- Email: [email protected]
Paleoenvironmental reconstruction of a Late Quaternary lagoon system in southern Brazil (Jagurana region, Santa Catarina state) based on multi-proxy analysis
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Abstracts / Quaternary International 279-280 (2012) 9–120
materials. A possible provenance lies to the east of the Khwebe Hills from where the BaTawana find their roots; some 100km to the east and eastwards from there are expanses of Stormberg Basalts which could have been the source for the more mafic clays found in the pottery.
Brazil evidencing the stability of coastal vegetation during the last 6 kyr BP. The multi-proxy analysis suggests that the changes in the coastal ecosystems could be related directly to local coastal dynamic processes, which are not necessarily linked to RSL fluctuations and/or climatic variations.
THE SUBMERGED LATE QUATERNARY PALAEO-LANDSCAPES OF THE OUTER THAMES ESTUARY
POLLEN-BASED BIOME RECONSTRUCTION TO THE MID-HOLOCENE TRANSITION IN SAHEL AND SAHARA: FIRST PALYNOLOGICAL RESULTS OF A LACUSTRINE RECORD FROM THE MEGA-LAKE CHAD
Justin Dix. National Oceanography Centre, Southampton, United Kingdom E-mail address: [email protected]
Paula G.C. do Amaral. Instituto de Geociências, Universidade de São Paul, Brazil
A recent Government/Industry funded geoarchaeological research project has identified an extensive, submerged palaeo-landscape in the Outer Thames Estuary, which provides a record of landscape evolution from the early Middle Pleistocene through to its final submergence during the Holocene transgression. The integration of: bathymetry, sub-bottom data, more than 460 vibro-cores and the extant, terrestrial, morphological, geological and archaeological records of the adjacent coastal strip; facilitates the geological reconstruction of 3,000 km2 of, exceptionally preserved, palaeo-landscape. Our understanding of the Late Quaternary evolution of this landscape has been further enhanced through a combination of direct chronological dating of material from a sub-set of the vibrocores and correlation with the onshore, well dated, stratigraphic sequences. Further, this part of the North-west European shelf is spatially bracketed by the internationally significant Palaeolithic sites of Clacton (to the south) and Pakefield (to the north), a coastline which has produced archaeological evidence from one of the earliest occupation sites of the British Isles (at c. 600 – 700 kaBP) through to the historic period. The exceptional level of preservation of this landscape holds great potential for enhancing both our understanding of the Palaeolithic occupation and reoccupation of the British Isles and the broader geological changes which have occurred during multiple episodes of sea level transgression and regression.
E-mail address: [email protected]
PALEOENVIRONMENTAL RECONSTRUCTION OF A LATE QUATERNARY LAGOON SYSTEM IN SOUTHERN BRAZIL (JAGURANA REGION, SANTA CATARINA STATE) BASED ON MULTI-PROXY ANALYSIS Paula G.C. do Amaral. Instituto de Geociências, Universidade de São Paul, Brazil E-mail address: [email protected]
The high variability of energy and depositional processes in coastal lagoon areas determine rapid spatial and temporal changes. Paleoenvironmental reconstructions in these zones should be based on multi-proxy approach, including biological, geochemical and sedimentological indicators. Here we present integrated results from bulk sedimentary organic matter characterization (d13C, d15N and C/N), grain-size analysis and microfossil (pollen and diatom) studies aiming to reconstruct the evolution of a Quaternary lagoon system in the southern Brazil (Jaguaruna region, Santa Catarina state). This multi-proxy analysis was carried out in three shallow cores (w2.5 m depth) collected from paleolagoon sediments. At ca. 5 kyr BP, the study area had a more extensive complex of interconnected lagoons than observed today. This is verified in the cores by the record of paleolagoon deposits in areas currently occupied by restinga forest. The connection of this larger lagoon system with the sea is evidenced by the presence of marine diatoms and by the composition of the sedimentary organic matter, which is indicative of marine phytoplankton. Our results show a gradual and continuous lagoon-sea disconnection during the last 5 kyr BP, which does not confirm the existence of two regressive phases, linked to rapid relative sea level (RSL) drops during the Late Holocene, as assumed by previous works. Palynological data showed that no major change in the mainland vegetation ecosystem took place at least since 4 kyr BP. These results are in agreement with other evidences from pollen and charcoal studies conducted in coastal areas in South and Southeast
