Quaternary Environments and Geoarchaeology (QEG)
QEG contributions to INQUA 2011
Quaternary Glaciations in the Mediterranean Mountains of Southern Europe and their Impact on River Behaviour
Kathryn Adamson, Philip Hughes, Jamie Woodward.
Abstract: Over the last decade our understanding of Pleistocene glacial activity in the mountains of Mediterranean southern Europe has been transformed by a new phase of field mapping, stratigraphical appraisal and the development of robust dating frameworks. The wider application of U-series, cosmogenic nuclide and luminescence methods has allowed us to conduct a Mediterranean-wide synthesis of Quaternary glacial history. A database of over 200 published dates from glaciated catchments has been constructed. This is used to explore regional patterns of glacial and fluvial dynamics and test current hypotheses of landscape response to Pleistocene glacial activity. This paper highlights the variable extent and timing of Pleistocene glaciation in southern Europe and considers its impacts upon meltwater routes and river system behaviour downstream before discussing the wider geomorphological and palaeoclimatic significance. Pleistocene glacial records are highly fragmentary across the Mediterranean. Middle Pleistocene glaciation is recorded in river catchments on the Iberian, Italian and Balkan Peninsulas, but has not yet been recognised in other regions such as Anatolia. During the Late Pleistocene, some mountain ranges record a local glacial maximum several thousand years earlier than the global LGM (MIS 2). These patterns reflect regional variations in palaeoclimate and the preservation of the glacial sedimentary record. In some regions the fluvial archive can provide a more complete record of upstream glacial activity. This continent-wide analysis provides important context for new research on long-term river behaviour in glaciated catchments of Montenegro. These sites provide a range of fluvial environments and depositional contexts which are representative of glaciated basins across much of Mediterranean southern Europe. New stratigraphical and sedimentological data from the Quaternary records of Mount Orjen are presented here, before discussing their wider significance.
Dating and impacts of Holocene Alaskan volcanic eruptions
Jeff Blackford, Richard Payne, Marianne Presthus Heggen, Hans van der Plicht.
Abstract: For time periods prior to historical and meteorological records, palaeoecological data can be used to assess the impacts of past volcanism. This paper will present data on the timing and impacts of Aniakchak II, the White River Ash and a further eruption c. 300 BP by examining the microfossils above and below associated tephras found in distal peat deposits. The mid-Holocene eruption of Aniakchak volcano was one of the largest in Alaska in the post-glacial period. In this study we estimate the age of this eruption through a sequence of radiocarbon dates using selected plant macrofossils to be approximately 1608-1458 cal. BC, younger than previous estimates, perhaps questioning the identification of this ash and its age in the GRIP core, or the effectiveness of AMS radiocarbon analysis of peat components. Pollen and oribatid mite data, and a probable century-scale hiatus in the sequence of radiocarbon dates, show a significant impact on the arctic ecosystem at the sampling point. Microtephras in peat from SE Alaska have been linked to the White River Ash and a possible more recent Mt. Churchill eruption around 300 BP (Payne and Blackford, 2008). Testate amoebae are used to reconstruct the water table and acidity across the tephra layers, and their assemblage changes are tested against a volcanic impacts model using RDA. The results are variable, with statistically significant changes associated with some tephras but not others. Overall, we conclude that volcanic impacts on peatlands have been significant, and that future eruptions could cause long-term changes through a range of mechanisms. Proximity to the eruption, tephra loading, seasonality and antecedent mire conditions are all significant in determining the impacts. Ref. Payne, R.J, Blackford, J.J., 2008. Volcanic impacts on peatlands: Palaeoecological evidence from Alaska. Quaternary Science Reviews 27, 2012-2030.
Millennial-scale climate variability in the eastern Mediterranean region during Marine Isotope Stages 8 and 9 a-c (240 to 310 ka)
William Fletcher, Ulrich C. Müller, Kimon Christanis, Jörg Pross.
