Numerische Simulation der geologischen Entwicklungsgeschichte des permokarbonen Saar-Nahe-Beckens

The burial, erosion, and temperature history of the Permo-Carboniferous Saar-Nahe Basin was reconstructed by integrating geological, geochemical, and petrophysical analysis and applying 1D, 2D, and 3D petroleum systems modelling programs. Vitrinte reflectance was measured on 180 samples and was complemented by published data sets. Coalification maps were reconstructed revealing a synkinematic coalification pattern. Vitrinite reflectance values of 0.5 to 0.8 % VRr at the surface indicate up to several thousand meters of Permo-Carboniferous eroded overburden. Apatite fission track analyses on 13 samples allowed quantifying the Mesozoic/Cenozoic temperature history. But no information about the Permo-Carboniferous could be obtained by this method. Rocks which are at the surface at present day, reached temperatures of more than 110 °C during the Mesozoic. Subsequent cooling started earlier in the western part of the basin but was faster in the eastern part. In the eastern part of the basin a Tertiary temperature increase of 10 °C can be observed. The 1D simulation results show that present day heat flow ranges between 50 and 55 mW/m² throughout the basin (calibrated with present day formation temperatures). Apatite fission track data indicate - at least for the eastern part - a temperature increase of 10 °C in the Tertiary. This can either be explained by an increased heat flow of 10 mW/m² (from 55-60 to 65-70 mW/m²) or an additional 300 m of Eocene/Oligocene sediments. The regional geology allows both scenarios. To explain the Mesozoic temperature increase, 1600 m of additional Mesozoic overburden have to be assumed. The data indicate an increased heat flow in the eastern part of the basin with up to 75 mW/m² for the Upper Jurassic. During the Cretaceous the heat flow was around 60 mW/m². Thermal maturity of the sediments can only be explained by deep burial and moderate heat flows during time of maximum burial in the Permo-Carboniferous. In contrast to previous work, higher amounts of missing sediments have to be assumed. During Permian times, between 1700 and 3200 m of Permo-Carboniferous sediments were eroded. The maximum thickness of Rotliegend sediments reached 2500 m in the Prims syncline (St. Wendel 1), 3700 m in the Zweibrücken syncline (Landstuhl 1), 3700 in the Nahe syncline (Monzingen 1), 2900 m on the flank of the Pfalz anticline (Meisenheim 1), and 3800 m in the Alzey-Nierstein horst (Olm 1). Different sedimentation and erosion histories are characteristic for the anticlines and synclines, respectively. Calculated heat flows are variable and range between 50 and 75 mW/m², which implies a crustal thickness between 30 and 40 km during the time of maximum burial. These values are in accordance with the geodynamic setting of the basin. The 2D and 3D results show the synsedimentary activity of the synclines and anticlines in the Saar-Nahe Basin, especially for the Rotliegend time. In transect 1 ca. 3700 m of Rotliegend sediments were deposited in the Nahe syncline, compared to only around 2200 m towards the crest of the Pfalz anticline. Permo-Carboniferous heat flows increased from 57 to 67 mW/m² toward the Hunsrück boundary fault. Transect 2 and the 3D model show that in the central part of the Saarbrücken anticline no or only minor Rotliegend sedimentation took place. The simulation of the Donnersberg intrusion body showed that maturity is only increased locally around the intrusions in the Saar-Nahe basin. Based on the calibrated temperature history of the basin, the timing of methane generation from the Permo-Carboniferous coal seams could be evaluated. Methane generation started around 305 Ma and stopped at the latest after the erosion of 2000 to 3500 m of sediments in the Permian. This is the main reason why exploration in the 50ties and 60ties was not successful.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Hertle, Michael

Contributors dc:contributor

• Littke, Ralf

• info:eu-repo/classification/ddc/550
• Saar-Nahe-Senke
• Permokarbon
• Geologie
• Numerisches Modell
• Geowissenschaften
• Numerische Simulation
• Beckensimulation
• Saar-Nahe Becken

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123593%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:61992