Evaporites through space and time

Evaporites are fascinating deposits not only becauseof their hydrocarbon potential and usually excellentpreservation of depositional structures but alsofrom their important role in the interpretation of basinevolution and palaeogeography. They have an unusualpotential to record in detail the final stage of developmentof many sedimentary basins. For these reasons,there was widespread research on evaporites in thesecond half of the 20th century, which resulted in severalkey books and special volumes that outlined thegeological conditions and processes controlling theformation of these deposits. It is worth stressing herethe outstanding efforts in this field of the first of the coeditorsof the volume. It is now clear, for example, thatevaporites are unusually differentiated with regard totheir lithology, petrography and mineralogy, sedimentologyand diagenesis, composition, origin and evolutionin space and time.As a result of this expansion inresearch many fundamental questions relating to thegeology of evaporites have been identified. Some ofthese, however, such as diagenetic conversion, theprocesses leading finally to the evaporitic rocks and thegeochemistry of these rocks, to mention only a few;have received little attention from researchers so farand remain for future investigation. In this context, theorigin of evaporites, their sedimentology and diagenesis,and their economic potential are still at the descriptivestage, as exemplified by the book under review.The volume documents evaporites of different agesand regions around the world, attributed to variousmodels and processes of origin, composition and diagenetictransformations, and occurring essentially inthe ancient record. There is first a critical overview bythe editors of the results of the papers comprising thevolume, placing these into the context of the state-ofthe-art of current research. The compilation is dividedinto five parts of unequal length, each comprising fromtwo to six contributions. The first part of the volume isrelatively long and deals with Tectonics, basin evolutionand evaporites (five papers). Then follow twovery short parts devoted to Working depositional models(two papers) and Post-depositional evolution ofsediments (two papers). The fourth part is the largestand deals with Ancient basins (seven papers). Thebook finishes with two examples of Regional reviews(two papers). In my view it is the first and fourth partsof the volume that are the most interesting.The volume covers a great range of evaporite topics.In their selection of papers, the editors have tendedto concentrate on those describing gypsum and salt deposits,but there is one paper on clastic deposits predatingtheMioceneMediterranean evaporites and twopapers on carbonates supposedly associated with theAlpine Triassic and Neoarchaean evaporites respectively.With regard to evaporite mineralogy, the topicscovered range from gypsum, through anhydrite, KMgsulphate to halite, potash salts and sylvite. The volumepresents evaporites from South Africa, northAfrica, through theMediterranean and eastAsia, fromthe European Alpine systems to South Atlantic saltsettings and the Permian Basin of Texas and NewMexico; the evaporites described were deposited in intracratonic,through orogenic, foreland and platform tosyn- and post rift evaporitic basins, and range in agefrom Precambrian to modern saline brines. The methodsused by the authors range from classic field and regionalinvestigations, through seismic to geochemical(fluid inclusions and stable isotopes) and even experimentalstudies. The reader will find in this volume regionalsyntheses, discussions of local phenomena(“pseudocarniole”, sylvite), short and long contributions,standard research papers and overviews, newideas and repetitions of old hypot