Abstract
Temperature history is one of the most important factors driving subsidence and the overall tectono-stratigraphic evolution of a sedimentary basin. The McKenzie model has been widely applied for subsidence modelling and stretching factor estimation for sedimentary basins formed in an extensional tectonic environment. Subsidence modelling requires values of physical parameters (e.g., crustal thickness, lithospheric thickness, stretching factor) that may not always be available. With a given subsidence history of a basin estimated using a stratigraphic backstripping method, these parameters can be estimated by quantitatively comparing the known subsidence curve with modelled subsidence curves. In this contribution, a method to compare known and modelled subsidence curves is presented, aiming to constrain valid combinations of the stretching factor, crustal thickness, and lithospheric thickness of a basin. Furthermore, a numerical model is presented that takes into account the effect of sedimentary cover on thermal history and subsidence modelling of a basin. The parameter fitting method presented here is first applied to synthetically generated subsidence curves. Next, a case study using a known subsidence curve from the Campos Basin, offshore Brazil, is considered. The range of stretching factors estimated for the Campos basin from this study is in accordance with previous work, with an additional estimate of corresponding lithospheric thickness. This study provides insight into the dependence of thermal history and subsidence modelling methods on assumptions regarding model input parameters. This methodology also allows for the estimation of valid combinations of physical lithospheric parameters, where the subsidence history is known.
Highlights
The thermal history of a sedimentary basin is inherently associated with the basin’s tectono-stratigraphic evolution history
Our results indicate that the minimum E1 curve typically lies within the region of the minimum best fit curve and that the zero-line of E1 represents a good approximation for the lithospheric thickness and the corresponding stretching factor value for the best fit case
It is worth noting that, with the same lithospheric thickness, a higher value of stretching factor is required for fitting the subsidence curve
Summary
The thermal history of a sedimentary basin is inherently associated with the basin’s tectono-stratigraphic evolution history. A numerical model in 1-dimension is presented here, which considers the effect of sediment cover during thermal subsidence. Subsidence models, whether analytical or numerical, are as good as the assumptions they use All of these models depend upon the values taken for physical parameters such as density and thickness of crust and lithosphere. The aim of this paper is to compare subsidence profiles estimated through the backstripping method [18,19] with forward subsidence models (i.e., McKenzie’s analytical model and the numerical model introduced here) and to explore optimum estimation of values for stretching factor, crustal, and lithospheric thickness. A simple quantitative method for comparing measured subsidence curves with numerical and/or analytical outputs is proposed over the sample space of stretching factor, crustal, and lithospheric thickness. The methodology is tested using synthetic data and is applied to a natural subsidence dataset obtained from the Campos basin, offshore Brazil [25], to estimate a range of stretching factors and lithospheric thicknesses suitable for basin modelling
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