The quest for chron E23r at Partridge Island, Bay of Fundy, Canada: CAMP emplacement postdates the end-Triassic extinction event at the North American craton

2011 ◽  
Vol 48 (8) ◽  
pp. 1282-1291 ◽  
Author(s):  
M.H.L. Deenen ◽  
W. Krijgsman ◽  
M. Ruhl
Keyword(s):  
Magnetic Polarity ◽  
Bay Of Fundy ◽  
Long Distance ◽  
The North ◽  
Extinction Event ◽  
Maritime Canada ◽  
North American Craton ◽  
Geomagnetic Polarity ◽  
Central Atlantic ◽  
Geomagnetic Polarity Time Scale

The Partridge Island stratigraphic section at the Bay of Fundy, Maritime Canada, reveals a continental sedimentary succession with the end-Triassic mass extinction level closely followed by basalts of the Central Atlantic Magmatic Province (CAMP). New Paleomagnetic data show that a short reverse magnetic polarity chron, correlative to E23r of the Newark Geomagnetic Polarity Time Scale (GPTS), is present below the extinction event. Organic carbon isotope data and basalt geochemistry further indicate that the onset of CAMP emplacement in the Bay of Fundy was roughly synchronous with emplacement in the Newark basin, but slightly postdates the oldest CAMP volcanism in Morocco by ∼20 ka. These results confirm the potential for long-distance CAMP correlations based on geochemical trace elements, indicate substantiate provincialism of latest Triassic palynoflora, and suggest a very concise period (<<100 ka) of CAMP emplacement in the northern Atlantic region.

New 42 Ma cratonic North American paleomagnetic pole from the Yukon underscores another Cordilleran paleomagnetism-geology conundrum

2003 ◽  
Vol 40 (10) ◽  
pp. 1321-1334 ◽  
Author(s):  
David TA Symons ◽  
Philippe Erdmer ◽  
Phil JA McCausland
Keyword(s):  
North American ◽  
Magnetic Polarity ◽  
Eastern Coast ◽  
The North ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
North American Craton ◽  
Host Rocks ◽  
Pacific Plate Subduction ◽  
Plate Subduction

Eocene posttectonic plutons of the Beaver River alkalic complex in southeastern Yukon intruded Devonian–Mississippian and Triassic sandstones in the Foothills of the Canadian Cordillera. A paleomagnetic collection of 27 sites from three separate plutons produced 326 specimens that were analyzed using alternating field and thermal step demagnetization methods. The A component characteristic remanent magnetization (ChRM) resides in magnetite with normal polarity in the 42.6 ± 0.8 Ma Beaver River pluton, reversed polarity in the 42.1 ± 0.7 Ma Larson Creek East pluton, and both polarities in the 41.3 ± 0.4 Ma Larson Creek West pluton, corresponding with magnetic polarity chrons 20n, 19r, and the boundary between chron 19r and 18n, respectively. The ChRMs of the plutons are indistinguishable (2σ) with a mean for the 42.0 ± 0.5 Ma complex of D = 158.8°, I = –73.1° (N = 21 sites, α95 = 3.0°, k = 116.8). A positive paleomagnetic contact test shows the A component to be primary, and the poorly isolated B component suggests the host rocks for Larson Creek West are Early to Middle Devonian. The paleopole for the Beaver River complex at 79.2°N, 145.8°E (N = 21, dp = 4.8°, dm = 5.4°; Q = 7) is concordant with interpolated 42 Ma reference poles for the North American craton. In contrast, paleopoles from the accreted Intermontane and eastern Coast Belt terranes record clockwise rotations of 24° ± 10° (Eocene) and 13° ± 5° (Oligocene–Pliocene), indicating that the allochthonous Intermontane terranes have been progressively driven ~240 ± 120 km eastwards up and over pericratonic and cratonic North American lower crust by Pacific plate subduction since the mid-Eocene.

scholarly journals Magnetostratigraphy and magnetic properties of the Jurassic to Lower Cretaceous Girón Group (northern Andes, Colombia)

Geosphere ◽  
2021 ◽  
Author(s):  
Giovanny Jiménez ◽  
Helbert García-Delgado ◽  
John W. Geissman
Keyword(s):  
Magnetic Properties ◽  
Lower Cretaceous ◽  
Regional Scale ◽  
Magnetic Polarity ◽  
Class B ◽  
Positive Class ◽  
Normal Polarity ◽  
Geomagnetic Polarity ◽  
Del Rio ◽  
Geomagnetic Polarity Time Scale

