Palaeomagnetic evidence for large-scale dextral movement along the Trollfjord-Komagelv Fault,Finnmark, north Norway

Palaeomagnetic data from Late Precambrian dykes from the northern part of Varanger peninsula, north Norway, suggest a two-axis magnetization structure. The dominant component is considered to be syn- to late-tectonic and probably acquired at around 640 m.y. B.P. Superposed on this magnetization is a minor component which is compatible with the relative Lower-Middle Palaeozoic field; i.e. it was most likely imposed during the climax of the Caledonian orogenic movements in north Norway. The estimated relative Late Precambrian palaeopole cannot easily be reconciled with the European Late Precambrian polar path. This disagreement can be accounted for by assuming a post-magnetization dextral megashear, of the order of 500–1000 km, along the Trollfjord-Komagelv fracture zone. This type of displacement is in line with geological evidence and the palaeomagnetic reconstruction supports the long-held view of there having been continuity between the depositional environments of the Varanger Peninsula Barents Sea Group, the Eleonore Bay Group of east Greenland and the Hecla Hoek Formation of east Spitsbergen. The character and age of the horizontal displacement, post-640 to pre-500 m.y. B.P., is seen in conjunction with the opening up of the lapetus Ocean and reactivation of ancient deep-seated fractures during both the spreading and the contraction phases of ocean development.     

Aspects of Caledonian palaeomagnetism and their tectonic implications

Palaeomagnetic results from the Lower Palaeozoic inliers of northern England cover the upper part of the (Middle Ordovician) Borrowdale Volcanic Series (palaeomagnetic pole 208°E, 18°S, A₉₅ = 9.4°), minor extrusive units relating to the Caradoc and Ashgill stages of Ordovician times, intrusive episodes of Middle Ordovician and Middle Silurian to Late Devonian age, and the Shap Granite of Devonian (393 m.y.) age (palaeomagnetic pole 313°E, 33°S, A₉₅ = 5.6°).A complete assessment of Ordovician to Devonian palaeomagnetic data for the British region shows that the pole was nearly static relative to this region for long intervals which were separated by shifts occupying no more than a few millions of years. The mean palaeomagnetic poles are: Ordovician (6°E, 16°S), Lower Silurian (58°E, 16°N), Middle Silurian/Lower Devonian (318°E, 6°N) and Middle/Upper Devonian (338°E, 26°S); the first two shifts separating these mean poles can be explained predominantly in terms of rotational movements of the crustal plate but the last involved appreciable movement in palaeolatitude.Comparison of Lower Palaeozoic palaeomagnetic data from the British region with contemporaneous data from continental Europe/North America on the Pangaean reconstruction reveals a systematic discrepancy in palaeolatitude between the two regions prior to Middle Devonian times. This discrepancy was eliminated during a few millions of years of Lower/Middle Devonian times (ca. 395 m.y.) and can be explained in terms of ca. 3500 km of sinistral strike-slip movement close to the line of the orthotectonic Caledonides. This motion is linked both in time and place to the impingement of the Gondwanaland and Laurentian supercontinents during the Acadian orogeny; this appears to have displaced the British sub-plate until it became effectively locked between the Baltic and Laurentian regions. Although movement of the dipole field relative to the British region in Lower Palaeozoic times is now well defined, nearly one fifth of the total data show that the geomagnetic field was more complex than dipolar during this interval. Until the significance of these anomalies is fully resolved, the tectonic model derived from the palaeomagnetic data cannot be regarded as unambiguous.     

Palaeomagnetic study of the (Late Precambrian) West Greenland kimberlite-lamprophyre suite: definition of the Hadrynian Track

