Age determination and color reflectance of ODP Hole 165-1002D

Attempts to place Palaeolithic finds within a precise climatic framework are complicated by both uncertainty over the radiocarbon calibration beyond about 21,500 14C years bp (Reimer et al., 2004) and the absence of a master calendar chronology for climate events from reference archives such as Greenland ice cores or speleothems (Svensson et al., 2006, doi:10.1016/j.quascirev.2006.08.003). Here we present an alternative approach, in which 14C dates of interest are mapped directly onto the palaeoclimate record of the Cariaco Basin by means of its 14C series (Hughen et al., 2004, doi:10.1126/science.1090300), circumventing calendar age model and correlation uncertainties, and placing dated events in the millennial-scale climate context of the last glacial period. This is applied to different sets of dates from levels with Mousterian artefacts, presumably produced by late Neanderthals, from Gorham's Cave in Gibraltar: first, generally accepted estimates of about 32,000 14C years bp for the uppermost Mousterian levels (Pettitt and Bailey, 2000; Bronk Ramsey et al., 2002, doi:10.1111/1475-4754.00040); second, a possible extended Middle Palaeolithic occupation until about 28,000 14C years bp (Finlayson et al., 2006, doi:10.1038/nature05195); and third, more contentious evidence for persistence until about 24,000 14C years bp (Finlayson et al., 2006, doi:10.1038/nature05195). This study shows that the three sets translate to different scenarios on the role of climate in Neanderthal extinction. The first two correspond to intervals of general climatic instability between stadials and interstadials that characterized most of the Middle Pleniglacial and are not coeval with Heinrich Events. In contrast, if accepted, the youngest date indicates that late Neanderthals may have persisted up to the onset of a major environmental shift, which included an expansion in global ice volume and an increased latitudinal temperature gradient. More generally, our radiocarbon climatostratigraphic approach can be applied to any 'snapshot' date from discontinuous records in a variety of deposits and can become a powerful tool in evaluating the climatic signature of critical intervals in Late Pleistocene human evolution.

Planktonic foraminiferal biostratigraphy and stable carbon isotope ratios of late middle Eocene sediments from Blake Plateau, West Atlantic Ocean

The muricate planktonic foraminiferal genera Morozovella and Acarinina were abundant and diverse during the upper Palaeocene to middle Eocene and dominated the tropical and subtropical assemblages. A significant biotic turnover in planktonic foraminifera occurred in the latest middle Eocene with a notable reduction in the acarininid lineage and the extinction of the morozovellids. These genera are extensively employed as palaeoclimatic and biostratigraphic markers and, therefore, this turnover episode is an important event in the record of the Cenozoic planktonic foraminifera. Sediments from the western North Atlantic (Ocean Drilling Program Site 1052) were examined in order to investigate these extinction events, in terms of both timing and mechanisms. Biostratigraphic events of the middle and late Eocene have been examined with a sampling resoluti on of approximately 3 kyr. These have been calibrated to the magneto- and astrochronology to accurately define the timing of key biostratigraphic events, particularly the extinction of Morozovella spinulosa which is a distinct biomarker for late middle Eocene sediments. High-resolution biostratigraphy reveals that the extinctions in the muricate group occurred in a stepwise form. The large acarininids (Acarinina praetopilensis) terminate 10 kyr prior to the extinction of M. spinulosa and small acarininids (Acarinina medizzai and Acarinina echinata) continue into the upper Eocene. High-resolution stable isotope analyses have been conducted on planktonic and benthic foraminifera from the western North Atlantic to reconstruct sea surface temperatures (SSTs) and deep water temperatures and the structure of the water column around this major biotic turnover. Whilst the extinctions of M. spinulosa and A. praetopilensis occur during a long-term cooling trend, the biotic turnover in the muricate group does not appear to be related to significant climatic change. Sea surface temperatures decrease slowly prior to the extinction events, and there is no evidence for a large-temperature shift associated with the faunal changes. The turnover event was therefore probably related to the increased surface water productivity and the deterioration of photosymbiotic partnerships with algae.

