Episodic hydrothermal fluid flow in the Upper Rhinegraben (Germany)

An anomalous, stratigraphically confined maturity trend, delineated by vitr inite reflectance data, is observed in the Tertiary strata of the northern Upper Rhinegraben, Germany. Our analysis of coupled fluid flow, heat transf er and source rock maturation suggests that the observed anomaly in vitrint e reflectance can only be explained by episodic hydrothermal fluid flow alo ng fault zones. Sensitivity study results suggest that the resulting hydrot hermal regime had to persist long enough to elevate vitrinite reflectance ( 10,000 yr) yet must have dissipated before steady state thermal conditions were reached (similar to 200,000 yr). (C) 2000 Elsevier Science B.V. All ri ghts reserved.