Quaternary Geology

I DEPOSITI DEL PLEISTOCENE INFERIORE DELLA BASSA VAL DI CECINA (TOSCANA, ITALIA): RICOSTRUZIONE STRATIGRAFICO–DEPOSIZIONALE E PROPOSTA DI SUDDIVISIONE IN UNITA’ ALLOSTRATIGRAFICHE

by Florence ReSeT

Giovanni Sarti, Andrea Ciampalini, Ilaria Consoloni & Andrea Cerrina Feroni

Fault array evolution in extensional basins: insights from statistical analysis of gravel deposits in the Cecina River (Tuscany, Italy)

by Florence ReSeT

Andrea Ciampalini, Ilaria Consoloni, Giovanni Sarti

Two statistical analyses of gravel clasts from the Lower Pleistocene deposits in the Lower Cecina Valley (Tuscany,... more Two statistical analyses of gravel clasts from the Lower Pleistocene deposits in the Lower Cecina Valley (Tuscany, Italy) have been combined to unravel changes in the palaeo-drainage system. Data from 16 outcrops were collected and 6400 clasts described. Facies analysis, micro-palaeontology and macro-palaeontology and petrographic characteristics of the gravel deposits have highlighted the presence of three allostratigraphic units. Clast lithology is the main discriminator among these units. Cluster and principal component analyses of the 6400 clasts have improved understanding of the stratigraphy of the Lower Pleistocene deposits and constrain the re-routing of the lower palaeo-Cecina River from a supposedly south-east to north-west direction to the present east to west direction. Short rivers feeding small fan deltas represented by the oldest allostratigraphic units were abandoned in the Lower Pleistocene, when the re-routing of the Cecina River caused the capture of these streams. This evolution suggests a change in the tectonic regime of the area. The fan deltas developed on the hanging wall of normal faults sub-parallel to the coast; a change to a transtensile tectonic regime caused the deviation of the main river channel toward the present coast and the formation of a pull-apart basin, which is now exploited by the Cecina River. This study illustrates the value of lithological analyses of gravel deposits for understanding the tectonic evolution of an area.

BURIAL DATING OF LATE-CENOZOIC DEPOSITS USING IN-SITU PRODUCED COSMOGENIC NUCLIDES

by Florence ReSeT

Andrea Ciampalini, Cristina Persano, Derek Fabel, Marco Firpo

Dating the Miocene to Pleistocene deposition of fluvial and deltaic sediments is often difficult because of the... more Dating the Miocene to Pleistocene deposition of fluvial and deltaic sediments is often difficult because of the absence of suitable biostratigraphic markers. Temporal limits on sediment deposition, however, are fundamental constraints in many geological, geomorphological, stratigraphical and archeological studies. In particular a dated stratigraphy of sedimentary basins provides information about timing of evolution of the sediment source and routing system due to tectonics, sea-level and/or climate changes. Traditional techniques, such as luminescence, radiocarbon dating of organic material, etc. only permit us to date sediments that are no older than ~250,000 years. Recently a method for dating sediment burial using the radioactive decay of cosmogenic nuclides 26Al and 10Be has been developed. 26Al and 10Be are produced by the continuous bombarding by high-energy cosmic rays of the Earth surface where they penetrate into rocks and sediments at a depth that varies, depending on rock density, between 2 and 3 m. The long half-life of the 26Al (7.05X105 yr) and 10Be (1.5X106 yr) make them optimal for dating sediments that were deposited over the past five million years, as long as the sediments were at the surface and exposed to cosmic rays before sedimentation and burial. The sediments that can be dated using the cosmogenic isotopes technique need to have the following characteristics: (1) quartz needs to be present and have been exposed at the surface for a time necessary to accumulate measurable cosmogenic radionuclides concentration (i.e., depending
on latitude and altitude, at least ~ 200 years); (2) transport time needs to have been negligible (3) burial was rapid and deep (>10 m) to avoid cosmogenic nuclides production after deposition, otherwise a correction needs to be introduced. This method is useful in many Italian areas where deltaic or fluvial Miocene to Pleistocene deposits crop out.

