Unit is named the Gibraltar Rock Member of the Tiger Formation (revised) in the Cusick region of northeastern WA. Consists of massive to horizontally and planar cross-stratified polymictic conglomerate and conglomeratic sandstone that has feldspar-rich clasts and matrix. Plant fossils are locally abundant in finer grained sandstone and siltstone. Unconformably overlies the Sanpoil Volcanics and O'Brien Creek Formation; is a facies equivalent of, intertongues with, and is separated by a vertical arbitrary boundary from the Locke Member (new) and the Winchester Creek Member (new), both of the Tiger. Thickness at the type section is 105 m; maximum thickness is 400 m. Age ranges from early middle Eocene, based on the inclusion of late early to early middle Eocene volcanic rock clasts, through middle Miocene, based on middle Miocene regional faults that bound the Tiger Formation, although the age determination of middle Miocene is less definite. (B1565)

Source: GNU records (USGS DDS-6; Menlo GNULEX).