David A. Sommers
G.E. McGill
1967
<p><span>Several well-exposed and little-deformed </span>Belt<span> </span>Supergroup<span> sections have been studied in the </span>southern<span> </span>Lewis<span> and </span>Clark<span> </span>Range<span>. In the area studied, the </span>Belt<span> thins eastward or northeastward due both to primary sedimentation and to pre-Middle Cambrian erosion. These rocks can now be more precisely correlated with the well-known sections near Bonner, Helena, and Glacier National Park. In the western part of the area, the Missoula Group is thickest and lithologically intermediate between the sections at Bonner and Marias Pass. Formation names from these two sections are applied in the </span>southern<span> </span>Lewis<span> and </span>Clark<span> </span>Range<span>. The thin </span>Belt<span> sequence in the eastern part of the area includes the lower part of the Missoula Group and older formations that may be traced southward into the Helena, Empire, and Spokane Formations of the Helena area. Consequently, the Helena Dolomite of the Helena area, the Siyeh Formation of the Marias Pass area, and the "Newland Limestone" of the Bonner area are probably lateral equivalents.</span></p>
application/pdf
10.1130/0016-7606(1967)78[343:SACOTP]2.0.CO;2
en
Geological Society of America
Stratigraphy and correlation of the precambrian belt supergroup of the southern Lewis and Clark Range, Montana
article