We report paleomagnetic results from the Jurassic to Lower Cretaceous continental sedimentary succession exposed in the eastern limb of the Los Yariguíes anticlinorium, Eastern Cordillera, Colombia. About 820 m of a strati­graphic section of the upper part of the Girón Group (Angostura del Río Lebrija and Los Santos Formations) was sampled to construct a magnetic polarity stratigraphy. A total of 199 independent samples that yield interpretable and acceptable data have a characteristic remanent magnetization component (ChRM) isolated between 400 °C and 680 °C in progressive thermal demagneti­zation. Demagnetization behavior and rock magnetic properties are interpreted to indicate that hematite is the principal magnetization carrier with a possible contribution by magnetite in some parts of the section. After tilt correction, 123 samples are of normal polarity (declination [D] = 44.9°, inclination [I] = +9.7°, R = 110.64, k = 9.87, and α95 = 4.3°), and the other 76 accepted samples are of reverse polarity (D = 216.4°, I = −6.1°, R = 68.29, k = 9.72, and α95 = 5.5°). The sta­tistical reversal test conducted on virtual geomagnetic poles is positive (class B). Based on paleontologic age estimates for the Cumbre and Rosablanca Formations, we assume a Berriasian age for the Los Santos Formation. The magnetostratigraphic data from the Girón Group strata are interpreted to suggest an age for the sampled part of the section between early Kimmerid­gian and early Valanginian (ca. 157–139 Ma). The age of the Angostura del Río Lebrija Formation is estimated as between early Kimmeridgian and early Tithonian (ca. 157–146.5 Ma). The age of the Los Santos Formation is esti­mated between early Tithonian and early Valanginian (146.5–139.3 Ma). With our proposed, but nonunique, correlation with the Geomagnetic Polarity Time Scale, the Jurassic-Cretaceous boundary is interpreted to be located within the Los Santos Formation. The Girón Group is characterized by two periods of high (&gt;8 cm/k.y.) and two periods of low (&lt; 2 cm/k.y.) sedimentation rates. An inferred clockwise rotation of ~44°, based on paleomagnetic declination data from the Girón Group, is similar to rotation estimates reported in some previous studies in the general area, and this facet of deformation could be related to local and regional response to displacement along regional-scale strike-slip faults.

Accuracy and precision of the late Eocene–early Oligocene geomagnetic polarity time scale

2019 ◽  
Vol 132 (1-2) ◽  
pp. 373-388 ◽  
Author(s):  
Diana Sahy ◽  
Joe Hiess ◽  
Anne U. Fischer ◽  
Daniel J. Condon ◽  
Dennis O. Terry ◽  
...  
Keyword(s):  
Time Scale ◽  
Late Eocene ◽  
Magnetic Polarity ◽  
White River ◽  
Early Oligocene ◽  
White River Group ◽  
Astronomical Tuning ◽  
Normal Polarity ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale

AbstractAn accurate and precise geomagnetic polarity time scale is crucial to the development of a chronologic framework in which to test paleoclimatic and paleoenvironmental interpretations of marine and terrestrial records of the Eocene–Oligocene transition (EOT). The magnetic polarity patterns of relatively continuous marine and terrestrial records of the EOT have been dated using both radio-isotopic techniques and astronomical tuning, both of which can achieve a precision approaching ±30 k.y. for much of the Paleogene. However, the age of magnetic reversals between chrons C12n and C16n.2n has proved difficult to calibrate, with discrepancies of up to 250 k.y. between radio-isotopically dated and astronomically tuned marine successions, rising to 600 k.y. for comparisons with the 206Pb/238U-dated terrestrial record of the White River Group in North America. In this study, we reevaluate the magnetic polarity pattern of the Flagstaff Rim and Toadstool Geologic Park records of the White River Group (C12n–C16n.2n). Our interpretation of the Flagstaff Rim polarity record differs significantly from earlier studies, identifying a previously unreported normal polarity zone correlated to C15n, which eliminates discrepancies between the WRG and the 206Pb/238U-dated marine record of the Rupelian Global Stratotype Section and Point in the Italian Umbria-Marche basin. However, residual discrepancies persist between U-Pb–dated and astronomically tuned records of the EOT even when stratigraphic and systematic uncertainties associated with each locality and dating method are taken into account, which suggests that the uncertainties associated with astronomically tuned records of the EOT may have been underestimated.

scholarly journals Reversal in the nonlocal large-scale αΩ-dynamo

2014 ◽  
Vol 1 (2) ◽  
pp. 1715-1734
Author(s):  
L. K. Feschenko ◽  
G. M. Vodinchar
Keyword(s):  
Time Scale ◽  
Geomagnetic Field ◽  
Large Scale ◽  
Magnetic Polarity ◽  
Scale Model ◽  
Power Law Model ◽  
Large Scale Model ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale ◽  
The Magnetic Field

Abstract. Inversion of the magnetic field in a large-scale model of αΩ-dynamo with nonlocal α-effect is under the investigation. The model allows us to reproduce the main features of the geomagnetic field reversals. It was established that the polarity intervals in the model are distributed according to the power law. Model magnetic polarity time scale is fractal. Its dimension is consistent with the dimension of the real geomagnetic polarity time scale.

