Sequence Stratigraphy of the North Alpine Foreland Basin: A Case Study from the Early Miocene Hall Formation

Grunert, Patrick ¹; Hinsch, Ralph ²; Ćorić, Stjepan ³; Soliman, Ali ¹; Harzhauser, Mathias ⁴; Piller, Werner E.¹; Sperl, Hanns ²
(1) Institute for Earth Sciences, University of Graz, Graz, Austria. (2) Rohöl-Aufsuchungs AG, Vienna, Austria. (3) Geological Survey of Austria, Vienna, Austria. (4) Geological-Paleontological Department, Natural History Museum Vienna, Vienna, Austria.

The regional stratigraphic concept of the Central Paratethys is largely based on the biostratigraphy of benthic, often endemic species thus hampering a precise correlation to the international time scale. Alternative approaches to address this problem like sequence- or cyclostratigraphy have been widely ignored.

The North Alpine Foreland Basin (NAFB) comprises one of the main sedimentary basins of the Central Paratethys from Oligocene to Early Miocene and contains important source and reservoir rocks. A project co-funded by the Rohöl-Aufsuchungs AG (RAG) and the Austrian Academy of Science intends to provide a high-resolution analysis for three N-S-oriented wells from the Late Oligocene-Early Miocene in the NAFB. Based on the combined information from micropaleontology, geochemistry, well-log data and seismic images the outcome of the project will contribute to an improved age-model for the Central Paratethys as well as it will reveal new insights on the paleoceanographic and paleogeographic setting.

The potential of the integrated approach is exemplary shown for the Early Miocene Hall Formation. Facies analysis from benthic foraminifers and geochemical proxies has been applied to the interpretation of seismic images and allows the detailed description of a sedimentary sequence within the Hall Fm. A succession of turbiditic channels, slope environments and a prograding delta can be clearly distinguished by microfossil data, representing the systems tracts of the sequence. A time frame of c. 19-20.4Ma (early Burdigalian) and a correlation to the Bur 1 cycle (Abreu & Haddad, 1998) is indicated for the sequence by biostratigraphy (foraminifers, dinoflagellates, nannoplankton) and cyclostratigraphy (gamma and sonic logs).

In a next step, the established stratigraphic and paleoenvironmental framework from the autochthonous deposits will be compared to drill sites and seismic images from the southern margin of the basin where RAG is facing new ventures in oil and gas exploration. This area adjacent and below the Alps is heavily tectonised and imbricated and the results of the present study will help to unravel the relations between these highly deformed and dislocated deposits and their connection to the undisturbed northern part of the basin. The improved knowledge about the timing of deformation and imbrication along the Alpine thrust front will facilitate future hydrocarbon exploration in the NAFB.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.