Reconstruction of paleowind directions during the Cambrian-Ordovician in the Tarim Basin, Northwestern China.

The Tarim Basin was in the lower latitudes during the Cambrian-Ordovician, during which it experienced marine carbonate platform deposition. Although the platform is in the Trade Winds belt, the specific prevailing quantitative paleowind direction remains uncertain. This study integrated drill core and outcrop sedimentological data with outcrop magnetic fabric data to document sedimentary differentiation and anisotropy of magnetic susceptibility (AMS) within the Tarim Carbonate Platform (TCP). The aims of this study were to infer paleowind directions during each epoch of the Cambrian-Ordovician and to constrain the paleogeographic location of the TCP. The characteristics of the south, central, and northern sides of the platform were indicative of high-energy deposition (e.g., sub-angular to sub-rounded intraclasts with sparite cements), medium-energy deposition (e.g., angular to sub-rounded intraclasts with microspar and sparite cements), and low-energy deposition (e.g., angular to sub-angular intraclasts with microspar cements), respectively. AMS measurements yielded mean paleocurrent directions for the Early, Middle, and Late Cambrian of 226° ± 42°, 207° ± 43°, and 193° ± 36° from present north, respectively, whereas those for the Early, Middle, and Late Ordovician were 178° ± 39°, 165° ± 43°, and 155° ± 52° from present north, respectively. The results of sedimentary differentiation and AMS indicated that the prevailing wind directions of the Early Cambrian, Middle Cambrian, Late Cambrian, Early Ordovician, Middle Ordovician, and Late Ordovician were 226° ± 42°, 207° ± 43°, 193° ± 36°, 178° ± 39°, 165° ± 43°, and 155° ± 52° from present north, respectively. Since the TCP has rotated clockwise by ∼90° since the Ordovician, the paleowind directions of the Early, Middle, and Late Cambrian were 146° ± 42°, 117° ± 43°, and 103° ± 36° from paleo-north, respectively. The paleowind directions of the Early, Middle, and Late Ordovician were 88° ± 39°, 75° ± 43°, and 65° ± 52° from paleo-north, respectively. The TCP shifted from Southern Hemisphere to the Northern Hemisphere from the Early Cambrian to the Late Ordovician. The TCP was close to the Equator during the Early Ordovician. The novelty of this study related to: (1) integrating microfacies and AMS analyses to establish paleowind patterns; (2) constraining the paleo-hemispheric location of the TCP during the Cambrian-Ordovician; (3) providing references for the further study of paleoclimate and paleogeography of the TCP during the Cambrian-Ordovician. • Quantitative measurements of sediment properties across the platform were documented. • Quantitative measurements of anisotropy of magnetic susceptibility across the platform were documented. • Quantitative paleowind directions of the platform were reconstructed during the Cambrian-Ordovician. • Paleo-hemispheric location of Tarim Block was constrained during Cambrian-Ordovician. • An integrated methodology of standard petrographic and magnetic anisotropy data. [ABSTRACT FROM AUTHOR]