Abstract: Recent drilling at Tenaghi Philippon (NE Greece), where the sedimentary sequence is known to cover the last 1.3 Ma continuously, provides a remarkable opportunity to detect and characterise millennial-scale climate variability in the Mediterranean region over multiple climatic cycles, and to improve understanding of the boundary conditions which promote rapid climate variability. Here, we present a centennial-scale pollen record from Tenaghi Philippon for the interval 240-310 ka, including the antepenultimate glacial stage (MIS8) and part of the preceding interglacial complex (MIS 9a-c). The pollen record documents major shifts in vegetation and climate on orbital timescales between warm, humid forested intervals (MIS 9c and 9a) and cold, dry intervals with forest-steppe and steppe vegetation (MIS 9b and 8). Superimposed on these changes are multiple short-term (sub-orbital and millennial-scale) events. Contrasting expression of millennial-scale variability within the interval 240-310 ka is evident. The glacial climate of MIS 8 appears not to have been characterised by strong millennial-scale variability. In contrast, during a cold interval of the preceding interglacial complex (MIS 9b) abrupt temperate forest expansions are recorded which closely match the palynological characteristics of last glacial Dansgaard-Oeschger events as detected in the same core. Global boundary conditions during MIS 9b of continental ice-sheet extent equivalent to sea-level 40-80 m below present and high obliquity are similar to those which prevailed in the middle part of MIS 3 and during MIS 6e, during which strong millennial-scale variability is also evident at Tenaghi Philippon (Müller et al., 2011, INQUA abstract). The findings confirm the occurrence of high-amplitude, high-frequency variability in eastern Mediterranean climate prior to the last glacial, and suggest that intermediate ice-volume and high obliquity favoured the expression of millennial-scale climate variability.
Extent, timing and palaeoclimatic significance of glaciation in the High Atlas, Morocco
Philip Hughes, Cassandra Fenton, David Fink, Christoph Schnabel, Henrik Rother.
Abstract: Glacial geomorphological mapping, 10Be terrestrial cosmogenic isotope analyses and palaeoglacier-climate modelling in the highest peaks of the Atlas Mountains, Morocco (31.1°N, 7.9°W), provides new and novel data toward understanding the history and evolution of the largest desert region on Earth. The Atlas Mountains display evidence of extensive and multiple Pleistocene glaciations. The largest ice field and valley glaciers formed in the Toubkal massif. Here, the oldest moraines have yielded 10Be ages scattered in the range 74-31 ka. A later phase of glaciation is dated to c. 24 ka. Moraines belonging to a third phase of glaciation has yielded a series of very close exposure ages (within error) at around 12 ka, and falling within the Younger Dryas (12.9-11.7 ka). The glacial record of the High Atlas effectively reflects moisture supply to the north-western Sahara Desert and can provide an indication of shifts between arid and pluvial conditions. The low altitude of the glaciations in all three glacial episodes indicate that climate was not only significantly cooler than today, but also very much wetter. The new evidence on the extent, timing and palaeoclimatic significance of glaciations in this region has major implications for understanding moisture transfer between the North Atlantic Ocean and the Sahara Desert during Pleistocene cold stages. The findings are highly significant for understanding atmospheric circulation during pluvial phases recorded in the Sahara, such as during the African Humid Period at the Pleistocene/Holocene transition (15 to 6 ka). Glacier advance in the High Atlas during this interval provides insight into the seasonal distribution of precipitation and provides valuable insight into the respective roles of moisture supply from the North Atlantic depressions and the West African Monsoon. This in turn then has important bearing on the strengths of meridional vs. zonal circulation at mid-latitudes during pluvial phases.
Ice caps in the Balkans: their, extent, age, and palaeoclimatic significance
Philip Hughes, Jamie Woodward, Peter van Calsteren, Louise Thomas and Kathryn Adamson.
Abstract: Ice caps covered large areas of the Balkans during cold stages of the Quaternary. In Montenegro, the largest ice caps (>1000 km2) extended over the Durmitor, Sinjajevina and Mora massifs. At lower elevations, on the Adriatic coast, a smaller ice cap (165 km2) developed on Mount Orjen (1894 m) in response to locally very high precipitation. Detailed field mapping allied to 30 uranium-series ages from glacial sediments has allowed a new model of Quaternary glacial history to be developed for the Balkan Peninsula. This is in good agreement with recent work in the Pindus Mountains of Northern Greece. The most extensive glaciation in Montenegro took place during the Middle Pleistocene (correlating with a major phase of glaciation in Greece) during MIS 12 (c. 480-430 ka). Later and less extensive glaciations are recorded in cirques and valleys across Montenegro and these correlate with glaciations during MIS 6 (190-130 ka) and MIS 5d-2 (110-11.7 ka) also recognised in Greece. In the Durmitor massif, the highest in Montenegro, valley glaciers were present during the Younger Dryas (12.9-11.7 ka) and confirm the influence of North Atlantic Ocean circulation on Pleistocene climate change in this part of the Mediterranean.
