The Relationship Between Bedform and Log Orientation in a Paleogene Fluvial Channel, Wei{beta}elster Basin, Germany: Implications for the Use of Coarse Woody Debris for Paleocurrent Analysis

摘要

Isolated logs preserved in the Älterer Flußsande of the Weißelster basin, Germany, are examined relative to their subjacent bedform. Paleocurrent analyses conducted on both the log orientation and its underlying bedform are used to determine whether or not any relationship exists between these two structures. Two patterns emerge from this investigation. When the data set is taken collectively, the mean vector of the log orientation is in a subperpendicular relationship to the mean vector of their bedforms. This coarse woody detritus is not oriented preferentially parallel to paleocurrent direction as has been previously hypothesized. In addition, when individual log orientations are compared with their underlying bedforms, logs may be oriented parallel, subperpendicular, or perpendicular to the bedform. There is no statistical preference for any particular orientation in the data set. Comparison is made with an actualistic data set from the Lassa Distributary of the Rajang River delta where a similar trend is documented, and with previously published experimental and field data. This comparison indicates that there is no statistical preferred orientation of wood clasts in fluvial systems. Hence, these results caution against the use of woody phytoclasts as independent indicators of paleocurrent trends in fluvial systems.