Early and Middle Miocene calcareous nannofossil distribution in the North Atlantic Ocean

Deep Sea Drilling Project Site 563, located on the west flank of the northern Mid-Atlantic Ridge, recovered a long Miocene section from which magnetostratigraphic and isotopic stratigraphy are available. Quantitative analyses of calcareous nannofossil assemblages have been performed in the Lower and Middle Miocene sediments from Site 563. The abundance patterns of the identified species allow us to determine several bioevents for this time interval. The recognized biohorizons, related to the available magnetostratigraphy, provide new data on the biostratigraphic value of many species and on the synchroneity of the events over a wide geographic area. Relations with the oxygen isotope stratigraphy are also reported. Sphenolith distribution is examined in particular detail due to their biostratigraphic importance in the Early Miocene. In particular the recently described species Sphenolithus procerus, Sphenolithus tintinnabulum and Sphenolithus multispinatus can be useful to subdivide the Lower Miocene zones NN2 and NN3. A large variety of Reticulofenestra pseudoumbilicus has been identified within zones NN6 and NN7.

Sedimentological, physical, bulk geochemical, elemental and rock magnetic properties of the Middle to Late Pleistocene Rodderberg (Eifel/Germany)

The sediment record from Rodderberg potentially provides a climate and environmental record spanning at least the last ca 130 ka. Results from a low resolution pilot study reveal characteristic fluctuations that can be related to global climate variability as reflected in marine isotope stages and document the potential of this site for continuous and high-resolution investigations of the Middle to Late Pleistocene. Here we document the tentative lithology drilled, and show how the elemental composition can be interpreted with regard to lake level fluctuations, related redox conditions, but also to grain-size distribution and changes in lacustrine productivity. Finally, based on major lithological changes, a preliminary depth/age model is suggested that allows reassessing published luminescence ages from the same site.

Siliceous microfossils in middle Eocene sediments of ODP Holes 120-748B and 120-749B

The Middle Eocene Climatic Optimum (MECO) is a major transient warming event that occurred at ~ 40 Ma and reversed a long-term cooling trend through the early and middle Eocene. We report the results of a high-resolution, quantitative study of siliceous microfossils at Ocean Drilling Program Sites 748 and 749 (Southern Kerguelen Plateau, Southern Ocean, ~ 58°S) across a ~ 1.4 myr interval spanning the MECO event. At both sites, a significant increase in biosiliceous sedimentation is associated with the MECO event. Rich siliceous planktonic microfossil assemblages in this interval are unusual in that they are dominated by ebridians, with radiolarians as a secondary major component. Silicoflagellates and diatoms comprise only a minor fraction of the assemblage, in contrast to siliceous microfossil assemblages that characterize modern Southern Ocean sediments. Based on our new siliceous microfossil records, we interpret two ~ 300 kyr periods of elevated nutrient availability in Southern Ocean surface waters which span the peak warming interval of the MECO and the post-MECO cooling interval. A diverse assemblage of large silicoflagellates belonging to the Dictyocha grandis plexus is linked to the rapid rise in sea-surface temperatures immediately prior to peak warmth, and a pronounced turnover is observed in both ebridian and silicoflagellate assemblages at the onset of peak warming. The interval of peak warmth is also characterized by high abundance of cosmopolitan ebridians (e.g., Ammodochium spp.) and silicoflagellates (e.g., Naviculopsis spp.), and increased abundance of tropical and subtropical diatom genera (e.g., Asterolampra and Azpeitia). These observations confirm the relative pattern of temperature change interpreted from geochemical proxy data at multiple Southern Ocean sites. Furthermore, rapid assemblage changes in both autotrophic and heterotrophic siliceous microfossil groups indicate a reorganization of Southern Ocean plankton communities in response to greenhouse warming during the MECO event.

