Reconstruction of Late Paleozoic heat flows and burial histories at the Rhenohercynian-Subvariscan boundary, Germany

Abstract

The thermal and burial history of the Herzkamp syncline, located in the transition zone between the Variscan Rhenish Massif and the Ruhr foreland basin (western Germany), was reconstructed using PDI/PC-1D-basin modelling software (IES). The models were calibrated with new vitrinite reflectance data measured on Palaeozoic outcrop samples. High sample density and quality of the calibration data allowed a 3D reconstruction of the heat flow as well as of burial and erosion history. Vitrinite reflectance values range from 0.8 to 4.9%R r and generally increase with increasing stratigraphic age. The coalification pattern confirms pre-tectonic maturation, especially in the western part of the study area. A ªlow-coalification zoneº showing stagnating/decreasing coalification with increasing stratigraphic age exists, however, northeast of the Ennepe thrust, indicating synorogenic coalification. This anomaly is explained by early thrusting in the northern Rhenish Massif resulting in restricted burial/early uplift and thus lower thermal maturity. One result of numerical modelling is that palaeo-heat flows during maximum burial (Westphalian or post-Westphalian) decreased southwards from approximately 65 to less than 50 mW/m 2 . Maximum burial depths for the base and top of the Namurian also decrease southwards from 7000 to 3600 m and 4600 to 1800 m, respectively, resulting in southwards-decreasing coalification of the respective stratigraphic horizon. Eroded overburden increases southwards (3100±5700 m), with the exception of the low-coalification zone, which is characterised by lower amounts of eroded overburden (1300±2900 m) and an earlier onset of erosion, i.e. in the Westphalian B rather than Westphalian D or post-Westphalian.

Burial history and thermal maturity of Mesozoic rocks of the Dolomites, Northern Italy

“…To obtain VR r vs. depth trends from field data without expensive drilling campaigns pseudowells were created according to the method of Nöth et al (2001). Therefore, sediments of different formations were sampled at the surface and measured for VR r and BR r .…”

“…A common parameter to analyze thermal maturity is the reflectance of dispersed organic matter, such as vitrinite or solid bitumen particles (e.g. Nöth et al 2001;Schoenherr et al 2007;Littke et al 2012).…”

Late-Variscan fluid migration at the Variscan thrust front of Eastern Belgium: numerical modelling of the palaeothermal and fluid flow field

“…In the Bolland borehole, vitrinite reflectances up to 4.2% R r in Upper Devonian and Carboniferous sediments adjacent to thrust faults exceed clearly those in the Lower Devonian in deeper parts of the borehole. These deviations are clearly above standard deviations mentioned by Nöth et al (2001) for Palaeozoic strata in undisturbed deposits. The coalification pattern in the borehole of Bolland indicates significant reheating of the wall rocks near the thrust faults.…”

“…Compared with other regional studies of the Rhenohercynian orogen (Littke et al 2000) and the Campine Basin (Van Keer et al 1998), the values applied in our modelling are in the upper range of the results for this period or exceed them slightly. In contrast, Nöth et al (2001) determined lower heat flow densities within the range of mean continental heat flow for the Rhenohercynian-Subvariscan boundary east of the river Rhine (Ruhr basin) during maximum burial in Westphalian or post-Westphalian times.…”

“…They may reflect palaeothermal anomalies that may be due to variations in subsidence or heat flow densities (e.g. Nöth et al 2001). Anomalous high coalification due to palaeothermal modifications by fluid flow is considered in Subvariscan sediments (Gayer et al 1998;Lünenschloss et al 1997).…”