Basin Filling Model/J. Geology

Quantitative filling model for continental extensional basins with applications to early Mesozoic rifts of eastern North America

Abstract--In many half-graben, strata progressively onlap the hanging wall block of the basins, indicating that both the basins and their depositional surface areas were growing in size through time. Based on these constraints, we have constructed a quantitative model for the stratigraphic evolution of extensional basins with the simplifying assumptions of constant volume input of sediments and water per unit time, as well as a uniform subsidence rate and a fixed outlet level. The model predicts (1) a transition from fluvial to lacustrine deposition, (2) systematically decreasing accumulation rates in lacustrine strata, and (3) a rapid increase in lake depth after the onset of lacustrine deposition, followed by a systematic decrease. When parameterized for the early Mesozoic basins of eastern North America, the model's predictions match trends observed in Late Triassic-age rocks. Significant deviations from the model's predictions occur in Early Jurassic-age strata, in which markedly higher accumulation rates and greater lake depths point to an increased extension rate that led to increased asymmetry in these half-graben. The model makes it possible to extract from the sedimentary record those events in the history of an extensional basin that are due solely to the filling of a basin growing in size through time and those that are due to changes in tectonics, climate, or sediment and water budgets.

FIGURES
Figure 1 [18 k] Cross section and seismic lines of typical half graben.
Figure 2 [9 k] Full-graben geometry.
Figure 3 [18 k] Full-graben basin filling model.
Figure 4 [14 k] Half-graben basin filling model.
Figure 5 [18 k] Mesozoic rift basins of eastern North America.
Figure 6 [27 k] Stratigraphy of the Newark basin and accumulation rate data.
Figure 7 [32 k] Geologic map of the Newark basin.
Figure 8 [14 k] Cross section of the Newark basin, palinspastic reconstruction, and full-graben equivalent.
Figure 9 [27 k] Predictions of the basin filling model for the Newark basin.
Figure 10 [14 k] Effects of asymmetric basin subsidence.
Figure 11 [23 k] Chronostratigraphy and accumulation rate data for Mesozoic rift basins of eastern North America.

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