New Aspects in Sequence Stratigraphy: Lowstand Cyclesand Coal Formation in Paralic Environment

摘要

The approximately 250 m thick tertiary strata of the Lusatian Lignite District (Eastern Germany)shows many cyclic changes of shallow water deposits, paralic brown coal seams and partly terrestrialalluvial fans (Spremberg, Brieske, Meuro and Rauno Formation). Their paleogeographicposition at the southern shelf margin of the North-West European Tertiary Basin is mostly determinedof influences of sea-level fluctuations. The study complex, called the Brieske Formation(Lower-/Middle Miocene), is located between the 3rd Miocene Seam Complex at the base and the2nd Miocene Seam Complex at the top. Examples for coal formation during transgression is the3rd Miocene Seam Complex and for regressive phases the 2nd Miocene Seam Complex.The Tertiary coal-bearing sequence of the Lower-/ Middle Miocene Lusatian area reflects significantthird-order sea level changes. Within a major transgressive or regressive phase fine-scaledsea level oscillations of small-scale order can be recorded in a very marginal palaeogeographicalposition in the North-West European Tertiary Basin.Even the finest scaled fluctuations of groundwater levels with a magnitude of only few decimetres,resulted in bog-facial changes in the ancient peat bogs. These fluctuation which are thoughtto be related to the sea-level trend may be recorded in typical coal facies successions.