The Evolution of Forebulge Structure of Kuqa Rejuvenated Foreland Basin, North of Tarim Basin, Northwest China

Abstract

Abstract

Kuqa depression is located along the northern flank of the Tarim basin. It is widely interpreted as a rejuvenated foreland basin which experienced multiple orogeny in the adjacent Tianshan Mountains. According to the reflection from seismic data, the pre-existing forebulge associated with foreland basin evolution has been recognized in the southern Kuqa depression. This paper studies the areal distribution, geometrical characteristics, dynamic mechanics and evolutionary processes of the forebulge structure by utilizing the latest regional seismic profiles across the depression and crop data in the southern Tianshan overthrusts. Besides that, the deformation of forebulge has been analyzed according to the equilibrium recovery. The results show that four en-echelon paleo-uplifts developed in the southern margin of the Kuqa depression. were controlled by the basement faults. The location and scale of Tianshan overthrusts and the lithosphere's rheological characteristics are the primary factors for the formation of the forebulge zones. The evolution of forelbulge has been divided into three stages. During the End-Early Paleozoic Era, a wide original forebulge formed to be the orogeny of the middle Tianshan. At Late Paleozoic Era, the southern Tianshan ocean disappeared and formed the southern Tianshan overthrusts at the context of compression, the lithosphere transformed from oceanic crust to continental crust, a narrow uplift formed in the south of paleo-uplift. It suggests that oceanic crust leads to a wide, low forebulge whereas continental crust gives rise to a narrow, high forebulge. From Mesozoic to Early Cenozoic, compression between Tarim and Tianshan mostly like to be rest, the tectonic framework was influenced by the loading of southern Tianshan, forebulge continued uplift in this stage. The Mesozoic sequences in both flanks of uplift were analyzed. Until Miocene, Kuqa depression became compressional influenced by Himalayan movement, give a rise to forebulge deformation. The forebulge was the buried hill when the hydrocarbon was generated and migrated in the Kuqa depression, which proves the favorable condition for hydrocarbon accumulation.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016