Search

A range of mafic to intermediate extrusive and intrusive igneous rocks from the central part of King George Island were sampled for isotopic and palaeomagnetic studies. Single-grain U--Pb dating of zircon from basalts to trachytes from the upper part of the section gave Eocene ages (53.0 [+ or -] 0.7 to 47.8 [+ or -] 0.5 Ma), consistent with a whole-rock [sup.40]Ar-[sup.39]Ar age of 52.7 [+ or -] 0.6 Ma. These ages correspond to the first stages of the opening of the Drake Passage. A Late Cretaceous [sup.40]Ar-[sup.39]Ar age (75.4 [+ or -] 0.9 Ma) was obtained only from one basalt sample from the bottom part of the section (Uchatka Point Formation). These new age determinations change substantially the existing stratigraphic chart of King George Island. Palaeomagnetic poles show a marked departure from the East Antarctic apparent polar wander path, reflecting anticlockwise rotation of the rocks after the Early Eocene. The mean age of zircon grains from a basaltic lava flow overlying the tillite at Herve Cove (48.9 [+ or -] 0.7 Ma) and the normal polarity magnetization of surrounding basalts allow correlation of the tillite with the upper part of the C22 polarity chron (49.4-48.6 Ma). The consistency in age, crystal morphology, and U and Th contents strongly suggests that the zircon records the magmatic event. However, derivation of the zircon from an older magma and a slightly younger age for the tillite cannot be totally excluded. doi: 10.1144/0016-76492009-177.

To test whether the Tethyan Himalaya were part of the northern margin of India in the early Palaeozoic we have produced the first primary palaeomagnetic data (bedding-corrected declination 267.5[degrees], inclination 63.0[degrees], [[alpha].sub.95] = 10[degrees]; pole latitude 20.2[degrees]N, longitude 28.6[degrees]E) from low metamorphic grade Ordovician red beds in the Tethyan Himalaya (Shian Formation). The palaeomagnetic data are of excellent quality, and a statistically positive fold test combined with a comparison with late Cambrian--Ordovician Gondwana poles suggests a primary hematite-bearing magnetization, acquired between 470 and 500 Ma. This is in excellent agreement with stratigraphic, faunal and provenance age estimates, and the palaeomagnetic data demonstrate that the Tethyan Himalaya must have been located in proximity to the Indian craton during early Ordovician times, and are therefore consistent with a continuous margin at that time. The Shian Formation pole overlaps with 470-500 Ma Gondwana poles, but ah even better fit can be obtained by invoking a post-Ordovician clockwise rotation of 13[degrees][+ or -] 4[degrees]. Such a rotation is similar in both sense and magnitude to clockwise rotations recorded in primary Triassic sequences as well as Palaeogene palaeomagnetic overprint data from the Tethyan Himalaya: rotations of the Tethyan Himalaya compared with cratonic India are thus probably all of post late Eocene age. Triassic and Early Ordovician data do not imply any crustal shortening between Tethyan Himalaya and cratonic India. However, in the Early Ordovician, India was rotated 90[degrees] compared with its present orientation, and any enlargement of India would not be detected by palaeomagnetic data.

New magnetostratigraphic data from seven Western Ghats sections in the Deccan Volcanic Province are presented. These are combined with an established geochemically defined stratigraphy, and volcanological logs, to provide a correlated, chronological eruptive framework. We identify two magnetic polarities in five of the sections, and these are assigned to chrons 29r and 29n. Importantly, the reversal boundary represents an identifiable isochronous surface within the volcanic pile. This surface occurs at different elevations, as does the altitude of the geochemically defined formation boundary (i.e. Ambenali-Mahabaleshwar Fms), which defines a second isochronous surface. Inspection reveals significant differences in the number and thickness of lava units preserved between these two surfaces. This indicates that there was significant local topography (c. 80 m) across Deccan Volcanic Province lava fields during their development; an interpretation consistent with topographies observed across modern and historical examples (e.g. Hawaii, Iceland). These data also indicate that the geochemical stratigraphies of continental flood basalt provinces can mask local and sub-regional detail in lava stacking patterns when applied at smaller spatial scales (

