Geochemistry of black shales from Breitbach Creek, supplement to: Wortmann, Ulrich G; Hesse, Reinhard; Zacher, Katharina (1999): Major-element analysis of cyclic black shales: Paleoceanographic implications for the Early Cretaceous deep western tethys. Paleoceanography, 14(4), 525-541


Lower Cretaceous sediments are frequently characterized by a well expressed cyclicity. While the processes influencing environments above the carbonate compensation depth (CCD) are reasonably well understood, almost nothing is known about the deep ocean. Cretaceous sub-CCD sediments from the Tethys and Atlantic Oceans typically show rhythmic black/green shale successions. To gain insight into the nature of these black/green shale cycles, we performed detailed geochemical analyses (X-ray fluorescence, Rock-Eval and reactive iron analysis) on a 3 m long section of latest Aptian age. The major-element distribution of the analyzed shale sequence indicates a periodic change from a high-productivity and well-oxygenated green shale mode to a low-productivity oxygen-deficient black shale mode. It is proposed here that the preservation of organic matter was dependent on the strength of salinity-driven deepwater generation. Furthermore, the data show that the Corg content covaries with changes in the detrital composition. Therefore we hypothesize that Tethyan deepwater circulation was sensitive to changes in the monsoonal system. Time series analysis suggests that these changes are periodic in nature, although we are currently unable to prove that the dominant periodicity is related to the precession component of the Milankovitch frequencies.

Related Identifier
Metadata Access
Creator Wortmann, Ulrich G; Hesse, Reinhard; Zacher, Katharina
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 1999
Rights Creative Commons Attribution 3.0 Unported;
OpenAccess true
Language English
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 1545 data points
Discipline Earth System Research
Spatial Coverage (11.720 LON, 47.720 LAT); Bavarian Alps, Germany