Subcommission on Quaternary Stratigraphy
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Early-Middle Pleistocene transitions: the land-ocean evidence
Conference report
Martin J. HeadDepartment of Geography
University of Cambridge
A one-day international conference on the “Early-Middle Pleistocene transitions: the land-ocean evidence” was held in the Department of Geography, University of Cambridge on April 4, 2003. The scientific programme comprised nine invited talks and six posters. The meeting was sponsored by the Godwin Institute for Quaternary Research, INQUA Commission on Stratigraphy and INQUA Subcommission for European Quaternary Stratigraphy, The Quaternary Research Association, and the ICS Subcommission on Quaternary Stratigraphy. It was organised by Dr Martin J. Head and Dr Philip L. Gibbard. About 50 participants from England, France, Germany, Italy, Norway, Russia, and The Netherlands made this a truly international event.
The transition from Early to Middle Pleistocene is marked by fundamental changes in Earth’s climatic cyclicity. Orbital obliquity at 41 ka cycles which had dominated the earlier part of the Pleistocene was superceded progressively about a million years ago by a 100 ka rhythm of climate change and increased-amplitude climatic oscillations. This change has become known as the Mid-Pleistocene Revolution. The glacial–interglacial world in which we now live is the result of these changes, and the impact on terrestrial and marine biota has been profound and manifold. However, the timing and correlation of events during this transition has been problematic, leading to uncertainties over cause and effect. The purpose of this meeting was to explore the biotic responses to climatic and physical changes that characterized the Early–Middle Pleistocene transition in both the marine and terrestrial realms. In doing so we hoped to explore the very origins of our present biota.
The first talk, by Mark Maslin (UCL, London), addressed the Mid-Pleistocene Revolution from an Earth orbital perspective and questioned the assumption that eccentricity was responsible for 100 ka cyclicity in the Middle Pleistocene. Disabused of this notion, we were told that the more likely driving force was non-linear responses to orbital obliquity paced by every fouth or fifth precessional cycle. Precession is therefore the key to understanding 100 ka cyclicity in the Middle Pleistocene. And precession makes sense to some paleontologists who regard seasonality as a key to understanding their records.
Helga Flesche (“Kikki”) Kleiven (Bergen) talked about her research on deep-sea cores in the northern and southern hemispheres that is aimed at assessing climate change at sub-orbital frequencies across the E–M Pleistocene transition. She showed that these sub-orbital changes, which are well known for the past 500 ky, are constantly present throughout the E–M Pleistocene transition. Furthermore, her work has revealed a similar pattern of millennial-scale climate oscillations at both the northern and southern hemispheres, implying a link in climate variability between both hemispheres.
Erin McClymont (Durham) continued the marine theme by looking at the E–M Pleistocene transition from a lipid biomarker perspective. Her research, based on deep-sea cores in the North and South Atlantic and equatorial Pacific, has allowed a comparison of high- and low-latitude climate change at a resolution of about 5 ky. Results show important fluctuations in carbon inputs to the ocean floor that lead climate changes as observed in published records.
Enno Schefuß (Bremen) went on to discuss his own research on lipid biomarkers from the equatorial Atlantic. Long-term equatorial warming during the transition seems to be explained by a progressive reduction in Atlantic thermohaline circulation that would have led to weakening heat export from the tropical oceans to high latitudes. Although tropical sea surface temperature was found to closely match the pattern of high-latitude ice-volume changes, tropical warming at the end of glacial periods occurred significantly earlier than decreases in global ice volume. This underscores the role of the tropics in amplifying global climate changes.
Jean-Pierre Suc (Lyon) took us away from the deep-sea realm and into world of Mediterranean pollen analysis, where 14 localities allow the documentation of Late Pliocene to Middle Pleistocene climate cycles. Filtering out the influences of latitude and altitude, an understanding of the temporal changes in vegetational development is now emerging. In southern Italy, for example, interglacials of the earliest Plio-Pleistocene are signaled by Taxodiaceae, whereas those of the earliest Middle Pleistocene are characterized by deciduous oak. The need continues, however, to perform parallel analyses of oxygen isotopes and pollen on coastal marine sediments.
After lunch, we were treated to two talks on human evolution and adaptation across the E–M Pleistocene transition. The first, by John McNabb (Southampton), discussed the spread of hominins from Africa into Europe. The importance was stressed of understanding why it was not until the middle of the Middle Pleistocene in Europe that a strong hominin signal emerges. The second talk, by Mike Petraglia (Cambridge), shed new light on hominid adaptations by reviewing current field investigations in the Arabian Peninsula and Indian Subcontinent. Mike concluded that the transition marks an increasing ability of hominids to transcend environmental controls through greater behavioural flexibility and innovation.
The final talk, by Thijs van Kolfschoten (Leiden), dealt with the European record of mammals across the transition. Notable features are the End-Villafranchian “Event” representing a faunal turnover that is mainly caused by the migration of a number of larger mammals, and the evolutionary radiation of middle sized voles (e.g. Microtus). We were shown that a number of Microtus species have sufficiently wide geographic ranges to facilitate correlation between western and eastern Europe and even with Asia across the Urals. The stratigraphic utility of these fossils should therefore be taken into account when deciding where formally to place the boundary between Early and Middle Pleistocene.
The presentations also included a report of the ICS working group on the Early–Middle Pleistocene boundary (compiled by Davide Castradori and presented by Martin Head) and a round-table discussion on the boundary chaired by Charles Turner (Open University & Cambridge).
A poster session ran throughout the day and comprised presentations on the vegetational history from the Crotone Basin in southern Italy (L. Capraro and colleagues), the loess record of northern Eurasia (Andrey Dodonov), orbital and suborbital variability in North Atlantic deep-water circulation (P. Ferretti and colleagues), aminostratigraphy and integrated land-sea correlations in the North Sea basin (two posters by T. Meijer and P. Cleveringa), and floral evolution of the Colombian Andes (Torres and Hooghiemstra).
The conference provided an excellent overview of research developments from both marine and terrestrial realms. It is perhaps not greatly overstated to regard the E–M Pleistocene transition as one of the major ‘events’ in Earth history, and the high quality of all the presentations did justice to its importance. A volume on the E–M Pleistocene transition is being prepared and will include many of the presentations at this conference.
International Commission on Stratigraphy
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