--> ABSTRACT: Burial History and Diagenesis in Buntsandstein Aquifer Sandstones of the Thuringian Syncline (Germany), by Beyer, Daniel; Götze, Marika ; Peisker, Jörg; Kunkel, Cindy; Hilse, Ulrike ; Aehnelt, Michaela; Pudlo, Dieter; Voigt, Thomas ; Gaupp, Reinhard ; #90142 (2012)

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Burial History and Diagenesis in Buntsandstein Aquifer Sandstones of the Thuringian Syncline (Germany)

Beyer, Daniel *1; Götze, Marika 1; Peisker, Jörg 1; Kunkel, Cindy 1; Hilse, Ulrike 1; Aehnelt, Michaela 1; Pudlo, Dieter 1; Voigt, Thomas 1; Gaupp, Reinhard 1
(1) Friedrich Schiller University Jena, Jena, Germany.

The Lower Triassic Buntsandstein is a major aquifer in Thuringia and adjacent areas in central Germany. In the Thuringian Syncline the investigation of its reservoir characteristics is part of a BMBF-funded project on integrated fluid dynamics in sedimentary basins (INFLUINS). Petrophysical parameters like porosity and permeability are major parameters in controlling fluid flow in the rocks. In understanding porosity loss during sandstone evolution, investigations on the diagenetic and burial history of the aquifer sandstones are essential. Thereby knowledge on the reactivity of mineral components exposed to fluids during burial diagenesis and to recent fluids is fundamental to understand fluid migration.

Results of Buntsandstein sandstone petrography (gained from polarized-light microscopy, EMPA, SEM) reveal early precipitation of quartz cement, formation of illite- and hematite coatings, strong sulfate and carbonate cementation and dissolution of feldspar during eodiagenesis. Carbon-isotope data indicate an influence of meteoric water during carbonate cementation. At some locations, minor amounts of eodiagenetic kaolinite are present. Mineral alteration features are linked to complex mineral (rock) - fluid reactions during mesodiagenesis and telodiagenesis, such as hydration of anhydrite, dissolution of carbonate, precipitation of late diagenetic meshwork illite and albitization of K-feldspar. Porosity and permeability is related with distinct facies types and mineralogical rock content and consequently with fluid flow characteristics.

In order to investigate the burial history of the studied lithologies, vitrinite reflectance analysis was performed on underlying Zechstein and overlying Keuper sediments from wells and surface outcrops in the study area. The Rm-values indicate a maximum burial depth of 2.800 m for the Buntsandstein sandstones. Higher values are linked to nearby fault structures and related high heat flows, or to deep burial in inverted graben structures.

The diagenesis of the Buntsandstein proceeded in greater depths than formerly assumed. The erosional gap between Upper Triassic Keuper and Quaternary strata comprises approximately 1.500 m, associated with a change in underground fluid pathways. The present-day open pore space is generally linked to former cementation and dissolution of pore-filling sulfate and carbonate cement.  

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California