Kimberlite and potassic lamprophyre dykes were intensively intruded into the early Proterozoic Nagssugtoqidian mobile belt of West Greenland during an important phase of brittle reactivation in Late Precambrian-Early Cambrian times (ca. 580-570 Ma) and during at least one other minor phase. Thermal and alternating field demagnetisation studies of 52 of these dykes identify primary components residing in the critical blocking temperature range distributed between shallow westerly and steep positive directions. Near the axis of the Proterozoic shear belt the dykes (predominantly lamprophyres) have closely grouped shallow directions with a reversal; near the margins of the shear belt dykes (predominantly kimberlites) have steeper and distributed directions. The cleaned components of magnetisation appear to be single, and the distribution of directions is interpreted to record a migration of the palaeofield axis which intersecting relationships show to have been from shallow to steep. The dyke directions are grouped to define representative mean palaeopoles of 215°E 3°N (LK1, A₉₅ = 3.9°), 213°E 18°N (LK2, A₉₅ = 6.1°), 203°E 46°N (LK3, A₉₅ = 10.4°) and 259°E 54°N (LK4, A₉₅ = 11.0°); a subsidiary direction recorded in five dykes near the southern margin of the shear belt (LK5, palaeopole at 297°E 16°S (A₉₅ = 12.5°)) is derived entirely from lamprophyres and is possibly Silurian in age. An RbSr isochron on three lamprophyres of 1227 Ma and agreement of the remanence direction with ca. 1220 Ma rocks from elsewhere in Greenland suggests that the LK1 component is wholly or partly of that age.The remaining sequence of palaeopoles falls along the Hadrynian Polar Track and the age data relating to this track are re-evaluated. Evidence for a pre-800 Ma age is no longer valid and the new data from West Greenland confirm that the track is latest Precambrian to Early Cambrian in age. It is shown to connect poles of Late Precambrian and Lower Cambrian age and to embrace other data from the Laurentian shield. The rapid passage of the shield across the South Pole is consistent with the sedimentation sequences, and suggests a high-latitude origin for the tillite horizon of this age. The Hadrynian Track is also compared with the contemporaneous record from Gondwanaland and it is shown that the two shields were in juxtaposition in the identical reconstruction to the Proterozoic Supercontinent until earliest Cambrian times. This discovery links the Lower Cambrian marine transgression and the widespread ca. 580-560 Ma alkaline province in the Gondwanaland, Laurentian and Fennoscandian shields to major continental break up, and it conforms with evidence that the Iapetus Ocean did not open until Cambrian times.     

Magnetic properties of the Lower Old Red Sandstone lavas in the Midland Valley,Scotland; palaeomagnetic and tectonic considerations

Thermal demagnetization studies of lavas in the Strathmore area of the Midland Valley, Scotland, support overall palaeomagnetic data found in previous studies of these rocks. Reduced directional scatter as compared to some earlier studies, is attributed to more effective demagnetization, resolving some of the directional complexity of previous studies. Combined magnetic fabric and directional analysis suggest that at least some deviating directions may be explained by local tectonism. The existence of almost antiparallel directional groups and field tests give supporting evidence for a “primary” (deuteric) origin of the main magnetization of these rocks. Additionally, a second remanence component having shallow reverse directions of magnetization, is attributed to later remagnetization in Old Red Sandstone time. The Midland Valley results are seen in conjunction with other Palaeozoic palaeomagnetic results and possible geodynamic implications are discussed.     

Paleomagnetism of the Lower Ordovician and Cambrian sedimentary rocks in the section of the Narva River right bank: For the construction of the Baltic Kinematic model in the Early Paleozoic

The paleomagnetic study of the Lower Ordovician and Cambrian sedimentary rocks exposed on the Narva River’s right bank revealed a multicomponent composition of natural remanent magnetization. Among four distinguished medium- and high-temperature magnetization components, the bipolar component, which carries the reversal test, is probably the primary component and reflects the geomagnetic field direction and variations during the Late Cambrian and Early Ordovician. The pole positions corresponding to this component have coordinates 22°N, 87°E (dp/dm = 5°/6°) for the Late Cambrian, and 18°N, 55°E (dp/dm = 5°/7°) for the Early Ordovician (Tremadocian and Arenigian). Together with the recently published paleomagnetic poles for the sections of the Early Ordovician in the Leningrad Region and the series of poles obtained when the Ordovician limestones were studied in Sweden, these poles form new key frameworks for the Upper Cambrian-Middle Ordovician segment of the apparent polar-wander path (APWP) for the Baltica. Based on these data, we propose a renewed version of the APWP segment: the model of the Baltica motion as its clockwise turn by 68° around the remote Euler pole. This motion around the great circle describes (with an error of A₉₅ = 10°) both variations in the Baltic position from 500 to 456 Ma ago in paleolatitude and its turn relative to paleomeridians. According to the monopolar components of natural remanent magnetization detected in the Narva rocks, the South Pole positions are 2°S, 351°E (dp/dm = 5°/9°), 39°S, 327°E, (dp/dm = 4°/7°), and 42°S and 311°E (dp/dm = 9°/13°). It is assumed that these components reflect regional remagnetization events in the Silurian, Late Permian, and Triassic.     

