Bar B Formation
The Bar B Formation is a geologic formation found the Caballo Mountains of New Mexico. It preserves fossils showing it was deposited in the middle to late Pennsylvanian. Description. The Bar B formation is mostly cyclic beds of shale and limestone, with shale making up about 80% of the formation and limestone the other 20%. Chert is present in some of the limestone. The upper include reddish-brown siltstone, limestone conglomerate, and calcareous siltstone. The total thickness is about . The formation rests on the Nakaye Formation and is unconformably overlain by the Bursum Formation. The formation likely  correlates with the Panther Seep Formation in the San Andres Mountains. Fossils. The formation contains abundant bryozoan fossils. History of investigation. The formation was first defined by V.C.Kelley and Caswell Silver in 1952. Bachman and Myers criticized its definition in 1975, but it is accepted by Kues and Giles, though they restrict it to the Caballo Mountains.