Environmental Changes across the Mesolithic-Neolithic transition in north-west Europe: new data from March Hill, northern England
Sarah Kneen, Bruce Albert, Peter Ryan, Jeff Blackford, Jim Innes.
Abstract: The transition from Mesolithic to Neolithic is considered one of the most significant time periods in human history. Questions remain over the nature of the shift in north-west Europe, especially regarding the onset of agriculture, the interaction between climate and cultural activity, and the degree of overlap between the two economic systems. To better understand the dynamics of this period, a multi-proxy palaeoecological study of three contrasting north-west European sites is underway, aiming to reconstruct independent records of climate and anthropogenic impacts. This paper aims to present initial results from the first of these sites, where a multi-core palaeo-environmental study will examine the environmental changes associated with the later Mesolithic and earliest Neolithic periods. March Hill is a highly significant later- and terminal-Mesolithic archaeological area of the central Pennine upland (northern England) and is situated in a region with the highest density clustering of such flint find sites. Initial results from analyses of pollen, charcoal, fungi, peat humification and radiocarbon dating will be presented, with the aim of reconstructing land use, background environmental conditions and cultural activity. Previous work from the region has shown the presence of ‘early’ cereal pollen c. 5,800 radiocarbon years BP, suggesting pre-Neolithic agriculture, and substantial evidence for intensive and persistent burning. The data from March Hill will be used to test models of purposive landscape modification through the use of fire, and an ‘initial Neolithic’ phase in the pollen record prior to supporting archaeological finds.
The Campanian-Ignimbrite (CI) tephra at Crvena Stijena Rockshelter, Montenegro: A Key Marker Horizon for the Middle to Upper Palaeolithic Transition in Southern Europe
Mike Morley, Jamie Woodward.
Abstract: Clearly defined distal tephras with distinct upper and lower bounding surfaces are extremely rare in rockshelter sediment records. Crvena Stijena is a large rockshelter in southwest Montenegro that contains one of the longest rockshelter sediment records in Europe. Its deep (>20 m) and well-stratified record includes deposits ranging in age from Middle Pleistocene to mid-Holocene. These sediments have yielded a rich assemblage of Middle and Upper Palaeolithic artefacts and faunal remains. A highly distinctive tephra unit, which varies in thickness from 50 to 100 mm, and is stratified between two beds of coarse-grained sediment, is clearly exposed in the sedimentary record approximately 6 m below the present land surface. Importantly, the tephra forms the boundary between the Middle and Upper Palaeolithic cultural records at this site and is therefore a highly significant chronostratigraphic marker. This research shows that the tephra is a distal equivalent of the Campanian Ignimbrite (CI) deposits associated with the largest Late Pleistocene volcanic eruption in Europe. The distal tephra associated with this eruption has been recognised in both marine and terrestrial records in the central and eastern Mediterranean and, more recently, as far afield as the Don Valley in southwest Russia. Originating in the Campanian volcanic province of southwest Italy, this tephra has been independently dated from exposures in various contexts to 39 – 41 ka. The identification of this tephra in well-stratified Palaeolithic sites is especially important because it is found within a period when radiocarbon dating is problematic, and because the eruption was broadly coeval with important events in human and earth history; including the Middle to Upper Palaeolithic transition in Europe and climatic cooling associated with Heinrich Event 4. Macrostratigraphic, microstratigraphic and sedimentological observations show that this tephra layer is in a primary depositional context.
Neolithic Environments at Y Godor, Berwyn Mountains, North Wales, UK
Peter Ryan, Jeff Blackford.
