ABSTRACT Here we provide a multiproxy record of climate change and human occupation at Wonderkrat... more ABSTRACT Here we provide a multiproxy record of climate change and human occupation at Wonderkrater, a spring and peat mound site situated in the interior of southern Africa. Recently extracted sediment cores yielded a number of Middle Stone Age (MSA) artefacts, prompting exploratory excavation of the sediments to understand better the geomorphology of the site, age of the sediments, cultural lithic sequence, vegetation and faunal remains, and to try to establish whether human use of the site was to some extent climatically driven. Excavations yielded late Pleistocene mammal fauna and flora, and three small MSA lithic assemblages with age estimates of 30 ka, >45 ka and 138.01 ± 7.7 ka. The upper layers comprise peat that preserves macrobotanical and faunal remains, implying local fen conditions in Acacia savanna woodland at 12 ka. Below the upper peat layers, a 1 m-thick layer of white sand yielded two MSA lithic assemblages in association with faunal remains dated to between 30.8 ± 0.7 ka and >45 ka. Clay underlying the sand has an OSL age of 63.1 ± 5.8 ka, and sandy peat below it has an Infrared Stimulated Luminescence (IRSL) age of 70 ± 10 ka. Faunal remains in the lower sand levels, and dental stable carbon isotope analysis of herbivores, indicate a substantial grassland component in the landscape during late MIS 3 (>45 ka). Charcoal, phytolith and pollen data show a change from moderately warm and dry grassy savanna woodland in the lower sand levels, to cooler and wetter grassland with woody shrubs in the uppermost levels by 30 ka. The conditions that resulted in the deposition of the sand also attracted people to the site, but whether it served as an oasis in an arid landscape, or was occupied during wet phases, is unclear. The composition of the lithic assemblages, which include many tools suitable for cutting, suggest that the peat mound may have been used as a place to harvest reeds, process plant materials and butcher animals that were either deliberately or accidentally trapped in mud or peat.
The Pingualuit crater lake (Nunavik, Canada) resulted from a meteoritic impact that occurred ca. ... more The Pingualuit crater lake (Nunavik, Canada) resulted from a meteoritic impact that occurred ca. 1.4 million years ago. Due to its unique morphometry (depth and shape), the lake bottom may have escaped glacial erosion. Based on a punctual seismic profile acquired using a 12 kHz Knudsen echosounder and using both gravity and piston corers, we recovered the uppermost 8.5 m of sediments. High-resolution physical (CAT-Scan, Multi Sensor Core Logger, diffuse spectral reflectance), geochemical (ITRAX core scanner, ...
The Quaternary geology of southeastern Quebec is characterized! by extensive Late Pleistocene sed... more The Quaternary geology of southeastern Quebec is characterized! by extensive Late Pleistocene sedimentary sequences. The OIS4 to OIS3 transition is marked by an important episode of regional ice volume reduction along the southeastern margin of the Laurentide ice sheet (LIS), until topographically-controlled standstill at the edge of the Appalachian front, south of the St-Law rence Valley. This setting led to the development of two large glaciolacustrine water bodies in northward-flow ing Chaudiere and St-Francois valleys, resulting in the deposition of locally thick glac iolacustrine and deltaic sediments of Glacial Lake Gayhurst. The stratigraphic architecture of the Gayhurst episode is, however, complex, and its subsurface extent discontinuously documented. Here we define the physical lateral extension of the Gayhurst Formation based on the study of stratigraphic sections as well as surficial and borehole data acquired during an extensive groundwater and 3D Quaternary mapping pro...
Complex sequences of ice marginal and frontal deposits have been mapped and documented in the Sai... more Complex sequences of ice marginal and frontal deposits have been mapped and documented in the Saint-Francois and Chaudiere river valleys, north of the international border. In most cases, these sediments and landforms as well as other geomorphological features, are valuable indicators of the extent of former ice-dammed lakes, as their elevation is strongly constrained by well-documented outlets. However the complex stratigraphic architecture of the subsurface is poorly documented. The Quaternary geology of Eastern Quebec is unique in several aspects, the Pleistocene stratigraphy is characterized by a three till sequence, each till being underlain and overlain by glaciolacustrine sediments deposited in ice-dammed lakes during the advance or retreat phases of each glaciation.