New insights on the Holocene marine transgression in the Bahía Camarones (Chubut, Argentina)

by Ilaria Consoloni

GIOVANNI ZANCHETTA, ILARIA CONSOLONI, ILARIA ISOLA, MARTA PAPPALARDO, ADRIANO RIBOLINI, MARINA AGUIRRE, ENRIQUE FUCKS, ILARIA BANESCHI, MONICA BINI, LUCA RAGAINI, FILIPPO TERRASI & GABRIELLA BORETTO. Italian Journal of Geosciences (Boll.Soc.Geol.It.), Vol. 131, No. 1 (2012), pp. 19-31, 6 figs., 2 tabs. (DOI: 10.3301/IJG.2011.20)

The stratigraphic reconstruction of the northern sector of the Bahía Camarones (Chubut, Argentina) allowed to improve... more The stratigraphic reconstruction of the northern sector of the Bahía Camarones (Chubut, Argentina) allowed to improve our understanding of the Holocene marine transgression in the area. The first phase of the maximum of the transgression, is interpreted as dominated by the high rate of eustatic rise of sea level until ca. 6-7 ka BP possibly associated to sedimentary starvation as suggested by fossil accumulation. After this first phase, the general trend indicates a progressive fall of the relative sea level after the Middle Holocene high stand as documented in other parts of south America Atlantic coast. Our data, coupled with the robust radiocarbon data set available for the area from literature, indicate three main local steps of coastal aggradation between ca. 6600 and 5400 yr BP (ca. 7000-5600 yr cal BP), ca. 3300 and 2000 yr BP (ca. 3100-1700 yr cal BP), and ca. 1300-500 yr BP (ca. 1000-300 yr cal BP). A significant age gap in coastal aggradation is present between ca. 5300 and 4400 yr BP (ca. 5600-4500 yr cal BP), and perhaps between ca 2000 and 1300 yr BP (ca. 1700-1000 yr cal BP). These can be linked to phases of local sea level fall and/or phases of sedimentary starvation and/or changes in drift transport which can have produced local coastal cannibalization. However, no conclusive data can be advanced. Data obtained from careful measurements of sea level markers represented by the top of marsh and fluvial terraces indicate lower values for the sea level estimation compared with the data set previously proposed for the area. This stigmatizes the fact that field-oriented works are still the priority in the Patagonia coast along with accurate age measurement, especially for obtaining the fundamental information we need for predicting the environmental impact, in these coastal areas, from accelerate sea level rise as effect of global warming.
KEY WORD: Relative sea level, sea level markers, Patagonia, Holocene

Fault array evolution in extensional basins: insights from statistical analysis of gravel deposits in the Cecina River (Tuscany, Italy)

by Ilaria Consoloni

ANDREA CIAMPALINI, ILARIA CONSOLONI, GIOVANNI SARTI. Sedimentolgy, 58, 1895-1913

Two statistical analyses of gravel clasts from the Lower Pleistocene deposits in the Lower Cecina Valley (Tuscany,... more Two statistical analyses of gravel clasts from the Lower Pleistocene deposits in the Lower Cecina Valley (Tuscany, Italy) have been combined to unravel changes in the palaeo-drainage system. Data from 16 outcrops were collected and 6400 clasts described. Facies analysis, micro-palaeontology and macro-palaeontology and petrographic characteristics of the gravel deposits have highlighted the presence of three allostratigraphic units. Clast lithology is the main discriminator among these units. Cluster and principal component analyses of the 6400 clasts have improved understanding of the stratigraphy of the Lower Pleistocene deposits and constrain the re-routing of the lower palaeo-Cecina River from a supposedly south-east to north-west direction to the present east to west direction. Short rivers feeding small fan deltas represented by the oldest allostratigraphic units were abandoned in the Lower Pleistocene, when the re-routing of the Cecina River caused the capture of these streams. This evolution suggests a change in the tectonic regime of the area. The fan deltas developed on the hanging wall of normal faults sub-parallel to the coast; a change to a transtensile tectonic regime caused the deviation of the main river channel toward the present coast and the formation of a pull-apart basin, which is now exploited by the Cecina River. This study illustrates the value of lithological analyses of gravel deposits for understanding the tectonic evolution of an area.

