Middle Eocene foraminifera from the type Giralia Calcarenite, Gascoyne Platform, southern Carnarvon Basin, Western Australia

Abstract

Foraminifea from the type section of the Giralia Calcarenite indicate an upper zone P12 correlation and a Middle Eocene age (probably within the interval 41.5–40.5 Ma, BKSA95 time scale). The type Giralia Calcarenite is considered to represent one sequence (with maximum thickness of 40–50 m preserved on the Gascoyne Platform) and to reflect late transgressive and early highstand deposition about a maximum flooding event. Initial retrogradation of the shoreline produced a maximum water depth of about 50 m at the type locality (5–6 m above base of stratigraphic section). The formation may correlate with shallow marine deposits found elsewhere in the Southern Carnarvon Basin (e.g. Eocene limestones at Yaringa and Red Bluff, and the Merlinleigh Sandstone), and correlates with Middle Eocene transgressive units in the Perth, Eucla, Great Australian Bight and Otway Basins.