A biochronologic tie-point for the base of the Tortonian stage in European terrestrial settings: Magnetostratigraphy of the topmost Upper Freshwater Molasse sediments of the North Alpine Foreland Basin in Bavaria (Germany)

2016 ◽  
Vol 49 (3) ◽  
pp. 445-467 ◽  
Author(s):  
U. Kirscher ◽  
J. Prieto ◽  
V. Bachtadse ◽  
H. Abdul Aziz ◽  
G. Doppler ◽  
...  
Keyword(s):  
Foreland Basin ◽  
The North ◽  
Upper Freshwater Molasse ◽  
North Alpine Foreland Basin ◽  
Alpine Foreland ◽  
Alpine Foreland Basin

Bivalves from the Innviertel Group of Allerding in the North Alpine Foreland Basin (lower Miocene, Upper Austria)

2020 ◽  
Vol 297 (1) ◽  
pp. 47-100
Author(s):  
Oleg Mandic ◽  
Simon Schneider ◽  
Mathias Harzhauser ◽  
Wolfgang Danninger
Keyword(s):  
Shallow Water ◽  
Time Window ◽  
Foreland Basin ◽  
Migration Route ◽  
Central Paratethys ◽  
Seagrass Meadows ◽  
The North ◽  
North Alpine Foreland Basin ◽  
Alpine Foreland ◽  
Alpine Foreland Basin

During the Ottnangian (Burdigalian, early Miocene), the North Alpine Foreland Basin operated as a sea-way connecting the Central Paratethys Sea with the Rhône Basin in the Western Mediterranean. Within this short time window, an intensive faunal exchange between the two paleo-biogeographic units occurred, which is reflected in macrofossil assemblages. The extraordinarily rich fossil record of the study site, Allerding, located in the westernmost Central Paratethys, provides valuable insights into the composition and origins of the bivalve fauna colonizing the marine gateway. The site documents the early Ottnangian marine transgression over deeply weathered crystalline basement, grading from fossil bearing shallow water clay and sand into the open marine "Schlier" facies of the Ottnang Formation. Despite considerable taphonomic overprint including aragonite leaching and mechanical abrasion of bivalve shells under turbulent shallow-water conditions, a total of 46 species are recorded, including two new species (Lima allerdingensis n. sp. and Astarte danningeri n. sp.). The dominance of suspension feeders, and the presence of several deposit feeders and chemosymbiotic taxa point to well diversified inshore settings, including low intertidal mudflats, as well as seagrass meadows. An abundance of primary and secondary hardgrounds is reflected in the high number of cementing and byssate species, as well as in the occurrence of species drilling actively into hard substrate. Finally, the dominance of active burrowers suggests a patchwork of habitats, where sandy and muddy soft bottoms occur interspersed. Biostratigraphic analysis constrains the deposits to the early to middle Ottnangian, based on the presence of the index species Flexopecten davidi and the concurrence of several taxa, which have their last or first occurrences within this interval. These are predominantly taxa persisting into the Badenian, therefore allowing for a straightforward differentiation between late Eggenburgian and early Ottnangian assemblages. While a few Central Paratethys endemics reflect a continued semi-isolated position of the area, the majority of the newly arriving species are shared with the Mediterranean and NE Atlantic, documenting the establishment of a faunal migration route via the North Alpine Foreland Basin. In the present study the lectotypes of Nucula mayeri Hörnes, 1865, Saccella subfragilis (Hörnes, 1875) and Lucinoma wolfi (Hoernes, 1875) are designated.

Diagenetic Evolution and Reservoir Quality of Sandstones in the North Alpine Foreland Basin: A Microscale Approach

2015 ◽  
Vol 21 (5) ◽  
pp. 1123-1137 ◽  
Author(s):  
Doris Gross ◽  
Marie-Louise Grundtner ◽  
David Misch ◽  
Martin Riedl ◽  
Reinhard F. Sachsenhofer ◽  
...  
Keyword(s):  
Foreland Basin ◽  
Gas Production ◽  
Coarse Grained ◽  
Reservoir Quality ◽  
Reservoir Properties ◽  
The North ◽  
North Alpine Foreland Basin ◽  
Alpine Foreland ◽  
Alpine Foreland Basin ◽  
The Impact

AbstractSiliciclastic reservoir rocks of the North Alpine Foreland Basin were studied focusing on investigations of pore fillings. Conventional oil and gas production requires certain thresholds of porosity and permeability. These parameters are controlled by the size and shape of grains and diagenetic processes like compaction, dissolution, and precipitation of mineral phases. In an attempt to estimate the impact of these factors, conventional microscopy, high resolution scanning electron microscopy, and wavelength dispersive element mapping were applied. Rock types were established accordingly, considering Poro/Perm data. Reservoir properties in shallow marine Cenomanian sandstones are mainly controlled by the degree of diagenetic calcite precipitation, Turonian rocks are characterized by reduced permeability, even for weakly cemented layers, due to higher matrix content as a result of lower depositional energy. Eocene subarkoses tend to be coarse-grained with minor matrix content as a result of their fluvio-deltaic and coastal deposition. Reservoir quality is therefore controlled by diagenetic clay and minor calcite cementation.Although Eocene rocks are often matrix free, occasionally a clay mineral matrix may be present and influence cementation of pores during early diagenesis. Oligo-/Miocene deep marine rocks exhibit excellent quality in cases when early cement is dissolved and not replaced by secondary calcite, mainly bound to the gas–water contact within hydrocarbon reservoirs.

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