Optically stimulated luminescence (OSL) dating of sand-filled wedge structures and their alluvial host sediment from Jonzac, Southwest France

by Kathryn Fitzsimmons

Guhl, A., Bertran, P., Zielhofer, C., Fitzsimmons, K.E. (in press) Optically stimulated luminescence (OSL) dating of sand-filled wedge structures and their alluvial host sediment from Jonzac, Southwest France. Boreas.

Two sand wedge structures and their host sediments, from Jonzac in Southwest France, were successfully dated using... more Two sand wedge structures and their host sediments, from Jonzac in Southwest France, were successfully dated using optically stimulated luminescence (OSL) measurements on both small aliquots and single grains of quartz from the 180-212 µm size fraction. One of both the sand wedges clearly contains primary infilling. However, grain-size analysis and field observations do not clearly indicate if the other feature represents a primary sand wedge or a composite sand wedge with primary and secondary infilling. OSL results and the geological setting justify using the Central Age Model (CAM) for the calculation of age estimates. Grain-size analysis and detailed investigations of OSL results revealed contamination of one sand wedge sample with host sediment. However, age calculation using the Finite Mixture Model (FMM) provided what is considered the most reliable age estimate for the contaminated sample. The age estimates for all samples correspond to Marine Isotope Stage (MIS) 3. While fine-grained sediments were deposited in the middle of MIS 3 (~43-55 ka), the sand wedges unexpectedly correspond to the end of this period (~33 ka) or the onset of MIS 2 (~27 ka). The sand wedges are most likely to have formed during a relatively short period of comparatively cold conditions, and may correlate to a Heinrich event. Resolution limits of OSL age estimates and differing statements regarding the ages of Heinrich events within this time period prevent an unequivocal correlation of the sand wedge ages to Heinrich events, but the most likely association is with events H2 and H3. The results help to assess the capability of luminescence dating on sand wedges and contribute to the debate on timing of cryogenic formation processes and the permafrost distribution in Southwest France.

I DEPOSITI DEL PLEISTOCENE INFERIORE DELLA BASSA VAL DI CECINA (TOSCANA, ITALIA): RICOSTRUZIONE STRATIGRAFICO–DEPOSIZIONALE E PROPOSTA DI SUDDIVISIONE IN UNITA’ ALLOSTRATIGRAFICHE

by Ilaria Consoloni

Giovanni Sarti, Andrea Ciampalini, Ilaria Consoloni & Andrea Cerrina Feroni. Il Quaternario, 20, 151-162

