Mesozoic stratigraphy of northwestern Australian and northern Himalayan margins

Conference · Wed Mar 01 04:00:00 EST 1989 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:6132893

Ogg, J; Kopaskamerkel, D C

The Mesozoic stratigraphies of the Himalayan margin, the Argo abyssal plain, and the Exmouth Plateau exhibit marked contrasts in their sedimentation histories. The sedimentary sequence on the northeastern Exmouth Plateau off Australia includes a Carnian to Rhaetian sequence of fluviodeltaic and marine clastics and carbonates, capped by a shallowing-upward sequence of platform carbonates overlain, with a major unconformity, by marine Aptian sediments deposited during rapid subsidence of the plateau. Argo abyssal plain basement is overlain by red-brown, bioturbated, inoceramid-rich quartzose claystones, bentonites, and quartz siltstones, dated by radiolarians and benthic foraminifera as lowest Cretaceous. This is overlain by red and green claystones and nannofossil chalks. The basal age indicates that sea-floor spreading began in the earliest Cretaceous, not Oxfordian as had been thought. In the Thakkola region of Nepal, uppermost Triassic through Lower Jurassic shelf and carbonate platform facies are capped by a ferruginous oolite deposit of latest Bathonian to earliest Callovian age. Sedimentation resumed in the middle Oxfordian with deposition of Berriasian( ) deep-water black organic-rich mud. Following a valanginian regression and progradation of terrigenous clastics, Aptian black shales were deposited. In geological studies of the northwestern Australian margin, the ubiquitous hiatus within the Callovian-Oxfordian has been termed the breakup unconformity. Existence of a similar-aged hiatus in the Himalayas on a margin which formed during the late Paleozoic, absence of any Jurassic on the Exmouth Plateau, and the apparent initiation of spreading in the Argo basin during the earliest Cretaceous suggest that this widespread unconformity is not associated with a continental breakup in these regions.

• Research Organization: Purdue Univ., West Lafayette, IN (USA)
• OSTI ID: 6132893
• Report Number(s): CONF-890404-
• Conference Information: Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 73:3
• Country of Publication: United States
• Language: English

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