Doris Reischenbacher

Evolution of lacustrine systems along the Miocene Mur-Mürz fault system (Eastern Alps, Austria) and implications on source rocks in pull-apart basins

Tectonically controlled lakes developed during Miocene lateral extrusion of the Eastern Alps. Mineralogy, and the inorganic and organic geochemistry of rocks from three boreholes were investigated to reconstruct the evolution of Lake Ingering and Lake Groisenbach and to study the distribution of source rocks in pull-apart basins. Gas-prone coal and oil-prone sapropelic shale accumulated during the initial, shallow stages of Lake Ingering. Thereafter, the lake deepened rapidly. 125-m-thick prodelta shale containing a type II kerogen was deposited in the brackish, several hundred meter deep, hydrologically closed lake. Afterwards, decreasing subsidence allowed the filling of the lake by prograding deltas. During the advance of the deltaic systems, the lake became shallower, hydrologically open, and the brackish influence terminated. Source rock quality decreased significantly during the filling stage of the lake, a consequence of dilution of autochthonous organic matter and of enhanced input of land plants. Despite its considerable dimensions, formation and filling of Lake Ingering lasted only two million years. Lake Groisenbach was considerably smaller and more susceptible to high-frequency changes in lake chemistry. Although the water body was temporarily oligosaline, brackish conditions did not occur. High sulphur contents were due to anoxic events and the inflow of Ca-rich waters. Abundant dissolved silica favoured diatoms blooms.

Palaeozoic source rocks in the Dniepr–Donets Basin, Ukraine

ABSTRACT The Dniepr–Donets Basin (DDB) is a major petroleum province in Eastern Europe. In order to understand the regional and stratigraphic distribution of source rocks for the dominantly gas-prone petroleum system, 676 fine-grained rocks from 30 wells were analysed for bulk parameters (total organic carbon (TOC), carbonate, sulphur, RockEval). A subset of samples was selected for maceral and biomarker analysis, pyrolysis-gas chromatography and kinetic investigations. Organic-rich sediments occur in different intervals within the basin fill. Maximum TOC contents (5.0 ± 1.9%) occur in the Rudov Beds, several tens of metres thick. The oil-prone rocks (Type III–II kerogen) were deposited in basinal settings above an unconformity separating Lower and Upper Visean sections. While maximum TOC contents occur in the Rudov Beds, high TOC contents are observed in the entire Tournaisian and Visean section. However, these rocks are mainly gas condensate-prone. Highly oil-prone black shales with up to 16% TOC and hydrogen index values up to 550 mgHC g–1TOC occur in Serpukhovian intervals in the northwestern part of the DDB. Oil-prone Lower Serpukhovian and gas condensate-prone Middle Carboniferous coal is widespread in the southern and southeastern part of the basin. Although no source rocks with a Devonian age were detected, their presence cannot be excluded.

Basin formation during the post-collisional evolution of the Eastern Alps: the example of the Lavanttal Basin

The Miocene Lavanttal Basin formed in the Eastern Alps during extrusion of crustal blocks towards the east. In contrast to basins, which formed contemporaneously along the strike-slip faults of the Noric Depression and on top of the moving blocks (Styrian Basin), little is known about the Lavanttal Basin. In this paper geophysical, sedimentological, and structural data are used to study structure and evolution of the Lavanttal Basin. The eastern margin of the 2-km-deep basin is formed by the WNW trending Koralm Fault. The geometry of the gently dipping western basin flank shows that the present-day basin is only a remnant of a former significantly larger basin. Late Early (Karpatian) and early Middle Miocene (Badenian) pull-apart phases initiated basin formation and deposition of thick fluvial (Granitztal Beds), lacustrine, and marine (Mühldorf Fm.) sediments. The Mühldorf Fm. represents the Lower Badenian cycle TB2.4. Another flooding event caused brackish environments in late Middle Miocene (Early Sarmatian) time, whereas freshwater environments existed in Late Sarmatian time. The coal-bearing Sarmatian succession is subdivided into four fourth-order sequences. The number of sequences suggests that the effect of tectonic subsidence was overruled by sea-level fluctuations during Sarmatian time. Increased relief energy caused by Early Pannonian pull-apart activity initiated deposition of thick fluvial sediments. The present-day shape of the basin is a result of young (Plio-/Pleistocene) basin inversion. In contrast to the multi-stage Lavanttal Basin, basins along the Noric Depression show a single-stage history. Similarities between the Lavanttal and Styrian basins exist in Early Badenian and Early Sarmatian times.

Paleozoic Source Rocks in the Dniepr-Donets Basin, Ukraine

The Dniepr-Donets Basin (DDB) is a major hydrocarbon province in eastern Europe. Moreover organic-rich sediments in the DDB may offer a shale gas potential. However, only limited data on source rocks are available. Within the frame of the present study, a

Sequence Stratigraphic Setting of Lower Carboniferous Black Shales in England and the Netherlands

Black shales are well-known from Lower Carboniferous units in the Northwest European Carboniferous Basin, but they are poorly understood in terms of sequence stratigraphy. The aim of the study was the creation of a sequence stratigraphic frame for Lower Carboniferous sediments in England and the Netherlands and to study the shale gas potential of black shales. The study is based on well logs, 2D-seismic data and bulk geochemical parameters. The Upper Dinantian basinal sediments in the Widmerpool Gulf display three TSTs separated by two HSTs. TOC contents reach up to 4%. The sequence stratigraphic subdivision of the Widmerpool Gulf cannot be transferred to the Stainmore Trough. This is a consequence of the narrow horst/graben configuration. Log facies and seismo-stratigraphic setting of the Namurian Upper Bowland Shale and the Lower Sabden Shale in Middle England show two general coarsening upward trends. TOC contents are up to 9% despite of partly high maturity. The Geverik Member in the Netherlands is a time-equivalent to the Upper Bowland Shale. It is also organic matter rich and lateral continuous. In contrast to the Upper Bowland Shale, the Geverik Member represents a TST. In general there is a close relationship between TOC contents and systems tracts.