scholarly journals Magnetostratigraphy of the Baynunah Formation

2020 ◽  
Author(s):  
Daniel J. Peppe ◽  
David A.D. Evans ◽  
Mark Beech ◽  
Andrew Hill ◽  
Faysal Bibi
Keyword(s):  
Late Miocene ◽  
Arabian Peninsula ◽  
Magnetic Polarity ◽  
Abu Dhabi ◽  
Fluvial System ◽  
First Order ◽  
Abu Dhabi Emirate ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale ◽  
Late Tortonian

The Baynunah Formation in the Al Gharbia region of Abu Dhabi Emirate was deposited by a major fluvial system and preserves the only known late Miocene terrestrial fossils in the Arabian Peninsula. We analyzed paleomagnetic samples from six sections (Jebel Barakah, Shuwaihat 2, Hamra 5, Mleisa 1, Mleisa 2, and Kihal 2) to develop a polarity stratigraphy for the Baynunah Formation. Based on these analyses, we documented a magnetic polarity stratigraphy, which, in combination with lithostratigraphy, allows us to propose a correlation of these six sections and their fossil localities. We show that first-order facies variations in the Baynunah Formation are diachronous. Confident correlations with the Geomagnetic Polarity Time Scale during the late Miocene cannot be determined; however, correlations based on the local polarity stratigraphy and biostratigraphy suggests that the Baynunah Formation was deposited over a duration of less than 750 kyr between ~7.7 and ~7.0 Ma during the late Tortonian and early Messinian. These results suggest that the fossil sites occurring throughout the lower part of the Baynunah unit and the fossil trackway sites found in the upper part of the formation are likely no more than a few hundred thousand years apart and could have been generated by the same taxa.

Systematics and paleobiogeography of Late TriassicGryphaea(Bivalvia) from the North American Cordillera

1992 ◽  
Vol 66 (1) ◽  
pp. 28-39 ◽  
Author(s):  
Christopher A. Mcroberts
Keyword(s):  
North American ◽  
Late Triassic ◽  
South American ◽  
Long Distance ◽  
Low Latitude ◽  
North American Cordillera ◽  
The North ◽  
North American Craton ◽  
Far Eastern ◽  
North And South

Evaluation of previously undescribed collections of Late TriassicGryphaeafrom the North American Cordillera increases the temporal range and geographic distribution of the genus.Gryphaea(Gryphaea)arcuataeformisKiparisova,G.cf.G.(Gryphaea)keilhauiBöhm, and a new species,G.(Gryphaea)nevadensis, occur in lower Carnian to upper Norian strata from Alaska, British Columbia, Oregon, and Nevada. The distribution is mostly primary with respect to the Upper Triassic North American Craton, and requires long-distance larval dispersal along the latitude of far-eastern Panthalassa. Unlike most modern oysters, the distribution of these Triassic gryphaeids may have been restricted to cool and deeper water environments.An early Carnian age ofGryphaea(Gryphaea)arcuataeformisplaces this species as the oldest knownGryphaea. When combined with late Carnian and Norian occurrences from the North and South American Cordillera, these data indicate that a low-latitude origin for the genus cannot be overlooked. Gryphaeids survived the end-Triassic extinction event presumably by living in refugia.

Refinements of the European Mammal Biochronology from the Magnetic Polarity Record of the Plio–Pleistocene Zújar Section, Guadix-Baza Basin, SE Spain

1999 ◽  
Vol 51 (1) ◽  
pp. 94-103 ◽  
Author(s):  
Oriol Oms ◽  
Jaume Dinarès-Turell ◽  
Jordi Agustı́ ◽  
Josep M. Parés
Keyword(s):  
Time Scale ◽  
Magnetic Polarity ◽  
Time Constraints ◽  
Se Spain ◽  
Lowermost Part ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale ◽  
Early Late ◽  
New Time

AbstractThe magnetobiostratigraphy study of the 130-m-thick Zújar section (Negratı́n clays unit, Guadix-Baza Basin, Spain) provides a remarkable opportunity to improve the correlation of European mammal biostratigraphy to the Geomagnetic Polarity Time Scale. The occurrence of 12 well-defined magnetozones and four paleontological sites with diagnostic faunas ranging from the MN 15 biozone (Ruscinian) to the MN 17 biozone (Villanyian), leads to an unambiguous correlation to chrons spanning from the Gilbert to the Matuyama epochs. This provides two new time constraints: (1) the boundary between MN 15 (Ruscinian) and MN 16 (Villanyian) biozones is recorded between chron C2An.3n and the base of chron C2An.2n and (2) the boundary between the upper and lower MN 16 subzones (Villanyian) is located between chron C2An.2n and the base of chron C2An.1n. The correlation between the Ruscinian–Villanyian boundary and the 3.3-myr-B.P. cooling event seems to be confirmed, while the early/late Villanyian boundary could be tentatively correlated to the glacial event at 2.6 myr B.P. Furthermore, MN 15 faunas are found in the lowermost part of chron C2Ar, which is in agreement with and reinforces the emplacement of the MN 14–MN 15 Ruscinian zones boundary at the reversal from chron 3n.1n to chron C2Ar.

