Integrated Micropaleontology and Geochemistry of the Lower and Upper Puchkirchen Formation (North Alpine Foreland Basin, Chattian-Early Aquitanian)

Grunert, Patrick ¹; Sachsenhofer, Reinhard F.²; Hinsch, Ralph ³; Harzhauser, Mathias ⁴; Piller, Werner E.¹; Sperl, Hanns ³
(1)Institute for Earth Sciences, University of Graz, Graz, Austria. (2) Department of Applied Geosciences and Geophysics, University of Leoben, Leoben, Austria. (3) Rohöl-Aufsuchungs AG, Vienna, Austria. (4) Geological-Paleontological Department, Natural History Museum Vienna, Vienna, Austria.

The North Alpine Foreland Basin (NAFB) comprises one of the main depositional basins of the vanished Central Paratethys from Oligocene to Early Miocene. Within the NAFB, the Puchkirchen Trough (eastern Bavaria, Upper Austria, Salzburg) contains prominent source and reservoir rocks. Currently, the Rohöl-Aufsuchungs AG (RAG) is facing new ventures of oil and gas exploration in the southern Puchkirchen Trough comprising the Foreland, the Imbricated and the Overthrust Molasse. This area adjacent and below the Alps is heavily tectonised and imbricated. A project co-funded by the RAG and the Commission for the Paleontological and Stratigraphical Research of Austria (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 to unravel the relations between these highly deformed and dislocated deposits and their connection to the undisturbed northern part of the basin. Based on the combined information from micropaleontology, geochemistry, well-log data and seismic images the outcome of the project will reveal new insights into stratigraphy as well as the paleoceanographic and paleogeographic setting.

The integrated approach has been successfully tested on the Burdigalian Hall Fm. for which a sequence stratigraphic framework has been established. The Upper and Lower Puchkirchen Fms. underlie the Hall Fm. and represent basinal deposits of the Puchkirchen Trough during Chattian and Early Aquitanian. The sedimentary environment at the time is characterised by an axial channel belt with prominent turbiditic and mass-flow deposits. Initial analysis on benthic foraminifers and geochemical proxies (TOC, S, CaCO3, RockEval, δ13Cbulk) allows differentiating various facies types in the Upper and Lower Puchkirchen Fms. which document trends in primary productivity, organic matter flux, transport and water depth. The revealed facies development are applied to seismic images to evaluate their potential use for a sequence stratigraphic model.

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