SEDIMENTOLOGY AND PALYNOFACIES OF THE ZECHSTEIN-2 CARBONATE (UPPER PERMIAN, NORTHWEST GERMANY) - IMPLICATIONS FOR SEQUENCE STRATIGRAPHIC SUBDIVISION

The Zechstein 2 Carbonate (Stassfurt Carbonate, or Ca2) of the second Zechstein cycle has been subdivided into third-order and higher-order sequences, using sedimentology and palynofacies analysis as complement ary tools. This combination of tools provides a logical approach to th e correlation of parasequences across different depositional settings in a platform to basin transect. The Ca2 reservoir overlies the anhydr ites of the first Zechstein cycle (Z1), the Werra Anhydrite (A1), and is sealed by the anhydrites of the second Zechstein cycle (Z2), the Ba sal Anhydrite (A2). The Ca2 can be subdivided into platform, upper slo pe, middle slope, lower slope and basinal facies. These facies can be further subdivided into a total of twenty-six subfacies types. The Ca2 comprises-a-nearly complete third-order sequence (ZS3) and part of th e lowstand systems tract of the fourth Zechstein sequence (ZS4). It ca n be further subdivided into seven parasequences identified by subfaci es succession, gamma-ray-log response and palynofacies interpretation, indicating higher-order intra-Ca2 relative sea-level fluctuations. Se a-level fluctuations at third-order and higher-order scale are reflect ed by cyclic changes in palynomaceral assemblages. Transgressive depos its including the maximum flooding surface are characterized by a high proportion of vitrinitic and inertinitic, frequently blade-shaped pal ynomacerals, whereas various types of degraded palynomacerals occur mo st frequently during lowstand and highstand progradation phases. Inter tidal carbonates at the base of the Ca2 third-order lowstand wedge are particularly distinct due to the abundance of palynomorphs resembling colonial green algae (Plaesiodictyon spp.). The proposed chronostrati graphic subdivision of the Ca2 into third- and higher-order sequences improves the prediction of lateral and vertical reservoir facies distr ibution.