SEQUENCE STRATIGRAPHY AND CYCLIC DEVELOPMENT OF BASAL ZECHSTEIN CARBONATE-EVAPORITE DEPOSITS WITH EMPHASIS ON ZECHSTEIN-2 OFF-PLATFORM CARBONATES (UPPER PERMIAN, NORTHEAST GERMANY)

Although the Basal Zechstein is classically subdivided into two cycles (Z1 and Z2, lower part) it can, alternatively, be subdivided into thr ee complete third-order depositional sequences (ZS1-ZS3) and the assoc iated lowstand systems tract/transgressive systems tract of a fourth s equence (ZS4). Third- and higher-order sea-level fluctuations influenc ed the depositional and diagenetic history of the carbonate-evaporite alternations within the Basal Zechstein. The main subject of the prese nt study, the Zechstein 2 Carbonate (Stassfurt Carbonate, or Ca2), is interpreted to encompass both transgressive (predominantly in slope an d basinal settings) and highstand systems tracts of Zechstein sequence ZS3 as well as part of the lowstand systems tract of the fourth Zechs tein sequence (ZS4). In northeastern Germany, hydrocarbon reservoirs o f the Ca2 developed along both northern and southern margins of the So uthern Permian basin on top of the topography of the Zechstein 1 cycle (Z1), This Z1 topography resulted from deposition of the Werra Anhydr ite (A1), the highstand systems tract of the second Zechstein sequence (ZS2). The northern Ca2 carbonate platform is consistently narrow and fringed by coated-grain and composite-grain bars and shoals. It is ch aracterized by a steep, fault-controlled slope which precluded the for mation of in situ shallow-water, grain-dominated carbonates during rel ative sea-level lowstands, Displaced shallow-water coated-grain and co mposite-grain packstones/wackestones may, however, occur as slope-fan deposits (turbidites). In contrast, the southern carbonate platform is wide, tectonically dissected and fringed by grain-dominated shallow-w ater carbonates (coated-grain and composite-grain bars and shoals). Ze chstein 2 shallow-water carbonates, detectable by Basal Zechstein seis mic anomalies, also developed on pre-existing topographical highs in o ff-platform positions. Three depositional cycles (Ca2 cycles I, II and III), most probably reflecting high-amplitude, fourth-order sea-level fluctuations, can be identified within the Stassfurt Carbonate.