A palaeomagnetic study and age determinations have been performed on Ediacaran basalts from the northwestern Ukraine. Whole-rock [40.sup.Ar]/[39.sup.Ar] age determination revealed plateau ages at 590-560 Ma and 393 Ma, the latter probably reflecting a resetting of the radiometric system. Palaeomagnetic poles have been calculated from five basalt flows, two of which (A poles) are considered reliable with ages that range from 580 to 560 Ma. Tentative poles (B poles), calculated from most probably primary magnetizations, have ages estimated at 580-545 Ma. Secondary magnetizations, possibly of late Ediacaran or Devonian age, have also been isolated (C poles). Based on the new poles, Baltica drifted together with Laurentia from an equatorial position at c. 750 Ma to occupy high southern latitude positions at c. 580 Ma. Baltica during that time period was joined to Laurentia in a similar relative position to that at 750 Ma. The two shields then split up from each other and from c. 550 Ma Baltica drifted at moderately high latitudes and rotated some 180[degrees] during the final opening of the Iapetus ocean. This reconstruction suggests that during the Ediacaran glaciation Baltica occupied high-latitude positions, which contradicts the high-obliquity model to explain low-latitude Neoproterozoic glaciations.

A large-scale palaeomagnetic study (125 specimens from 88 sampling localities) has been carried out on the Whin Sill complex and its associated dykes in northern England. The dominant carrier of remanent magnetization of the doleritic rocks is relatively pure magnetite of pseudo-single domain size, and the characteristic remanent magnetizations are typically well defined and unidirectional. Regionally consistent palaeomagnetic directions are obtained from three geographically distinct parts of the Whin Sill complex, here named as the Holy Island Sill (Declination/Inclination (D/I) = 189.5/-2.8, [[alpha].sub.95] 6.3), the Alnwick Sill (D/I = 194.6/-25.6, [[alpha].sub.95] = 8.1) and the Hadrian's Wall-Permines Sill (D/I = 189.2/3.3, [[alpha].sub.95] = 3.5). Although the Holy Island Sill and the Hadrian's Wall--Pennines Sill are of similar age (c. 296 Ma) and indistinguishable on palaeomagnetic grounds, the difference in palaeomagnetic directions between them and the Alnwick Sill demonstrates the multi-component nature of the complex; magma-flow indicators suggest that the Holy Island Sill and the Hadrian's Wall--Pennines Sill may also represent separate intrusion events. Dykes local to the three sills have remanence directions corresponding to their respective sills and can tentatively be identified as their feeder dykes. Virtual geomagnetic poles for the three palaeomagnetic sites are: Holy Island Sill and Holy Island Dyke, 346.8E, 35.4S; Alnwick Sill, High Green Dyke and St. Oswald's Chapel Dyke. 337.1E, 47.1S; Hadrian's Wall-Pennines Sill and Hett Dyke, 347.1E, 32.9S. Keywords: sills, dykes, palaeomagnetism, emplacement, dolerite.

New palaeomagnetic data from Lower Carboniferous granitoids of the orogenic root of the eastern Variscan belt (Moldanubian domain) show a polyphase palaeomagnetic record. Comparison of the data with existing palaeomagnetic measurements from Lower Palaeozoic sequences of the Bohemian Massif demonstrates a Carboniferous remagnetization of these latter units. All the data presented suggest that the Saxothuringian basement, the Moldanubian orogenic root system as well as the eastern Neoproterozoic Brunovistulian basement were already assembled during the Early Carboniferous. The whole Variscan belt subsequently rotated in a clockwise direction during Mid-Late Carboniferous times. Structural and geochronological data indicate that this rotation was accompanied by large-scale dextral wrenching along NW-SE-trending lithospheric faults. In a first stage, the blocks limited by wrench-faults rotated anticlockwise in bookshelf manner. The data presented rule out the existing model of oroclinal bending of the Rhenohercynian zone at the eastern termination of the Variscan belt. Keywords: palaeomagnetism, Carboniferous, Bohemian massif, rotation, wrenching.

