137-2 Neogene Cold Episodes on the Northwest Greenland Margin Inferred from Glendonite-Bearing Strata

Session: Joint SGD-SEPM-IAS Focus on the Sedimentary Record of Climate Change

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The timing of ice-sheet development in northwest Greenland remains poorly constrained compared to the better-documented eastern margin. While marine-based glaciers were active in sectors of eastern Greenland as early as the Miocene, full-scale development of the Greenland Ice Sheet is generally associated with intensification of Northern Hemisphere glaciation during the late Pliocene. The chronology and extent of westward ice expansion into Baffin Bay remain uncertain. In this regard, IODP Expedition 400 recovered Neogene strata from the Northwest Greenland Shelf that contain abundant glendonites. These are calcite pseudomorphs after ikaite (CaCO₃·6H₂O), a metastable hydrate that forms under near-freezing conditions. Due to ikaite’s narrow stability field, its pseudomorphs serve as valuable proxies for frigid depositional conditions. To investigate the paleoenvironmental significance of the glendonites, their chronostratigraphic distribution, sedimentological context, petrographic characteristics, and stable isotopic compositions were examined. Results confirm that the glendonites formed under cold, early diagenetic conditions and occur within discrete intervals of clast-poor, bioturbated mud predating full-scale glaciation. They are concentrated in two main units: (1) upper Oligocene–middle Miocene hemipelagic sediments that infilled remnant rift basins from the opening of Baffin Bay, and (2) late Miocene-Pliocene deposits associated with a sedimentary drift system formed by poleward-flowing boundary currents. These currents, linked to heat transport to northern latitudes, are thought to have suppressed widespread glaciation in northwest Greenland and the Canadian Arctic until the late Pliocene. Although ice-rafted debris is rare to absent, the presence of glendonites in these strata indicates episodes of near-freezing conditions. Cooling may have been driven by intermittent weakening or reorganization of boundary currents. Results underscore the sensitivity of the northwest Greenland margin, offering new insight into the paleoclimate and paleoceanographic evolution of the region prior to full-scale glaciation.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7559

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