ABSTRACT: G. Sarti et.al., Stratigraphic and depositional reconstruction of the Lower Pleistocene deposits from lower... more ABSTRACT: G. Sarti et.al., Stratigraphic and depositional reconstruction of the Lower Pleistocene deposits from lower Val di Cecina (Tuscany, Italy): a proposal of subdivision in Allostratigraphic Units. (IT ISSN 0394-3356, 2007).
In the area comprised between the villages of Riparbella and Casale Marittimo (lower Cecina Valley, Tuscany, Italy) a large amount of Pleistocene deposits outcrops. Through a detailed geological survey integrated with facies analysis five litostratigraphic units, grouped in three Allostratigraphic Units (UA), have been detected. The oldest (UA7), lower pleistocenic in age, is formed by two litostratigraphic units (“Conglomerati delle Ginepraie” and “Sabbie ed argille ad Arctica islandica”) showing latero-vertical relationships and are organized
in a transgressive-regressive cycle. The “Conglomerati delle Ginepraie” are arranged in a fining upwards trend and were deposited in small coalescent deltaic environments. Three depositional facies are recognized within the “Sabbie ed argille ad Arctica islandica” recording a fining-coarsening and deepening shallowing upward trend. The UA7 lies in unconformity above pre-quaternary deposits.
The second (UA6), lower pleistocenic in age, is also constituted by two heteropic and transgressive litostratigraphic units
(“Conglomerati delle Lame” and “Arenarie e Sabbie di Montescudaio”) lying in angular unconformity on the UA7. The “Conglomerati delle Lame”, showing a well developed imbrication, were deposited in a foreshore to upper shoreface depositional environment. The “Arenarie e Sabbie di Montescudaio” are characterized by a high to low planar-cross stratification and sometimes by overturned stratification
and were deposited in a shallow marine environment. The regressive phase of this UA is not preserved due to erosive processes. The youngest unit (UA4, “Conglomerati di Serra all’Olio”), was instead deposited in fluvial-braided environment and lies in angular unconformity on the others UA. The middle pleistocenic age of this unit has been inferred on the basis of its stratigraphic position. This stratigraphic reconstruction strongly conflict from previous interpretations. Important climatic and geological remarks derive from the finding of two taxa (Arctica islandica and the coral Cladocora caespitosa) at different stratigraphic positions within the oldest unit (“Sabbie ed argille ad Arctica islandica”). The Arctica islandica testifying cold temperatures (4°C to 13°C) characterizes the first 5
meters of the unit, while beds of Cladocora caespitosa (15°C to 22°C the temperature range of this coral) only occur upwards. We
retain that the deposition of the “Sabbie ed argille ad Arctica islandica” takes place during a warming phase and that the development of Cladocora caespitosa beds could be related to the maximum flooding conditions at the end of the transgressive phase. This interpretation leads to some notable chronostratigraphic implications.

GEOCHEMICAL AND PETROGRAPHICAL ANALYSES FOR SELECTING QUATERNARY MARINE SHELLS FOR RADIOMETRIC DATING AND PALEOCLIMATE RECONSTRUCTIONS: EXAMPLES FROM PATAGONIA

by Ilaria Consoloni

Ilaria Consoloni, Giovanni Zanchetta, Marina L. Aguirre, Ilaria Baneschi, Monica Bini, Gabriella M. Boretto, Luigi Dallai, Massimo D’Orazio, Anthony E. Fallick, Massimo Guidi, John C. Hellstrom, Ilaria Isola, Enrique Fucks, Francesco Mazzarini, Marta Pappalardo & Adriano Ribolini. Il Quaternario 24, 208-210.

ABSTRACT: Consoloni I. et al., Geochemical and petrographical analyses for selecting Quaternary marine shells for more ABSTRACT: Consoloni I. et al., Geochemical and petrographical analyses for selecting Quaternary marine shells for
radiometric dating and paleoclimate reconstructions: examples from Patagonia. (IT ISSN 0394-3356, 2011)
The selection of suitable samples is a fundamental target in order to obtain reliable results in the field of radiometric
dating and paleoclimate. Marine molluscs are particularly interesting in this respect in what different radiometric
methods (e.g. U/Th, ESR) can be applied coupled with chemical analyses to reconstruct past environment. For this kind
of material is imperative that the samples have not undergone any alteration. We present, as example, the study of
marine molluscs from Quaternary beach ridges from the Atlantic Patagonian coast. Multiproxy analyses show that the
degree of weathering is quite variable but not enough for undermining the paleoclimatic values of the stable isotopes
content and of some trace element, but enough severe to make problematic the application of U/Th dating methods.
However, the careful petrographic observation and trace element analyses can support the selection of suitable
samples for U/Th dating.