A key area to study past environmental changes in Sahelian and Saharan regions is the Lake Chad. During the past, this lake has experienced huge fluctuations reaching more than 350,000 km2 during the Holocene African Humid Period (AHP, w14 to 5.5 cal kyr BP). These sediments have recorded the climatic and vegetational changes that occurred over the whole active basin during that period. Here we present the first palynological results obtained from a core collected in Lake Chad that encompasses the midHolocene transition. Pollen-based biome reconstructions were made using the biomization method, where the pollen data are assigned to plant functional types (PFT) and biomes, for which affinity scores are calculated. For all samples the dominant potential biome reconstructed is savanna. However, both pollen assemblages and biome scores affinity indicate an important contribution of southern moister biomes before 6 cal kyr BP, much more than at the present time. That period seems to have known a fluvial transport change likely associated with a decrease in rainfall in the southern part of Lake Chad basin after 6ka BP, reducing the transport of pollen types of distant biomes. From 6 cal kyr BP onwards, fossil samples present very similar characteristics (pollen types and percentages, and biome scores affinities) with the modern sample collected in the Chari river delta station suggesting that comparable conditions to modern ones probably established in the Chad basin at this time. These results are confirmed by the reconstruction of precipitation using the modern analogue method. The change observed in pollen record around 6 cal kyr BP was also documented by other proxies studied on the same core (see F. Sylvestre et al. communication in the same conference). These first results show the highly promising potential of lacustrine records retrieved from Lake Chad and highlight the need to develop a higher resolution dataset spanning the entire Holocene. LATE PLEISTOCENE RAISED SHORELINES ON THE HATAY-SAMANDAGı COAST OF TURKEY, EASTERN MEDITERRANEAN Ugur Dogan. Ankara University, Turkey E-mail address: [email protected]
ı coast is the most important region in Turkey where Hatay-Samandag raised Quaternary shorelines can be seen above the current sea level. This study which was conducted in the region between the north of Çevlik ı) and the Syrian border identified four shorelines (except raised (Samandag two Holecene shorelines) as high as 116 m above the present sea level by using geomorphological markers and stratigraphic-sedimentological data. All of these four shorelines have been dated to the Late Pleistocene radiometrically by using electron spin resonance and uranium series techniques and relative chronology. The relative chronology has been established using uplift rate from radiometrically dated shorelines, morphostratigraphy, and Paleolithic findings on raised shorelines. According to the age data and the morphostratigraphy obtained, the Late Pleistocene raised shorelines do not extend at the same level throughout the entire coast. The Late Pleistocene shorelines can be seen at 22, 41-48, 77-80 and 116 m with a slight eastward ı; the single shoreline in Tekebas¸ı at 59tilt between Çevlik and Samandag at 7-12, 21, 43, 75 m with 60 m with a slight southward tilt; and in Keldag a slight southward tilt.
Abstracts / Quaternary International 279-280 (2012) 9–120
materials. A possible provenance lies to the east of the Khwebe Hills from where the BaTawana find their roots; some 100km to the east and eastwards from there are expanses of Stormberg Basalts which could have been the source for the more mafic clays found in the pottery.
Brazil evidencing the stability of coastal vegetation during the last 6 kyr BP. The multi-proxy analysis suggests that the changes in the coastal ecosystems could be related directly to local coastal dynamic processes, which are not necessarily linked to RSL fluctuations and/or climatic variations.
THE SUBMERGED LATE QUATERNARY PALAEO-LANDSCAPES OF THE OUTER THAMES ESTUARY
POLLEN-BASED BIOME RECONSTRUCTION TO THE MID-HOLOCENE TRANSITION IN SAHEL AND SAHARA: FIRST PALYNOLOGICAL RESULTS OF A LACUSTRINE RECORD FROM THE MEGA-LAKE CHAD
Justin Dix. National Oceanography Centre, Southampton, United Kingdom E-mail address: [email protected]
Paula G.C. do Amaral. Instituto de Geociências, Universidade de São Paul, Brazil
A recent Government/Industry funded geoarchaeological research project has identified an extensive, submerged palaeo-landscape in the Outer Thames Estuary, which provides a record of landscape evolution from the early Middle Pleistocene through to its final submergence during the Holocene transgression. The integration of: bathymetry, sub-bottom data, more than 460 vibro-cores and the extant, terrestrial, morphological, geological and archaeological records of the adjacent coastal strip; facilitates the geological reconstruction of 3,000 km2 of, exceptionally preserved, palaeo-landscape. Our understanding of the Late Quaternary evolution of this landscape has been further enhanced through a combination of direct chronological dating of material from a sub-set of the vibrocores and correlation with the onshore, well dated, stratigraphic sequences. Further, this part of the North-west European shelf is spatially bracketed by the internationally significant Palaeolithic sites of Clacton (to the south) and Pakefield (to the north), a coastline which has produced archaeological evidence from one of the earliest occupation sites of the British Isles (at c. 600 – 700 kaBP) through to the historic period. The exceptional level of preservation of this landscape holds great potential for enhancing both our understanding of the Palaeolithic occupation and reoccupation of the British Isles and the broader geological changes which have occurred during multiple episodes of sea level transgression and regression.
