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.

scholarly journals Carnivora from the Baynunah Formation

2021 ◽  
Author(s):  
Camille Grohe
Keyword(s):  
Late Miocene ◽  
Arabian Peninsula ◽  
Coastal Region ◽  
Abu Dhabi ◽  
Abu Dhabi Emirate ◽  
Postcranial Remains ◽  
New Material

I describe new specimens of carnivoran mammals from the continental late Miocene Baynunah Formation, exposed in the western coastal region of Abu Dhabi Emirate. New material collected between 2002 and 2014 includes dental specimens of the mustelid Plesiogulo sp. and a large-sized hyaenid, postcranial remains and an upper canine of a large- sized machairodontine felid, postcrania and a tooth of a medium-sized felid, and postcrania of a medium-sized mustelid. The latter two are new taxonomic records for the Baynunah Formation. With a minimum of six species, the carnivoran assemblage from the Baynunah Formation is the richest known from the Miocene of the Arabian Peninsula.

scholarly journals Rodents from the Baynunah Formation

2021 ◽  
Author(s):  
Brian Kraatz
Keyword(s):  
Late Miocene ◽  
New Genus ◽  
Arabian Peninsula ◽  
Abu Dhabi ◽  
Intermediate Species ◽  
New Genus And Species ◽  
Fossil Mammals ◽  
Significant Relationships ◽  
Abu Dhabi Emirate

The Baynunah Formation of western Abu Dhabi Emirate includes the only record of late Miocene fossil mammals from the Arabian Peninsula. This study reports on new fossil rodents, recording three species previously unknown from the fauna. The first fossil squirrel from the Baynunah Formation is described here, although the limited material makes a detailed taxonomic assessment difficult. An additional indeterminate dendromurine species is also identified. Additionally, a new genus and species of an exceedingly large fossil gerbil, [gen et sp nov], is described. This species exhibits several primitive traits relative to the co-occurring Abudhabia baynunensis, yet is more derived than closely related (yet older) Ameuromys grandis. [gen et sp nov] most likely represents an intermediate species in the Ameuromys grandis — Abudhabia baynunensis group. The rodent fauna also supports previous biochronological estimates for the Baynunah Formation (8 to 6 Ma). The absence of leporids among the Baynunah micromammals suggests the fauna is older than 7 Ma. Lastly, although the Baynunah fauna shows a strong African biogeographic signal overall, the rodents represent a portion of the fauna with significant relationships with Asia.

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.

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.

scholarly journals Birds from the Baynunah Formation

2021 ◽  
Author(s):  
Antoine Louchart ◽  
Faysal Bibi ◽  
John R. Stewart
Keyword(s):  
East Africa ◽  
United Arab Emirates ◽  
Late Miocene ◽  
Abu Dhabi ◽  
Fossil Species ◽  
Abu Dhabi Emirate

The late Miocene Baynunah Formation in western Abu Dhabi Emirate (United Arab Emirates) has yielded new bird fossils, including both skeletal and eggshell remains that we describe here, together with a revision and summary of previous findings. A ratite pelvis is characterized by its larger size compared with extant ostriches and is assigned to Struthio cf. karatheodoris. Fossil eggshells belong to the ootaxon Diamantornis laini as well as to an aepyornithoid type. Diamantornis laini is previously recorded from contemporaneous sites in Africa, and aepyornithoid eggshells are widespread across Neogene sites in Eurasia and Africa. Neognath birds are represented by three taxa, a cormorant Phalacrocorax sp. (size of P. fuscicollis), a darter Anhinga cf. hadarensis, and a heron of the tribe Nycticoracini. The darter attests to a link with Africa, being tentatively referred to a fossil species known from East Africa. The Baynunah birds provide valuable information on the biogeographic origins of different components of the avifauna in the late Miocene, near the junction between the Palaearctic, Indomalayan and Afrotropical zoogeographical regions.

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.

Constraints on late Miocene ice volume variability from a global benthic δ18O compilation (8.0-5.0 Ma)

2020 ◽  
Author(s):  
Anna Joy Drury ◽  
Thomas Westerhold ◽  
David Hodell ◽  
Sarah White ◽  
Ana Christina Ravelo ◽  
...  
Keyword(s):  
Late Miocene ◽  
Deep Sea ◽  
Climate System ◽  
Sea Temperature ◽  
Ice Volume ◽  
Global Ice Volume ◽  
Pleistocene Climate ◽  
Geomagnetic Polarity ◽  
Low Amplitude ◽  
Geomagnetic Polarity Time Scale

&lt;p&gt;Accurate stable isotope stratigraphies are essential for understanding how past climates are influenced by orbital forcing. Deep-sea benthic foraminiferal &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C stratigraphies can provide precise astronomical age control and record changes in past deep-sea ocean temperatures, global ice volume and the carbon cycle. Our understanding of Plio-Pleistocene climate dynamics has improved through the development of global (LR04; Lisiecki &amp; Raymo, 2005) and regional stacks (Ceara Rise; Wilkens et al., 2017). However, the late Miocene climate system remains poorly understood, in part because the late Miocene benthic foraminiferal &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O stratigraphy is notoriously low amplitude.&lt;/p&gt;&lt;p&gt;Here, we present the first global late Miocene global benthic foraminiferal &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O compilation spanning 8.00-5.33 Ma. We formed a &amp;#8220;Base Stack&amp;#8221; using six continuous benthic stratigraphies from the Atlantic (ODP Sites 982 (N), 926 (E) and 1264 (S)) and Pacific Oceans (IODP Sites U1337 and U1338 (E), ODP Site 1146 (W)). To avoid misidentification of individual excursions between sites, we verified existing splices, generated isotope data where necessary and established independent astrochronologies. To accompany the &amp;#8220;Base Stack&amp;#8221;, we compiled a &amp;#8220;Comprehensive Stack&amp;#8221;, which incorporates single-hole benthic &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O stratigraphies to optimise global coverage.&lt;/p&gt;&lt;p&gt;The new global late Miocene benthic foraminiferal &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O stack represents a stratigraphic reference section back to 8.00 Ma. The stack is accurately tied to the Geomagnetic Polarity Time Scale between Chrons C3r and C4n.2n using the magnetostratigraphy from IODP Site U1337. We recognise 68 new &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O Marine Isotope Stages (MIS) between 7.7 and 6.5 Ma. An exceptional global response is imprinted on the dispersed sites between 7.7-6.9 &amp; 6.4-5.4 Ma, when a strong 40 kyr heartbeat dominates the climate system. The origin of these cycles remains unclear. The influence of deep-sea temperature on the benthic &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O stack is explored at IODP Site U1337 using Mg/Ca data. The dominant 40-kyr &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O cycles are asymmetric, suggesting at least a partial ice volume imprint and raising the possibility that these cycles relate to early signs of northern hemisphere glaciation.&lt;/p&gt;

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.

Sign in / Sign up

Export Citation Format

Share Document