Abstract

A sequence of 55 glauconitic graywacke beds making up two members of the Early Cretaceous Gault Formation has been traced for 115 km along strike of the Flysch Zone of the East Alps in Bavaria by correlation of individual beds between 44 sections. Four different lines of evidence were used for these correlations: (1) Visual comparison of bed thickness and sequence. The average thickness is 1 m for the graywacke beds and 0.75 m for the claystone inter-layers, respectively. (2) Discovery of a marker bed petrographically defined by its relatively high feldspar content. (3) Remarkable constancy of mineral content, of individual beds. (4) Statistical analysis particularly quartz content, at the base of individual beds. (4) Statistical analysis employing a moving correlation coefficient.

The bed-by-bed correlations lead to the following conclusions: (1) The graywacke beds of the Gault Formation are continuous for a distance of at least 115 km. Over this distance, they were laid down as continuous blankets of sediment by turbidity currents. The calculated minimum volume contained in the average bed of 1-m thickness is 1 km3 assuming a 10-km-wide area of deposition. Estimates for possible maximum volumes of thicker beds are in the range of 25 km3. (2) Transport of sedimentary material in the elongate, east-west–trending flysch belt in Aptian-Albian time was from west to east, more or less parallel to present structural strike, as evidenced by sole marks and systematic downcurrent variations in grain size, mineralogical composition, and thickness, of individual beds. There was no supply from lateral sources at the “trough” margin in the area studied. (3) Continuity and lateral uniformity in thickness of the turbidites over a relatively long distance suggest a sea floor with virtually no relief. Three major reversals of the paleocurrent directions in the younger formations overlying the Gault were possible because the sea floor was almost level.

The Gault Formation may represent a trench–abyssal plain environment.

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