PALEOMAGNETISM OF UPPER TRIASSIC CONTINENTAL SEDIMENTARY-ROCKS FROM THE DAN-RIVER-DANVILLE RIFT BASIN (EASTERN NORTH-AMERICA)

A magnetic polarity stratigraphy and a corresponding paleomagnetic pol e position are reported from 113 sampling sites representing 3000 m of Upper Triassic continental sedimentary rocks that crop out in the Dan River-Danville basin of North Carolina and Virginia. Characteristic m agnetizations isolated by thermal demagnetization for either the hemat ite-bearing red siltstones or the interbedded magnetite-bearing gray t o black mudstones of the Leakesville Formation are indistinguishable i n mean direction and pass reversal tests. The magnetic polarity sequen ce consists of 11 magnetozones that vary from approximate to 100 m to 800 m in thickness and can be uniquely correlated within biostratigrap hic constraints to magnetochrons E9n to E14n of the Newark geomagnetic polarity time scale. According to this correlation, the sampled secti on is the age equivalent of the uppermost Stockton, the entire Lockato ng, and the lowermost Passaic formations of the Newark basin, and repr esents approximate to 7.5 m S' of deposition. The late Carnian Dan Riv er-Danville paleopole is located at 55.4 degrees N 100.1 degrees E (A( 95) = 1.9 degrees), which is not significantly different from paleopol es reported from essentially coeval rocks in the Newark basin. Conside ring that the Dan River-Danville and Newark basins are approximate to 600 km apart, the close agreement of the coeval paleopoles argues stro ngly for the overall tectonic coherence of these rift basins with resp ect to each other and, most probably, with respect to cratonic North A merica. Discordant latest Triassic paleopoles from the southwestern Un ited States, which have tended to be attributed to fast apparent polar wander for North America in the Late Triassic and predict anomalously high paleolatitudes for eastern North America, are best accounted for by a large net clockwise rotation of the Colorado Plateau.