Palaeomagnetic investigations on the East African rift in Northern Tanzania

Near Lake Manyara and north of Monduli, Northern Tanzania, Precambrian gneisses and Neogene basalts on the East African rift were sampled. Rock magnetic and microscope investigations established coarse and fine grained magnetite as carrier of the NRM in the basalts, and hematite in the gneisses. In all three sections only reversed magnetization directions were found. The Precambrian gneisses show very hard magnetizations which is known to be prefolding and possibly of Proterozoic age.     

A Nd isotope investigation of sediments related to crustal development in the British Isles

The times of original fractionation of the Sm and Nd component of clastic sediments from a mantle source (≡ crustal residence age) have been estimated from Sm-Nd model ages calculated relative to a depleted mantle evolution. In this way the provenance and evolution of selected Precambrian and Phanerozoic sediments and metasediments from the British Isles have been examined. Whereas some Archaean and early Proterozoic sediments have Sm-Nd model ages that are close to their stratigraphic age, the Phanerozoic sediments analysed have model ages as much as 2.0 Ga in excess of their stratigraphic age.A more detailed study of Lower Palaeozoic sediments deposited on the northern margin of the Iapetus Ocean provides evidence for a marked change of provenance in the Ordovician after the deposition of the Dalradian Supergroup. A component with comparatively high¹⁴³Nd/¹⁴⁴Nd and Sm/Nd ratio (presumably basaltic) is present in the sediments throughout the accretionary prism. Crustal residence age estimates average about 1.5 Ga for both these Lower Palaeozoic sediments, and modern pelagic clays, and collectively fail to provide any evidence for significant continental growth during the Phanerozoic.     

Discovery of Precambrian rocks in New Zealand: Age relations of the Greenland Group and Constant Gneiss,West Coast,South Island

Rb-Sr whole-rock analyses yield a Cambro-Ordovician (495 ± 11 m.y.) sedimentation age for the supposed Precambrian Greenland Group and a late Precambrian age, 680 ± 21 m.y., for parts of the Constant Gneiss, the first confirmation of Precambrian rocks in New Zealand. A Precambrian age for the Greenland Group is thus unlikely and the large area of Upper Cambrian-Lower Ordovician rocks now established can be considered as a lateral equivalent of the fossiliferous Lower Palaeozoic succession of northwest Nelson to the east. The Greenland Group, especially in the Paparoa Range has been affected subsequently by a thermal metamorphic overprint about 360 m.y. ago during the Tuhuan Orogeny. Although the Constant Gneiss must form the local basement to the Greenland Group in north Westland, the former does not appear to be the source of the sediments and the true provenance must lie elsewhere.     

塔里木地块奥陶纪古地磁新结果及其构造意义

本文报道塔里木地块阿克苏—柯坪—巴楚地区奥陶纪古地磁研究新结果.对采自44个采点的灰岩、泥灰岩及泥质砂岩样品的系统岩石磁学和古地磁学研究表明,所有样品可分成两组：第一类样品以赤铁矿和少量磁铁矿为主要载磁矿物,该类样品通常可分离出特征剩磁组分A;第二类样品以磁铁矿为主要载磁矿物,系统退磁揭示出这类样品中存在特征剩磁组分B.特征剩磁组分A分布于绝大多数奥陶纪样品中,具有双极性,但褶皱检验结果为负,推测其可能为新生代重磁化.特征剩磁组分B仅能从少部分中晚奥陶世样品中分离出,但褶皱检验结果为正,且其所对应古地磁极位置（40.7°S,183.3°E,dp/dm=4.8°/6.9°）与塔里木地块古生代中期以来的古地磁极位置显著差别,表明其很可能为岩石形成时期所获得的原生剩磁.古地磁结果表明塔里木地块中晚奥陶世位于南半球中低纬度地区,很可能与扬子地块一起位于冈瓦纳古大陆的边缘;中晚奥陶世之后,塔里木地块通过大幅度北向漂移和顺时针旋转,逐步与冈瓦纳大陆分离、并越过古赤道;至晚石炭世,塔里木地块已到达古亚洲洋构造域的南缘.     

