Storm features of siliciclastic shelf sedimentation in the mid-Cretaceous epeiric seaway of northern Australia

Abstract

Late Aptian to Early Cenomanian strata were deposited in a large epeiric seaway which covered much of the northern Australian landmass during mid-Cretaceous time. The seaway stretched from the Carpentaria Basin in the north to the Eromanga Basin in the south. During this period siliciclastic sediments accumulated on a gently sloping epeiric shelf, which formed the western margin of the Carpentaria Basin. The shelf maintained a relatively similar configuration throughout the mid-Cretaceous with water depths rarely exceeding 50 m, and the seafloor was apparently within the influence of storm waves over much of the area. The shelf was storm- and wave-dominated, and most early formed or fair-weather sedimentary structures were destroyed or extensively modified during episodic storms. Storm features include hummocky cross-stratification, shelly lags, erosional conglomeratic lags, gutter casts, lenticular micro-hummocky sand beds, megaripples, characteristic low-diversity and opportunistic ichnofacies, various styles of wave-ripple lamination, and poorly preserved event beds. Most storm-influenced units are preserved as coarsening- and shallowing-upwards facies successions, which aggraded during high relative sea level and prograded during falling relative sea level. Some of these successions were subsequently eroded during further cyclic fluctuations of relative sea level.