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Kenneth E. Williams
Texaco Inc.
Houston, Texas, U.S.A.
Abstract
Calibrated geohistory
analyses of single data points and cross sections are used to construct
tectonic subsidence curves. There are a limited number of distinct curve
types, of which seven end-members are discussed. These curve types and
their shapes are genetically related to plate tectonic processes. One regional
backstripped cross section across South America is discussed. The tectonic
subsidence curves are used as calibration for a paleogeographic analysis
of Gondwana in the Phanerozoic. It is suggested that the southern part
of South America and parts of Antarctica are composed of terranes that
were formerly located west of the present position of the Arequipa massif
in Chile and Peru. These displaced terranes formed the western edge of
Gondwana from the Cambrian-Ordovician to the end of the Devonian. During
these periods, they were involved in intracratonic rifting. During the
time of the basal Carboniferous unconformity, the terranes were translated
southward to approximately their present positions. Seven reconstructions
are presented that are representative of the major episodes in the development
of Gondwana. |
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