New insights on faults in the Peace River Arch region, northwest Alberta, based on existing well-log data and refined trend surface analysis

This paper presents the results of structural mapping in the Peace River Arch region, obtained by applying a refined trend surface analysis to existing well-log data. Maps generated with the new approach allow for accurate location of formation-top offsets and recognition of faults associated with small, metre-scale offsets. Consequently, new faults were identified in the Mesozoic strata, and faults previously recognized as only offsetting Paleozoic strata were found to extend into the Cretaceous strata but with much smaller formation-top offsets. This provided direct evidence for re-activation of the Dawson Creek Graben Complex (DCGC) during the Cretaceous. An additional structural feature named Clear River Graben was recognized to have affected Permian to Jurassic strata. Relationships among previously interpreted faults were clarified and the structural controls on the DCGC were more accurately evaluated.

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Geologist-controlled trends versus computer-controlled trends: introducing a high-resolution approach to subsurface structural mapping using well-log data, trend surface analysis, and geospatial analysisA companion paper to Mei, S. 2009. New insights on faults in the Peace River Arch region, northwest Alberta, based on existing well-log data and refined trend surface analysis. Canadian Journal of Earth Sciences, 46(1): 41–65.

Canadian Journal of Earth Sciences ◽

10.1139/e09-024 ◽

2009 ◽

Vol 46 (5) ◽

pp. 309-329 ◽

Cited By ~ 3

Author(s):

Shilong Mei

Keyword(s):

Surface Analysis ◽

Polynomial Method ◽

Well Log ◽

Fish Scale ◽

Trend Surface Analysis ◽

Trend Surface ◽

Log Data ◽

Peace River ◽

Computer Controlled ◽

Peace River Arch

This paper introduces a refined trend surface analysis (TSA) for detecting faults with small, metre-scale offsets (5–20 m). Conventional TSA uses a global polynomial method to model the trend; the power of the polynomial (e.g., first, second, or third order) is the only parameter for input. The refined approach is different in that it uses local-fit techniques to generate the trend. The refined approach provides greater flexibility for inputting geological knowledge in the trend surface modelling process. This results in a trend surface with the maximum amount of unwanted information, which is removed from the residual surface after removal of the trend from the data, leaving features of interest optimally highlighted in the residuals. Such a trend is referred to as a geologist-controlled trend to differentiate it from the trend surface modelled by conventional TSA, which is primarily a computer-controlled global polynomial surface. The refined approach goes one step beyond conventional TSA by incorporating advanced geostatistics for modelling the trend, interpolating the resultant residuals, and then extracting formation-top offset patterns from the residual surface using spatial analysis. Modelling the geologist-controlled trend in the refined approach results in higher resolution in detecting formation-top offsets and higher accuracy in digitizing fault locations, compared with various techniques that have been traditionally used in subsurface structure mapping of the West Canada Sedimentary Basin (WCSB) (e.g., structural and isopach contour mapping, cross-section construction, and seismic and aeromagnetic data interpretation). The refined approach is demonstrated using the Basal Fish Scale Zone in the Peace River Arch region as an example.

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The elevation of the Lower Greensand ridge, south-east England

Geological Magazine ◽

10.1017/s0016756800057940 ◽

1969 ◽

Vol 106 (3) ◽

pp. 231-248 ◽

Cited By ~ 5

Author(s):

R. J. Chorley

Keyword(s):

Surface Analysis ◽

Stepwise Regression ◽

Geological Structure ◽

Relative Importance ◽

Trend Surface Analysis ◽

Spatial Control ◽

Trend Surface ◽

Structural Controls ◽

South East England

SUMMARYThe influence of three classes of factors—geological structure, lithologic composition and spatial control over erosion—are examined by trend-surface analysis, followed by stepwise regression, in order to determine their relative importance in explaining the variation observed in the elevation of the Lower Greensand ridge of south-east England. It is concluded that structural controls are dominant, lithological controls very subordinate and the spatial control of very marginal significance.

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