Geodynamic evolution of Korea: A view

Abstract Evidence for South Korean Palaeozoic geodynamic evolution is restricted to the Ogcheon Belt, which is a complex polycyclic domain forming the boundary between the Precambrian Gyeonggi Block to the northwest and the Ryeongnam Block to the southeast. Two independent sub-zones can be distinguished: the Taebaeksan Zone to the northeast and the Ogcheon Zone sensu stricto. The Taebaeksan Zone and Ryeongnam Block display characteristic features of the North China palaeocontinent. This domain remained relatively stable during the Palaeozoic. In contrast, the Ogcheon Belt s. s. is a highly mobile zone that belongs to the South China palaeocontinent and corresponds to a rift that opened during the Early Palaeozoic. In lowermost Devonian times, the rift basin was closed and the Ogcheon Belt was structured in a pile of nappes. From the lack of suture in the Ogcheon Belt it can be inferred that the Gyeonggi Block belongs to the South China palaeocontinent. Thus, the boundary between the North China and South China blocks should be located to the north of Gyeonggi Block, that is, in the Palaeozoic Imjingang Belt. From the Middle Carboniferous, sedimentation started again on a weakly subsiding paralic platform located in the hinterland of the Late Palaeozoic orogen of southwest Japan. In the Late Carboniferous, increasing subsidence recorded extensional tectonics related to the opening of the Yakuno Oceanic Basin (southwest Japan). In the Middle Permian, the end of marine influences in the platform and emplacement of terrestrial coal measures, may be correlated with the closure of the oceanic area and subsequent ophiolite obduction. In Late Permian to Early Triassic times, the Honshu Block (the eastern palaeomargin of the Yakuno Basin) collided with Sino-Korea. Post-collisional intracontinental tectonics reached the Ogcheon Belt in the Middle Triassic (Songnim tectonism). Ductile dextral shear zones associated with synkinematic granitoids were emplaced in the southwest of the belt. In the Upper Triassic, the late stages of the intracontinental transcurrent tectonics generated narrow intramontane troughs (Daedong Supergroup). The Daedong basins were deformed during two tectonic events, in the Middle (?) and Late Jurassic. The Upper Jurassic to Lower Cretaceous basins (Gyeongsang Supergroup), that are controlled by left-lateral faults, may have resulted from the same tectonic event.     

Palaeomagnetism and K/Ar results from the Duncansby volcanic neck,NE Scotland: superimposed magnetizations,age of igneous activity,and tectonic implications

The Duncansby volcanic neck, intruding the Middle Devonian red beds of north Caithness, Scotland, has revealed two significantly different axes of magnetization, yielding pole positions at 149°E, 24°N and 126.5°E, 60°N, respectively. The first pole, which is interpreted as corresponding to the oldest magnetization, is in perfect agreement with Devonian polar estimates from west of the Great Glen Fault. It is tentatively suggested therefore that the Duncansby neck correlates with the Late Devonian volcanism in the nearby Orkney Islands though palaeomagnetism allows an upper age estimate of around Middle Carboniferous. The data support an earlier proposition of there being a palaeomagnetic discordance across the Great Glen Fault that can be interpreted in terms of a large-scale late- or post-Devonian transcurrent movement along this fracture zone. The original (? Late Devonian) magnetization has been nearly completely erased by the second phase of magnetization which, according to its pole position, most likely dates from about the Middle Jurassic. The latter magnetization is thought to be a consequence of burial, the coastal districts of Caithness having participated in the general subsidence of the North Sea area in late Palaeozoic and Mesozoic times. The burial magnetization, involving VPTRM and or TCRM processes, is considered to have been “frozen-in” as a result of uplift in connection with the well-documented mid-Jurassic tectonic phase that affected the northern North Sea basin, including the adjacent Moray Firth area. K/Ar analyses of the Duncansby intrusion give apparent ages ranging from 258 to 239 Ma. These dates, which lie between the two geological events inferred from palaeomagnetism, are not seen as true rock ages but rather as the result of a partial Ar loss during burial reheating.     