New palaeomagnetic data from upper Triassic to Pliocene sediments reveal that in eastern Sicily a major 70[degrees] clockwise (CW) rotation took place between Oligocene and late Tortonian time, followed by a further 30[degrees] CW rotation. Results from central Sicily are less coherent. They show 44-83[degrees] post-Oligocene CW rotation, local 14[degrees] post-late Tortonian counterclockwise (CCW) rotation, and 25[degrees] post-mid-Pliocene CW rotation. We interpret the larger CW rotation observed in eastern Sicily as related to a more internal palaeogeographical position with respect to central Sicily. Our results complement pre-existing data from the northwestern Sicily carbonates, and indicate that all the internal carbonate nappes coherently rotated by c. 100[degrees] CW during tectonic emplacement, implying a west-to-east increase of shortening in the Sicilian Maghrebian belt. In Sicily, compressive deformation started during the Langhian, i.e. just after the deposition of the upper Oligocene-upper Burdigalian Numidian Flysch turbidites. Therefore the age of the older 70[degrees] palaeomagnetic rotation (synchronous to the thrusting) is constrained to occur between the Langhian and late Tortonian. Furthermore, by considering a maximum possible rotation rate of 20[degrees] [Ma.sup.-1] we infer that CW rotation started in Sicily in Langhian-Serravallian times, between 15-16 and 11-12 Ma ago. The 100[degrees] CW rotation observed in pre-orogenic strata from the whole of Sicily is mirrored by 80[degrees] orogen-scale CCW rotations characterizing the internal southern Apennines. Palaeomagnetism therefore shows that during orogenesis, the southern Apennines and the Sicilian Maghrebides rotated in a `saloon-door' fashion, synchronous to back-arc spreading of the southern Tyrrhenian Sea. Consequently, our palaeomagnetic data suggest that the southern Tyrrhenian back-arc basin started to spread during Langhian-Serravallian times (from 15-16 to 11-12 Ma), significantly earlier than the late Tortonian age (8 Ma) suggested so far by oceanic drilling data. Keywords: Sicily, Tyrrhenian Sea, Maghrebides, palaeomagnetism, plate rotation.

We report on a palaeomagnetic study of upper Miocene sediments from the Amantea basin, located on the Tyrrhenian coast of Calabria. The magnetic mineralogy is dominated by greigite and subordinate magnetite in the Tortonian-Messinian clays (ten sites), and by hemoilmenite and magnetite in the underlying sands and volcanic ashes (three sites), which have not been dated. Data from the Tortonian-Messinian clays pass both a reversal and a fold test, and define a 19[degrees] [+ or -] 11[degrees] clockwise rotation (with respect to the geocentric axial dipole field direction) for the whole basin. The variable amounts of westward declinations observed in the underlying sands and volcanic ashes can be due to (1) a large counterclockwise rotation episode occurring before the clockwise rotation, (2) the effects of a transitional geomagnetic field in these rapidly deposited sediments, or (3) the observed complex magnetic mineralogy. These new results, when compared with previous palaeomagnetic studies from other Calabrian basins, show that the Neogene drifting of the Calabro-Peloritan block from the eastern margin of Sardinia to the present-day position was accompanied by a (probably Pleistocene) 15-20[degrees] rigid clockwise rotation recorded in both the Tyrrhenian and Ionian margins. This tectonic regime is shown to be very different from the one observed by previous studies in the northern Tyrrhenian domain, where large rotations associated with thrust sheet activity in the external Apennines were coeval with the onset of an irrotational extensional regime in the Tuscan and Latium Tyrrhenian margins. Palaeomagnetism thus confirms the significant geodynamical differences between the southern and northern Tyrrhenian Sea spreadings. Keywords: Calabria, Neogene, palaeomagnetism, tectonics.

The Red Arch Formation is a continental red bed succession of uncertain age exposed on the northeast coast of Ireland. There are lithological similarities with the Old Red Sandstone of the Highland Border region, although unconformities within the succession, the presence of reworked aeolian sand grains and variations in the induration of the rocks have prompted earlier workers to suggest that the upper part of the succession may be Triassic in age. This paper reports palaeomagnetic results from the Red Arch Formation. The characteristic magnetizations (ChRMs) are exclusively of reversed polarity and the palaeomagnetic pole position for the sequence bears close comparison with other results from the Old Red Sandstone in Scotland and southern Britain. These poles are regarded as magnetic overprints formed during the Kiaman Superchron because they fall in the Permo-Carboniferous segment of the apparent polar wander path. Sandstone dykes that cut the Red Arch Formation on a NNE-SSW and NNW-SSE trend have also been studied palaeomagnetically. The dykes show more steeply inclined ChRMs predominantly of normal polarity. The dykes are therefore interpreted to be post-Kiaman in age, a conclusion consistent with our structural observations. The age of the dykes cannot be determined precisely because they have also been, at least partially, remagnetized. Lithological and regional geological considerations suggest the dykes are Triassic in age and formed in an extensional stress regime prior to the opening of the North Atlantic. They were remagnetized in Tertiary times, possibly associated with uplift and emplacement of the British Tertiary Igneous Province. Keywords: Old Red Sandstone, Kiaman, Antrim, paleomagnetism.