E-mail address: [email protected]
PALEOENVIRONMENTAL RECONSTRUCTION OF A LATE QUATERNARY LAGOON SYSTEM IN SOUTHERN BRAZIL (JAGURANA REGION, SANTA CATARINA STATE) BASED ON MULTI-PROXY ANALYSIS Paula G.C. do Amaral. Instituto de Geociências, Universidade de São Paul, Brazil E-mail address: [email protected]
The high variability of energy and depositional processes in coastal lagoon areas determine rapid spatial and temporal changes. Paleoenvironmental reconstructions in these zones should be based on multi-proxy approach, including biological, geochemical and sedimentological indicators. Here we present integrated results from bulk sedimentary organic matter characterization (d13C, d15N and C/N), grain-size analysis and microfossil (pollen and diatom) studies aiming to reconstruct the evolution of a Quaternary lagoon system in the southern Brazil (Jaguaruna region, Santa Catarina state). This multi-proxy analysis was carried out in three shallow cores (w2.5 m depth) collected from paleolagoon sediments. At ca. 5 kyr BP, the study area had a more extensive complex of interconnected lagoons than observed today. This is verified in the cores by the record of paleolagoon deposits in areas currently occupied by restinga forest. The connection of this larger lagoon system with the sea is evidenced by the presence of marine diatoms and by the composition of the sedimentary organic matter, which is indicative of marine phytoplankton. Our results show a gradual and continuous lagoon-sea disconnection during the last 5 kyr BP, which does not confirm the existence of two regressive phases, linked to rapid relative sea level (RSL) drops during the Late Holocene, as assumed by previous works. Palynological data showed that no major change in the mainland vegetation ecosystem took place at least since 4 kyr BP. These results are in agreement with other evidences from pollen and charcoal studies conducted in coastal areas in South and Southeast
A key area to study past environmental changes in Sahelian and Saharan regions is the Lake Chad. During the past, this lake has experienced huge fluctuations reaching more than 350,000 km2 during the Holocene African Humid Period (AHP, w14 to 5.5 cal kyr BP). These sediments have recorded the climatic and vegetational changes that occurred over the whole active basin during that period. Here we present the first palynological results obtained from a core collected in Lake Chad that encompasses the midHolocene transition. Pollen-based biome reconstructions were made using the biomization method, where the pollen data are assigned to plant functional types (PFT) and biomes, for which affinity scores are calculated. For all samples the dominant potential biome reconstructed is savanna. However, both pollen assemblages and biome scores affinity indicate an important contribution of southern moister biomes before 6 cal kyr BP, much more than at the present time. That period seems to have known a fluvial transport change likely associated with a decrease in rainfall in the southern part of Lake Chad basin after 6ka BP, reducing the transport of pollen types of distant biomes. From 6 cal kyr BP onwards, fossil samples present very similar characteristics (pollen types and percentages, and biome scores affinities) with the modern sample collected in the Chari river delta station suggesting that comparable conditions to modern ones probably established in the Chad basin at this time. These results are confirmed by the reconstruction of precipitation using the modern analogue method. The change observed in pollen record around 6 cal kyr BP was also documented by other proxies studied on the same core (see F. Sylvestre et al. communication in the same conference). These first results show the highly promising potential of lacustrine records retrieved from Lake Chad and highlight the need to develop a higher resolution dataset spanning the entire Holocene. LATE PLEISTOCENE RAISED SHORELINES ON THE HATAY-SAMANDAGı COAST OF TURKEY, EASTERN MEDITERRANEAN Ugur Dogan. Ankara University, Turkey E-mail address: [email protected]
ı coast is the most important region in Turkey where Hatay-Samandag raised Quaternary shorelines can be seen above the current sea level. This study which was conducted in the region between the north of Çevlik ı) and the Syrian border identified four shorelines (except raised (Samandag two Holecene shorelines) as high as 116 m above the present sea level by using geomorphological markers and stratigraphic-sedimentological data. All of these four shorelines have been dated to the Late Pleistocene radiometrically by using electron spin resonance and uranium series techniques and relative chronology. The relative chronology has been established using uplift rate from radiometrically dated shorelines, morphostratigraphy, and Paleolithic findings on raised shorelines. According to the age data and the morphostratigraphy obtained, the Late Pleistocene raised shorelines do not extend at the same level throughout the entire coast. The Late Pleistocene shorelines can be seen at 22, 41-48, 77-80 and 116 m with a slight eastward ı; the single shoreline in Tekebas¸ı at 59tilt between Çevlik and Samandag at 7-12, 21, 43, 75 m with 60 m with a slight southward tilt; and in Keldag a slight southward tilt.