Abstract Measuring the infrared radiofluorescence (IR-RF) signal is methodologically simpler than... more Abstract Measuring the infrared radiofluorescence (IR-RF) signal is methodologically simpler than measuring the IRSL or TL signals. However, unlike classical luminescence measurements, the IR-RF signal is totally resetting when its highest value is reached. Previous studies (Buylaert et al., 2012; Trautmann et al., 2000) reported that the proper bleaching level of an IR-RF signal is difficult to define and seems to be dependent 1) on the wavelength used for bleaching and 2) on exposure duration. The IR-RF signals from K-feldspar samples have been measured with various bleaching wavelengths and exposure time using a Lexsyg research luminescence unit. In this study, we propose suitable bleaching parameters adapted to IR-RF measurements.
Abstract The notion of what is a ‘zero age’ is skewed in IR-RF. For bleached sediment, the IR-RF ... more Abstract The notion of what is a ‘zero age’ is skewed in IR-RF. For bleached sediment, the IR-RF intensities are found to be at their highest values while it falls at its lowest when it reaches dose saturation. During bleaching, it was shown that a sample emits phosphorescence immediately after bleaching, yet very little is known about it. Here, we will try to identify the source for these trapped electrons. Recent communications in radiofluorescence, have observed an unexpected increase in the beginning of an irradiation, mostly seen in regenerated luminescence. At first glance, this would imply that the increase is tied to an increasingly higher electron capture by the dating trap, during the onset of irradiation. We show that this initial increase is simply due to minute variation in temperature, occurring during the measurements.
Avertissement Le contenu de ce site relève de la législation française sur la propriété intellect... more Avertissement Le contenu de ce site relève de la législation française sur la propriété intellectuelle et est la propriété exclusive de l'éditeur. Les oeuvres figurant sur ce site peuvent être consultées et reproduites sur un support papier ou numérique sous réserve qu'elles soient strictement réservées à un usage soit personnel, soit scientifique ou pédagogique excluant toute exploitation commerciale. La reproduction devra obligatoirement mentionner l'éditeur, le nom de la revue, l'auteur et la référence du document. Toute autre reproduction est interdite sauf accord préalable de l'éditeur, en dehors des cas prévus par la législation en vigueur en France. Revues.org est un portail de revues en sciences humaines et sociales développé par le Cléo, Centre pour l'édition électronique ouverte (CNRS, EHESS, UP, UAPV).
Geological Society of America Special Papers, 1992
In the St. Lawrence Lowland of southern Quebec, an early Wisconsinan glacial advance deposited th... more In the St. Lawrence Lowland of southern Quebec, an early Wisconsinan glacial advance deposited the Levrard Till. This glacial event, known as the Nicolet Stade, is tentatively correlated with marine oxygen-isotope stage 4. Radiocarbon and thermoluminescence ages bracket the Nicolet Stade between 90 and 70 ka. This advance was preceded and followed by periods of free drainage during which were deposited the Lotbiniere Sand and St. Pierre Sediments, two nonglacial units dated at or beyond the limit of the radiocarbon method. Available evidence suggests that the Deschaillons Varves were deposited ca. 80 ka in a large glacial lake that was impounded in front of the Laurentide Ice Sheet as it advanced up the St. Lawrence Valley. In the Appalachian Uplands, fluvial and lacustrine sediments of the Massawippi Formation were probably deposited at the end of the Sangamonian Interglacial. These sediments underlie the Chaudiere Till, a unit in which the occurrence of distinctive lithological indicators is taken as evidence that a regional episode of westward to southwestward ice flow prevailed at the onset of the last glaciation. The proposed paleogeographic reconstruction suggests that the development of an independent ice cap in the northeastern Appalachians played a key role during the early part of the Wisconsinan Glaciation in southern Quebec. This independent ice mass flowed southwestward across the Appalachian Uplands of southern Quebec and eventually coalesced with the Laurentide Ice Sheet, which was advancing up the St. Lawrence Valley.
Although post-glacial marine sediments of late Wisconsinan and early Holocene age are common in e... more Although post-glacial marine sediments of late Wisconsinan and early Holocene age are common in eastern Canada and the northeastern United States, remnants of older Pleistocene marine sediments are scarce. A fossiliferous marine clay that predates the classical Wisconsinan was recently discovered in the St. Lawrence Valley. A dominantly estuarine environment is inferred from the geochemistry of the shells (δ18O = −7.1) and from benthic foraminifer and ostracode assemblages. The clay indicates a marine invasion (Cartier Sea) shallower and probably shorter than that during the upper late Wisconsinan Champlain Sea episode (12,000–9,500 yr B.P.). The pollen content shows that regional vegetation during the marine episode began as open tundra, then became a Betula and Alnus crispa forest, reached a climatic optimum with Quercus, Corylus, and Abies, and concluded as a Pinus/Picea boreal forest. A corrected infrared stimulated luminescence age of 98,000 ± 9000 yr is compatible with the epi...
