Evolution of the Arabian Carbonate Platform Margin Slope and its Response to Orogenic Closing of a Cretaceous Ocean Basin, Oman
- Maurice E. Tucker3,
- James Lee Wilson4,
- Paul D. Crevello5,
- J. Rick Sarg6 and
- J. Fred Read7
Published Online: 15 APR 2009
Copyright © 1990 The International Association of Sedimentologists
Carbonate Platforms: Facies, Sequences and Evolution
How to Cite
Watts, K. F. and Blome, C. D. (1986) Evolution of the Arabian Carbonate Platform Margin Slope and its Response to Orogenic Closing of a Cretaceous Ocean Basin, Oman, in Carbonate Platforms: Facies, Sequences and Evolution (eds M. E. Tucker, J. L. Wilson, P. D. Crevello, J. Rick Sarg and J. F. Read), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303834.ch11
New Braunfels, Texas, USA
Littleton, Colorado, USA
Midland, Texas, USA
Blacksburg, Virginia, USA
- Published Online: 15 APR 2009
- Published Print: 22 DEC 1986
Print ISBN: 9780632027583
Online ISBN: 9781444303834
- evolution of Arabian carbonate platform margin slope – response to orogenic closing of Cretaceous ocean basin, Oman;
- Oman mountains;
- Qumayrah Formation;
- Jurassic Sahtan Formation;
- Palaeoceanographic effects
The Jurassic to Cretaceous Mayhah Formation formed along the passive continental margin slope between the extensive shallow-marine Arabian carbonate platform and the deep-oceanic Hawasina Basin (South Tethys Sea). Near Wadi Qumayrah, it is overlain by pre- and syn-orogenic sediments of the Upper Cretaceous Qumayrah Formation. These strata record the initial response of the platform margin to a late Cretaceous orogeny and impending ophiolite emplacement resulting from closing of an ocean basin. Tectonism along the platform margin, supply of platform carbonate sediment, and palaeoceanographic effects all influenced slope sedimentation.
During the passive margin phase, redeposited oolitic calcarenite, megabreccia and calcirudite of Jurassic age formed a base-of-slope apron along an east-facing block-faulted platform margin. Redeposited limestone and slump deposits become uncommon up-section suggesting a transition into basinal sedimentation. With tectonic quiescence this basin developed ramp-like margins along which mass movements were unlikely. It may have been a relatively shallow embayment or marginal basin adjacent to the deeper Hawasina Basin.
A well-documented drowning of the platform during late Jurassic–early Cretaceous led to formation of bedded chert in this marginal basin. The chert is primarily silicified limestone indicating a shallower-depositional setting (above the carbonate compensation depth, CCD) or greater supply of carbonate sediment than for equivalent radiolarian chert at the type locality, Jebel Sumeini. Basinal carbonate sedimentation became re-established in post-Valanginian time. In the uppermost Mayhah Formation, slump deposits and intra-formational breccias indicate steepening of the slope, possibly resulting from tectonic downbowing associated with basin closing.
Cenomanian to Coniacian chert and siliceous mudstone of the Qumayrah Formation formed below the CCD. Siliceous sedimentation resulted from tectonically-induced deepening of the ocean basin, upwelling in a relatively narrow closing ocean basin and/or global sea-level highstand and shallowing of the CCD. Beds of calcirudite and calciturbidite in the unit were derived from an uplifted shelf edge and local rudist banks. A thick lenticular synorogenic megabreccia may have been derived from erosion of adjacent anticlinal highs.
The Arabian carbonate platform margin was influenced by repeated intervals of tectonism along the continental margin in Oman. Block-faulting associated with Triassic and Jurassic rifting events led to the development of steep escarpment slopes and base-of-slope debris aprons. Tectonic quiescence led to reduced platform margin slopes, so the marginal basin at Wadi Qumayrah developed ramp margins. With changing plate motions, the outer part of the platform was drowned due to a major rise in sea-level, in part resulting from rapid tectonic subsidence in the latest Jurassic and earliest Cretaceous. Later, a carbonate ramp was able to prograde over the drowned platform. In late Cretaceous time, steepening and deepening of the slope, accompanied by faulting on the Arabian platform, preceded oceanic nappe emplacement as the Oman continental margin approached a northward-dipping subduction zone.