A paleomagnetic reinvestigation of the Upper Devonian Perry Formation: evidence for Late Paleozoic remagnetization

In view of the recent recognition of widespread Late Paleozoic remagnetization of Devonian formations across North America, we undertook a reinvestigation of the Upper Devonian Perry Formation of coastal Maine and adjacent New Brunswick. Thermal demagnetization of samples from the redbeds yielded a characteristic direction (D = 166°, I = 4°) that fails a fold test. Comparison of the corresponding paleopole (312°E, 41°S) with previously published Paleozoic poles for North America suggests that the sediments were remagnetized in the Late Carboniferous. After the removal of a steep, northerly component, the volcanics also reveal a shallow and southerly direction ( D = 171°, I = 25° without tilt correction). No stability test is available to date the magnetization of the volcanics; however, similarity of several of the directions to those seen in the sediments raises the suspicion that the volcanics are also remagnetized. Although the paleopole without tilt correction (303°E, 32°S) could be taken to indicate an early Carboniferous age for the remagnetization, scatter in the data suggests that the directions are contaminated by the incomplete removal of a steeper component due to present-day field. Thus, it is more likely that the volcanics were remagnetized at the same time as the sediments. Isothermal remanent magnetization (IRM) acquisition curves, blocking temperatures, coercivities and reflected light microscopy indicate that the magnetization is carried by hematite in the sediments and by both magnetite and hematite in the volcanics. It is therefore likely that the remagnetization of the Perry Formation involved both thermal and chemical processes related to the Variscan/Alleghenian orogeny. Our results indicate that previously published directions for the Perry Formation were based on the incomplete resolution of two magnetic components. These earlier results can no longer be considered as representative of the Devonian geomagnetic field.     

Continental drift during the Palaeozoic

Rapid polar shifts relative to Gondwanaland are identified in the Late Ordovician and Carboniferous. These shifts form part of the “Common polar wander path” interpretation of the palaeomagnetic poles for the Gondwana continents during the Palaeozoic. For western Europe a transition occurs between the Ordovician and Silurian poles, but is of smaller magnitude than the Late Ordovician Gondwana shift. Similarly Carboniferous shifts with respect to Europe and North America are smaller than the Gondwana shifts. A third shift in Europe is dated as mid-Devonian, but could be as old as Late Silurian, and has no counterpart in Gondwanaland. The differences in timing and magnitudes of these shifts provide evidence of the predominant role of continental drift rather than polar wandering. Attempts to explain the data exclusively in terms of polar wandering lead to geologically and geometrically untenable conclusions. Whilst there were one or perhaps two supercontinents in most of the upper Palaeozoic, it seems Laurasia was itself a set of separate fragments.     

Palaeozoic radiometric age provinces in the Andean basement,latitudes 25°–30°S

More than fifty new K-Ar age determinations are reported for mineral separates and whole-rock samples from igneous and metamorphic basement rocks of northwestern Argentina and contiguous Chile between 25° and 30°S. The age data define three thermal events, occurring in the late Ordovician-Silurian (400–450 m.y.), mid-Carboniferous (310–340 m.y.) and Permian (225–270 m.y.), and confirm deductions of previous workers that the crystalline basement rocks of the Pampean Ranges of northwestern Argentina are not of Precambrian age, but rather evolved predominantly during the Palaeozoic. The proposed radiometric age provinces and the inferred orogenic history of the area are compared with those for the rest of South America, and it is confirmed that, by the late Ordovician, the focus of major orogenic activity in South America was located along the present western and southern margins of the craton, and tended to migrate westwards during the Palaeozoic.     

Evidences for multiple remagnetization of Proterozoic dykes from Iguerda inlier (Anti-Atlas Belt,Southern Morocco)

No paleomagnetic data exist for Paleo-Mesoproterozoic times of the West African Craton (WAC). Therefore, paleogeographic reconstructions for such old geological times are difficult to constrain. Gaps on the sedimentary record and intense remagnetizations are the major problems that paleomagnetic studies come across. Recent geochronological results for dyke swarms that intrude several Proterozoic inliers of WAC in the Anti-Atlas Belt (southern Morocco) revealed ages between Paleoproterozoic and early Neoproterozoic, opening for the first time a window of opportunity to conduct paleomagnetic studies and tentatively infer about the paleoposition of WAC during Proterozoic. On this scope we conducted a paleomagnetic study on seven Proterozoic dykes of the Iguerda inlier. The meaning of the obtained paleomagnetic directions was evaluated by rock magnetic and mineral analyses, complemented by petrographic observations. Our samples record the presence of a complex history of remagnetization, mostly assigned to several Phanerozoic thermal/chemical events, in particular to the late stages of Pan African orogeny (s.l.), to the Late Carboniferous Variscan orogeny, and even to more recent events. The recognized remagnetization processes are related to widespread metamorphic events under greenschist facies followed by low-temperature oxidation, both responsible for the formation of new magnetic phases, like magnetite and hematite. These events obliterated the primary (magmatic) thermo-remanent magnetization and promoted multiple remagnetizations of the dykes, thermally and chemically. For only one dyke the presence of primary magnetization is possible to infer, though not to confirm, and would place WAC at an equatorial position around 1750 Ma.     

