Date of Award:

1986

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geology

Advisor/Chair:

Robert Q. Oaks, Jr.

Abstract

Throughout the James Ranges and Gardiner Range the Arumbera Sandstone forms prominent strike ridges with distinctive dark reddish slopes and pale red to orange-white cliffs. Because of their lithologic and stratigraphic similarities, the names Eninta and ''Quandong" for these units should be suppressed in favor of the name of Arumbera Sandstone, which has precedence. The stratigraphic and lithologic differences observed between the Quandong Conglomerate in the type locality and the Arumbera Sandstone in the study area suggest that these units are not equivalent. Similarites with the Areyonga Formation suggest the Quandong Conglomerate could be part of the Areyonga Formation.

Lithofacies la, ld, and 2b, and Unit 3 of the Arumbera and its equivalents are typically recessive arkoses, subarkose, and mudrocks. They are interpreted as nearshore-marine to coastal deltaic deposits which include intertonguing tidal-flat, tidal-channel, and beach

sediments. Lithofacies 1b and 2a consist of cliff-forming arkoses, subarkoses, and lithic arkoses. Lithofacies 2c is also resistant, and consists of orthoconglomerates and conglomeratic sandstones. Lithofacies 1e is moderately resistant, and consists of paraconglomerates, conglomeratic sandstones, and mudrocks. It and lithofacies 2c contain pebbles and small cobbles of chert, quartzite, vein quartz, silicified ooids, and limestone, dolostone, shale, and sandstone. These four lithofacies are interpreted as braidplain and fluvial sheet sands.

In the east-central part of the Amadeus Basin the Arumbera Sandstone probably was deposited in a coastal environment as a sequence of deltaic sediments that was dominated by fluvial processes. The Arumbera Sandstone appears to be the molasse derived from the Late Proterozoic and Early Cambrian Petermann Ranges orogeny. Source rocks include sedimentary, low- to middle-rank metamorphic, and plutonic granites. Grain mineralogy and weathering characteristics suggest a hot, semiarid climate during deposition of the Arumbera.

The Arumbera Sandstone and Quandong Conglomerate contain fair to good porosity and permeability, and petrographic evidence shows mesogenetic generation of secondary porosity. Previous and present burial depths are adequate for the generation of petroleum. The presence of suitable underlying .source rocks, overlying salt of the Chandler for a seal, and stratigraphic and structural traps suggest a good potential for petroleum. Production of dry gas from the lower part of the Arumbera at Dingo field, north of Deep Well Homestead, confirms the petroleum potential of this formation.

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