Fjord network in Namibia

Autor(en)

Pierre Dietrich, Neil P. Griffis, Daniel P.Le Heron, Isabel P. Montañez, Christoph Kettler, Cécile Robin, François Guillocheau

Abstrakt

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.

Organisation(en)

Institut für Geologie

Externe Organisation(en)

Université Rennes-I, University of Johannesburg (UJ), University of California, Davis, Berkeley Geochronology Center

Journal

Geology

Band

49

Seiten

1521-1526

Anzahl der Seiten

6

ISSN

0091-7613

DOI

https://doi.org/10.1130/G49067.1

Publikationsdatum

12-2021

Peer-reviewed

Ja

ÖFOS 2012

105101 Allgemeine Geologie

ASJC Scopus Sachgebiete

Geology

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/6c055aed-54ac-4ea3-8c96-efd18a30fd27