A palaeomagnetic study was carried out in the Silurian-Devonian clastic sedimentary rocks of the Sierra Grande Formation, exposed in northeastern Patagonia (41.6 [degrees] S, 65.3 [degrees] W). Thirteen sites (n = 88) were located on opposite limbs of a syncline-anticline structure. Stepwise thermal demagnetization permitted the identification of a very stable magnetic component of reversed polarity carried by hematite. Stepwise performance of the fold test yielded negative results both in situ and after 100% bedding correction, but positive after partial unfolding (19%). This indicates a syntectonic origin for the isolated magnetization. A pole position was computed for the partially (19%) corrected remanence: SG3: 77.3 [degrees] S, 310.7 [degrees] E, [Delta] p = 7.7 [degrees], [Delta]m = 6.6 [degrees], N = 13. Its position is coincident with late Early to Late Permian palaeomagnetic poles from South America, suggesting that age for the previously undated folding of the Sierra Grande sequence and therefore for the main tectonic event that affected the northern boundary of Patagonia. Palaeozoic palaeomagnetic poles from Patagonia obtained to date agree with those from Gondwana of Devonian or younger age, suggesting that Patagonia did not undergo important displacements relative to South America since those times. This and the Permian age of deformation determined in this study invalidates tectonic models involving collision of a far-travelled Patagonia with Gondwana in the mid- or Late Palaeozoic. Keywords: Patagonia, Palaeozoic, Gondwana, palaeomagnetism.

A palaeoplain that cuts across Lewisian Gneiss in the Cape Wrath area, northwest Scotland, is weathered to depths of 1-6 m beneath fluvial red conglomerates and sandstones of the Applecross Formation of the early Neoproterozoic Torridon Group. Weathered Lewisian rocks are enriched in [K.sub.2]O and [Fe.sub.2][O.sub.3], and contain hematite as an alteration product of biotite and magnetite. Palaeomagnetic analysis of the weathering profiles has been carried out to constrain the age of alteration. Thermal step demagnetization of 87 oriented core specimens of biotite-gneiss and amphibolite spanning four profiles at Poll a' Mhurain and Sheigra reveal a stable, high-temperature component with a mean direction of remanence of D = 149.1 [degrees], I = 57.2 [degrees] ([[Alpha].sub.95] = 5.0 [degrees]) (corrected for dip of the overlying Applecross strata) that gives a pole at 9.8 [degrees] S, 199.2 [degrees] E (dp = 5.3 [degrees], dm = 7.3 [degrees]). This direction differs significantly from that for little-weathered Lewisian at those two localities and also from directions for the late Mesoproterozoic Stoer Group. The remanence direction for the weathered rocks is, however, near the dip-corrected high-temperature remanence direction (D = 122.3 [degrees], I = 50.5 [degrees], [[Alpha].sub.95] = 10.8 [degrees]) obtained by us from the thermal step demagnetization of 39 sandstone specimens of the Applecross Formation in the Cape Wrath area. Furthermore, the direction for the weathered rocks agrees closely with other dip-corrected results for the Torridon Group, such as the detrital remanent magnetization (DRM) mean direction (D = 148.3 [degrees], I = 59.9 [degrees], [[Alpha].sub.95] = 13.8 [degrees]) for the Applecross Formation on Rum and that for the main outcrop of the Aultbea Formation (D = 139.7 [degrees], I = 52.6 [degrees], [[Alpha].sub.95] = 14.5 [degrees]). The concordance of palaeomagnetic results for the sediments and weathered rocks implies that the weathering profiles in the Cape Wrath area acquired their remanence penecontemporaneously with deposition of the Applecross and Aultbea formations. The palaeomagnetic results therefore argue strongly that the weathering profiles are palaeosols of Applecross age (c. 980 Ma) that formed at a palaeolatitude of 38 [degrees] and constitute the oldest known palaeosols in the British Isles - views that the weathering is substantially older or younger than Applecross deposition cannot be sustained. Our findings carry implications for Applecross palaeoclimate and source and strengthen the conclusion that atmospheric oxygen was a substantial fraction of its present abundance by early Neoproterozoic time. Keywords: Scotland, Proterozoic, Torridonian, palaeomagnetism, weathering.

