Subsidence analysis of the Cordilleran miogeocline: Implications for timing of late Proterozoic rifting and amount of extension

A Paleogeographic Model for Vendian and Cambrian Time

“…Furthermore, recent studies of thermal subsidence histories support the hypothesis that one or more large continental masses broke up shortly before the Precambrian-Cambrian boundary (Armin and Mayer 1983;, with intermittent episodes of rifting which began somewhat earlier. These are appealing hypotheses because, if true, the presence of one or more amalgamations of continental masses would greatly simplify the problem of reconstructing their positions.…”

“…In the tectonic model, however, it is necessary for Laurentia to move in a southerly direction during the late Vendian to accomodate the Caborca (and perhaps the Sept-lies) paleomagnetic results. It is possible that this motion was initiated by a Late Proterozoic rifting event along the Cordilleran margin and some other craton (e.g., Armin and Mayer 1983;, and from our previous analysis, Siberia, almost by default, happens to be in the correct orientation for this missing rift partner.…”

Phanerozoic evolution of sedimentary basins in the Uinta-Piceance Basin region, northwestern Colorado and northeastern Utah

“…Geologic data (including widespread volcanic rocks) suggest that the main rifting event occurred between 700 and 800 Ma (Stewart, 1972;Stewart and Suczek, 1977;Link, 1984;Link and others, 1987). In contrast, quantitative analysis of tectonic subsidence for Cambrian and Ordovician strata indicates that thermally driven subsidence of the passive margin began after about 590 Ma, in latest Proterozoic or earliest Cambrian time (Armin andMayer, 1983,1984;others, 1983, 1985). Christie-Blick and Levy (1989, p. 19) reconciled the geologic data with the results of subsidence modeling by suggesting that "at least two extensional events took place in the western United States during Late Proterozoic and Early Cambrian time."…”

“…4, Oquirrh basin) indicates that thermally driven subsidence, characteristic of rifted passive margins, began about 590 Ma (Armin andMayer, 1983,1984;others, 1983,1985). The presence of volcanic rocks interbedded with the lower part of the Lower and Middle Cambrian Tintic Quartzite in western Utah (Morris and Levering, 1961;Crittenden and others, 1971) supports Early Cambrian rifting.…”

Geology of the Stensgar Mountain Quadrangle, Stevens County, Washington

“…Subsidence analyses have suggested that major Cordilleran rifting during which the Cordilleran miogeocline and possibly also the Pacific Ocean began to form during latest Proterozoic to earliest Cambrian (Armin and Mayer, 1983;Bond and Kominz, 1984). However, the date of initial rifting, and the timing of the Windermere sedimentation with respect to continental break-up continues to be debated (Devlin and others, 1985).…”