Nanodiamonds and wildfire evidence in the Usselo horizon postdate the Allerød-Younger Dryas boundary

by Annelies van Hoesel

Co-authored with: Wim Z. Hoek, Freek Braadbaart, Johannes van der Plicht, Gillian M. Pennock and Martyn Drury

The controversial Younger Dryas impact hypothesis suggests that at the onset of the Younger Dryas an extraterrestrial... more The controversial Younger Dryas impact hypothesis suggests that at the onset of the Younger Dryas an extraterrestrial impact over North America caused a global catastrophe. The main evidence for this impact—after the other markers proved to be neither reproducible nor consistent with an impact—is the alleged occurrence of several nanodiamond polymorphs, including the proposed presence of lonsdaleite, a shock polymorph of diamond. We examined the Usselo soil horizon at Geldrop-Aalsterhut (The Netherlands), which formed during the Allerød/Early Younger Dryas and would have captured such impact material. Our accelerator mass spectrometry radiocarbon dates of 14 individual charcoal particles are internally consistent and show that wildfires occurred well after the proposed impact. In addition we present evidence for the occurrence of cubic diamond in glass-like carbon. No lonsdaleite was found. The relation of the cubic nanodiamonds to glass-like carbon, which is produced during wildfires, suggests that these nanodiamonds might have formed after, rather than at the onset of, the Younger Dryas. Our analysis thus provides no support for the Younger Dryas impact hypothesis.

Pleistocene environmental dynamics recorded in the loess of the middle and lower Danube basin

by Kathryn Fitzsimmons

Fitzsimmons, KE, Markovic S, Hambach, U. (2012) Pleistocene environmental dynamics recorded in the loess of the middle and lower Danube basin. Quaternary Science Reviews 41, 104-118. DOI: 10.1016/j.quascirev.2012.03.002.

The substantial loess deposits of the middle and lower Danube basin in southeastern Europe represent one of the... more The substantial loess deposits of the middle and lower Danube basin in southeastern Europe represent one of the thickest and most comprehensive terrestrial palaeoenvironmental records on the continent, yet are also the least well understood. Environmental conditions over the last million years have resulted in relatively continuous deposits uninterrupted by glaciation and tundra conditions, which nevertheless reflect oscillations between relatively warm-humid (“interglacial”) and cold-dry (“glacial”) intervals. This relative environmental stability may have proven important for hominins migrating into and through the region.
The loess stratigraphy comprises distinct loess-paleosol sequences, reflecting glacial-interglacial phases which can be quantified for intensity using environmental magnetism and geochemistry. These phases are emphasised by variations in vegetation and malacofauna which respond to climatic change. The loess deposits demonstrate broadly similar sedimentological characteristics across the basin.
Danubian loess deposits initiated in response to the tectonic formation of the Pannonian basin, retreat of the large palaeolakes, and increased sediment supply from the Danube. The period from ~1 Ma – 500 ka (MIS 27-13) was characterised by alternating loess deposition and pedogenesis during glacial and interglacial periods respectively, in response to relatively humid, forested conditions. This period represents the opening of the Danube corridor and provides the backdrop for initial hominin arrival into Europe. After ~500 ka, and particularly after MIS 9, loess accumulation rates increased in response to relatively more steppic, arid, environments. MIS 9 and 13-15 were the most humid phases of the last ~600 ky. The MIS 5 interglacial period was the warmest, and relatively most humid, period preceding the Holocene, and was followed by substantially increased loess accumulation during MIS 4, which may be linked to North Atlantic circulation. The complexity of the MIS 3 interstadial paleosol suggests that conditions were not uniformly warm and wet during this time. MIS 3 corresponds with the first arrival of anatomically modern humans to Europe. The last glacial maximum and Younger Dryas of MIS 2 were characterised by substantially increased loess accumulation indicating cold steppe environments most likely influenced by the North Atlantic, although conditions were sufficiently mild that the region acted as a refugium for thermophilic biota, as may also have been the case for most of the Pleistocene glacial cycles. The Holocene soil represents relatively wamer and more humid conditions corresponding to the current interglacial.

Aridity in the monsoon zone as indicated by desert dune formation in the Gregory Lakes basin, northwestern Australia

by Kathryn Fitzsimmons

Fitzsimmons, K.E., Miller, G.H., Spooner, N.A., Magee, J.W. (2012, in press) Aridity in the monsoon zone as indicated by desert dune formation in the Gregory Lakes basin, northwestern Australia. Australian Journal of Earth Sciences.