Coast-parallel dykes in SW Norway, primarily of Permo-Triassic age, have been linked regionally to the early tectonic evolution of the Norwegian continental shelf. We demonstrate from palaeomagnetic data (mean declination = 206.1 [degrees], inclination = -30.1 [degrees], [[Alpha].sub.95] = 11.8 [degrees]) that dolerite dykes in the coastal Sunnfjord region of Western Norway and immediately west of the Devonian Basins are also of Permian (c. 250-270 Ma) age, and not lower- or pre-Devonian as previously advocated. The Sunnfjord dykes appear to be contemporaneous with dykes from SW Norway at Sotra (262 [+ or -] 6 Ma) and the oldest dykes from Sunnhordland (260-280 Ma), and geochemical data attest to a transition from sub-alkaline to alkaline magmatism at the dawn of the Mesozoic. The Sunnfjord dykes are not simple records of E-W extension and magma intrusion, but instead represent significant mid-late Permian time markers within a complex zone of fault activation and rejuvenation. Late Mesozoic-Cenozoic magnetic overprinting (mean declination = 348.6 [degrees], inclination = +68.9 [degrees], [[Alpha].sub.95] = 12 [degrees]) and metamorphic alteration documented by these dykes are directly dependent upon proximity to major E-W brittle faults south of the Hornelen Devonian Basin, hence some motion and related fluid activity do post-date dyke intrusion. The E-W high-angle normal or oblique-slip faults can be regionally traced offshore to the Oygarden Fault Zone. Onshore, these faults truncate the Hornelen low-angle detachment, which in turn cuts folded Devonian strata. These observations, along with evidence for Permian and Late Jurassic-Cretaceous extension from the nearby Dalsfjord region, demonstrate important reactivation of a Late to post-Caledonian detachment and high-angle fault system in Western Norway. Keywords: Norway, Permian, dykes, faults, reactivation.

Magnetizations of Late Ordovician (Caradoc - early Ashgill) age in the paratectonic Caledonides of Wales and the Lake District are directed westerly and northerly respectively. They identify c. 55 [degrees] of relative rotation of probable Acadian age. Southward subduction of Iapetus ocean crust occurred in Ordovician times beneath a latitudinally oriented orogen sited in mid-southerly latitudes with the Borrowdale and Snowdonia Volcanic provinces forming parallel fore-arc and back-arc lineaments respectively. Mid-Ordovician to mid-Devonian palaeomagnetic poles from the orogen correlate with contemporaneous Gondwana data to identify a former location sited west of the South American perimeter and not near to North Africa as assumed in previous reconstructions. Keywords: Caledonides, Lower Palaeozoic, Gondwana, plate tectonics, rotation.

A well-exposed 2 km section through the Eastern Subbetic, immediately to the south of the Crevillente wrench fault zone can be divided into an upper thrust sheet of Triassic rocks, a middle thrust sheet of Cenomanian-Turonian basinal sediments, and a lower thrust sheet of Jurassic limestones unconformably overlain by Upper Cretaceous-Palaeocene sediments. Structural relationships suggest that the middle sheet overthrust the lower sheet; and both units were subsequently folded and imbricated. This sequence was then overthrust by the upper sheet, incorporating a footwall duplex of Cenomanian-Turonian sediments. These structures can be related to the complex deformation associated with a single overthrusting event. The dominant thrust transport direction is to the east, strongly oblique to the overall trend of the orogen. However, a palaeomagnetic study isolates stable components which indicate no cumulative vertical axis rotation of the thrust sheets. The section is cut by strike-slip faults whose displacements appear to be relatively minor. The Triassic rocks of the upper thrust sheet form a highly disrupted thrust sheet extending over much of the Subbetic, rather than being local to the Crevillente fault zone. This section through the Subbetic can be interpreted as the result of a major east-directed thrust of basinal sediments of the Median Subbetic over marginal shelf facies of the Internal Subbetic, strongly oblique to the general ESE trend of the orogen. The shortened sequence is cut by a later set of strike slip faults which are probably related to movement on the Crevillente fault.

