Multiphase reddening and weathering events in Upper Carboniferous red beds from the English West Midlands

Abstract

Sediments of the Halesowen and Salop Formations (Westphalian D-Stephanian) in the West Midlands were deposited on the southern margin of the Pennine Basin during a period of relative tectonic quiescence during the Variscan Orogeny. The clastic framework of the predominantly red sandstones and mudstones in the Salop Formation includes large detrital hematite grains; these yield a primary component of magnetization indicating that sediments were deposited close to the Carboniferous palaeo-equator. Variscan uplift, erosion and subsequent deep oxidation in an arid climate during the Permian resulted in the precipitation of finer hematite in rocks of both formations (which are now found at depths of over 150 m below the present-day ground level). These grains carry secondary magnetizations which indicate formation at palaeolatitudes of between 5° and 15°N, the position that Britain occupied during the Permian. The pattern of Permian remagnetization (particularly in borehole samples) suggests that the secondary fine-grained hematite was precipitated as a result of lateral flow of meteoric water through connected, permeable sandstone units, rather than downward percolation through the entire succession. Present-day surface weathering has resulted in the dissolution of the finer grains of hematite and, in some cases, where permeabilities are relatively high, it has also affected the coarser fraction. Consequently, the record of late Carboniferous and Permian magnetization events is commonly incomplete in strata close to the present day ground level.

A multivariate taxonomic analysis of the Late Carboniferous vertebrate ichnofauna of Alveley, southern Shropshire, England

“…Interbedded red mudstones and red to red-brown, ®ne-and medium-grained sublitharenitic sandstones, interspersed with thin, white and black Spirorbis limestone horizons form the bulk of the succession, in association with clay bands comprising illite and kaolinite (Besly and Cleal 1997). The presence of minor caliche palaeosols is indicative of the proposed semi-arid climatic conditions of the Late Carboniferous (Johnson et al 1997). Two facies associations were recognized within the Alveley Member by Glover and Powell (1996), and interpreted to be the result of¯uctuating water levels across the alluvial plain.…”

“…The Halesowen and Salop formations of the Warwickshire Group were deposited on the southern margin of the Pennine Basin, which occupied a region near the palaeoequator during the Late Carboniferous and Early Permian (Cope et al 1992;Johnson et al 1997;Woodcock and Strachan 2000). The Halesowen Formation represents an ephemeral stage of coal-forming swamp conditions, with caliche palaeosols indicative of an increasingly arid environment (Johnson et al 1997), whilst the Salop Formation is principally composed of oxidised, well-drained, alluvial¯oodplain red-beds, typical of the Upper Westphalian D and lowest Permian strata across Europe (Anderton et al 1979).…”

“…The Halesowen Formation represents an ephemeral stage of coal-forming swamp conditions, with caliche palaeosols indicative of an increasingly arid environment (Johnson et al 1997), whilst the Salop Formation is principally composed of oxidised, well-drained, alluvial¯oodplain red-beds, typical of the Upper Westphalian D and lowest Permian strata across Europe (Anderton et al 1979). Depositional environments represented by Upper Westphalian sediments are predominantly¯uvio-deltaic, and the sediments of the Warwickshire Group in the British Midlands are primarily alluvial red-beds with a lack of well-de®ned marker beds or biostratigraphical elements (Powell et al 2000).…”

“…1B; Powell et al 2000). The type area contains 152±247 m of Westphalian D (Moscovian) sediments (Besly and Cleal 1997;Johnson et al 1997;Powell et al 2000), described by Whitehead and Pocock (1947) as those of an alluvial¯oodplain. Interbedded red mudstones and red to red-brown, ®ne-and medium-grained sublitharenitic sandstones, interspersed with thin, white and black Spirorbis limestone horizons form the bulk of the succession, in association with clay bands comprising illite and kaolinite (Besly and Cleal 1997).…”

Paleomagnetic and geochemical evidence for a pre-Triassic age for the Lower Amaranth Member of the Williston Basin of Manitoba (Canada)

“…There is an obvious complicating factor to the presence of a Permian primary magnetization -the widespread Alleghenian orogenic remagnetization that occurred during the Permian (Kiaman remagnetization), documented by many paleomagnetic studies conducted in the North American Craton and elsewhere (Jackson et al 1988b;McCabe and Elmore 1989;Elmore et al 1993;Elmore et al 1998). In many cases, the Permian remagnetization is observed in hematite-rich redbeds (Johnson et al 1997;Elmore et al 1998). Moreover, a Kiaman remagnetization carried in hematite was found in the evaporites of the Middle Devonian Prairie Formation from Saskatchewan (Koehler et al 1997).…”