Abstract: Depositional and Tectonic Interpretation of Limestone Insoluble Residues from Modern and Ancient Carbonate Rocks, Caribbean and Southeastern United States
Wayne C. Isphording, Maria E. Bundy, Sheri M. George, R. Bradford Jackson
Mineral compositions have long been used as indicators of the provenance and tectonic setting of source rocks for sandstones and shales. Extraction of the same information from limestones is less common because of the general paucity of the non-carbonate phase and the greater processing time that is required to concentrate the frequently encountered small quantities of detrital (and authigenic) minerals. The insoluble component, however, contains a great deal of valuable information and should not be ignored. The clays and other insoluble minerals in limestones from southeastern United States and the Caribbean region, for example, clearly reflect the volcanic activity that was associated with formation of the Mid-Atlantic Ridge rift system and the opening of the Atlantic cean and Gulf of Mexico. Similarly, major periods of orogeny during the Paleozoic and Mesozoic have left their signature, even in carbonate rocks that originated far from the sites where uplift was taking place. In other cases, the insoluble residue component clearly manifests periods of quiescence in adjacent land areas or testifies to the airborne transport of insoluble components from sources as far distant as the Saharan Desert of Africa. Similarly, insoluble components have convincingly shown that the origin of the extensive bauxite deposits found in Jamaican limestones are the result of alteration of interbedded volcanic ash units and have not resulted from accumulation of the detritus in the limestones. Residue analysis in Gulf Coast limestones can be successfully used for subsurf ce identification and correlation of carbonate units in the exploration for hydrocarbons, to reconstruct sedimentary environments, to identify missing sections, and to identify paraconformable relationships between adjacent carbonate units that are otherwise similar in appearance. The latter is especially useful where extensive recrystallization has taken place and fossils have been destroyed.
AAPG Search and Discovery Article #90955©1995 GCAGS 45th Annual Meeting and Gulf Section SEPM, Baton Rouge, Louisiana