Stratigraphy and fluvial sedimentary facies of the Neocomian lower Strzelecki Group, Gippsland Basin, Victoria

The Strzelecki Group Incorporates Berriasian to Albian, fluvial sediments d eposited in the Gippsland Basin during initial rifting between Australia an d Antarctica. Neocomian strata of the lowermost Strzelecki Group are assign ed to the Tyers River Subgroup (exposed in the Tyers area) and the Rhyll Ar kose (exposed on Phillip Island and the Mornington Peninsula). The Tyers Ri ver Subgroup incorporates two formations: Tyers Conglomerate and Rintoul Cr eek Formation. The latter is subdivided into the Locmany and Exalt Members. Ten fluvial sedimentary facies are identified in the lowermost Strzelecki Group: two gravelly facies: four sandy facies: and four mudrock facies. Ass ociations of these facies indicate: (i) prevalence of gravelly braided-rive r and alluvial-fan settings during deposition of the Tyers Conglomerate: (i i) more sluggish, sandy braided to meandering fluvial systems during Locman y Member sedimentation: and (iii) a return to active, sandy, braided-river settings for deposition of the Exalt Member. The Tyers Conglomerate and Rhy ll Arkose rest on an irregular erosional surface incised into Palaeozoic ro cks of the Lachlan Fold Belt. The overlying Rintoul Creek Formation incorpo rates more mature sediments where lithofacies associations varied according to base-level change, variations in subsidence rates, and/or tectonic upli ft of the principal sediment-source terranes to the northwest.