Keuper magnetostratigraphy in the southern Mesozoic margin of the Holy Cross Mts. (southeastern edge of the German Basin)

Abstract

Magnetostratigraphy of the Keuper succession in the southern Mesozoic margin of the Holy Cross Mountains is presented based on investigations of two sections of Brzeziny and Wolica. They cut an ~60 m thick succession of variegated siltstones and claystones, which overlies the Reed Sandstone (Stuttgart Formation). The succession has been correlated with the Patoka Member of the Grabowa Formation, defined in the Upper Silesia region as an equivalent of the Steinmergelkeuper (Arnstadt Formation). The primary Late Triassic magnetization was obtained from component B carried by fine-grained haematite. Twelve magnetic polarity zones, six of normal and six of reversed polarity, have been defined. The obtained polarity pattern corresponds to the Norian (E13–E16 Newark zones) according to the Long-Rhaetian option of the Late Triassic Magnetic Polarity Time Scale. The mean normal polarity characteristic direction (N = 24, D/I = 31/62, k = 28.24, a95 = 6.04) differs significantly from the reversed one (N = 18, D/I = 223/-25, k = 16.38, a95 = 8.65): the primary magnetic signal is partly overlapped by component A carried by magnetite of recent viscuous remanent magnetization. Some samples do contain also coarse-grained haematite that, however, does not form any clustered magnetization. The palaeopole position calculated from the transposed reversed and normal polarity directions of component B corresponds to the Late Triassic (Norian) segment of the reference Baltica/Europe Apparent Polar Wander Path