon budgets – was held. The main aim of this session was to enable researchers working on this important yet much neglected part of the Earth’s system to present their latest findings. Five out of 13 papers included in this special issue were presented during this session. This volume is a contribution by the Sub-commission on Continental Shelves, INQUA Commission on Coastal and Marine Processes, and International Geoscience Programme Project No. 526 ‘Risk, resources, and record of the past on the continental shelf’. Korsakova identified three Late Pleistocene marine units in the coastal areas of the Kola Peninsula using a combination of field and laboratory evidences including electron spin resonance and optically stimulated luminescence dating. The oldest marine unit containing thermophilic fauna and diatoms is attributed to the Boreal transgression of MIS 5e–5c age. The next oldest is the marine unit of the Belomorian transgression of Early Weischselian age with lower salinity and temperature either similar or cooler than the present day. The youngest marine unit of Middle Weichselian age was deposited in a regressing shallow cooler and less saline sea than the present day. The development of the Baltic Ice Lake in the eastern Baltic is discussed by Rosentau et al., using a shoreline database containing more than 1000 sites from Finland, NW Russia, Estonia, and Latvia with a modern digital terrain model. The Baltic Ice Lake occupied five different levels, represented by 492 shoreline features. It extended to the ice-free areas of Latvia, Estonia and NW Russia ca. 13.3 ka BP. The Baltic Ice Lake initially had the same water level as glacial lakes Peipsi and Vo˜rtsja¨rv, as these water bodies were connected via strait systems in central Estonia. These strait systems were closed at about 12.8–11.7 cal. ka BP prior to the final drainage of the Baltic Ice Lake due to isostatic uplift. Shaw et al. investigated submerged early-Holocene coastal and terrestrial landforms on the inner shelves of Atlantic Canada. Although coastal and terrestrial landforms formed under lowered relative sea-levels during the early postglacial period and were submerged during the Holocene transgression, these landforms are seldom seen on sea-floor imagery. Factors that contribute to their destruction include the brevity of sea-level low stands and high wave energy on shallow modern shelves. Preservation is enhanced beneath large coastal lakes that existed before being inundated by mid-Holocene rising sea-level, including Bedford Basin, near Halifax, and the Bras d’Or Lakes in Cape Breton. The preservation of shore platforms, barrier beaches and spits, and 1040-6182/$ – see front matter Ó 2009 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2009.03.006
fluvial systems was due to the rapid onset of the transgression and the relatively low marine wave energy. The well-preserved early-Holocene coastlines are highly favourable targets in the search for evidence of early- to mid-Holocene human occupation. Zong et al. presented detailed litho-, bio- and chronostratigraphic evidence for the two phases of marine transgression which took place in the Pearl River mouth region during the Late Quaternary. Their records suggest that the nature and geographic extent of the two marine sedimentary units are very similar, resulted from two sea-level highstands. Based on the data presented, the changing sedimentary dynamics in the area during the two periods of rapid rising sea-level before and soon after w8.2 cal. ka BP can be identified. The spatial and temporal variation of organic carbon in the Pearl River estuary and adjacent northern South China Sea over the last 100 years was studied by Hu et al. The stratigraphic profiles of organic carbon concentration, TOC/TN ratios and d13Corg indicate that terrestrial organic matter decreased from 68.3% to 27.4% of the TOC in the Pearl River estuary, while Dapeng Bay (east of Hong Kong) apparently had little terrestrial organic matter input. The highest deposited organic carbon concentration occurs at the Humen river mouth. Increased concentrations could be caused by high precipitation of land-derived organic matter and the high input of terrestrial organic matter, perhaps related to the rapid urbanization and industrial development in the Pearl River Delta since the 1970s. Algal-derived OC concentration inferred from the d13Corg values increased from 1980 to 2000 in the outer Pearl River estuary and Dapeng Bay, presumably caused by enhanced primary marine productivity supported by higher anthropogenic nutrient inputs. Mahiques et al. present a high-resolution Holocene record from the Southern Brazilian shelf. The core covers a time interval of about 7650 years, with sedimentation rates varying from 0.025 cm a1 to 0.250 cm a1, which represent time intervals of between 8 and 80 a per sample. Textural, geochemical, and magnetic susceptibility results indicate the occurrence of conspicuous changes between 5.2 and 5.0 cal. ka BP, as well as between 3.0 and 2.8 cal. ka BP. The later Holocene sedimentary changes may be correlated with the onset of modern climatic conditions in South America, and especially, with the onset of the Plata Water Plume, a water mass that carries cold, less saline waters towards the north. Minor changes observed at ca. 1500 cal. ka BP are correlated with an increase in atmospheric humidity. Time-series analysis indicated the occurrence of sub-Milankovitch cycles.
