Sequence Stratigraphy - Trace Fossils as Indicators of Sedimentary Environments - page 163

FIGURE 2 Maximum regressive surfaces (MRS) and transgressive surfaces of erosion (TSE;
arrows) in vertical subsurface cores from a Late Permian carbonate platform of the Khuff Formation,
South Pars gas field, offshore Iran (A and B; see Knaust, 2009 ). A dense root system (probably
resulting from Cordaitales ) deeply penetrates from an erosive, blackened surface and is filled with
organic-rich sediment, dolomite, and gypsum. MRS in vertical section (C, arrows) and in plan view
(D) from the Middle Triassic Lower Muschelkalk Group, Thuringia, Germany (Upper Oolithe Bed;
see Knaust, 1998; Knaust et al., 2012 ). The top of the lime mudstone represents an omission surface
with Balanoglossites triadicus (B), Rhizocorallium jenense (R), and Trypanites weisei (T), indica-
tive of a gradual transition from firmground to hardground (sub- to intertidal) conditions. It is
overlain by a rudstone/packstone (shoal deposit). Scale bars ¼ 1 cm.
typical of landward positions (e.g., Skolithos Ichnofacies). Suites in the upward-
deepening interval associated with transgression would show the opposite trend.
The MRS itself may reflect sediment consolidation and early lithification and be
demarcated by omission suites reflecting firmground palimpsest burrows and/or
hardground borings belonging to the Glossifungites and Trypanites ichnofacies
( Fig. 2 C and D), respectively (e.g., Bromley, 1975 ). Successions reflecting upward
deepening are widespread in the transgressive portions of sequences and are most
distinctive during initial flooding across theMRS and at theMFS capping the plat-
form (e.g., Rodr ´ guez-Tovar et al., 2007 ). Nevertheless, due to their susceptibility
to early diagenetic cementation, carbonate successions also host minor firm-
grounds and hardgrounds associated with autogenically induced subaqueous ero-
sion and omission ( Hillg¨rtner, 1998 ). These discontinuities differ from major
bounding surfaces by their rather limited lateral extent and lack of change in the
overlying stratal stacking pattern.