SEQUENCE STRATIGRAPHY AND CYCLIC DEVELOPMENT OF BASAL ZECHSTEIN CARBONATE-EVAPORITE DEPOSITS WITH EMPHASIS ON ZECHSTEIN-2 OFF-PLATFORM CARBONATES (UPPER PERMIAN, NORTHEAST GERMANY)
C. Strohmenger et al., SEQUENCE STRATIGRAPHY AND CYCLIC DEVELOPMENT OF BASAL ZECHSTEIN CARBONATE-EVAPORITE DEPOSITS WITH EMPHASIS ON ZECHSTEIN-2 OFF-PLATFORM CARBONATES (UPPER PERMIAN, NORTHEAST GERMANY), Sedimentary geology, 102(1-2), 1996, pp. 33-54
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.