Journal Article

Structural Analysis of Fault Systems in the Weald and Hampshire Basins Using Published Geological Maps of South-Eastern England

Elgarmadi, Salah Eldin M, Worden, Richard. H, Potts, Graham. J, Benshatwan, Mohamed. S

2021

Overview

An analysis of the information associated with the faults in the Wealden and Hampshire basins of southeastern England contained in digital geological maps is presented. For each fault, information about the fault trace length, fault orientation and strata affected by the fault were extracted. The fault lengths for both the observed and the inferred faults were analyzed graphically using various combinations of linear and logarithmic axes. This analysis showed that the data for inferred faults were unreliable and they were not used in any subsequent analysis. The fault trace lengths were used to estimate faults heights using different aspect ratios. This analysis showed that only a small number of faults had heights comparable to the thickness of the basins and the stratigraphy that they contain. Using published relationships for normal and strike-slip faults the fault trace lengths were used to estimate faults displacements. Fault strike orientations for all faults and for observed faults were presented as a series of rose diagrams for three stratigraphic intervals separated by the two principal unconformity surfaces. The orientation patterns of the inferred faults are different to the observed faults and analysis was restricted to faults classified as observed from which a possible deformation history was produced. Modes identified in the younger intervals were removed in a stepwise fashion from the older sequences. From this analysis it was possible to identify the main modes in each of the three stratigraphic sequences that are separated by the two unconformities surfaces and assign ages to the fault directions. Although the method has limitations and several sources of error it does analyse a population of faults in a systematic and reproducible way that uses an established geological procedure. A three-stage faulting history has been identified by this approach. Two fault orientations trending ENE-WSW and ESE-WNW, cut parts of the Wealden Group but no younger units. This suggests that they are possibly syn-or post-Wealden, pre-Lower Greensand Group in age (Lower Cretaceous (Ryazanian to Barremian)) and they may be related to rifting. Four fault orientations, N-S, ENE-WSW, NE-SW, E-W and ESE-WNW have been identified and assigned a syn-or post-Cretaceous, pre-Palaeocene age. These faults may represent the later stages of rifting or the early stages of basin inversion. Two fault orientations NNE-SSW and NE-SW have been assigned a Cenozoic age younger than the Alpine unconformity and they may represent post-inversion tectonics. Unfortunately, greater temporal resolution could not be achieved with this dataset.

• Publisher: جامعة المرقب - كلية الآداب والعلوم بمسلاته
• Subject: الأحواض الرسوبية / الجيولوجيا الرقمية / الخرائط الجيولوجية / الوحدات الصخرية