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M. Thierens, H. Pirlet, C. Colin, K. Latruwe, F. Vanhaecke, J.R. Lee, J.-B. Stuut, J. Titschack, V.A.I. Huvenne, B. Dorschel, A.J. Wheeler, J.-P., Henriet
Quaternary Science Reviews
Ice-rafting from the British-Irish ice sheet since the earliest Pleistocene (2.6 million years ago): implications for long-term mid-latitudinal ice-sheet growth in the North Atlantic region
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The Plio-Pleistocene intensification of Northern Hemisphere continental ice-sheet development is

known to have profoundly affected the global climate system. Evidence for early continental glaciation is

preserved in sediments throughout the North Atlantic Ocean, where ice-rafted detritus (IRD) layers attest

to the calving of sediment-loaded icebergs from circum-Atlantic ice sheets. So far, Early-Pleistocene IRD

deposition has been attributed to the presence of high-latitudinal ice sheets, whereas the existence and

extent of ice accumulation in more temperate, mid-latitudinal regions remains enigmatic.

Here we present results from the multiproxy provenance analysis of a unique, Pleistocene-Holocene

IRD sequence from the Irish NE Atlantic continental margin. There, the Challenger coral carbonate

mound (IODP Expedition 307 site U1317) preserved an Early-Pleistocene record of 16 distinctive IRD

events, deposited between ca 2.6 and 1.7 Ma. Strong and complex IRD signals are also identified during

the mid-Pleistocene climate transition (ca 1.2 to 0.65 Ma) and throughout the Middle-Late Pleistocene

interval. Radiogenic isotope source-fingerprinting, in combination with coarse lithic component analysis,

indicates a dominant sediment source in the nearby BritisheIrish Isles, even for the oldest, Early-

Pleistocene IRD deposits. Hence, our findings demonstrate, for the first time, repeated and substantial

(i.e. marine-terminating) ice accumulation on the BritisheIrish Isles since the beginning of the Pleistocene.

Contemporaneous expansion of both high- and mid-latitudinal ice sheets in the North Atlantic

region is therefore implied at the onset of the Pleistocene. Moreover, it suggests the recurrent establishment

of (climatically) favourable conditions for ice sheet inception, growth and instability in midlatitudinal

regions, even in the earliest stages of Northern Hemisphere glacial expansion and in an

obliquity-driven climate system.

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