Fjord network in Namibia: A snapshot into the dynamics of the late Paleozoic glaciation - INSU - Institut national des sciences de l'Univers Access content directly
Journal Articles Geology Year : 2021

Fjord network in Namibia: A snapshot into the dynamics of the late Paleozoic glaciation

Abstract

Fjords are glacially carved estuaries that profoundly influence ice-sheet stability by draining and ablating ice. Although abundant on modern high-latitude continental shelves, fjord-network morphologies have never been identified in Earth’s pre-Cenozoic glacial epochs, hindering our ability to constrain ancient ice-sheet dynamics. We show that U-shaped valleys in northwestern Namibia cut during the late Paleozoic ice age (LPIA, ca. 300 Ma), Earth’s penultimate icehouse, represent intact fjord-network morphologies. This preserved glacial morphology and its sedimentary fill permit a reconstruction of paleo-ice thicknesses, glacial dynamics, and resulting glacio-isostatic adjustment. Glaciation in this region was initially characterized by an acme phase, which saw an extensive ice sheet (1.7 km thick) covering the region, followed by a waning phase characterized by 100-m-thick, topographically constrained outlet glaciers that shrank, leading to glacial demise. Our findings demonstrate that both a large ice sheet and highland glaciers existed over northwestern Namibia at different times during the LPIA. The fjords likely played a pivotal role in glacier dynamics and climate regulation, serving as hotspots for organic carbon sequestration. Aside from the present-day arid climate, northwestern Namibia exhibits a geomorphology virtually unchanged since the LPIA, permitting unique insight into this icehouse.

Domains

Stratigraphy
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Origin : Publication funded by an institution

Dates and versions

insu-03331205 , version 1 (01-09-2021)

Licence

Attribution - CC BY 4.0

Identifiers

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Pierre Dietrich, Neil P Griffis, Daniel P Le Heron, Isabel P Montañez, Christoph Kettler, et al.. Fjord network in Namibia: A snapshot into the dynamics of the late Paleozoic glaciation. Geology, 2021, 49 (12), pp.1521-1526. ⟨10.1130/G49067.1⟩. ⟨insu-03331205⟩
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