Depositional setting and implications of Paleoproterozoic glaciomarine sedimentation in the Hamersley Province, Western Australia

A combination of facies analysis and the identification of dropstones as we ll as striated and faceted clasts in diamictites and associated sedimentary rocks from the Hamersley Province confirms earlier suggestions of their gl acial origin. Ten lithofacies, comprising two diamictite, four sandstone, a nd four fine-grained facies, have been identified and arranged into three g laciomarine facies associations. Massive diamictite interbedded with lamina ted siltstone in the southern part of the province is interpreted to have b een deposited peripheral to the margin of rapidly melting tidewater glacier s emanating from more extensive ice cover in highlands to the south. Distal diamictites, sandstones, and laminated siltstones preserved north of the H ardey syncline were deposited from sediment gravity flows, sediment plumes, and rain-out from rare icebergs. Background marine sedimentation consisted of banded iron formation and siltstone, Using these glacial deposits as an event marker, it can be shown that similar to 2000 m of turbidites and sha llow-marine sedimentary rocks in the Turee Creek Group, on the southern mar gin of the Hamersley Province, are lateral facies equivalents of as much as 400 m of banded iron formation and mudrock to the north. This correlation demonstrates the markedly asymmetric nature of sub sidence in the McGrath t rough, which has previously been interpreted as a foreland basin with an or ogenic margin to the southwest. New geochronologic data constrain the age o f these glacigenic deposits to 2.45-2.20 Ga, which is within the range of p resent constraints for similar deposits in North America, Fennoscandia, and South Africa, Available paleomagnetic data suggest low-latitude (5 degrees -11 degrees) glaciation for the North American, South African, and West Aus tralian deposits.