Slab of bioclastic limestone lens from base of Mulberry Member

Polished slab of lenticular clayey limestone that was resting on the
contact between the Mulberry Member and the underlying varicolored
claystone. Grain types in the limestone are obscure, but articulated and
disarticulated bivalved shells are visible, along with several plates of
calcareous algae and a small rugosan coral (upper left center). At the
upper right is a "lump" of limestone that became welded to the main
lenticular body. Most of the granular rock components are indeterminate
due to their small size and to bleaching of the rock. The bleaching was
caused by prolonged immersion in reactive fluids that were concentrated
above the iron-oxide-rich layer because they could not infiltrate into the
varicolored claystone below. The tiny round black objects, some of which
are arrayed in branching rows, are spherules and dendrites of manganese
oxide. These are especially prominent in the most thoroughly bleached
zones--where fluids most easily penetrated the rock.

Return to Technical Discussion

Main Menu