Mid-Pliocene warm-period deposits in the High Arctic yield insight into camel evolution

Abstract

The mid-Pliocene was a global warm period, preceding the onset of Quaternary glaciations. Here we use cosmogenic nuclide dating to show that a fossiliferous terrestrial deposit that includes subfossil trees and the northern-most evidence of Pliocene ice wedge casts in Canada’s High Arctic (Ellesmere Island, Nunavut) was deposited during the mid-Pliocene warm period. The age estimates correspond to a general maximum in high latitude mean winter season insolation, consistent with the presence of a rich, boreal-type forest. Moreover, we report that these deposits have yielded the first evidence of a High Arctic camel, identified using collagen fingerprinting of a fragmentary fossil limb bone. Camels originated in North America and dispersed to Eurasia via the Bering Isthmus, an ephemeral land bridge linking Alaska and Russia. The results suggest that the evolutionary history of modern camels can be traced back to a lineage of giant camels that was well established in a forested Arctic.

Late Cenozoic onset of the latitudinal diversity gradient of North American mammals

“…Furthermore, the lack of a LDG previously observed in the mid-Paleocene (21) was not merely a lingering consequence of the K/Pg extinction and subsequent mammalian radiation but rather a persistent feature of mammalian biogeography in North America for most of the Cenozoic. The fossil slope is indistinguishable from the modern (negative) LDG during only three intervals: the earliest Paleocene (63-65 Ma), the late Eocene (36)(37)(38), and the Pliocene-Pleistocene (2-4 Ma). The modern-like LDG slope during the earliest Paleocene interval is surprising given the strong support for a lack of a LDG during the mid-Paleocene shown in this and our previous study (21), which used different approaches than we do here.…”

Climate variability and long-term expansion of peatlands in Arctic Norway during the late Pliocene (ODP Site 642, Norwegian Sea)

“…However, model simulations indicate a similarto-present AMOC during the mPWP, supporting the notion that the amplified warming in the Nordic Seas was a result of increased radiative forcing . On land, boreal taiga forests reached the coast of the Arctic Ocean during the Piacenzian and tundra biomes were markedly reduced (Bennike et al, 2002;Rybczynski et al, 2013;Salzmann et al, 2008;Willard, 1996). In the high Artic, Pliocene deposits reveal mean annual temperatures (MATs) ∼ 19 • C warmer than at present, favouring the growth of larch-dominated forests on Ellesmere Island (Ballantyne et al, 2006(Ballantyne et al, , 2010Rybczynski et al, 2013).…”

The emergence of modern sea ice cover in the Arctic Ocean

“…6). A reduction in sea ice cover has been reported during the upper Miocene 7 and the Pliocene 8 , and modelling experiments indicate that the removal of Arctic sea ice around the early-to-late Pliocene transition (B3.6 Ma) explains the proxy-based high paleotemperature reconstruction in the Canadian high Arctic 9,10 . Other simulations, however, reveal reduced, but still significant Arctic sea ice cover during the same period 11 .…”