Abstract A sequence comprising 6,500 feet of Permian and Triassic rocks is exposed in the Medicin... more Abstract A sequence comprising 6,500 feet of Permian and Triassic rocks is exposed in the Medicine Range, south-central Elko County Nevada. Permian rocks include the Riepetown (1,100+ ft.), Pequop (2,400 ft.), and Loray (500 ft.) formations of the Arcturus Group; and the Kaibab (280 ft.), Plympton (510 ft.), and Gerster (1,200 ft.) formations of the Park City Group. Triassic strata are represented by the Thaynes Formation (500+ ft.). The succession of faunas and lithologies in the Pequop and Loray formations demonstrates a gradual regression from open marine deposits in the lower Pequop to very shallow marine and brackish or hypersaline deposits in the upper Pequop and Loray. Fusulinid limestones at the base of the Pequop in the northern Medicine Range grade southward within the Range to shallow-water silty deposits. The Thaynes Formation in the Medicine Range is interpreted as part of a transgressive sequence deposited by a westward-advancing interior sea during the late Early Triassic. A basal conglomeratic unit overlies the Gerster Formation (Upper Permian) on a disconformity with several feet of relief. A peak zone, characterized by the multi-element conodont Ellisonia triassica, is used to correlate the basal unit with the Meekoceras-bearing limestones to the east near Currie, Nevada. Ammonites of the Columbites Zone, including a specimen of Tirolites sp. cf. T. illyricus and several small specimens belonging to Columbites, were found about 250 feet above the base. Conodonts referable to Platyvillosus asperatus occur in a thin limestone bed about 300 feet above the base. Near the top of the section, poorly preserved ammonites occur in limestone beds that could be mistaken for the Meekoceras beds.
Fossil plants are the primary means of correlating sedimentary rock sequences in Antarctica of La... more Fossil plants are the primary means of correlating sedimentary rock sequences in Antarctica of Late Paleozoic to Early Mesozoic age. A high-resolution zonation will be difficult to attain because of the widespread heating effects of Jurassic diabase intrusions. However, careful stratigraphie collecting from selected sections could greatly improve correlations. Exept for R.A. Askin’s (i.e., Kyle 1977) study in southern Victoria Land in which she compared Antarctic palynomorph floras to those of eastern Australia, no systematic biostratigraphic studies have been attempted. Most plant collections have come from a few isolated localities with only a general knowledge of their stratigraphic position.
The late Paleozoic-early Mesozoic Pacific margin of Gondwanaland from eastern Australia to Patago... more The late Paleozoic-early Mesozoic Pacific margin of Gondwanaland from eastern Australia to Patagonia was characterized by a series of back-arc and foreland basins associated with subduction and volcanism. The Transantarctic basin including the present Transantarctic Mountains and Tasmania evolved from a middle Paleozoic passive continental margin to an Early Permian back-arc basin and a Late Permian-Triassic foreland basin. The earliest
... MOLLY F. MILLER Geology Department, Box 6001 Station B, Vanderbilt University, Nashville, TN ... more ... MOLLY F. MILLER Geology Department, Box 6001 Station B, Vanderbilt University, Nashville, TN 37235 ... In contrast, there has been little study of the fluvial benthic communities, in spite of the fact that trace fossils are abundant in medium and fine-grained sandstones of both the ...
The late Paleozoic-early Mesozoic Pacific margin of Gondwanaland from eastern Australia to Patago... more The late Paleozoic-early Mesozoic Pacific margin of Gondwanaland from eastern Australia to Patagonia was characterized by a series of back-arc and foreland basins associated with subduction and volcanism. The Transantarctic basin including the present Transantarctic Mountains and Tasmania evolved from a middle Paleozoic passive continental margin to an Early Permian back-arc basin and a Late Permian-Triassic foreland basin. The earliest
Abstract A sequence comprising 6,500 feet of Permian and Triassic rocks is exposed in the Medicin... more Abstract A sequence comprising 6,500 feet of Permian and Triassic rocks is exposed in the Medicine Range, south-central Elko County Nevada. Permian rocks include the Riepetown (1,100+ ft.), Pequop (2,400 ft.), and Loray (500 ft.) formations of the Arcturus Group; and the Kaibab (280 ft.), Plympton (510 ft.), and Gerster (1,200 ft.) formations of the Park City Group. Triassic strata are represented by the Thaynes Formation (500+ ft.). The succession of faunas and lithologies in the Pequop and Loray formations demonstrates a gradual regression from open marine deposits in the lower Pequop to very shallow marine and brackish or hypersaline deposits in the upper Pequop and Loray. Fusulinid limestones at the base of the Pequop in the northern Medicine Range grade southward within the Range to shallow-water silty deposits. The Thaynes Formation in the Medicine Range is interpreted as part of a transgressive sequence deposited by a westward-advancing interior sea during the late Early Triassic. A basal conglomeratic unit overlies the Gerster Formation (Upper Permian) on a disconformity with several feet of relief. A peak zone, characterized by the multi-element conodont Ellisonia triassica, is used to correlate the basal unit with the Meekoceras-bearing limestones to the east near Currie, Nevada. Ammonites of the Columbites Zone, including a specimen of Tirolites sp. cf. T. illyricus and several small specimens belonging to Columbites, were found about 250 feet above the base. Conodonts referable to Platyvillosus asperatus occur in a thin limestone bed about 300 feet above the base. Near the top of the section, poorly preserved ammonites occur in limestone beds that could be mistaken for the Meekoceras beds.
Fossil plants are the primary means of correlating sedimentary rock sequences in Antarctica of La... more Fossil plants are the primary means of correlating sedimentary rock sequences in Antarctica of Late Paleozoic to Early Mesozoic age. A high-resolution zonation will be difficult to attain because of the widespread heating effects of Jurassic diabase intrusions. However, careful stratigraphie collecting from selected sections could greatly improve correlations. Exept for R.A. Askin’s (i.e., Kyle 1977) study in southern Victoria Land in which she compared Antarctic palynomorph floras to those of eastern Australia, no systematic biostratigraphic studies have been attempted. Most plant collections have come from a few isolated localities with only a general knowledge of their stratigraphic position.
The late Paleozoic-early Mesozoic Pacific margin of Gondwanaland from eastern Australia to Patago... more The late Paleozoic-early Mesozoic Pacific margin of Gondwanaland from eastern Australia to Patagonia was characterized by a series of back-arc and foreland basins associated with subduction and volcanism. The Transantarctic basin including the present Transantarctic Mountains and Tasmania evolved from a middle Paleozoic passive continental margin to an Early Permian back-arc basin and a Late Permian-Triassic foreland basin. The earliest
... MOLLY F. MILLER Geology Department, Box 6001 Station B, Vanderbilt University, Nashville, TN ... more ... MOLLY F. MILLER Geology Department, Box 6001 Station B, Vanderbilt University, Nashville, TN 37235 ... In contrast, there has been little study of the fluvial benthic communities, in spite of the fact that trace fossils are abundant in medium and fine-grained sandstones of both the ...
The late Paleozoic-early Mesozoic Pacific margin of Gondwanaland from eastern Australia to Patago... more The late Paleozoic-early Mesozoic Pacific margin of Gondwanaland from eastern Australia to Patagonia was characterized by a series of back-arc and foreland basins associated with subduction and volcanism. The Transantarctic basin including the present Transantarctic Mountains and Tasmania evolved from a middle Paleozoic passive continental margin to an Early Permian back-arc basin and a Late Permian-Triassic foreland basin. The earliest
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