Products and timing of diagenetic processes in Upper Rotliegend sandstones from Bebertal (North German Basin, Parchim Formation, Flechtingen High, Germany)

Abstract

Aeolian-fluvial Upper Rotliegend sandstones from Bebertal outcrops (Flechtingen High, North Germany) are an analogue for deeply buried Permian gas reservoir sandstones of the North German Basin (NGB). We present a paragenetic sequence as well as thermochronological constraints to reconstruct the diagenetic evolution and to identify periods of enhanced mesodiagenetic fluid–rock reactions in sandstones from the southern flank of the NGB. Bebertal sandstones show comparatively high concentrations of mesodiagenetically formed K-feldspar but low concentrations of illite cements. Illite-rich grain rims were found to occur preferentially directly below sedimentary bounding surfaces, i.e. aeolian superimposition surfaces, and indicate the lowest intergranular volume. Illite grain rims also indicate sandstone sections with low quartz and feldspar cement concentrations but high loss of intergranular volume due to compaction.40Ar–39Ar age determination of pronounced K-feldspar grain overgrowths and replacements of detrital grains indicates two generations: an early (Triassic) and a late (Jurassic) generation. The latter age range is similar to published diagenetic illite ages from buried Rotliegend reservoir sandstones. The first generation suggests an early intense mesodiagenetic fluid flow with remarkably high K+activity synchronous with fast burial of proximal, initial graben sediments on the southern flank of the NGB. Accordingly, zircon fission-track data indicate that the strata already reached the zircon partial annealing zone of approximately 200°C during early mesodiagenesis. Zircon (U–Th)/He ages (92 ± 12 Ma) as well as apatite fission-track ages (~ 71–75 Ma) indicate the termination of mesodiagenetic processes, caused by rapid exhumation of the Flechtingen High during Late Cretaceous basin inversion.

Formation of the Iberian‐European Convergent Plate Boundary Fault and Its Effect on Intraplate Deformation in Central Europe

“…The syntectonic sedimentary record of the marginal troughs suggests that the main phase of inversion occurred during Late Santonian and Campanian. The timing is consistent with apatite fission track data from the CEBS, which is interpreted to record exhumation related cooling during the Campanian (apatite fission track ages of ~81–69 Ma; Fischer et al, ; Senglaub et al, ; Thomson & Zeh, ).…”

“…Based on and Scheck-Wenderoth and Lamarche (2005). Apatite fission track ages (orange circles) from Thomson and Zeh (2000), Senglaub et al (2005), and Fischer et al (2012). (c) Cross section through the primary and secondary marginal trough formed during inversion of the Norwegian-Danish Basin.…”

Clay mineral occurrence and burial transformations: reservoir potential of the Permo‐Triassic sediments of the Iberian Range

“…In the Autunian succession illite clay rims and fibrous illite are the dominant clay cements of diagenetic origin. This authigenic illite (fibrous illite) is a widespread cement in various sandstone reservoirs, where its fibrous morphology affects permeability and hampers hydrocarbon production (Marfil et al, 1996a;Fischer et al, 2012). Fibrous illite appears to form by reaction of kaolin minerals and K + .…”

What can be learned from the K-Ar ages of illite from Rotliegend sandstones of the Fore-Sudetic Monocline, SW Poland?

“…7), in di cat ing large-scale un der ly ing pro cesses. The older sig nal (~180-200 Ma) has been fre quently noted in Rotliegend sandstones of north ern Ger many (Platt, 1993;Clauer et al, 1996Clauer et al, , 2012Zwingmann et al, 1998Zwingmann et al, , 1999Liewig and Clauer, 2000;Fischer et al, 2012); it is known also from some Rotliegend sand stones of the south ern North Sea (Ziegler et al, 1994). More over, Tri as sic sand stones of the Paris Ba sin (Mossmann et al, 1992) and north ern Af rica (Clauer et al, 1996) re corded 190 Ma hy dro ther mal ac tiv ity.…”

“…the crystallisation of K-feldspar from sa line, K-rich so lu tions. Be sides, ob ser va tions by Ziegler (2006) and Fischer et al (2012) from the south ern North Sea and Ger many in di cate that the crystallisation of K-feld spar was syn chro nous with the crystallisation of fi brous illite.…”