168 Laurentia Without Borders: Pre-Pangea Intercontinental Connections
The ancient core of North America is surrounded by Neoproterozoic to early Paleozoic rifts, indicating former juxtaposition with several other cratons. This session will explore these former connections and their paleogeographic, tectonic, and paleoenvironmental implications.
Tuesday, 21 October 2025
8:00 AM - 12:00 PM
HBGCC, 217C
Coats Land, a Piece of West Texas in Antarctica
Paper number: 168-3
Program: Technical Sessions
Time: 8:45 AM – 9:00 AM
Authors
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Ian DalzielThe University of Texas at Austin, Austin, TX
Abstract
Coats Land, Antarctica appears to be a tectonic tracer that links Southern Laurentia to both Kalahari and East Antarctica during the Meso- and Neoproterozoic. Natal-Maud sutures (~1 Ga) separate Coats Land from the Kalahari Craton in Gondwana. Pan-African sutures (~600 Ma) separate Coats Land from the Mawson Craton (East Antarctica). This indicates that Coats Land’s Mesoproterozoic history was independent of both the Kalahari and Mawson cratons. Loewy et al. (2011, Geology) identifies similar ages and colinear Pb isotope signatures of igneous rocks in Coats Land and Laurentia (West Texas and the Keweenawan Mid-Continent Rift) and concludes that Coats Land was part of Laurentia. Paleomagnetic reconstruction allows juxtaposition of Coats Land, southern Laurentia, and the Natal margin of Kalahari at ~1 Ga.
Coats Land bedrock is only exposed in 3 nunataks. As previously identified, the ~1.1 Ga granophyres and rhyolites that comprise the Littlewood and Bertrab nunataks have similar composition and are contemporaneous with the ~1.1 Ga Red Bluff Granite Suite (RBGS) and Thunderbird Rhyolite in the Franklin Mountains of West Texas. New Pb and Hf isotope data from Coats Land and the RBGS further corroborate the correlation of these igneous rocks. Quartzo-feldspathic gneiss and amphibolite from the Moltke Nunatak resemble the less-deformed basement lithologies of the RBGS. Comparison of the Sm-Nd isotope compositions of the RBGS basement and new Sm-Nd data from the Moltke rocks indicate that these rocks had similar sources. Additional isotopic and trace element analyses of rocks from Coats Land and comparable lithologies in the Franklin Mountains of West Texas are currently underway. We will present this new data and use it to rigorously evaluate the proposed Coats Land – West Texas connection.
Confirmation that Coats Land was part of southern Laurentia at 1.1 Ga provides evidence that Kalahari was adjacent to southern Laurentia in Rodinia. The Coats Land-West Texas link combined with evidence that rifting did not occur in Southern Laurentia until after the amalgamation of Gondwana supports the fleeting existence of the late Neoproterozoic-Early Paleozoic supercontinent of Pannotia.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-414367
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