Death of a Carbonate Basin: The Niagara-Salina Transition in the Michigan Basin

LEIBOLD, ART W., and PAUL D. HOWELL, University of Michigan, Ann Arbor, MI

The A-0 Carbonate in the Michigan basin comprises a sequence of laminated calcite/anhydrite layers intercalated with bedded halite at the transition between normal marine Niagaran carbonates and lower Salina Group evaporites. The carbonate/anhydrite interbeds represent freshening events during initial evaporative concentration of the Michigan basin. Recent drilling in the Michigan basin delineates two distinct regions of A-0 Carbonate development: a 5 to 10 m thick sequence of six "laminites" found throughout most of the western and northern basin and a 10 to 25 m thick sequence in the southeastern basin containing both thicker "laminates" and thicker salt interbeds. Additionally, potash deposits of the overlying A-1 evaporite unit are restricted to the northern and western basin regi ns. The distribution of evaporite facies in these two regions is adequately explained by a source of basin recharge in the southeast--perhaps the "Clinton Inlet" of earlier workers. This situation suggests either that: (1) the source of basin recharge is alternately supplying preconcentrated brine and more normal marine water, or (2) that the basin received at least two distinct sources of water during A-0 deposition.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)