| Bar B Formation | |
| Type: | Formation |
| Period: | middle Pennsylvanian |
| Prilithology: | Limestone, shale |
| Namedfor: | Barbee Draw (drainage) |
| Namedby: | V.C. Kelley and Caswell Silver |
| Year Ts: | 1952 |
| Region: | New Mexico |
| Country: | United States |
| Coordinates: | 33.0185°N -107.239°W |
| Underlies: | Bursum Formation |
| Overlies: | Nakaye Formation |
| Thickness: | 339feet |
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.[1] [2]
The Bar B formation is mostly cyclic[2] 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 50feet include reddish-brown siltstone, limestone conglomerate, and calcareous siltstone. The total thickness is about 339feet.[3] The formation rests on the Nakaye Formation and is unconformably overlain by the Bursum Formation.[2]
The formation likely correlates with the Panther Seep Formation in the San Andres Mountains.[1] [2]
The formation contains abundant bryozoan fossils.[3]
The formation was first defined by V.C.Kelley and Caswell Silver in 1952.[3] Bachman and Myers criticized its definition in 1975,[1] but it is accepted by Kues and Giles, though they restrict it to the Caballo Mountains.[2]