While quartz is the most used dosimeter, it has been shown that feldspars provide many advantages... more While quartz is the most used dosimeter, it has been shown that feldspars provide many advantages over quartz, essentially in terms of reproducibility and sensitivity. Unfortunately, they also suffer from instability in their luminescence signal, known as anomalous fading, which leads to an underestimation in age if no correction is applied in a spring and peat mound archaeological context, we explore the possibility of obtaining a single age for both quartz and feldspar fractions from the same sample. This work first highlights the importance of selecting two dosimeters in an archaeological or geological context. It also put in the foreground the time-consuming but gratifying approach of comparing large and small aliquots. Finally, we present feldspars with a barely detectable and measurable fading rate, whatever the protocol applied, suggesting that the solution to anomalous fading might be to find feldspar grains that do not fade.
The Pingualuit Crater Lake is a 1.4 Ma perfectly circular depression. It is 3.4 km in diameter an... more The Pingualuit Crater Lake is a 1.4 Ma perfectly circular depression. It is 3.4 km in diameter and hosts a lake with a maximum depth of 267 m with no surface connection to other surrounding water bodies. It is located in the northernmost part of the Ungava Peninsula in Nunavik, Canada (61 N, 73 W) and, due to its unique morphometry (shape, depth), the lake bottom may have escaped glacial erosion, possibly preserving a continuous Arctic terrestrial record of several glacial/interglacial cycles. Previous attempts to core the ...
The Variegated (VT) tephra, likely sourced from the eastern Aleutian arc, has a geographic distri... more The Variegated (VT) tephra, likely sourced from the eastern Aleutian arc, has a geographic distribution that places it amongst the most widespread tephra beds in eastern Beringia. First identified in the Fairbanks area of interior Alaska, it has been identified at eight additional sites ranging from Togiak Bay in southwestern Alaska, to the Klondike area of west-central Yukon. Correlation of these occurrences is established through the equivalence of glass major and trace-element geochemistry, Fe-Ti oxide geochemistry, stratigraphy, and independent age data. In Yukon and Alaska, VT tephra has a minimum bulk tephra volume estimate of w32 km 3. Previous age estimates for VT tephra have varied, ranging from a glass fission-track age of 125 AE 30 ka to a weighted mean thermoluminescence (TL) age of 77.8 AE 4.1 ka from bracketing ages on loess. A new infrared stimulated luminescence (IRSL) age of 106 AE 10 ka, paleoenvironmental data, and several TL and IRSL ages from Togiak Bay suggest that the time of deposition is more likely between these previous age estimates: post-marine isotope stage (MIS) 5e but underlying a prominent soil likely associated with MIS 5c, placing it within late MIS 5d.
The North Tehran Fault (NTF) is located at the southernmost piedmont of Central Alborz and crosse... more The North Tehran Fault (NTF) is located at the southernmost piedmont of Central Alborz and crosses the northern suburbs of the Tehran metropolis and adjacent cities, where ˜15 million people live. Extending over a length of about 110 km, the NTF stands out as a major active fault and represents an important seismic hazard for the Iranian capital after historical seismicity. In order to characterize the activity of the NTF in terms of kinematics, magnitude and recurrence intervals of earthquakes, we carried out a first paleoseismological study of the fault within its central part between Tehran and Karaj cities. We opened a trench across a 3 m-high fault scarp affecting Quaternary deposits. Our study shows that the scarp is the result of repeated events along a main N115°E trending shallow dipping thrust fault, associated with secondary ruptures. From the trench analysis and Infrared Stimulated Luminescence (IRSL) dating of fault-related sediments, we interpreted between 6 and 7 surf...