Desert dunes within the monsoon-fed Gregory Lakes basin form valuable archives for Quaternary paleoenvironments, in a... more Desert dunes within the monsoon-fed Gregory Lakes basin form valuable archives for Quaternary paleoenvironments, in a region where such records are scarce. Optically stimulated luminescence (OSL) chronologies from two dunes identify the timing of aeolian processes, interpreted as a complex response to aridification and increased sediment availability during lake transgressions and associated fluvial activity. The earliest aeolian deposition in our record occurred ca 91.5 ka, which postdates the last “mega-lake” phase but predates a smaller lake transgression during early MIS 3. Sand plain accretion took place around ca 47 ka during contemporaneous periodic high lake levels. This was followed by intermittent linear dune building, between ca 35 and 11.5 ka, which most likely took place during an interval of relative aridity. Close spacing of mid-Holocene ages within one dune indicates rapid sediment accumulation in a single arid event ca 5 ka. At no time in the last 50 ka have lake levels reached those of the last "mega-lake” phase prior to ca 91.5 ka, suggesting a substantially weakened present-day monsoon.

The Paks loess-paleosol sequence: A record of chemical weathering and provenance for the last 800 ka in the mid-Carpathian Basin

by János Kovács

Újvári et al.  published in 'Quaternary International'

The Paks loess-paleosol sequence is one of the most important terrestrial records of Middle and Late Pleistocene... more The Paks loess-paleosol sequence is one of the most important terrestrial records of Middle and Late Pleistocene environmental changes in East Central Europe, spanning the last ca. 0.8 Ma. While geochemical proxies demonstrate a general decreasing chemical weathering trend over the last 0.8 Ma in the Carpathian Basin, mineralogy and derived indices reflect intensifying physical erosion. In theory, the observed chemical weathering trend can be accounted for both by enhanced input of relatively unweathered material and by climate deterioration during the Quaternary, as the proxies such as CIA are not capable of distinguishing between pre- and post-depositional weathering. Enhanced physical erosion of the source areas, driven by tectonism, and resulting increased sedimentation of fresh mineral dust at the depositional site are demonstrated by increasing dolomite, illite and chlorite contents and sme/ill, sme/(ill+chl) ratios from older to younger sediments in the profile, together with increasing thickness of loess layers towards the youngest part of the sequence. At the same time, constant smectite contents (30-40%) in paleosols appear to disprove progressive aridization of interglacials through time and suggest that the duration of pedogenesis played an important role in determining soil types. Further, the increasing proportion of inherited phyllosilicates (illite and chlorite) would, in theory, raise the possibility that the decreasing values of chemical weathering indices are just artifacts of enhanced physical erosion and resulting increased dust deposition by a dilution effect. The above findings highlight the fact that the general view on chemical weathering is oversimplistic, as its ’equation’ includes two basic variables, tectonism and time beyond climate and the interplay of these equally important factors will eventually determine its final value. To get a better grasp of these processes needs further data (more age control in loess profiles, data on uplift in and around sedimentary basins) and more sophisticated proxies, as the mineralogical data presented here can be considered only semi-quantitative.

Regarding the provenance of sediments in the Paks profile, geochemical data demonstrate that felsic rocks dominated the source areas and there have been only very little variations in provenance over the last ca. 0.8 Ma. Significant contributions from mafic/ultramafic rocks to the sediments can be ruled out as revealed by lower abundances of ferromagnesian trace elements. The appearance of amphiboles and high dolomite contents suggest that loess material was at least partly sourced from local rocks and geochemical data reveal a genetic link between floodplain sediments and loess deposits.

