Late Archaean synorogenic basins of the Eastern Goldfields Superterrane, Yilgarn Craton, Western Australia: Part II. Kurnalpi Terrane

The Penny Dam, Belches, Yilgangi, White Hills, Granny, Royal, Lucky, Brock and Wallaby Supersequences of the Kurnalpi Terrane crop out in synclines that are the erosional remnants of basins that developed as linear zones of subsidence between approximately north-trending compartment-bounding faults. Dominant sedimentary facies range from gravel-rich and sand-rich concentrated density-flow deposits to thickly and thinly bedded Bouma-type turbidites. Background deposits are black shales or laminated green mudstones, and banded iron formation is preserved in some condensed sections. Periods of non-deposition are recorded by bedded chert, which is the product of early diagenetic sea-floor silicification. The basins were separate deep-marine canyon to linear-fan systems that were linked laterally and distally by mud-rich deposits. There is only minor evidence for fault-anchored, canyon-margin slope aprons.Basin development occurred during two stages separated by a period of deformation, uplift and erosion. Sparse palaeocurrents establish sediment dispersal was to the south or southeast, indicating that uplift to the north or northwest controlled palaeoslopes. Stacking of lithofacies is aggradational, and consistent with deposition in fault-bound basins. Tectonostratigraphic equivalence with siliciclastic supersequences of the Kalgoorlie and Gindalbie Terranes is established by common depositional systems, stratigraphic styles and stratigraphic responses to tectonic forcing. Consequently, the siliciclastic supersequences represent overlap (or late-stage) basins that tied together arc-related terranes following terrane amalgamation. Similar depositional facies, aggradational styles of facies stacking and two-stage development characterise the syncollisional Plio-Pleistocene Coastal Range Basin of Taiwan. Modern analogues are the deep-marine Southern Longitudinal and Taitung Troughs off southeastern Taiwan that are being filled by synorogenic sediments derived from the Taiwan Orogen.