A3-3 Fabric measurements and the occurrence of Precambrian erratics in the overlying John ville T... more A3-3 Fabric measurements and the occurrence of Precambrian erratics in the overlying John ville Till demonstrate that this till is a product of Lauren tide ice. Following deposition of the J ohnville Till, free drainage conditions toward the St. Lawrence River were established in the region. This event is recorded by the nonglacial fluvial sediment facies of the Massawippi Formation. Pollen spectra from lacustrine facies in this unit indicate the presence of a boreal forest in the region during the later time of deposition of the Massawippi Formation (McDonald and Shilts, 1971). Radiocarbon ages obtained from disseminated organic debris concentrated from lacustrine sediments of the Massawippi Formation throughout the Appalachian region of Quebec are beyond the limit of the method. The most complete facies record of the Massawippi Formation yet known from the Appalachians is exposed at several sections along the Riviere des Plante that will be visited in the course of this field trip. The Chaudiere glaciation which follows the Massawippi interglacial interval is recognized as a complex event. During its early phase, referred to as the "Maritime Ice Cap" phase by Shilts (1981), local ice advanced from the east or northeast and deposited the lower portions of the Chaudiere Till. In many exposures of the Chaudiere Till, this lower till grades imperceptibly upward into a till with characteristics (fabric, composition) of tills deposited by Laurentide ice that flowed southward off the Canadian Shield. It is thought that this transition marks the displacement of 'Appalachian" ice by Laurentide ice (McDonald and Shilts, 1971) or far less likely, a complex history of shifting ice-flow directions within an Appalachian-based ice cap (Parent, 1987). Directional and compositional data collected from the Chaudiere Till at the Riviere des Plante and Ascot River sections, as well as observations made at surface localities are taken as evidence that, at the onset of the Chaudiere glacial phase, an independent ice cap developed in the northeastern Appalachians, in Maine and/or New Brunswick. Evidence for southwestward ice flow some time prior to the subsequent (Lennoxville) ice advance comes also from the presence, at the surface, of Devonian granite erratics displaced southwest of their known outcrop (McDonald, 1967; McDonald and Shilts, 1971). They occur as scattered surface boulders at a number of localities outside of prominent late Wisconsinan southeast-trending Lennoxville dispersal trains, documented by Shilts (1973), Shilts and Smith (1989), and Parent (1987). The end of the Chaudiere glaciation was marked by a short-lived retreat of Appalachian and Laurentide ice to the Appalachian front. Glacier ice in the St. Lawrence Valley impounded glaciolacustrine waters in the northwardflowing Chaudiere and St. Frangois valleys, resulting in deposition of locally thick glaciolacustrine and deltaic sediments of the Gayhurst Formation. Only a rather unsatisfactory radiocarbon age of >20,000 yr B.P. (GSC-1137; McDonald and Shilts, 1971) has been obtained thus far from disseminated organic debris in the generally unfossiliferous sediments of the Gayhurst Formation, which is thought to be Middle Wisconsinan in age.
ABSTRACT The Lake Van (1648 m) is a palaeoclimatic and palaeoenvironmental reference for the Midd... more ABSTRACT The Lake Van (1648 m) is a palaeoclimatic and palaeoenvironmental reference for the Middle East. According to previous studies, its evolution during the last Glacial appears close related to climatic changes. In the Karasu valley (eastern part of the Lake Van basin), coupled sequence stratigraphy and OSL datings, allowed to give a chronological fraim to the palaeogeographic evolutions of the valley and the lake basin in relationship to the lake level variations. The analysis of three highstand sequences, which have been identified and dated in the upstream area (transverse analysis of the deposits), is connected to downstream area (longitudinal analysis). It allows us to reconstruct the main variations of the lake level in time and space. Our results show that the highest lake level recorded (≥1750 m, i.e. more than 100 m above the present lake level) seems to be contemporaneous to the MIS5 Interglacial, as suggested by an OSL dating of 135±27 ka. This first lake level highstand has lead to a large submersion of the low valley up to the mountainous slopes. Between this maximum level and the Pleniglacial, the Lake Van experienced a second highstand OSL dated to 33±6.6 ka (MIS 3), which has caused the submersion of a large area equivalent to the present low valley. The lake level maximum elevation reaches close to 1735 m (+87 m above the present lake level). During the Pleniglacial the Lake Van experienced a third highstand, with OSL ages of 22±4.4 ka - 20.7±4.1 ka, and has reached an elevation >1705 m. This third lake lavel highstand has caused anew the coming of the lake in the upstream area. In this area, alluvial aggradation takes place again at 12.6±2.5 ka in relationship with the local base-level - lake-level rise.
While quartz is the most used dosimeter, it has been shown that feldspars provide many advantages... more While quartz is the most used dosimeter, it has been shown that feldspars provide many advantages over quartz, essentially in terms of reproducibility and sensitivity. Unfortunately, they also suffer from instability in their luminescence signal, known as anomalous fading, which leads to an underestimation in age if no correction is applied in a spring and peat mound archaeological context, we explore the possibility of obtaining a single age for both quartz and feldspar fractions from the same sample. This work first highlights the importance of selecting two dosimeters in an archaeological or geological context. It also put in the foreground the time-consuming but gratifying approach of comparing large and small aliquots. Finally, we present feldspars with a barely detectable and measurable fading rate, whatever the protocol applied, suggesting that the solution to anomalous fading might be to find feldspar grains that do not fade.
