Fjord network in Namibia
- Author(s)
- Pierre Dietrich, Neil P. Griffis, Daniel P.Le Heron, Isabel P. Montañez, Christoph Kettler, Cécile Robin, François Guillocheau
- 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.
- Organisation(s)
- Department of Geology
- External organisation(s)
- Université Rennes-I, University of Johannesburg (UJ), University of California, Davis, Berkeley Geochronology Center
- Journal
- Geology
- Volume
- 49
- Pages
- 1521-1526
- No. of pages
- 6
- ISSN
- 0091-7613
- DOI
- https://doi.org/10.1130/G49067.1
- Publication date
- 12-2021
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105101 General geology
- ASJC Scopus subject areas
- Geology
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/6c055aed-54ac-4ea3-8c96-efd18a30fd27