Description of sampling sites in Northern Russia

The youngest ice marginal zone between the White Sea and the Ural mountains is the W-E trending belt of moraines called the Varsh-Indiga-Markhida-Harbei-Halmer-Sopkay, here called the Markhida line. Glacial elements show that it was deposited by the Kara Ice Sheet, and in the west, by the Barents Ice Sheet. The Markhida moraine overlies Eemian marine sediments, and is therefore of Weichselian age. Distal to the moraine are Eemian marine sediments and three Palaeolithic sites with many C-14 dates in the range 16-37 ka not covered by till, proving that it represents the maximum ice sheet extension during the Weichselian. The Late Weichselian ice limit of M. G. Grosswald is about 400 km (near the Urals more than 700 km) too far south. Shorelines of ice dammed Lake Komi, probably dammed by the ice sheet ending at the Markhida line, predate 37 ka. We conclude that the Markhida line is of Middle/Early Weichselian age, implying that no ice sheet reached this part of Northern Russia during the Late Weichselian. This age is supported by a series of C-14 and OSL dates inside the Markhida line all of >45 ka. Two moraine loops protrude south of the Markhida line; the Laya-Adzva and Rogavaya moraines. These moraines are covered by Lake Komi sediments, and many C-14 dates on mammoth bones inside the moraines are 26-37 ka. The morphology indicates that the moraines are of Weichselian age, but a Saalian age cannot be excluded. No post-glacial emerged marine shorelines are found along the Barents Sea coast north of the Markhida line.

Abb. 2 Pollen stratigraphy of the Miocene in Middle Europe

Anknüpfend an die von V. D. RRELIE (1961) erläuterte pollenanalytische Gliederung für das Miozän der Niederrheinischen Bucht soll untersucht werden, inwieweit diese auch für die angrenzenden Gebiete allgemeingültig ist oder noch vervollkommnet werden kann. Damit werden die Möglichkeiten einer weitergehenden Gliederung des Miocäns für den gesamten mitteleuropäischen Raum einschließlich der Nordsee-Umrandung zur Darstellung gebracht.

The Fohsella chronocline in middle Miocene sediments from the Ontong Java Plateau, Pacific Ocean

Micropaleontologists have traditionally recognized the mid-Miocene Fohsella lineage as a flagship for phyletic gradualism within the planktic foraminifera. However, study of a deep-sea record from the western equatorial Pacific (ODP Site 806) reveals that coiling ratios within this clade suddenly (<5 kyr) shift after a prolonged, ancestral state of near randomness (~50%) to a transient phase (13.42-13.43 Ma) of dextral dominance (~75%) immediately following the first common occurrence of keeled fohsellids. This brief period of dextral dominance was abruptly (<5 kyr) succeeded by an irreversible change to sinistral dominance (~96%). Fohsellid abundances decline markedly through the interval in which the sinistral preference is established. The shift to sinistrality (13.42 Ma) predated the deepening of fohsellid depth ecology by ~240-488 kyr, indicating that these two events were unrelated. This view is supported by a lack of delta 18O evidence for depth-habitat differences between the two chiral forms, which refutes the notion that sinistral fohsellids were "pre-adapted" for ensuing hydrographic change because they occupied a deeper depth habitat than their dextral counterparts. Planktic foraminiferal assemblages become strongly oligotrophic in character through the interval in which the fohsellid delta 18O increase is recorded, indicating that the migration to deeper depths was fostered by an expansion of the mixed layer in the western equatorial Pacific. Salient aspects of this brief, but conspicuous faunal change are a marked increase in the abundance of symbiont-bearing globigerinoidids, a concomitant collapse of local Jenkinsella mayeri/siakensis populations, and reduced fohsellid abundances. The rapid and permanent nature of the Fohsella sinistral shift provides a distinct, unequivocal datum that may prove useful for correlating mid-Miocene sections throughout the Caribbean Sea and tropical regions in the western sectors of the Pacific and Atlantic. The coiling ratio changes that occurred during the evolution of the Fohsella chronocline probably reflect changing population dynamics between cryptic genotypes with different coiling preferences.

