--> --> Abstract: Contribution to the Sedimentary and Structural Evolution of the Mesozoic Khorat-Basin, Thailand, by H. Heggemann, H. Dietrich, and T. Klaus-Werner; #90982 (1994).

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Abstract: Contribution to the Sedimentary and Structural Evolution of the Mesozoic Khorat-Basin, Thailand

Heiner Heggemann, Helmcke Dietrich, Tietze Klaus-Werner

In the ongoing discussion on the formation of Pangea and the history of the Tethys Ocean, the sedimentary evolution of the continental Mesozoic Khorat group in Thailand was interpreted by most authors as the molasse stage of the Triassic Indosinian orogeny. In their theory, this event marks the collision of Indochina and Shan-Thai along the Nan-Uttaradit suture zone in Thailand and the Bentong-Raub suture zone in Malaysia in the Upper Triassic.

The sedimentary evolution of the Mesozoic Khorat basin was studied in northeast and north Thailand. During the Upper Triassic and until the Paleogene, the basin was filled with approximately 4000 m of mainly fluvial and flood-plain dominated continental red beds, which also include lacustrine and brackish deposits, thick probably nonmarine salt deposits, and massive eolian sandstones. The drainage of the basin was oriented into west, southwest, and south. In connection with the results on K/Ar age dating on detrital micas, it is evident that the source rocks have had a Variscan age.

The initial extensional stage in the structural evolution of the basin was due to the thinned lithosphere and resulted in the development of Triassic half grabens. During the second stage, which lasted from the Upper Triassic to the Upper Cretaceous, slow subsidence rates affected wide areas in southeast Asia and resulted in the formation of an intracontinental sag basin. The widely distributed continental sediments were then accumulated in the extended Khorat basin, also including parts of Cambodia, Laos, and Vietnam, and can probably even be traced into southwest China (Yunnan). During the Cretaceous and Paleogene, the sediments were deformed and the basin was uplifted.

The results of the sedimentology, the paleogeography, and the subsidence history of the Khorat basin do not confirm the theory of a major Indosinian orogeny in the central parts of southeast Asia during the Upper Triassic, but they support the theory of an important Paleozoic orogeny.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994