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The AAPG/Datapages Combined Publications Database
Journal of Sedimentary Research (SEPM)
Abstract
Paleocurrent Analysis of Trough
Cross
Stratification
R. H. Dott, Jr.
ABSTRACT
Additional documentation of the economy and superiority as a paleocurrent indicator of trough-axis orientation data in contrast to cross
-set orientations is provided from studies of Cambrian sandstones around Baraboo, Wisconsin. Separate concentric polar histogram portrayals of both types of data allowed direct comparison of
cross
-set and trough-axis distributions, and several interpretable patterns emerged. In many cases bimodal
cross
-set distributions are bisected by axis azimuths; these reflect symmetrical filling of troughs. In other cases, a single dominant
cross
-set mode is perpendicular to the axes, indicating asymmetrical filling of troughs, which is commonly observable in
cross
-
section
views. In both of these cases, an error of 90° in paleocurrent interpretation is possib
e if the trough-origin of such sets goes unrecognized. Sets with a single mode parallel to the axes reflect readings of
cross
-set dips mainly from the "heads" of the troughs. Most puzzling are bimodal trough-axis distributions, which are common in Wisconsin. Reflecting the great complexity of sand-wave bedforms, they represent the fillings of canoe-shaped depressions whose counterparts can be seen in modern sediments. Even the bimodal trough-axis data tends to yield better orientation results than do associated
cross
sets.
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