Reconstructing the paleoenvironment of East Central Europe in the Late Pleistocene using the oxygen and carbon isotopic signal of tooth in large mammal remains

by János Kovács

Kovács et al. published in 'Quaternary International'

Stable carbon and oxygen isotope values (δ13C, δ18O) of structural carbonate were determined in the bioapatite... more Stable carbon and oxygen isotope values (δ13C, δ18O) of structural carbonate were determined in the bioapatite component of fossil teeth from the Czech Republic, Slovakia and Hungary. Oxygen isotope compositions of enamel and dentin samples provide new quantitative records of the Late Pleistocene climate in East Central Europe (ECE). These δ18O data were combined with records of oxygen isotope values of recent and paleogroundwaters to study the spatial patterns and temporal variations in the oxygen isotope composition of precipitation and the thermal climate over ECE. The new isotopic data suggest that surface air temperatures in the study region between 33 and 12 ka were 2–9°C colder than present. Specimens of woolly mammoth, rhino and horse from the Late Pleistocene were primarily C3 grazers.

Depozitele cuaternare din Dobrogea (cu privire speciala asupra argilelor rosii)

by Peuce Journal

Cotet V. in Peuce 5, 1978

The Pleistocene of Schöningen, Germany: a complex tunnel valley fill revealed from 3D subsurface modelling and shear wave seismics

by Jörg Lang

Lang, J., Winsemann, J. Steinmetz, D., Polom, U., Pollok, L., Böhner, U., Serangeli, J., Brandes, C., Hampel, A. & Winghart, S. (2012) Quaternary Science Reviews, 39, 86-105.

The Pleistocene deposits of Schöningen represent an outstanding geological and archaeological archive, where an up to... more The Pleistocene deposits of Schöningen represent an outstanding geological and archaeological archive, where an up to 45 m thick Middle to Late Pleistocene succession has been preserved and unique artefacts from the Lower Palaeolithic have been discovered. The preservation of such a thick and complete glacial/interglacial succession is very rare in the geological record and requires a specific depositional setting. We will present a new depositional model for the Pleistocene succession of Schöningen, integrating outcrop data, borehole data and high-resolution shear wave seismics. A total of four outcrop sections and 744 borehole logs were examined to document the complex facies architecture. All collected sedimen-tological and geophysical data sets were integrated into a high-resolution 3D geological model (GOCAD®) for reconstructing the spatial distribution of facies associations and the large-scale depositional architecture. The spatial distribution of the artefacts will be discussed with respect to the depositional environment.
The Elsterian and Holsteinian deposits are restricted to a NNW-SSE trending, elongated trough, which is deeply incised into unconsolidated lignite-bearing Palaeogene deposits. The geometry of this erosional structure points to a tunnel valley origin that was incised below the Elsterian ice sheet. The basal tunnel valley fill consists of cross-stratified pebbly sand and gravel overlain by till. After deglaciation the tunnel valley remained underfilled and acted as a depocentre for interglacial deposition. During the subsequent Holsteinian interglacial (MIS 9) a lake formed within this depocentre and lacustrine sediments accumulated. This interglacial succession consists of peat, organic-rich silt and fine-grained sand interpreted as lake-bottom and deltaic sediments fed by surface run-off shed from the Elm ridge. The lacustrine deposition was controlled by repeated lake-level fluctuations in the range of 1 to 6 metres leading to the formation of laterally stacked delta systems. These lake-level changes were probably triggered by climate, causing variations of precipitation and surface run-off. During the late Saalian glaciation the remnant tunnel valley was completely filled with meltwater deposits. The sedimentary facies and depositional architecture point to a shallow-water delta. Subsequently the meltwater deposits were overlain by till.
The deposition of the Middle Pleistocene sediments within an Elsterian tunnel valley explains the unique preservation of the sedimentary succession of Schöningen. The long-lived inter-glacial lake provided an attractive site for animals and early humans ambushing them. Arte-facts mainly became embedded on the delta plain, which rapidly was transgressed during lake-level rise and artefacts were thus preserved.

