Evidence of Rain Shadow in the Geologic Record: Repeated Evaporite Accumulation at Extensional and Compressional Plate Margins

ABSTRACT: Arid climates have been common and effected water resources throughout Earth history. This climatic history provide a key to understanding current causes for desertification and a means to devise realistic strategies for coping with its effects. Desert climates are often indicated in the geologic record by thick sections of evaporites (anhydrite, gypsum and halite) that have accumulated in both lacustrian and marine settings either adjacent to margins of recently pulled apart continental plates, in compressional terrains of colliding margins, or in areas of local tectonic uplift or sediment accumulation that have isolated standing bodies of water from the sea. These linear belts of evaporitic rocks can be directly related to rain shadow caused by: 1) The aerial extent of adjacent enveloping continental plates 2) The occurrence of uplifted crust marginal to linear belts of depressed crust 3) The occurrence of linear belts of depressed crust, with surfaces that are often below sea level 4) The occurrence of internal drainage and/or limited access to open ocean waters 5) The location within a climatic belt already characterized by low rainfall Examples of evaporite generation in depressed extensional basins belong to the Mesozoic sedimentary section of the North and South Atlantic margins: the Mesozoic of the northern Gulf of Mexico; the Mesozoi