Maritime and River Traders, Landing Places, and Emporia Ports in the Merovingian Period in and Around the Low Countries

2020 ◽  
pp. 763-796
Author(s):  
Dries Tys
Keyword(s):  
North Sea ◽  
Institutional Economics ◽  
New Institutional Economics ◽  
Central Position ◽  
Economic Activities ◽  
Early Medieval ◽  
Low Countries ◽  
Long Distance ◽  
The North ◽  
The North Sea

The origin, rise, and dynamics of coastal trade and landing places in the North Sea area between the sixth and eighth centuries must be understood in relation to how coastal regions and seascapes acted as arenas of contact, dialogue, and transition. Although the free coastal societies of the early medieval period were involved in regional to interregional or long-distance trade networks, their economic agency must be understood from a bottom-up perspective. That is, their reproduction strategies must be studied in their own right, independent from any teleological construction about the development of trade, markets, or towns for that matter. This means that the early medieval coastal networks of exchange were much more complex and diverse than advocated by the simple emporium network model, which connected the major archaeological sites along the North Sea coast. Instead, coastal and riverine dwellers often possessed some form of free status and large degrees of autonomy, in part due to the specific environmental conditions of the landscapes in which they dwelled. The wide estuarine region of the Low Countries, between coastal Flanders in the south and Friesland in the north, a region with vast hinterlands and a central position in northwestern Europe, makes these developments particularly clear. This chapter thus pushes back against longstanding assumptions in scholarly research, which include overemphasis of the influence of large landowners over peasant economies, and on the prioritization of easily retrievable luxuries over less visible indicators of bulk trade (such as wood, wool, and more), gift exchange, and market trade. The approach used here demonstrates that well-known emporia or larger ports of trade were embedded in the economic activities and networks of their respective hinterlands. Early medieval coastal societies and their dynamics are thus better understood from the perspective of integrated governance and economy (“new institutional economics”) in a regional setting.

Paleomagnetism of the Clam Bank Formation and paleolatitude estimates for western Newfoundland

1993 ◽  
Vol 30 (4) ◽  
pp. 776-786
Author(s):  
G. Murthy ◽  
R. Pätzold
Keyword(s):  
North American ◽  
Early Paleozoic ◽  
The North ◽  
Northerly Direction ◽  
Deformation Event ◽  
Recent Origin ◽  
Component C ◽  
Acadian Orogeny ◽  
North American Craton ◽  
Devonian Age

The Pridolian Clam Bank Formation around Lourdes Cove on the Port au Port Peninsula, western Newfoundland, underwent deformation during the Acadian orogeny. As a result, some of the beds were overturned, but the stratification planes can be accurately determined everywhere. Paleomagnetic studies of the Clam Bank Formation have yielded three well-defined components of magnetization, all acquired subsequent to the deformation event: component A with D = 337.3°, I = −28.3°, (N = 16 sites, k = 25.3, α95 = 7.5°), with a corresponding paleopole at 23.2°N, 145.0°E (dp, dm = 4.5°, 8.2°); component B with D = 172.9°, I = 5.7° (N = 35 specimens, k = 10.2, α95 = 6.4°), with a corresponding paleopole at 38.2°N, 130.1°E (dp, dm = 3.2°, 6.4°); component C with D = 350.4°, I = 69.8° (N = 33 specimens, k = 8.9, α95 = 8.9°). A pre-Mesozoic origin of the A and B components is indicated by the presence of normal and reversed components in specific sites; by the lack of correspondence between the A and B paleopoles and the Mesozoic and later pole positions from the Appalachians and the North American craton; and by agreement with Paleozoic poles from the region. The A component was probably acquired immediately after deformation during the Acadian orogeny. The B component is probably a chemical remanence that was acquired during Permo-Carboniferous (Kiaman) time. The C component is of recent origin, probably acquired in the present Earth's field. Paleomagnetic data from western Newfoundland are used in a localized setting to construct a paleopole sequence and to estimate paleolatitudes for western Newfoundland during the Paleozoic. Keeping in mind the paucity of data for Siluro-Devonian age from this region, western Newfoundland seems to have been at its southernmost position at the end of the Ordovician and to have occupied equatorial latitudes during the Permo-Carboniferous. The paleolatitude trend suggests that this block, which is part of the North American craton, moved in a southerly direction during the early Paleozoic and in a northerly direction during the middle and late Paleozoic.

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