2
Editorial / Quaternary International 206 (2009) 1–2
Nagai et al. carried out sedimentological and foraminiferal analyses on a core from near the mid-shelf of Cabo Frio, southeastern Brazilian continental margin. They identified changes in the hydrodynamic and productivity regimes related to sea-level fluctuations and/or climatic changes during the last 9.4 ka cal BP. Prior to 7.0 ka cal BP the hydrodynamic and productivity regime was less intense followed by increases in intensities between 7.0 and 5.0 ka cal BP. From 5.0 to 3.0 kyr cal BP, bottom currents weakened and input of nutrients increased while from 3.0 ka cal BP to the present, the increase in both hydrodynamic and productivity regimes was attributed to upwelling resulting from the combined action of NE winds and the intensification of the meandering pattern of the Brazil Current. Oceanographic changes over the past 20 ka in the southeastern Arabian Sea are assessed by Narayana et al., through analysis of calcium carbonate, organic carbon, aluminum, and titanium. During MIS 2, low calcium carbonate and high metal concentrations suggest terrigenous influx. In contrast, higher values of calcium carbonate during the Holocene indicate reduced influx from the continent. The changes in organic carbon values over the Late Glacial/Holocene transition show inconsistencies between the cores analyzed. The distribution of organic carbon in the eastern Arabian Sea is controlled by organic matter from the water column, sediment texture, and dilution of sediment components. Santoro et al. conducted a study of uplifted marine terraces dating back to some 400 ka on the east coast of northern Calabria. Eleven terraces up to w480 m a.s.l. and a raised Holocene beach were mapped. Electron spin resonance and radiocarbon dating of shells were made to provide a chronological framework and corrections were made for the uncertainty of measurements, erosion and the bathymetric depth range of the markers. The highest terrace is estimated to be of MIS 11 age (w400 ka) while terraces T4, T3, T2 and T1 are estimated to be of MIS 5.5 (w124 ka), MIS 5.3 (w100 ka), MIS 5.1 (w80 ka) and MIS 3 (w60 ka) ages, respectively. An average rate of uplift of 1 mm a1 is estimated since 400 ka, but at times the rate may range from a low of w0.5 mm a1 to a high of w3.5 mm a1. Antonioli et al. investigate Holocene relative sea-level changes and vertical movements from 105 locations along the Italian and Istrian coasts using geomorphological and archaeological markers. In order to assess tectonic activity, data were compared with predicted sea-level curves for the Mediterranean Sea. Tectonic rates of sea-level change varied from 4.85 mm a1 to 5 mm a1. New MIS 5.5 data, supported by improved dating, indicates a mean subsidence of 0.62 mm a1 in the Venice area. For assessment of more recent change, tide gauge data and repeated levelling measurements from the NE Adriatic and Sicily allow consideration of longer time-spans, up to 100 years, than do altimetric and GPS measurements. The greater time-span allows for more stable differential rate estimates. The plain east of Mestre is subsiding, to 4 mm a1. The Messina tidal gauge demonstrates total subsidence of 77 cm, associated with the event of 1906. Raised coastal terraces along the Ionian Sea coast of northern Calabria, Italy, suggest space and time variability of tectonic uplift rates. The use of archaeology as indicators of sea-levels in the Mediterranean Sea was reviewed by Auriemma and Solinas. The occurrence
of submerged coastal structures including harbours, fishponds and dwellings are particularly valuable. For the evaluation of relative sea-level variations, archaeological interpretation must initially establish the maritime nature of the site, determine the type of usage, and analyze the elevation in relation to sea-level as well as identification of the timing of abandonment/destruction/ obliteration. Bini et al. investigated the mysterious disappearance of Luni Harbour of Roman age located on the central Tyrrhenian coast of Italy. Based on the study of boreholes, radiocarbon dating and archaeological evidence, the main environmental changes in the Luni coastal plain over the past 3000 years can be reconstructed. The coastline shifted south and west, isolating the ruins of the ancient Roman coastal settlement of Luni which was founded in 177 BC from the sea by means of a new coastal plain. The changes can be explained by a prograding complex of swamps, marshes, dune ridges and fluvial sand bars at the river mouth region of the coastline. De Guidi and Monaco studied the rapid uplift of the volcanic island, Pantelleria, located in the Sicily Channel of Italy. A survey of morphological and biological indicators was carried out resulting in the identification of raised palaeo-shorelines at three elevation ranges: 2.5–4.2 m a.s.l. (highest), 1.5–2.7 m a.s.l. (intermediate) and 0.4–1.0 m a.s.l. (lowest). Radiocarbon dating of corals and vermetids indicated that the uplift was centred on Cala del Gadir with tilting of the island towards the southwest from w900 years BP. The uplift rate of up to 5 mm a1 found was attributed to inflation processes related to magmatic intrusion along feeding fissures. In addition to all our anonymous referees, the following referees are thanked for their assistance: Gladys Bernal, Helmut Brueckner, John Cann, Eugenio Carminati, Andrea Dutton, Evan Edinger, Stefano Furlani, Andrew Heap, Stephen Kershaw, Angela Jayco, Barbara Mauz, Philip Myers, Sathy Naidu and Szymon Uscinowicz. Norm R. Catto* Department of Geography, Memorial University of Newfoundland, St. John’s, Newfoundland, Canada A1B 3X9 Corresponding author. Tel.: þ1 709 737 8413; fax: þ1 709 737 3119. E-mail address: [email protected] (N.R. Catto) Wyss W.-S. Yim Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China Fabrizio Antonioli ENEA, Special Project Global Change, via Anguillarese 301, 00060 S. Maria di Galeria, Roma, Italy Yusuke Yokoyama Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan Available online 2 April 2009