Systematics of Early Cambrian Paleomagnetic Directions from the Northern and Eastern Regions of the Siberian Platform and the Problem of an Anomalous Geomagnetic Field in the Time Vicinity of the Proterozoic–Phanerozoic Boundary

Representative paleomagnetic collections of Lower Cambrian rocks from the northern and eastern regions of the Siberian platform are studied. New evidence demonstrating the anomalous character of the paleomagnetic record in these rocks is obtained. These data confidently support the hypothesis (Pavlov et al., 2004) that in the substantial part of the Lower Cambrian section of the Siberian platform there are two stable high-temperature magnetization components having significantly different directions, each of which is eligible for being a primary component that was formed, at the latest, in the Early Cambrian. The analysis of the world’s paleomagnetic data for this interval of the geological history shows that the peculiarities observed in Siberia in the paleomagnetic record for the Precambrian–Phanerozoic boundary are global, inconsistent with the traditional notion of a paleomagnetic record as reflecting the predominant axial dipole component of the geomagnetic field, and necessitates the assumption that the geomagnetic field at the Proterozoic–Phanerozoic boundary (Ediacaran–Lower Cambrian) substantially differed from the field of most of the other geological epochs. In order to explain the observed paleomagnetic record, we propose a hypothesis suggesting that the geomagnetic field at the Precambrian–Cambrian boundary had an anomalous character. This field was characterized by the presence of two alternating quasi-stable generation regimes. According to our hypothesis, the magnetic field at the Precambrian–Cambrian boundary can be described by the alternation of long periods dominated by an axial, mainly monopolar dipole field and relatively short epochs, lasting a few hundred kA, with the prevalence of the near-equatorial or midlatitude dipole. The proposed hypothesis agrees with the data obtained from studies of the transitional fields of Paleozoic reversals (Khramov and Iosifidi, 2012) and with the results of geodynamo numerical simulations (Aubert and Wicht, 2004; Glatzmayer and Olson, 2005; Gissinger et al., 2012).     

Paleomagnetism of the latest Precambrian/Cambrian Unicoi basalts from the Blue Ridge, northeast Tennessee and southwest Virginia: evidence for Taconic deformation

Three components of magnetization have been observed in ninety-six samples (twelve sites) of amygdaloidal basalts and “sedimentary greenstones” of the Unicoi Formation in the Blue Ridge Province of northeast Tennessee and southwest Virginia. These components could be isolated by alternating field as well as thermal demagnetization. One component, with a direction close to that of the present-day geomagnetic field is ascribed to recent viscous remanent magnetizations; another component, with intermediate blocking temperatures and coercivities, gives a mean direction of D = 132°, I = +43°,α₉₅ = 9° for N = 10 sites before correction for tilt of the strata. This direction and the corresponding pole position are close to Ordovician/Silurian data from the North American craton and we infer this magnetization to be due to a thermal(?) remagnetization during or after the Taconic orogeny. This magnetization is of post-folding origin, which indicates that the Blue Ridge in our area was structurally affected by the Taconic deformation. The third component, with the highest blocking temperatures and coercivities, appears to reside in hematite. Its mean direction, D = 276°, I = ?17°,α₉₅ = 13.8° for N = 6 sites (after tilt correction) corresponds to a pole close to Latest Precambrian and Cambrian poles for North America. The fold test is inconclusive for this magnetization at the 95% confidence level because of the near-coincidence of the strike and the declinations. We infer this direction to be due to early high-temperature oxidation of the basalts, and argue that its magnetization may have survived the later thermal events because of its intrinsic high blocking temperatures. A detailed examination of the paleomagnetic directions from this study reveals that the Blue Ridge in this area may have undergone a small counterclockwise rotation of about 15°.     

Devonian of the isle of Rügen

Summary In the Rügen area of northern Germany, Old Red Sandstones, ranging from Late Emsian to Givetian in age, unconformably overlie deformed Ordovician strata. The Middle Devonian Old Red passes conformably up into a Late Devonian carbonate facies and then into the Lower Carboniferous, apparently without a break.