Condensation processes in shallow platforms

Abstract

Sequence stratigraphy allows elucidation of the time-space relationships of deposits in sedimentary basins. However, the relative distribution of unconformities and condensed sections can neither be used as diagnostic criteria for particular palaeogeographic settings, nor as indicators of maximum regional transgressions. Condensation processes also occur in the shallowest portions of platforms and during maximum regression episodes. Three separate processes of condensation are here distinguished: stratigraphic, sedimentary and taphonomic. These three categories of condensation can be used to analyze patterns of sediment distribution, and also to estimate lateral and vertical variations in sedimentation rates. Contrary to the usual interpretation, the maximum values of rate of sedimentation and degree of accommodation of sediments, as well as the highest relative sea level, occur in the lowest levels of the shallowing-upward sequences. The distinction between these condensation processes allows one to predict that the degree of sedimentary and stratigraphic condensation will be higher towards the distal portions of the platforms, whereas the stratigraphic condensation processes without sedimentary condensation will show the maximum intensity and frequency in the shallowest portions of the platforms.

Upper Maastrichtian depositional environments and sea-level history of the Kopet-Dagh Intracontinental Basin, Kalat Formation, NE Iran

“…7). The bivalve layer and sandy limestone and sandstone above the paleosol are interpreted as transgressive lag deposits similar to those that have been described by Gomez and Fernandez-Lopez (1994). The maximum transgression is marked by a sandy red algal grainstone that was deposited under open marine conditions (Fig.…”

Preservation of phosphatic wood remains in marine deposits of the Brentskardhaugen Bed (Middle Jurassic) from Svalbard (Boreal Realm)

“…Reworked fossils are the only evidence of sedimentary omission and phases of reworking in some outcrops. The Brentskardhaugen Bed shows faunal condensation (s. Fürsich 1978) or taphonomic condensation (Gómez and Fernández-López 1994) with a mixture of temporary successively organic remains of non-contemporaneous populations or communities. According to Fernández-López et al (2002), taphonomic condensation is an extreme case of time averaging.…”

Microfacies Data: Fabrics

“…Gomez and Fernandez Lopez (1994) drew attention to the fact that the relative distribution of unconformities and condensed sections should not be used as unequivocal diagnostic criteria for particular paleogeographical settings (e.g. basinal),or as indicators of maximum regional transgressions, because condensation processes also occur in the shallowest parts of carbonate platforms and during maximum regression periods.…”

“…Tertiary : Premoli Silva et al 1998; Vachard et al 1987 Cretaceous: Andrieux 1967 Company et al 1982, Garcia-Hernandez et al 1989, Greber 1988 Jurassic:Böhm et al 1999 Bouillin and Bellono 1990; Fabricius 1968; Fels and Seyfried 1993; Jurgan 1969; Lantos and Mallarino 2000; Lehner 1991; Martire 1996; Molina et al 1985; Schöll and Wendt 1971; Seyfried 1978 Seyfried , 1980 Vera et al 1984; Wendt 1969; Wiedenmayer 1963; Winterer and Sarti 1994 Triassic: Blendinger 1986; Cozzi 2000; Fabricius 1966; Fischer 1964; Füchtbauer and Richter 1983; Krystyn et al 1971; Schlager 1969; Schöll and Wendt 1971; Wendt 1973; Wiedenmayer 1963 Permian: Pray and Stanton 1992; Stanton and Pray 1993 Devonian: Belka 1989; Gischler 1992; Krebs 1968; Macdonald et al;1994 , Playford et al 1989 Szulczewski 1973; Tucker 1973; Wendt and Belka 1991; Wendt et al 1984 …”