Journal of Cave and Karst Studies - ISSN 1090-6924
Volume 61 Number 2: 79-83 - August 1999

A publication of the National Speleological Society

Sedimentology and Paleomagnetism of Sediments, Kartchner Caverns, Arizona
Carol A. Hill

Abstract

Clastic deposits in Kartchner Caverns consist of coarse deposits (breakdown, pebble gravel and micaceous 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 alteration 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 lateral 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.

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