Thermal History of the Ediacaran/Cambrian Sediments on the East European Craton Inferred From Low‐Temperature Thermochronology

ABSTRACT Organic maturation and clay mineral‐based estimates of the maximum paleotemperatures experienced by the Precambrian/Cambrian sediments on the East European Craton (EEC) are in disagreement. To resolve this conflict and reconstruct thermal histories of these sedimentary rocks we used three low‐temperature thermochronometers: zircon and apatite (U–Th)/He (ZHe, AHe) and apatite fission track (AFT) methods, complemented by AFT modelling of thermal histories. At the cratonic edge (Podillya), the ZHe ages are partially reset, implying that the AFT ages are fully reset, and that the maximum paleotemperatures were in the range of 160°C–200°C, similar to earlier estimates based on the degree of illitization of smectite. Comparison with analogous data for the overlying Silurian bentonites identifies the edge zone of the former Devonian/Carboniferous Variscan foreland basin. In the Podillya region the modelling of thermal history of the Cambrian/Ediacaran strata indicated exhumation in Carboniferous time. In the cratonic interior (Volyn, Belarus, and Lithuania), the AFT ages are totally or partially reset, implying the maximum paleotemperatures close to 120°C, which confirm earlier estimates based on the degree of illitization of smectite, but are higher than the estimates based on the organic geochemistry. The relatively short mean confined tracks lengths (13.6 ± 0.4 to 10.8 ± 0.4 μm), and their varied standard deviation values (2.1–0.9) indicate slow exhumation within the partial annealing zone.