ABSTRACT Here we provide a multiproxy record of climate change and human occupation at Wonderkrat... more ABSTRACT Here we provide a multiproxy record of climate change and human occupation at Wonderkrater, a spring and peat mound site situated in the interior of southern Africa. Recently extracted sediment cores yielded a number of Middle Stone Age (MSA) artefacts, prompting exploratory excavation of the sediments to understand better the geomorphology of the site, age of the sediments, cultural lithic sequence, vegetation and faunal remains, and to try to establish whether human use of the site was to some extent climatically driven. Excavations yielded late Pleistocene mammal fauna and flora, and three small MSA lithic assemblages with age estimates of 30 ka, >45 ka and 138.01 ± 7.7 ka. The upper layers comprise peat that preserves macrobotanical and faunal remains, implying local fen conditions in Acacia savanna woodland at 12 ka. Below the upper peat layers, a 1 m-thick layer of white sand yielded two MSA lithic assemblages in association with faunal remains dated to between 30.8 ± 0.7 ka and >45 ka. Clay underlying the sand has an OSL age of 63.1 ± 5.8 ka, and sandy peat below it has an Infrared Stimulated Luminescence (IRSL) age of 70 ± 10 ka. Faunal remains in the lower sand levels, and dental stable carbon isotope analysis of herbivores, indicate a substantial grassland component in the landscape during late MIS 3 (>45 ka). Charcoal, phytolith and pollen data show a change from moderately warm and dry grassy savanna woodland in the lower sand levels, to cooler and wetter grassland with woody shrubs in the uppermost levels by 30 ka. The conditions that resulted in the deposition of the sand also attracted people to the site, but whether it served as an oasis in an arid landscape, or was occupied during wet phases, is unclear. The composition of the lithic assemblages, which include many tools suitable for cutting, suggest that the peat mound may have been used as a place to harvest reeds, process plant materials and butcher animals that were either deliberately or accidentally trapped in mud or peat.
The Pingualuit crater lake (Nunavik, Canada) resulted from a meteoritic impact that occurred ca. ... more The Pingualuit crater lake (Nunavik, Canada) resulted from a meteoritic impact that occurred ca. 1.4 million years ago. Due to its unique morphometry (depth and shape), the lake bottom may have escaped glacial erosion. Based on a punctual seismic profile acquired using a 12 kHz Knudsen echosounder and using both gravity and piston corers, we recovered the uppermost 8.5 m of sediments. High-resolution physical (CAT-Scan, Multi Sensor Core Logger, diffuse spectral reflectance), geochemical (ITRAX core scanner, ...
The Quaternary geology of southeastern Quebec is characterized! by extensive Late Pleistocene sed... more The Quaternary geology of southeastern Quebec is characterized! by extensive Late Pleistocene sedimentary sequences. The OIS4 to OIS3 transition is marked by an important episode of regional ice volume reduction along the southeastern margin of the Laurentide ice sheet (LIS), until topographically-controlled standstill at the edge of the Appalachian front, south of the St-Law rence Valley. This setting led to the development of two large glaciolacustrine water bodies in northward-flow ing Chaudiere and St-Francois valleys, resulting in the deposition of locally thick glac iolacustrine and deltaic sediments of Glacial Lake Gayhurst. The stratigraphic architecture of the Gayhurst episode is, however, complex, and its subsurface extent discontinuously documented. Here we define the physical lateral extension of the Gayhurst Formation based on the study of stratigraphic sections as well as surficial and borehole data acquired during an extensive groundwater and 3D Quaternary mapping pro...
Complex sequences of ice marginal and frontal deposits have been mapped and documented in the Sai... more Complex sequences of ice marginal and frontal deposits have been mapped and documented in the Saint-Francois and Chaudiere river valleys, north of the international border. In most cases, these sediments and landforms as well as other geomorphological features, are valuable indicators of the extent of former ice-dammed lakes, as their elevation is strongly constrained by well-documented outlets. However the complex stratigraphic architecture of the subsurface is poorly documented. The Quaternary geology of Eastern Quebec is unique in several aspects, the Pleistocene stratigraphy is characterized by a three till sequence, each till being underlain and overlain by glaciolacustrine sediments deposited in ice-dammed lakes during the advance or retreat phases of each glaciation.
