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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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Analysis of drainage patterns can be used to delineate concealed structures. To do this effectively, a thorough understanding of the regional geology and general geomorphic history is necessary. In glaciated areas, air photographs and mosaics can be used to determine the general glacial history so that glacially controlled patterns are not confused with structurally controlled patterns. As with any unconventional technique, drainage pattern interpretation has been misunderstood, misused, and handicapped by the lack of a generally acceptable theory to explain the reflection of buried structures in surface stream patterns.
Geomorphic analyses are used in both regional and detailed studies. Regionally, the area between Fort St. John and Fort Nelson in northeastern British Columbia exhibited a pre-Pleistocene trellis drainage pattern, adjusted to structural conditions. Glaciation altered the existing base-level equilibrium. After the ice melted, large-scale stream piracy took place. Due to glaciation and subsequent piracy, non-structurally controlled
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anomalous drainage patterns exist which must not be confused with structurally controlled patterns.
The West Drumheller, Drumheller, Homeglen-Rimbey, and Redwater Devonian reef oil fields, all located in Alberta, were studied in detail. The drainage configuration above the West Drumheller oil field consists of a pronounced arc in the otherwise straight southeasterly course of the Red Deer River, and a repeated right-angular diversion of a tributary. The Drumheller oil field is reflected by a marked diversion and arcuate pattern of Michichi creek. The Homeglen-Rimbey oil field is in the Blindman River system in which the tributaries flow southeasterly. At the oil field all streams are diverted toward the west, resuming the southeasterly flow at the south end of the field. These three drainage anomalies are not related to glacial landforms. Finally, the Redwater oil field is an exampl of a structurally controlled drainage anomaly which has been partly masked by a complex glacial history.
Other oil fields exist which are not reflected in the drainage pattern. This does not weaken the technique of drainage analysis, but indicates that in the present state of knowledge not all possible types of drainage anomalies can be recognized. It is only through continued use and research that this technique, proved to be a fast and economical exploration tool in mantled areas, can be refined.
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