Neogene uplift and erosion in the Alpine Foreland Basin (Upper Austria and Salzburg)

Abstract

Abstract:In the present paper we apply a multi-technique approach (shale compaction data, seismic stratigraphy, isopach maps, moisture content of lignite, fission track data) to assess timing and amount of uplift and erosion of the Alpine Foreland Basin. The combination of the different techniques allows us to discriminate the effects of two different erosion events during the Neogene: (1) Seismic stratigraphy and isopach maps indicate a Karpatian (Early Miocene) regional tilting of the basin to the west (slope of about 0.5 %) and a minor erosion phase. (2) Moisture content of lignite combined with fission track data provides evidence for extensive regional uplift after deposition of Late Miocene fluvial deposits. It is estimated that sediments, 500 to 900 m thick, have been eroded. Shale compaction data derived from sonic logs indicates additional uplift of the eastern part of the basin (near the river Enns). Here, 300 to 1000 m of sediments were additionally eroded (giving a total erosion of about 1000 to 1900 m!), with a general increase of erosion thickness towards the northeast. While the regional uplift is probably related to isostatic rebound of the Alps after termination of thrusting, the local uplift in the east could be affected by Late Neogene E-W compressional events within the Alpine-Pannonian system. Both, tilting and erosion influence the hydrocarbon habitat in the Molasse Basin (tilting of oil-water contacts, PVT conditions, biodegradation).

Laterally varying structure and kinematics of the Molasse fold and thrust belt of the Central Eastern Alps: Implications for exploration

“…before present (Genser et al, 2007). Recent investigations show that exhumation is heterogeneously distributed in the study area (Gusterhuber et al, 2012). Apatite fission-track data from well W9 (Figures 1; 7A; 9) indicate at least 900 m (2950 ft) of exhumation after the deposition of the upper freshwater Molasse, likely commencing approximately 8 m.y.…”

“…Younger freshwater Molasse sediments have been deposited but were mostly eroded because of postdepositional uplift during the last 8 m.y. (Gusterhuber et al, 2012). Quaternary glacial and periglacial deposits partly cover the Molasse sequence.…”

The Trattnach Oil Field in the North Alpine Foreland Basin (Austria)

“…The basin was finally filled with sediments of the Innviertel Group. At the end of the Lower Miocene the Austrian part of the North Alpine Foreland Basin was tilted towards the west (Gusterhuber et al, 2012). Coal-bearing limnic and fluvial sediments of Middle and Late Miocene age (Freshwater Molasse) follow above the erosional unconformity.…”

“…Coal-bearing limnic and fluvial sediments of Middle and Late Miocene age (Freshwater Molasse) follow above the erosional unconformity. The entire area was uplifted after deposition of the Freshwater Molasse and sediments 500 to 900 m thick have been eroded (Gusterhuber et al, 2012). …”

Light Hydrocarbon Geochemistry of Oils in the Alpine Foreland Basin: Impact of Geothermal Fluids on the Petroleum System

“…Hydrocarbon migration commenced simultaneously with hydrocarbon generation and continued until the present day [29]. The hydrocarbon habitat is strongly influenced by Neogene uplift and erosion [30]. Neogene tilting of the basin changed migration pathways and oil-watercontacts ( [30,31]; Linzer, pers.…”