Abstract: The timing and nature of the transition from Mesolithic foraging to Neolithic farming is the subject of much debate. Were people or ideas the agents of change? How important was agro-pastoralism to the economy of the earliest Neolithic groups? Land-use models developed using data from the uplands of the British Isles suggest that Mesolithic groups actively managed woodland resources in order to improve grazing and browse for game animals and increase the quantity of edible plant foods. The sophisticated land management these models imply indicate that Mesolithic groups were socially and culturally ready to adopt agro-pastoralism. Early (pre-Ulmus decline) records of cereal-type pollen grains could indicate the presence and availability of cereals during the latest phase of the Mesolithic. Y Godor in the Berwyn Mountains, North Wales, is one site with early cereal-type pollen records. We present pollen, charcoal and fungal spore data from a new core collected from Y Godor. Pre-Ulmus decline cereal-type pollen grains were again recorded, but radiocarbon dating suggests that these are conventionally Neolithic in age. However, the pattern of repeated woodland disturbance associated with charcoal suggests the continuation of ‘Mesolithic’ type land-use and woodland management in this upland area, contemporary with Neolithic monuments, buildings and burials in neighbouring lowlands. It is only later in the Neolithic, that a more intensive agro-pastoral land-use system is recorded in the uplands. Our data suggests that Mesolithic lifeways continued to be practiced well into the Neolithic around this site; either by the co-existence of Mesolithic foraging communities alongside Neolithic farming groups or through early Neolithic groups continuing to use the uplands as foraging and hunting grounds.
Abrupt climate changes in the eastern Mediterranean region during Marine Isotope Stage 6 (130 to 190 ka BP)
Ulrich C. Müller, William Fletcher, Kimon Christanis, Jörg Pross.
Abstract: The Dansgaard-Oeschger (D-O) climate fluctuations of the last glacial have received great attention and much effort has been dedicated to elucidate their underlying mechanisms. However, we have barely begun to understand whether D-O-like climate fluctuations were unique to the last glacial and what the predisposing boundary conditions are. A last glacial pollen record from the site Tenaghi Philippon (TP), Greece, has shown a perfect match of tree taxa percentages with the Greenland ?18O record. Therefore, the recent recovery of a 200 m core from TP that covers the last 1.3 Ma continuously provides an unique opportunity to identify D-O-like variability in the NH during previous glacials and to elucidate their orbital and global boundary conditions. Here we present a continuous, centennial-resolution pollen record from TP of the penultimate glacial (MIS 6). The comparison with the last glacial pollen record from the same site shows that the frequency of climate fluctuations during MIS 6 (130-190 ka BP) was lower than during MIS 2-4 (10-70 ka BP). The amplitude of climate change is around the same as in MIS 2-4. The interval within MIS 6 that exhibits climate variability most reminiscent of D-O variability in MIS 3 was ~160 – 180 ka BP, i.e. MIS 6e. The orbital configuration of MIS 6e was characterised by high obliquity and by a changes from min. to max. precession (MIS 3: high obliquity and precession changes from min. to max. to min). The global land-based ice volume in MIS 6e equates to a sea level of 40-70 m below present (MIS 3: 60-90 m below present). The obliquity and ice-volume boundary conditions of MIS 3 and MIS 6e are similar to those of MIS 9b, the interval within MIS 8-9c that shows variability most similar to D-O fluctuations (Fletcher et al. 2011, INQUA abstract). We conclude a high obliquity constellation in combination with NH ice sheet dimensions equivalent to a sea-level of ~ 60-70 m below present are predisposing conditions for D-O-like variability.
New Records of Holocene Flooding in the Desert Nile
Jamie Woodward, Mark Macklin, Derek Welsby, Neal Spencer, Geoff Duller, Martin A. J. Williams and Frances Williams.
Abstract: The flow regime of the desert Nile in Egypt and Sudan is controlled by monsoon rainfall in the Ethiopian highlands and by equatorial rainfall in the headwaters of the White Nile. These components of the flow regime have fluctuated during the Holocene in response to changes in the global climate system. A better understanding of these fluctuations and their relationship to the archaeological record of human activity in the Nile Valley has been a key research objective for many decades, and this paper is part of an international multidisciplinary effort to reconstruct the history of the Nile basin over the last 30,000 years. Well dated geological records of Holocene flood history are lacking in the Nile Valley of Egypt because much of the geomorphological evidence has been obscured by development and modern dating methods have not been widely applied. This paper presents the first OSL-dated record of Holocene river history for the desert Nile. Our recent work in Northern Sudan has shown that the sedimentary records in abandoned Nile channels are important archives of Holocene flood history. These channel fills comprise stacked records of flood sediments intercalated with blown sands.. In Northern Sudan we are collaborating with two British Museum projects that involve large-scale archaeological survey of the valley floor and excavation of key riparian sites. A detailed OSL-based chronology of Holocene river behaviour and flooding has been assembled. This paper presents new data from Holocene-age palaeochannel fills in Northern Sudan and explores their archaeological and palaeohydrological potential to shed new light on the history of the world’s longest river.