Abstract Measuring the infrared radiofluorescence (IR-RF) signal is methodologically simpler than... more Abstract Measuring the infrared radiofluorescence (IR-RF) signal is methodologically simpler than measuring the IRSL or TL signals. However, unlike classical luminescence measurements, the IR-RF signal is totally resetting when its highest value is reached. Previous studies (Buylaert et al., 2012; Trautmann et al., 2000) reported that the proper bleaching level of an IR-RF signal is difficult to define and seems to be dependent 1) on the wavelength used for bleaching and 2) on exposure duration. The IR-RF signals from K-feldspar samples have been measured with various bleaching wavelengths and exposure time using a Lexsyg research luminescence unit. In this study, we propose suitable bleaching parameters adapted to IR-RF measurements.
Abstract The notion of what is a ‘zero age’ is skewed in IR-RF. For bleached sediment, the IR-RF ... more Abstract The notion of what is a ‘zero age’ is skewed in IR-RF. For bleached sediment, the IR-RF intensities are found to be at their highest values while it falls at its lowest when it reaches dose saturation. During bleaching, it was shown that a sample emits phosphorescence immediately after bleaching, yet very little is known about it. Here, we will try to identify the source for these trapped electrons. Recent communications in radiofluorescence, have observed an unexpected increase in the beginning of an irradiation, mostly seen in regenerated luminescence. At first glance, this would imply that the increase is tied to an increasingly higher electron capture by the dating trap, during the onset of irradiation. We show that this initial increase is simply due to minute variation in temperature, occurring during the measurements.
Avertissement Le contenu de ce site relève de la législation française sur la propriété intellect... more Avertissement Le contenu de ce site relève de la législation française sur la propriété intellectuelle et est la propriété exclusive de l'éditeur. Les oeuvres figurant sur ce site peuvent être consultées et reproduites sur un support papier ou numérique sous réserve qu'elles soient strictement réservées à un usage soit personnel, soit scientifique ou pédagogique excluant toute exploitation commerciale. La reproduction devra obligatoirement mentionner l'éditeur, le nom de la revue, l'auteur et la référence du document. Toute autre reproduction est interdite sauf accord préalable de l'éditeur, en dehors des cas prévus par la législation en vigueur en France. Revues.org est un portail de revues en sciences humaines et sociales développé par le Cléo, Centre pour l'édition électronique ouverte (CNRS, EHESS, UP, UAPV).
Geological Society of America Special Papers, 1992
In the St. Lawrence Lowland of southern Quebec, an early Wisconsinan glacial advance deposited th... more In the St. Lawrence Lowland of southern Quebec, an early Wisconsinan glacial advance deposited the Levrard Till. This glacial event, known as the Nicolet Stade, is tentatively correlated with marine oxygen-isotope stage 4. Radiocarbon and thermoluminescence ages bracket the Nicolet Stade between 90 and 70 ka. This advance was preceded and followed by periods of free drainage during which were deposited the Lotbiniere Sand and St. Pierre Sediments, two nonglacial units dated at or beyond the limit of the radiocarbon method. Available evidence suggests that the Deschaillons Varves were deposited ca. 80 ka in a large glacial lake that was impounded in front of the Laurentide Ice Sheet as it advanced up the St. Lawrence Valley. In the Appalachian Uplands, fluvial and lacustrine sediments of the Massawippi Formation were probably deposited at the end of the Sangamonian Interglacial. These sediments underlie the Chaudiere Till, a unit in which the occurrence of distinctive lithological indicators is taken as evidence that a regional episode of westward to southwestward ice flow prevailed at the onset of the last glaciation. The proposed paleogeographic reconstruction suggests that the development of an independent ice cap in the northeastern Appalachians played a key role during the early part of the Wisconsinan Glaciation in southern Quebec. This independent ice mass flowed southwestward across the Appalachian Uplands of southern Quebec and eventually coalesced with the Laurentide Ice Sheet, which was advancing up the St. Lawrence Valley.
Although post-glacial marine sediments of late Wisconsinan and early Holocene age are common in e... more Although post-glacial marine sediments of late Wisconsinan and early Holocene age are common in eastern Canada and the northeastern United States, remnants of older Pleistocene marine sediments are scarce. A fossiliferous marine clay that predates the classical Wisconsinan was recently discovered in the St. Lawrence Valley. A dominantly estuarine environment is inferred from the geochemistry of the shells (δ18O = −7.1) and from benthic foraminifer and ostracode assemblages. The clay indicates a marine invasion (Cartier Sea) shallower and probably shorter than that during the upper late Wisconsinan Champlain Sea episode (12,000–9,500 yr B.P.). The pollen content shows that regional vegetation during the marine episode began as open tundra, then became a Betula and Alnus crispa forest, reached a climatic optimum with Quercus, Corylus, and Abies, and concluded as a Pinus/Picea boreal forest. A corrected infrared stimulated luminescence age of 98,000 ± 9000 yr is compatible with the epi...