A Middle Pleistocene nannofossil record of sediment core MD03-2699

Changes in paleoclimate and paleoproductivity patterns have been identified by analysing, in conjunction with other available proxy data, the coccolithophore assemblages from core MD03-2699, located in the Portuguese margin in the time interval from the Marine Isotope Stage (MIS) 13/14 boundary to MIS 9 (535 to 300 ka). During the Mid-Brunhes event, the assemblages associated with the eccentricity minima are characterised by higher nannoplankton accumulation rate (NAR) values and by the blooming of the opportunistic genus Gephyrocapsa. Changes in coccolithophore abundance are also related to glacial-interglacial cycles. Higher NAR and numbers of coccoliths/g mainly occurred during the interglacial periods, while these values decreased during the glacial periods. Superimposed on the glacial/interglacial cycles, climatic and paleoceanographic variability has been observed on precessional timescales. The structure of the assemblages highlights the prevailing long-term influence of the Portugal (PC) and Iberian Poleward (IPC) Currents, following half and full precession harmonics, related to the migration of the Azores High (AH) Pressure System. Small Gephyrocapsa and Coccolithus pelagicus braarudii are regarded as good indicators for periods of prevailing PC influence. Gephyrocapsa caribbeanica, Syracosphaera spp., Rhabdosphaera spp. and Umbilicosphaera sibogae denote periods of IPC influence. Our data also highlights the increased percentages of Coccolithus pelagicus pelagicus during the occurrence of episodes of very cold and low salinity surface water, probably related to abrupt climatic events and millennial-scale oscillations of the AH/Icelandic Low (IL) System.

Calcareous nannofossil bioevents of early-middle Pleistocene sediments from the Mediterranean Sea and the Noth Atlantic

Quantitative distributions of calcareous nannofossils are analysed in the early-middle Pleistocene at the small Gephyrocapsa and Pseudoemiliania lacunosa zone transition in deep-sea cores from the Mediterranean Sea and North Atlantic Ocean (Ocean Drilling Program [ODP] Sites 977, 964 and 967, Deep Sea Drilling Project [DSDP] Site 607). The temporal and spatial mode of occurrence of medium-sized gephyrocapsids and reticulofenestrids has been examined to refine biostratigraphic constraints and evaluate possible relationships of stratigraphic patterns to environmental changes during a period of global climatic deterioration. The timing of bioevents has been calibrated using high-resolution sampling and correlation to the delta18O record in chronologically well-constrained sections. Newly identified events and ecostratigraphical signals enhance the stratigraphic resolution at the early-middle Pleistocene. The first occurrence (FO) of intermediate morphotypes between Pseudoemiliania and Reticulofenestra (Reticulofenestra sp.) is proposed as a reliable event within marine isotope stage (MIS) 35 or at the MIS 35/34 transition. The distribution of Reticulofenestra asanoi is characterized by rare and scattered occurrences in its lowest range, but the first common occurrence (FCO) is consistently identified at MIS 32 or 32/31; the last common occurrence (LCO) of the species is a distinctive event at MIS 23. In the studied interval, Gephyrocapsa omega dominates among medium-sized Gephyrocapsa. The FO of G. omega and contemporaneous re-entry of medium-sized gephyrocapsids at the lower-middle Pleistocene transition are diachronous between the Atlantic Ocean and Mediterranean Sea and from the western to eastern Mediterranean. In the Mediterranean, the LO of G. omega falls at MIS 15, insolation cycle 54 and is isochronous among the sites. Abundance fluctuations of G. omega show notable relations to early-middle Pleistocene climate changes; they considerably increase in abundance at the interglacial stages, suggesting warm water preferences. Gephyrocapsa omega temporarily disappears during the glacial MIS 22 and MIS 20. Above MIS 20, an impoverishment in G. omega and in the total abundance of medium-sized gephyrocapsids occurs. A decrease in abundance of G. omega is observed between the western Site 977 and the easternmost Site 967 in the Mediterranean Sea, as a possible response to high salinity and/or low nutrient content. Possible environmental influences on the distribution of R. asanoi and of Reticulofenestra sp. are discussed.