Ar ar dating of basalts

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For this reason, numerous palaeomagnetic studies have been undertaken all-over Asia in the last 25 yr.They all show that (pre-collision) Cretaceous palaeomagnetic poles from Central Asian blocks (e.g.situation map of studied area in Asia, with main blocks and limits indicated (AMU: Amuria, AFG: Afghanistan, EUR: Eurasia main plate, INC: Indochina, IND: India JUN: Junggar, KAZ: Khazakhstan, KF: Kunlun Fault, KUN: Kunlun, LH: Lhasa, MBT: Main Boundary Thrust, NCB: North China Block, QA: Qaidam, QI: Qiangtang, SCB: South China Block, SIB: Siberia, ST: Shantaï, TAR: Tarim).This analysis, however, has been, until recently, based on the Cretaceous part of a reference APWP that does not rely on palaeomagnetic data from the easternmost parts of the Eurasian continent.Rock magnetic analysis identifies fine-grained pseudo-single domain (PSD) magnetite and titanomagnetite as primary carriers of the remanence.Mean HTC palaeomagnetic direction is Dm = 8.2°, Im = 63.7° ( = 3.9°) for Arts-Bogd.Molnar & Tapponnier 1975; Tapponnier & Molnar 1979; Patriat & Achache 1984), it causes the Eurasian continent to deform.

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The HTC directions display normal polarity, consistent with the Cretaceous Long Normal Superchron.Following Zonenshain (1990), the Amuria microcontinent consists of a number of lithospheric blocks (Hangai, Hentei, Central Mongolia, Argun and Khingan-Bureya), which accreted together in the early Palaeozoic. We collected 164 cores at 20 sites (19 flows) from the Shovon locality (44.3°N, 103.8°E), and 282 cores at 34 sites (32 flows or necks) from the foothills of the Arts-Bogd range (e.g.Numerous palaeomagnetic studies showed that (1) NCB accreted to Amuria by the Late Carboniferous, (2) South China Block (SCB) then sutured with NCB around the Middle to Late Jurassic and (3) the final suturing between Amuria and Siberia was achieved by the Late Jurassic—Early Cretaceous with the closure of the Mongol-Okhotsk ocean (e.g. The Amuria block is a key region for understanding the transition between the Tarim and Jungar basins to the west, which exhibit significant post-Cretaceous convergence, and the Siberia craton (e.g. However, apart from the study of Pruner (1992), no Cretaceous data were yet available from within the interior of Amuria block, between the northern edge of Amuria block (Fig. With the aim of enlarging this dataset, we undertook a series of palaeomagnetic and geochronology sampling in Cretaceous basaltic formations from the Gobi desert in Mongolia (Fig. We focussed our sampling on effusive formations in order to (1) have good opportunities to date the sampled rocks and (2) avoid possible inclination shallowing processes which may occur in sediments. Whitford-Stark 1987) (44.4°N, 102.2°E; Arts-Bogd locality hereafter).We report a combined geochronology and palaeomagnetic study of Cretaceous igneous rocks from Shovon (44.4°N, 103.8°E) and Arts-Bogd (44.3°N, 102.2°E) localities in the Gobi Desert, south Mongolia.

K—Ar dating based on seven rock samples, with two independent measurements for each sample, allows us to propose an age of 94.7 ± 1.3 Ma for Shovon locality and a 98.2 ± 1.4 to 118.3 ± 1.7 Ma age range for Arts-Bogd.We finally propose a mid-Cretaceous mean palaeomagnetic pole for the Siberia-Amuria-North China Block assemblage which lies at: λ = 86.4°N, φ = 191.1°E( Central Asia is a fascinating place for testing palaeomagnetic tools that provide for tectonic constraints.

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74 Comments

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  2. eric   •  

    Pay attention to your date’s character while accentuating your positive traits.

  3. eric   •  

    However, I think we all know what Kurtz meant and the common sense that informs her view.

  4. eric   •  

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