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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 5. (May)

First Page: 559

Last Page: 559

Title: Arumbera Sandstone: A Possible Late Proterozoic-Early Cambrian Deltaic Complex, Central Australia: ABSTRACT

Author(s): Keith T. Conrad, Robert Q. Oaks, Jr.

Article Type: Meeting abstract

Abstract:

A detailed investigation of the Arumbera Sandstone was undertaken in the northeastern Amadeus basin, central Australia, where the unit forms distinctive strike ridges with orange-white cliffs and dark reddish slopes. The Arumbera is divisible into four informal, readily mappable units.

Approximately 80% of the "average" stratigraphic section is composed of recessive, pale-red, thin to medium-bedded, fine to medium-grained arkose with major proportions of siltstone and mudstone. These sediments are interpreted as a complex assemblage of coastal and nearshore marine environments including tidal flats, tidal channels, estuaries, and beaches. Evidence includes: (1) predominance of alpha, beta, and xi cross-stratification with common herringbone laminae, hummocky cross-strata, planar foreshore stratification, and flaser bedding; (2) bimodal paleocurrents; (3) records of intermittent subaerial exposure; and (4) rare to abundant marine trace fossils.

The remaining 20% of the Arumbera is composed of cliff-forming orange-white thick-bedded, fine to medium-grained arkose and lithic arkose with pebble to cobble conglomerate. This facies probably is a fluvial sheet sandstone. It is characterized by: (1) pi and omicron cross-stratification; (2) general paucity of mudrocks, but abundant shale pebbles; (3) unimodal, northeast-oriented paleocurrents; (4) wedging channel-sand bodies; (5) absence or extreme rarity of trace fossils; (6) sheet-like geometry; and (7) decrease in maximum grain size to the northeast.

The Arumbera probably was deposited in a coastal environment unrestricted by vascular land plants, but perhaps analogous in other ways to the delta of the modern Godavari River of India. Evidence includes: (1) a pronounced depocenter for the unit in the central part of the study area (thickness northeasterly from 216 to 1,123 m in 80 km); (2) unidirectional paleocurrents from fluvial sheet sands that radiate to the north, northeast, east, and southeast; (3) fluvial and coastal deposits in vertical, repetitive succession; and (4) east and northeast-trending zones of thicker deposits within fluvial sheet sands which may be distributary lobes.

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