Paleomagnetic investigation of organic-rich lacustrine deposits, Middle Old Red Sandstone, northern Scotland.

摘要

Organic-rich lacustrine carbonate laminates and mudstones in the Old Red Sandstone (middle Devonian) from the Orcadian Basin, Scotland, contain a number of remanent magnetizations residing in magnetite. After removal of a modern viscous magnetization at low demagnetization temperatures, a southerly and shallow Late Carboniferous component (before tilt: decl = 184, incl = -5, k= 36, alpha 95 = 7.3, n = 12 sites) is removed between 100-450°C in most specimens. A regional fold test on the shallowly dipping rocks is inconclusive, but suggests a post-folding time of remanence acquisition. A few specimens also contain a northerly and shallow component interpreted as the antipodal equivalent of the southerly and shallow direction. Some specimens contain a southwesterly and shallow, possibly Devonian component, which also resides in magnetite (after tilt: decl = 234, incl = -7, k = 27, alpha 95 = 10, n = 9 specimens). (Abstract shortened by UMI.)