Origin and Rarity of First-Cycle Quartzarenite

Prodip K. Dutta

Recent studies and the reinterpretation of pertinent literature reveal the presence of texturally immature first-cycle quartzarenite of fluvial origin. These finds contradict the generally accepted views that (a) quartzarenites are texturally mature and are the products of a multicycle process, and (b) first-cycle quartzarenites are rare in the geological record and genesis is attributed to a unique combination of tropical climate, low subsidence rate, and high-energy transport.

In India, quartzarenite of Rhaetic age (Mahadeva Formation) and Kungurian age (Barakar Formation) have been identified from the Gondwana basin overlying crystalline basement. Extensive quartzarenite of Middle Triassic age (Hawkesbury Sandstone) has also been reported from the Australian Gondwana basin. All these sediments were derived from crystalline provenances of close proximity in moderate to low-relief transport. Mineralogical maturity of these texturally immature sediments is attributed to chemical weathering within a climatic range of humid-cool to humid-warm conditions. Because of their derivation from crystalline rocks, the quartzarenites of India and Australia are interpreted to be of first-cycle origin. Probable first-cycle quartz-rich sandstone/quartzarenite of Triassic an Jurassic ages have been reported from Gondwanas of Australia (Expedition Sandstone) and Scotia Arc region (Springhill Sandstone).

First-cycle quartzarenite/quartz-rich sandstone, thus, seem to be more common than previously thought and form within a wider climatic, tectonic, and environmental spectrum. A renewed search may throw more light on our ideas of their genesis and rarity.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.