16 Tectonic Processes in the Circum-Atlantic Orogens I: A Celebration of the Career of Rob Strachan

Friday, 28 March 2025
1:30 PM - 5:30 PM
120

COMPLEX MORPHOLOGY OF COLLIDING MARGINS IN LAURUSSIA-GONDWANA SUPERCOLLISION

Paper number: 16-3
Program: Theme Sessions
Time: 2:10 PM – 2:30 PM

Authors

Abstract

Late Paleozoic convergence between Gondwana and Laurussia culminated in terminal collisions that produced the Ouachita-Alleghanian-Mauritanian-Variscan orogen within the interior of Pangea. The evolution and architecture of this orogen was profoundly influenced by a series of ca. 400-300 Ma promontory collisions, which terminated 100 m.y. of subduction and terrane accretion along the Laurussian margin and passive margin sedimentation along the Gondwanan margin. These promontory collisions compartmentalized the orogen into several domains with very different subsequent tectonic evolutions. In Europe, the Variscan belt records coeval collisional (e.g. Iberian massif) and “Mediterranean-style” orogens (e.g. Bohemian massif). The former are characterized by crustal thickening, followed by extensional collapse. The latter occur in re-entrants and are characterized by complex orogenic collages of limited lateral extent produced by the opening and closing of ephemeral oceans. This collage includes the products of subduction of varying polarities within these oceans and accretionary collisions of local significance that preceded terminal collision. Late-stage orogenic processes are characterized by the formation of oroclines, extensional collapse, and the transition to Tethyan tectonics. Because part of the Laurentian-Mauritanide domains were located to the southwest of the promontory collisions, remnants of the Rheic Ocean persisted between them and their respective evolutions, as recorded in the Appalachian belt, are dominated by Andean-style orogenesis that preceded terminal collision.

The geodynamic driver of Pangea amalgamation, by the Appalachian-Mauritanide-Variscan orogen, is consistent with the principles of orthoversion. In other collisional orogens, determining when geological continuity along converging continental margins gives way to compartmentalization may likewise document when promontory collisions have occurred.

Geological Society of America Abstracts with Programs. Vol. 57, No. 3

doi: 10.1130/abs/2025NE-408265

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.