Stratigraphic evolution of Mesozoic continental margin and oceanic sequences northwest Australia and north Himalayas
- Bedford Institute of Oceanography, Dartmouth, Nova Scotia (Canada)
- Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover (West Germany)
The authors are investigating continental margin to ocean sequences of the incipient Indian Ocean as it replaced central Tethys. Objectives of this study are the dynamic relation between sedimentation, tectonics, and paleogeography. Principal basins formation along the northern edge of eastern Gondwana started in the Late Permian to the Triassic. By the Late Triassic-Early Jurassic, platform carbonates with thin, organic-rich lagoonal shales were laid down in a subtropical climate. This unit, which harbors some of the oldest known nannofossils, shows repeated shallowing-upward sequences. Subsequent southward drift of the Gondwana margin during the Middle Jurassic increased siliciclastic input in Nepal, when widespread sediment starvation or erosion during local uplift took place off parts of northwest Australia. A middle Callovian-early Oxfordian hiatus in Nepal is submarine and appears global in extent. The overlying 250-m-thick organic-rich black shales, correlative to the Oxford/Kimmeridge clays of circum-Atlantic petroleum basins, may be traced along the northern Himalayan Range, and probably represent an extensive continental slope deposit formed under an oxygen minimum layer in southern Tethys. The deposit's diverse foraminiferal microfauna was previously only known from boreal Laurasia. The Callovian breakup unconformity, off northwest Australia, precedes onset of sea-floor spreading at least 15-25 Ma. Sea-floor spreading, leading to the present Indian Ocean started in the Argo Abyssal Plain around 140 Ma, at the end of the Jurassic, was about 15 m.y. later than previously postulated. Australia and Greater India separated as early as the Late Valanginian, about 130 Ma. Mafic volcaniclastics in Nepalese deltaic sediments probably testify to concurrent continental margin volcanic activity, which may be a precursor to the slightly younger Rajmahal traps in eastern India.
- OSTI ID:
- 6729007
- Report Number(s):
- CONF-900605-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:5; Conference: Annual convention and exposition of the American Association of Petroleum Geologists, San Francisco, CA (USA), 3-6 Jun 1990; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
AUSTRALIA
STRATIGRAPHY
TECTONICS
HIMALAYAS
BLACK SHALES
CONTINENTAL MARGIN
GEOLOGIC FORMATIONS
GEOLOGIC TRAPS
GONDWANA
JURASSIC PERIOD
PERMIAN PERIOD
PETROLEUM DEPOSITS
SEDIMENTARY BASINS
TRIASSIC PERIOD
AUSTRALASIA
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CHATTANOOGA FORMATION
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
MATERIALS
MESOZOIC ERA
MINERAL RESOURCES
MOUNTAINS
OIL SHALES
PALEOZOIC ERA
RESOURCES
020200* - Petroleum- Reserves
Geology
& Exploration
580000 - Geosciences