Abstract: Exploration in the Savannakhet Basin, Peoples Democratic Republic of Laos

P. J. Cullen, S. C. Wright, C. J. Kearney, A. T. Pink

The collision and suturing of four continental fragments during the Early Permian to the Middle Triassic formed present-day southeast Asia. Collapse of the overthickened crust in the Late Triassic (Indosinian) produced crustal extension and led to the development of an en echelon system of half grabens, which stretched across northeast Thailand and south-central Laos. Deposition of alluvial and fluvial sandstones and lacustrine mudstones rapidly infilled these depocenters and was succeeded by widespread continental mudstone deposition with occasional marine incursions through the Jurassic and Cretaceous.

The Late Cretaceous collision of the Kohistan arc and subsequent collision of India with Eurasia (Himalayan orogeny) inverted these half grabens along the preexisting extensional faults, producing large-scale anticlines. Continued regional uplift of the Khorat plateau area and denudation of the land surface has removed up to 3 km of sediments from the crests of the inversion anticlines.

The Savannakhet basin lies in the south-central part of the Peoples Democratic Republic of Laos, between the Mekong River and the eastern border with Vietnam. A group led by Enterprise Oil Exploration Ltd. licensed this area for hydrocarbon exploration in 1989. Gravity, aeromagnetic, seismic, geological, and geochemical data have all been acquired and used in an integrated interpretation of the geology and hydrocarbon prospectivity of the license area.

This paper examines the tectonic history of the Savannakhet basin. High-resolution seismic data and balanced section reconstruction are used to analyze the structural development of the inverted Late Triassic half graben. The application of apatite and zircon fission track analysis, vitrinite reflectance, spore coloration, and seismic velocity studies to constrain the maximum depth of burial is also demonstrated.

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