Sedimentology and paleomagnetism of sediments

Clastic deposits in Kartchner Caverns consist of coarse deposits (breakdown, pebble gravel and mica-ceous sand) and fine-grained deposits (fault gouge and blocky clay). The coarse deposits are all related to the vadose history of the cave, while the fine-grained deposits are related to the phreatic history of the cave and, probably, to the beginning of vadose conditions. The illite clay in fault zones was possibly derived from the underlying Pinal Schist. The clay mineral rectorite is most likely a hydrothermal alter-ation of illite within the faults prior to the dissolution of the cave. The blocky clay unit is autochthonous sediment that was at least partially derived from residual fault gouge clay at the time of cave dissolution. The pebble gravels were deposited during different flood events in different parts of the cave, with a lat-eral fining of micaceous sand in back-wash areas. The blocky clay, pebble gravel, and micaceous sand are all paleomagnetically normal and date from the Brunhes/Matuyama normal (<~780 Ka). The clay mineral nontronite probably reconstituted from residual illite/rectorite under high pH, low Eh flood-water conditions within the cave environment. Kartchner Caverns is in the Whetstone Mountains, ~13 km south of Benson, Arizona, USA, just west of Arizona State Highway 90. The cave is developed in a downdropped bloc