Provenance of the Tumblagooda Sandstone, Western Australia
The Ordovician Tumblagooda Sandstone is a thick red-bed fluvial-shallow-marine succession within the Carnarvon Basin of Western Australia. The well exposed Red Bluff coastal section, within Kalbarri National Park, consists of silty fine-grained to very coarse-grained sandstones that are occasionally pebbly. They are moderately to well sorted, with a bimodal distribution indicating more than one process of transportation/deposition (fluvial and aeolian). The coarser grains of the bimodally sorted sandstones are mostly rounded, and surrounded by angular to subrounded finer grains. The sandstones are poorly compacted, porous and permeable; the latter vary between ~6-26% and ~0.04-3814mD, respectively.
Iron oxide is the earliest type of cement followed by minor clay and finally silica as authigenic overgrowths on quartz and quartzite grains. In general the iron oxide cemented samples lack silica cement and have low porosities. The iron oxide is derived from the oxidation of the detrital hematite and ilmenite grains within concentrated lamina, which are both parallel to cross-bedding and randomly distributed. Percolating acidic meteoric waters probably oxidized the iron-bearing opaques and converted them to goethite and limonite.
Mineralogically, the sandstones are mature subarkoses and quartz litharenites consisting dominantly of quartz (mostly showing wavy extinction) and less feldspars (K-feldspar with rare plagioclase) and minor to negligible lithic grains (mostly quartzites, and rarely chert and granite). Tectonic discriminating triangular diagrams of the detrital grains (Qt-F-L) place them in the Craton Interior field within the Continental Block Provenance. The heavy minerals are mostly rounded, and are dominated by the ultrastable minerals (zircon>tourmaline>>rutile) and metastable opaques (ilmenite, hematite and leucoxene) confirming the highly mature nature of these sandstones. The source of the Tumblagooda Sandstone is the large Archaean Yilgarn Craton, which is dominated by granites, gneisses and greenstones and minor basic/ ultrabasic rocks and other rocks, veins and mineral deposits. The dominant granites and gneisses were the main source of quartz,feldspar, the rarely found granite lithics and the ultrastable heavy minerals; the basic/ultrabasic rocks as well as the banded iron formations within the craton are the main source of ilmenite and hematite.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009