Late Pliocene Greenland – The Kap København Formation in North Greenland

Abstract

The Kap København Formation, North Greenland, is a 100-m thick succession of predominantly shallow marine nearshore sediments, dated to c. 2.4 ma. The abundant well preserved remains of mosses, land plants, foraminifers, ostracodes, insects, cladocers, molluscs, and a few vertebrates enable a detailed reconstruction of terrestrial and marine environments and climate. The sediments indicate a complex sea-level history implying combined glacioisostatic and -eustatic control. This is supported by the faunal and floral development from arctic to subarctic and boreal conditions, and the record probably reflects the demise of the first major Cenozoic ice sheet, the Praetiglian, over the area, and the onset of the succeeding Tiglian A interglacial. The record ends with the attainment of the interglacial sea-level highstand and climate optimum when forest tundra reached the world’s northernmost coasts. It is inferred that the duration of sedimentation was a half obliquity cycle, i.e. 20,000 yr, at the most.

The Northwestern Greenland Ice Sheet During The Early Pleistocene Was Similar To Today

“…Low nuclide concentrations, yet high a 26 Al i / 10 Be i ratio, are consistent with erosion of several meters of surface material prior to 2.0 Ma (which would have higher 10 Be i and 26 Al i concentrations and a lower 26 Al i / 10 Be i ) followed by brief exposure at depth, then erosion and subglacial transport to the shelf margin. Such early glacial erosion followed by exposure fits with ice‐free conditions indicated by the ~2 Ma Kap København Formation that putatively predates the diamict we analyzed (Funder et al, ). The presence of 26 Al i supports the age model (Knutz et al, ); if the diamict was much older than 2.0 Ma, 26 Al i would not be preserved due to its 7 × 10 5 year half‐life.…”

“…Understanding Greenland Ice Sheet (GrIS) behavior during warmer‐than‐present climates is critical (Clark et al, ); yet, the behavior and state of the GrIS before the Last Glacial Maximum remain poorly understood (Bierman et al, ) because present ice cover obscures and glacial erosion removed terrestrial records of GrIS history (Funder et al, ; McFarlin et al, ). Much of the known GrIS deep time history relies on marine archives including seismic surveys (Knutz et al, ) and sediment cores from deep ocean drilling (Bierman et al, ; Helland & Holmes, ; Reyes et al, ; Tripati et al, ) (Figure ).…”

Extensive marine-terminating ice sheets in Europe from 2.5 million years ago

“…This can be achieved by either reducing ablation (lowering air temperatures) or enhancing accumulation (precipitation) or some combination of both. Compared with the Late Pleistocene, air temperatures in the Early Pleistocene appear higher (36)(37)(38)(39), while precipitation estimates are, at best, tentative (38,39). Assuming that air temperatures were warmer, enhanced precipitation (accumulation) would be required to sustain low-slung ice sheets in the Early Pleistocene, which, given the increased enthalpy, is not unrealistic.…”

Microporphyritic and microspherulitic melt grains, Hiawatha crater, Northwest Greenland: Implications for post-impact cooling rates, hydration, and the cratering environment

“…The origin and transformation of locally derived, impact-affected organic carbon from the crater was investigated by Garde et al (2020), who showed that it was derived from coniferous trees such as Pinus or Picea. Forests of coniferous trees cannot grow anywhere in Greenland today, but they existed up to ∼80°N in warm periods between 3.0 Ma and 2.4 Ma (Fyles et al, 1991;Funder et al, 2001).…”