Internal Structure of Carbonate Formations in Various Climate Regions

Abstract

Platform carbonate formations formed under various climate conditions differ both in the sets of rocks and in the character of their vertical structure and changes over the area. The humid formations are composed almost of limestones, often with diverse stenohaline fauna. The sections of the formations have a cyclic structure with microgranular partially weakly clayey limestones at the base and biomorphic and bioclastic ones in the middle and upper parts, and are often karstified in the roof. Such a composition and the similar structure are nearly constant within the entire distribution of the formation. The composition of the arid formations is more diverse. Dolomites predominate here. Gypsums and anhydrites are not uncommon, and limestones are dominant in the proximal parts close to the oceanic basins. The cyclites of these formations are trinomial with clayey dolomites, partially sulfates in the base, limestones in the middle part, and again dolomites and sulfates in the roof. The composition and structure of the arid zone formations are sharply asymmetric in space. In its proximal parts, they are limestones and the section is quite homogeneous, but in the distal parts, dolomites and sulfates predominate. The section is sharply inhomogeneous due to the appearance of gypsum and anhydrite packages.