Examination of side-looking radar imagery of the St. Francois Mountains of southeast Missouri has revealed many structural features which are obscure or only poorly depicted on conventional aerial photographs. Most prominent is a distinct linear element extending southward across the imagery from east of Flat River to southeast of Ironton, Missouri, through the southeast Missouri Lead Belt. Field examination has confirmed a fault zone, named the Roselle fault by the author. This structure has not previously been recognized; no mention of it was found in literature, nor is it shown on any geologic map of the area. The structure traverses Precambrian and Paleozoic rocks.

Analysis of geologic and topographic maps north and south of the area covered by radar imagery reveals a series of topographic and structural features remarkably well aligned with the Roselle fault. To the south, these include drainage alignments and a buried Precambrian scarp, and to the north, the Plattin anticline and the course of the Mississippi River north of Crystal City. These features form an almost continuous alignment extending for over 155 mi from southwest of Poplar Bluff, Missouri, north-northeast to the vicinity of the junction of the Mississippi and Missouri Rivers. This alignment of features is termed the Roselle lineament. I suggest this lineament has been in existence since the Precambrian as a major lineament of this portion of the crust and that it may have been important in localization of mineral deposition in southeast Missouri.

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