TY - JOUR

T1 - The exhumation of the Indo-Burman Ranges, Myanmar

AU - Najman, Yani

AU - Sobel, Ed

AU - Millar, Ian

AU - Stockli, Dan

AU - Govin, Gwladys

AU - Lisker, Frank

AU - Garzanti, Eduardo

AU - Limonta, Mara

AU - Vezzoli, Giovanni

AU - Copley, Alex

AU - Szymanski, Eugene

AU - Kahn, Alicia

AU - Zhang, Peng

N1 - This is the author’s version of a work that was accepted for publication in Earth and Planetary Science Letters. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Earth and Planetary Science Letters Volume 530, 2020 DOI: 10.1016/j.epsl.2019.115948

PY - 2020/1/15

Y1 - 2020/1/15

N2 - The Indo-Burman Ranges (IBR) are a mountain range comprised of Mesozoic-Cenozoic rocks which run the length of Western Myanmar, extending into India and Bangladesh; to the west lies the Indian Ocean, and to the east lies the Central Myanmar Basin (CMB) along which the Irrawaddy River flows. The IBR are considered to be an accretionary prism, developed at the juncture of the Indian and Sunda plates, and a number of hypotheses have been proposed for their evolution. However, in order for these hypotheses to be evaluated, the timing of IBR evolution needs to be determined. We undertook a two-pronged approach to determining the timing of uplift of the IBR. (1) We present the first low-temperature thermochronological age elevation profiles of the IBR using ZFT, AFT and ZHe techniques. Our data show: a major period of exhumation occurred around the time of the Oligo-Miocene boundary; we tentatively suggest, subject to further verification, an additional period of exhumation at or before the late Eocene. (2) We carried out a detailed multi-technique provenance study of the sedimentary rocks of the IBR and Arakan Coastal region to their west, and compared data to coeval rocks of the CMB. We determined that during Eocene times, rocks of the CMB and IBR were derived from similar local provenance, that of the Myanmar arc to the east. Therefore at this time there was an open connection from arc to ocean. By contrast, by Miocene times, provenance diverged. Rocks of the CMB were deposited by a through-flowing Irrawaddy River, with detritus derived from its upland source region of the Mogok Metamorphic Belt and Cretaceous-Paleogene granites to the north. Such a provenance is not recorded in coeval rocks of the IBR, indicating that the IBR had uplifted by this time, providing a barrier to transport of material to the west. To the previously published list of viable proposals to explain the exhumation of the range, we add a new suggestion: the period of exhumation around the time of the Oligo-Miocene boundary could have been governed by a change to wedge dynamics instigated by a major increase in the thickness of the incoming Bengal Fan sediment pile.

AB - The Indo-Burman Ranges (IBR) are a mountain range comprised of Mesozoic-Cenozoic rocks which run the length of Western Myanmar, extending into India and Bangladesh; to the west lies the Indian Ocean, and to the east lies the Central Myanmar Basin (CMB) along which the Irrawaddy River flows. The IBR are considered to be an accretionary prism, developed at the juncture of the Indian and Sunda plates, and a number of hypotheses have been proposed for their evolution. However, in order for these hypotheses to be evaluated, the timing of IBR evolution needs to be determined. We undertook a two-pronged approach to determining the timing of uplift of the IBR. (1) We present the first low-temperature thermochronological age elevation profiles of the IBR using ZFT, AFT and ZHe techniques. Our data show: a major period of exhumation occurred around the time of the Oligo-Miocene boundary; we tentatively suggest, subject to further verification, an additional period of exhumation at or before the late Eocene. (2) We carried out a detailed multi-technique provenance study of the sedimentary rocks of the IBR and Arakan Coastal region to their west, and compared data to coeval rocks of the CMB. We determined that during Eocene times, rocks of the CMB and IBR were derived from similar local provenance, that of the Myanmar arc to the east. Therefore at this time there was an open connection from arc to ocean. By contrast, by Miocene times, provenance diverged. Rocks of the CMB were deposited by a through-flowing Irrawaddy River, with detritus derived from its upland source region of the Mogok Metamorphic Belt and Cretaceous-Paleogene granites to the north. Such a provenance is not recorded in coeval rocks of the IBR, indicating that the IBR had uplifted by this time, providing a barrier to transport of material to the west. To the previously published list of viable proposals to explain the exhumation of the range, we add a new suggestion: the period of exhumation around the time of the Oligo-Miocene boundary could have been governed by a change to wedge dynamics instigated by a major increase in the thickness of the incoming Bengal Fan sediment pile.

KW - Indo-Burman Ranges

KW - age-elevation profile

KW - provenance

KW - Myanmar

KW - detrital thermochronology and geochronology

KW - palaeo-Irrawaddy

U2 - 10.1016/j.epsl.2019.115948

DO - 10.1016/j.epsl.2019.115948

M3 - Journal article

VL - 530

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

SN - 0012-821X

M1 - 115948

ER -