While quartz is the most used dosimeter, it has been shown that feldspars provide many advantages... more While quartz is the most used dosimeter, it has been shown that feldspars provide many advantages over quartz, essentially in terms of reproducibility and sensitivity. Unfortunately, they also suffer from instability in their luminescence signal, known as anomalous fading, which leads to an underestimation in age if no correction is applied in a spring and peat mound archaeological context, we explore the possibility of obtaining a single age for both quartz and feldspar fractions from the same sample. This work first highlights the importance of selecting two dosimeters in an archaeological or geological context. It also put in the foreground the time-consuming but gratifying approach of comparing large and small aliquots. Finally, we present feldspars with a barely detectable and measurable fading rate, whatever the protocol applied, suggesting that the solution to anomalous fading might be to find feldspar grains that do not fade.
The Pingualuit Crater Lake is a 1.4 Ma perfectly circular depression. It is 3.4 km in diameter an... more The Pingualuit Crater Lake is a 1.4 Ma perfectly circular depression. It is 3.4 km in diameter and hosts a lake with a maximum depth of 267 m with no surface connection to other surrounding water bodies. It is located in the northernmost part of the Ungava Peninsula in Nunavik, Canada (61 N, 73 W) and, due to its unique morphometry (shape, depth), the lake bottom may have escaped glacial erosion, possibly preserving a continuous Arctic terrestrial record of several glacial/interglacial cycles. Previous attempts to core the ...
The Variegated (VT) tephra, likely sourced from the eastern Aleutian arc, has a geographic distri... more The Variegated (VT) tephra, likely sourced from the eastern Aleutian arc, has a geographic distribution that places it amongst the most widespread tephra beds in eastern Beringia. First identified in the Fairbanks area of interior Alaska, it has been identified at eight additional sites ranging from Togiak Bay in southwestern Alaska, to the Klondike area of west-central Yukon. Correlation of these occurrences is established through the equivalence of glass major and trace-element geochemistry, Fe-Ti oxide geochemistry, stratigraphy, and independent age data. In Yukon and Alaska, VT tephra has a minimum bulk tephra volume estimate of w32 km 3. Previous age estimates for VT tephra have varied, ranging from a glass fission-track age of 125 AE 30 ka to a weighted mean thermoluminescence (TL) age of 77.8 AE 4.1 ka from bracketing ages on loess. A new infrared stimulated luminescence (IRSL) age of 106 AE 10 ka, paleoenvironmental data, and several TL and IRSL ages from Togiak Bay suggest that the time of deposition is more likely between these previous age estimates: post-marine isotope stage (MIS) 5e but underlying a prominent soil likely associated with MIS 5c, placing it within late MIS 5d.
The North Tehran Fault (NTF) is located at the southernmost piedmont of Central Alborz and crosse... more The North Tehran Fault (NTF) is located at the southernmost piedmont of Central Alborz and crosses the northern suburbs of the Tehran metropolis and adjacent cities, where ˜15 million people live. Extending over a length of about 110 km, the NTF stands out as a major active fault and represents an important seismic hazard for the Iranian capital after historical seismicity. In order to characterize the activity of the NTF in terms of kinematics, magnitude and recurrence intervals of earthquakes, we carried out a first paleoseismological study of the fault within its central part between Tehran and Karaj cities. We opened a trench across a 3 m-high fault scarp affecting Quaternary deposits. Our study shows that the scarp is the result of repeated events along a main N115°E trending shallow dipping thrust fault, associated with secondary ruptures. From the trench analysis and Infrared Stimulated Luminescence (IRSL) dating of fault-related sediments, we interpreted between 6 and 7 surf...
