Some recent palaeomagnetic measurements made at Imperial College, London

A geomagnetic polarity timescale for the Carboniferous

“…Everitt and Belshé (1960), Wilson (1960) and Wilson & Everitt (1963) were the first significant studies to use thermal demagnetization procedures on Carboniferous volcanic rocks, working on the Kinghorn successions in Fife (Scotland) to isolate cleaned dual polarity directions. This followed preliminary undemagnetised data published on these same sample sets by Clegg et al (1957), in which they identified a magnetic polarity boundary within the succession of lavas. Following Wilsons PhD work (Wilson 1960), partly on these units, Wilson and Everitt (1963) later synthesized their data on the succession of the Kinghorn Volcanic Fm, relating the detailed sampling by Everitt to the numbered stratigraphic log information in Geike (1900) to provide a detailed polarity record through part of the late Visean ( Fig.…”

“…These early studies did not use alternating field (AF) or thermal demagnetization (which all studies now use), to isolate the primary remanence since these methods were only beginning to be developed in the late 1950's, for AF 'cleaning', firstly using static AF fields (Brynjólfsson 1957;Creer 1958;As & Zijderveld 1958), and later tumbling of samples in AF (Creer 1959) with subsequent improvements (McElhinny 1966). In spite of this initial inadequacy, both polarities were present in Carboniferous rocks (Irving 1957;Belshe 1957;Clegg et al 1957, Howell & Martinez 1957. However, additional magnetizations from the present day and after the time of rock formation (secondary magnetizations ;Creer 1957;Irving 1959;Collinson & Runcorn 1960;Irving et al 1961) contaminated these early datasets, sometimes giving smeared directions along a great circle, called by Khramov (1958) the 'circle of remagnetisation'.…”

“…The undemagnetised samples of Clegg et al (1957) and Everitt (1960) from the Shatterford sill in the English West Midlands, shows reasonably well defined dual polarity, and was originally dated as Westphalian, since its emplaced into Westphalian-C (Bolsovian, early Moscovian) clastics (Kirton 1984). This is one of number of other genetically-related intrusions in the same area which have been dated at around 295 -296 Ma using K/Ar (Fitch & Miller 1964), probably providing only a minimum age (Bolsovian is now around 315-310 Ma; Aretz et al 2020).…”

The Stability of NRM of Deccan Traps Basalts in India

“…Very thick succession of the lavas is exposed along the scarp forming the western margin of the Western Ghats parallel to the Arabian coast line. Many paleomagnetic results have been obtained from the Deccan Trap Formation (ATHAVALE et al, 1964;ATHAVALE, 1970;BLACKETT et al, 1960;CLEGG et al, 1956CLEGG et al, , 1957DEUTSCH et al, 1958;DEUTSCH, 1959;MCELHINNY, 1968;PAL, 1969;PAL and BHIMA-SANKARAM, 1971;VERMA and RAO, 1963;WENSINK and KLOOTWIJK, 1971;WENSINK, 1972). Two interpretations have been based on these paleomagnetic studies.…”

Palaeomagnetism of Permian and Triassic red beds of NW Spain and implications for the tectonic evolution of the Asturian-Cantabrian Arc

“…Thus, if rotations were younger than the Permian, they would have affected the cover rocks. Except for early work by Clegg et al (1957), who interpreted a present-day field direction as Triassic, the first Permo-Triassic palaeomagnetic results were obtained by Vandenberg ( 1980). He reported declination discrepancies in Permo-Triassic and Late Jurassic rocks located in the northern part of the Asturian-Cantabrian Arc, and argued that the sampled rocks belonged to a crustal block that extends offshore.…”