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Paleogene evolution of the Burmese forearc basin and implications for the history of India-Asia convergence

Alexis Licht, Guillaume Dupont-Nivet, Zaw Win, Hnin Hnin Swe, Myat Kaythi, Pierrick Roperch, Tamas Ugrai, Virginia Littell, Diana Park, Jan Westerweel, Dominic Jones, Fernando Poblete, Day Wa Aung, Huasheng Huang, Carina Hoorn and Kyaing Sein
Paleogene evolution of the Burmese forearc basin and implications for the history of India-Asia convergence
Geological Society of America Bulletin (November 2018) 131 (5-6): 730-748


The geological history of the Burmese subduction margin, where India obliquely subducts below Indochina, remains poorly documented although it is key to deciphering geodynamic models for the evolution of the broader Tibetan-Himalayan orogen. Various scenarios for the evolution of the orogen have been proposed, including a collision of India with Myanmar in the Paleogene, a significant extrusion of Myanmar and Indochina from the India-Asia collision zone, or very little change in paleogeography and subduction regime since the India-Asia collision. This article examines the history of the Burmese forearc basin, with a particular focus on Eocene-Oligocene times to reconstruct the evolution of the Burmese margin during the early stages of the India-Asia collision. We report on sedimentological, geochemical, petrographical, and geochronological data from the Chindwin Basin-the northern part of the Burmese forearc-and integrate these results with previous data from other basins in central Myanmar. Our results show that the Burmese margin acted as a regular Andean-type subduction margin until the late middle Eocene, with a forearc basin that was open to the trench and fed by the denudation of the Andean volcanic arc to the east. We show that the modern tectonic configuration of central Myanmar formed 39-37 million years ago, when the Burmese margin shifted from an Andean-type margin to a hyper-oblique margin. The forearc basin was quickly partitioned into individual pull-apart basins, bounded to the west by a quickly emerged accretionary prism, and to the east by synchronously exhumed basement rocks, including coeval high-grade metamorphics. We interpret this shift as resulting from the onset of strike-slip deformation on the subduction margin leading to the formation of a paleo-sliver plate, with a paleo fault system in the accretionary prism, pull-apart basins in the forearc, and another paleo fault system in the backarc. This evolution implies that hyper-oblique convergence below the Burmese margin is at least twice older than previously thought. Our results reject any India-Asia convergence scenario involving an early Paleogene collision of India with Myanmar. In contrast, our results validate conservative geodynamic models arguing for a close-to-modern pre-collisional paleogeometry for the Indochina Peninsula, and indicate that any post-collisional rotation of Indochina, if it occurred at all, must have been achieved by the late middle Eocene.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 131
Serial Issue: 5-6
Title: Paleogene evolution of the Burmese forearc basin and implications for the history of India-Asia convergence
Affiliation: University of Washington, Department of Earth and Space Sciences, Seattle, WA, United States
Pages: 730-748
Published: 20181120
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 129
Accession Number: 2019-007050
Categories: StratigraphyStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2018336
Illustration Description: illus. incl. block diags., strat. cols., geol. sketch maps
N15°00'00" - N30°00'00", E90°00'00" - E99°00'00"
Secondary Affiliation: Universite de Rennes, FRA, FranceShwe Bo University, BUR, BurmaUniversity of Yangon, BUR, BurmaUniversity of Amsterdam, NLD, NetherlandsMyanmar Geosciences Society, BUR, Burma
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201906
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