Seismic interpretation of basin-basement relationships in the eastern Midland Valley of Scotland using quarry blasts

[摘要] This project was designed as a reconnaissance study in the Fife region where no previous geophysical projects have been executed. It also allowed the extension of the knowledge obtained by the MAVIS project for the Midland Valley of Scotland towards the north-east. The project consisted of four refraction lines recorded using quarry blasts. The first profile (line 1) trends N-S across the Fife region, while the second profile (line 2) trends NW-SE crossing the Central Coalfield Syncline and was planned to tie this project with the MAVIS project. The other two lines provided extra information from the area. Two refractors are recognised defining three crustal layers. The first layer has velocities between 3.3-5.2 km/s and depths between 0.0 and 2.3 km. This layer is interpreted as Carboniferous and Upper Old Red Sandstone rocks and it is exposed along the southern section of line 1 and most of line 2. The second layer was interpreted as Lower Old Red Sandstone and Lower Palaeozoic rocks. It has velocities of 5.3-5.8 km/s and occurs at depths of 2.1-5.2 km in the southern part of the study area and is exposed at the surface, extending down to the basement refractor at 5.2 km depth in the northern section of the study area. A basement refractor with a velocity of 6.04 km/s occurring at a depth of 5.2 km beneath line 1 was interpreted. This refractor is not completely horizontal since a step north of the Tay is envisaged with an estimated upward displacement of 0.3 km towards the axis of the Strathmore Syncline in the north. Four major faults are traversed by the profiles, namely, the Ochil Fault, the North Ochil Fault, the South Tay Fault and the North Tay Fault Only the North Tay Fault was not detected. The estimated throw of the Ochil Fault is 2.2 km near its position of maximum displacement steeply dipping towards the SE, the North Ochil Fault has a throw of 0.5 km dipping to the south and the South Tay Fault a throw of 0.6 km dipping towards the north. A flat basement is envisaged where no effect of surface structures on basement was observed. Therefore, the Ochil Fault, the North Ochil Fault and the South Tay Fault are interpreted as of listric nature soleing out either at the layer 1/2 interface (i.e. Middle Devonian unconformity) or within layer 2. This interpretation is consistent with that of the MAVIS project where a listric Ochil Fault was predicted.

[发布机构] University:University of Glasgow

[关键词] QE Geology