Marine and Terrestrial Biomarker Records for the Last 35,000 Years at ODP Site 658C Off NW Africa

by Simon Haslett

Last Glacial mammals in South America: a new scenario from the Tarija Basin (Bolivia)

by Lorenzo Rook

The chronology, sedimentary history, and paleoecology of the Tarija Basin (Bolivia), one of the richest Pleistocene... more The chronology, sedimentary history, and paleoecology of the Tarija Basin (Bolivia), one of the richest Pleistocene mammalian sites in South America, are revised here based on a multidisciplinary study, including stratigraphy, sedimentology, geomorphology, paleontology, isotope geochemistry, and 14C geochronology. Previous studies have indicated a Middle Pleistocene age for this classic locality. We have been able to obtain a series of 14C dates encompassing all the fossil-bearing sequences previously studied in the Tarija Basin. The dated layers range in age from about 44,000 to 21,000 radiocarbon years before present (BP), indicating that the Tarija fauna is much younger than previously thought. Glacial advances correlated to marine isotopic stages (MIS) 4 and 2 (ca. 62 and 20
ka BP, respectively) are also documented at the base and at the very top of the Tarija–Padcaya succession, respectively, indicating that the Bolivian Altiplano was not dry but sustained an ice cap during the Last Glacial Maximum. The results of this multidisciplinary study enable us to redefine the chronological limits of the Tarija sequence and of its faunal assemblage and to shift this paleontological, paleoclimatological, and paleoecological framework to the time interval from MIS 4 to MIS 2.

Late Pleistocene survival of the saber-toothed cat Homotherium in Northwestern Europe

by Lorenzo Rook

Saber-toothed cats (Machairodontinae) were wide-spread, top predators of the Pleistocene terrestrial ecosystem. In... more Saber-toothed cats (Machairodontinae) were wide-spread, top predators of the Pleistocene terrestrial ecosystem. In Europe, they previously were known only from the early and middle
Pleistocene, and their fossils are always extremely rare. The previous youngest record was from Steinheim a/d Murr, Germany, where an upper canine of Homotherium was found in a stratum dated to ca. 0.3 Ma. In this paper, we describe a well-preserved dentary of Homotherium latidens dated by 14C to be late Pleistocene, ca. 28,000 yrBP.

Hypothesis on the cause of extinction of the South American mastodonts

by Lorenzo Rook

Paleontological, geomorphological and sedimentological investigations on the Cangahua Formation in the Interandean... more Paleontological, geomorphological and sedimentological investigations on the Cangahua Formation in the Interandean depression of Northern and Central Ecuador have provided information on the evolution of the Andean paleoenvironment during the Late Pleistocene. Pyroclastic and windblown sediments were deposited during cold and dry phases of the last glaciation, interrupted many times by the development of forest-steppe and steppe paleosoils during interstadials. An erosional phase which closed the Cangahua sedimentation was followed by the deposition of colluvial sediments, characterized by a high number of minor pedogenetic episodes. The colluviums are confidently referable to the Holocene. The upper part of the Cangahua Formation is rich in mammal fossils and is probably referable to the Last Glacial Maximum.

The fossiliferous sequences suggest that mastodonts disappeared before mylodonts and equids. We hypothesize that the increased cold and aridity of the Last Glacial Maximum, which deeply affected the Cordillera, caused the extinction of most of the megafauna and the mastodonts seem to have been the most sensitive to the environmental degradation.

The final history of South American mastodonts, represented by Haplomastodon and Stegomastodon, spans the latest Pleistocene and probably the earliest Holocene. Haplomastodon was dispersed in the highlands within the tropical belt and Stegomastodon in plains of the southernmost part of Brazil, in Paraguay, Uraguay, Argentine, central and northern Chile.

Both Haplomastodon and Stegomastodon suffered the same negative effects of the Last Glacial Maximum when their habitats underwent intense desertifications under dry and cold conditions. They disappeared in a mosaic way in the course of the latest Pleistocene, the last representatives probably surviving in favorable restricted areas where however the considerably increased selective pressure was in the long run devastating. In our opinion the human impact was not a determinant in causing mastodont extinction.

Pleistocene subglacial tunnel valleys in the central North Sea basin: 3D morphology and evolution.

by Susannah Maidment