New palaeomagnetic data from the Caledonides of western Ireland indicate that the Silurian rocks of South Mayo underwent oroclinal bending, following folding, in Siluro-Devonian time. Bending was accommodated on faults cutting the Silurian sequence, and was driven by strike slip motion across the Antrim - Galway Line, a recently recognized major curvilinear lineament. We propose that the Silurian rocks in the east of the region suffered up to 30 degrees clockwise rotation, increasing towards the west to approximately 70 degrees. This newly inferred differential rotation of the Silurian rocks, about a sub-vertical axis, implies that the underlying Dalradian rocks of the Connemara Massif to the south must also have undergone clockwise rotation in late Silurian/early Devonian time. This is consistent with published palaeomagnetic data from the Connemara Gabbro and accounts for the swing in strike of the Caledonian orogen in this part of western Ireland. From this we deduce that the swing in strike of the Caledonian rocks elsewhere on the west coast of Ireland might have a similar explanation.

Silurian palaeomagnetic data from all continents are compiled in an attempt to define the polarity history of the Earth's magnetic field during the period. Data sets from Llandovery, Ludlow, and Pridoli strata often display evidence of field reversals (i.e. the presence of both normal and reverse polarity magnetization directions) despite the fact that the palaeomagnetic sample collections may cover only a limited stratigraphic range in each case. Palaeomagnetic data from rocks of Wenlock age are exclusively of normal magnetic polarity. A comparison of the available Silurian data with published Ordovician palaeomagnetic results suggests that the frequency of magnetic field reversals increased from Ordovician to Silurian times. Palaeomagnetic data sets are not yet available from a continuous Silurian stratigraphic sequence of any great duration, so the Silurian magnetostratigraphy is still at a much more preliminary stage than that for the Ordovician. Apart from the Wenlock, all Silurian series have some intervals with frequent (

Faunal and palaeomagnetic evidence suggests the existence of a c. 3000 km-wide Tornquist Sea between Gondwana and Baltica in Early Ordovician times, which narrowed to

An analysis of palaeomagnetic data is presented. Sampling sites from the Borrowdale Volcanic Group generate high unblocking temperature magnetization components which postdate structural tilt. This postdated process also applies to block-faulted formation. Hydrothermal alteration during the late Ordovician period is linked with the magnetization process. The block-faulted synclinal structure bounding the Borrowdale area is considered part of the pre-Acadian stage.

The presence of volcanic rocks from the early Wenlock generate primary palaeomagnetic directions which show southern Britain's location in Mid Silurian period. Combined data show that the Iapetus Ocean was closed in its British and Scandinavian parts, the initial docking of eastern Avalonia was post-dated by the British Acadian deformation and convergence limits of southern Britain and Baltica are eliminated by the closure of the Tornquist Sea into theMid-Sularian period.

Magnetic and gravimetric studies of the Mageroy nappe of Norway reveal anomalies in the Honningsvag igneous complex (HIC). Modeling of the HIC regarding the anisotropy of remanence as well as gravimetric data reveals a tilting of from 60 to 80 degrees in the structure extending for greater than 50 km and with a depth of 6 km. Subsequent information indicate that the HIC was formed by brittle upper-crust motion without normally accompanying volcanic activity.

Three Normal and three Reversed palaeomagnetic polarity zones were identified in the exposed 67 m section of Mercia Mudstone at St Audrie's Bay, Somerset, which has been regarded as being of Norian age on limited biostratigraphic evidence. The polarity sequence is correlated with magnetozones E15 to E17 in the Newark Basin, New Jersey, further supporting the inferred Norian age and tentatively placing it in the mid-Norian. Correlations with the northern North Sea and the Alps are also suggested. Results from Doniford Bay, where tectonic dips are steeper but which cannot be correlated precisely with the St Audrie's section. are incorporated for the calculation of the mean direction of Characteristic Remanent Magnetization which has declination 30.8 [degrees] and inclination +34.3 [degrees] (N = 27 horizons, [[Alpha].sub.95] = 5.1 [degrees]). The corresponding palaeomagnetic pole is 49.6 [degrees] N, 128.4 [degrees] E (dp = 3.3 [degrees], dm = 5.8 [degrees]), which also correlates with the Norian of the Newark Basin. while possibly indicating that small adjustments should be made to the orientation of all or part of Britain within the 1965 Bullard et al. configuration as a representation of Late Triassic geography. Keywords: Triassic, Norian, Somerset, magnetostratigraphy, palaeomagnetism.