Non-Marine Carbonates in Rifts

We are used to the fact that marine carbonates develop in a diverse range of depositional settings and climates. Non-marine carbonates also exhibit a wide variety of depositional styles and significant carbonate accumulations can develop within subsurface sediments, subaerially and subaqueously in continental rift settings. While lakes can be classified on the basis of accommodation space and climate, hydrological controls are equally important in producing the continuum of carbonates found in rifts. Extensive carbonates are produced in shallow aquifers, effectively interstitially in alluvial and fluvial deposits, and hydrocarbon reservoirs are known in such carbonates. Emerging groundwaters in rifts can produce a range of spring and fluvial carbonates. Discharge hardwater wetlands are also capable, under suitable conditions of producing thick (>200m) palustrine carbonates, apparently lacking a reservoir analogue. Lacustrine carbonates are diverse, but as a result of reduced wave energy and atidality fail typically to produce significant grainstone facies with reservoir potential. Microbial carbonates rarely develop significant dimensions. Although the diagenetic potentials of fresh and saline lakes are well understood, that of alkaline lakes is a gap in our knowledge.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California