A probable cave breccia in Middle Cambrian limestone, southern Nevada; petrography and paleomagnetic constraints on the time of formation

Spectacular limestone breccia, occurs at the contact between the Carrara Formation and Bonanza King Formation in the Desert Range, reflects a cave that has subsequently collapsed and "healed." Breccia blocks are angular; represent a diverse suite of shallow-water limestones that can be recognized laterally in undisputed strata; and exhibit clean truncation of late diagenetic fabrics, such as stylolites and blocky spar cements, at clast edges. In the blocks, the in situ directions of a secondary magnetization have been scattered. This magnetization probably lies in the range Late Cretaceous to mid-Cenozoic, which suggests that the time of brecciation is no older than Late Cretaceous. The breccia must be older than late Tertiary, however, because it is truncated by Basin-and-Range normal faulting.--Modified journal abstract.