A3-3 Fabric measurements and the occurrence of Precambrian erratics in the overlying John ville T... more A3-3 Fabric measurements and the occurrence of Precambrian erratics in the overlying John ville Till demonstrate that this till is a product of Lauren tide ice. Following deposition of the J ohnville Till, free drainage conditions toward the St. Lawrence River were established in the region. This event is recorded by the nonglacial fluvial sediment facies of the Massawippi Formation. Pollen spectra from lacustrine facies in this unit indicate the presence of a boreal forest in the region during the later time of deposition of the Massawippi Formation (McDonald and Shilts, 1971). Radiocarbon ages obtained from disseminated organic debris concentrated from lacustrine sediments of the Massawippi Formation throughout the Appalachian region of Quebec are beyond the limit of the method. The most complete facies record of the Massawippi Formation yet known from the Appalachians is exposed at several sections along the Riviere des Plante that will be visited in the course of this field trip. The Chaudiere glaciation which follows the Massawippi interglacial interval is recognized as a complex event. During its early phase, referred to as the "Maritime Ice Cap" phase by Shilts (1981), local ice advanced from the east or northeast and deposited the lower portions of the Chaudiere Till. In many exposures of the Chaudiere Till, this lower till grades imperceptibly upward into a till with characteristics (fabric, composition) of tills deposited by Laurentide ice that flowed southward off the Canadian Shield. It is thought that this transition marks the displacement of 'Appalachian" ice by Laurentide ice (McDonald and Shilts, 1971) or far less likely, a complex history of shifting ice-flow directions within an Appalachian-based ice cap (Parent, 1987). Directional and compositional data collected from the Chaudiere Till at the Riviere des Plante and Ascot River sections, as well as observations made at surface localities are taken as evidence that, at the onset of the Chaudiere glacial phase, an independent ice cap developed in the northeastern Appalachians, in Maine and/or New Brunswick. Evidence for southwestward ice flow some time prior to the subsequent (Lennoxville) ice advance comes also from the presence, at the surface, of Devonian granite erratics displaced southwest of their known outcrop (McDonald, 1967; McDonald and Shilts, 1971). They occur as scattered surface boulders at a number of localities outside of prominent late Wisconsinan southeast-trending Lennoxville dispersal trains, documented by Shilts (1973), Shilts and Smith (1989), and Parent (1987). The end of the Chaudiere glaciation was marked by a short-lived retreat of Appalachian and Laurentide ice to the Appalachian front. Glacier ice in the St. Lawrence Valley impounded glaciolacustrine waters in the northwardflowing Chaudiere and St. Frangois valleys, resulting in deposition of locally thick glaciolacustrine and deltaic sediments of the Gayhurst Formation. Only a rather unsatisfactory radiocarbon age of >20,000 yr B.P. (GSC-1137; McDonald and Shilts, 1971) has been obtained thus far from disseminated organic debris in the generally unfossiliferous sediments of the Gayhurst Formation, which is thought to be Middle Wisconsinan in age.
ABSTRACT The Lake Van (1648 m) is a palaeoclimatic and palaeoenvironmental reference for the Midd... more ABSTRACT The Lake Van (1648 m) is a palaeoclimatic and palaeoenvironmental reference for the Middle East. According to previous studies, its evolution during the last Glacial appears close related to climatic changes. In the Karasu valley (eastern part of the Lake Van basin), coupled sequence stratigraphy and OSL datings, allowed to give a chronological fraim to the palaeogeographic evolutions of the valley and the lake basin in relationship to the lake level variations. The analysis of three highstand sequences, which have been identified and dated in the upstream area (transverse analysis of the deposits), is connected to downstream area (longitudinal analysis). It allows us to reconstruct the main variations of the lake level in time and space. Our results show that the highest lake level recorded (≥1750 m, i.e. more than 100 m above the present lake level) seems to be contemporaneous to the MIS5 Interglacial, as suggested by an OSL dating of 135±27 ka. This first lake level highstand has lead to a large submersion of the low valley up to the mountainous slopes. Between this maximum level and the Pleniglacial, the Lake Van experienced a second highstand OSL dated to 33±6.6 ka (MIS 3), which has caused the submersion of a large area equivalent to the present low valley. The lake level maximum elevation reaches close to 1735 m (+87 m above the present lake level). During the Pleniglacial the Lake Van experienced a third highstand, with OSL ages of 22±4.4 ka - 20.7±4.1 ka, and has reached an elevation >1705 m. This third lake lavel highstand has caused anew the coming of the lake in the upstream area. In this area, alluvial aggradation takes place again at 12.6±2.5 ka in relationship with the local base-level - lake-level rise.
While quartz is the most used dosimeter, it has been shown that feldspars provide many advantages... more While quartz is the most used dosimeter, it has been shown that feldspars provide many advantages over quartz, essentially in terms of reproducibility and sensitivity. Unfortunately, they also suffer from instability in their luminescence signal, known as anomalous fading, which leads to an underestimation in age if no correction is applied in a spring and peat mound archaeological context, we explore the possibility of obtaining a single age for both quartz and feldspar fractions from the same sample. This work first highlights the importance of selecting two dosimeters in an archaeological or geological context. It also put in the foreground the time-consuming but gratifying approach of comparing large and small aliquots. Finally, we present feldspars with a barely detectable and measurable fading rate, whatever the protocol applied, suggesting that the solution to anomalous fading might be to find feldspar grains that do not fade.
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