CLASSIFICATION OF CONTINENTAL CARBONATES

The types of continental carbonates that are described in the literature seem to represent a plethora of origins and textures. These nonmarine carbonates are documented from all latitudes so climate is a minor control on deposition. A classification of these carbonates should involve an understanding of the depositional environment as well as the hydrologic controls of water or calcium ion input. Large quantities of water with carbonate load, whether dissolved load, suspended load, or bedload, are needed to accumulate significant carbonate deposits in subaerial and subaqueous continental environments since time is short in the context of geologic time and landscape evolution. Provenance is key to predicting patterns of deposition as well, especially for eolian carbonate deposits. Microbialites are components of many of these carbonate types and require significant input of Ca-rich water, especially groundwater. Classification categories for depositional environments include: (1) soil, (2) palustrine to playa, (3) lacustrine, (4) fluvial above and at the regional springline, (5) fluvial below the springline and (5) eolian. Inputs include: (1) surface water, (2) groundwater, and (3) wind. Input directly by precipitation occurs but is very minor and difficult to distinguish. Types of continental carbonates can be (1) pedogenic carbonates and calcrete, (2) groundwater calcrete, (3) spring/seep deposits at or above the regional springline, (4) artesian spring/seep deposits, (5) subaqueous lacustrine carbonates, (6) palustrine margin carbonates of perennial lakes, (7) palustrine-playa carbonates of ephemeral lakes, (8) spring/seep deposits at ephemeral and perennial lake margins, including beachrock, (9) carbonate pond sediments on sheetflood plains containing pedogenic mud aggregates, (10) lacustrine delta carbonates, (11) eolian carbonates, (12) carbonate lake deposits on anastomosing river floodplains, and (13) carbonate eolianites.