Time Lines in Evaporitic Environments--Salina Versus Sabkha: ABSTRACT

Abstract

Over the past 20 years, there has been an explosion in our knowledge of Holocene evaporitic environments, mainly due to the excellent studies completed on the (supratidal) sequences of the Persian Gulf. Our detailed knowledge of these sabkhas has given us an excellent tool for interpreting ancient evaporite sequences. The implies that an ancient evaporitic sequence was deposited as a prograding sequence of three laterally extensive, continguous environments: the shallow subtidal, intertidal, and supratidal. However, some of us have called the model the dogma of the decade; few would dispute that in some ancient evaporitic sequences the analogy has been overextended. There is another area of Holocene evaporite deposition, namely the carbonate-gypsum salinas of southern Australia, when subaqueous (?subtidal) millimeter-laminated evaporites have been forming for the past 6,000 years. The stratigraphy is a bull's eye pattern with nearly vertical carbonate to gypsum facies boundaries, and yet within each facies one finds horizontal bedding. This type of deposition, with major nearly vertical boundaries, and minor nearly horizontal bedding surfaces, is due to the rapid infilling of a density-stratified brine pond. A depositional model (the model) based on the southern Australia salinas is a model characterized by predominantly vertical rather than horizontal accretion. Both the salina and the sabkha models have characteristics which can be used to refine a versus interpretation in ancient sequences. End_of_Article - Last_Page 567------------