Metamorphosed supracrustal rocks in the central Ross Sea sector of the Transantarctic Mountains are of Neoproterozoic age and not Cambrian. They include pillow basalts with a mantle separation age of 700–800 Ma. In the Skelton Glacier area, these rocks experienced two strong phases of deformation that produced folds and associated foliations. Both rocks and structures are cut by a 551 ± 4 Ma unfoliated quartz syenite (late Neoproterozic). The deformation and limited geochemical data suggest an active Antarctic plate margin whose late Neoproterozoic history is markedly different from that of the temporally equivalent rift to drift transition recorded along the autochthonous western margin of Laurentia. If these two cratons were ever contiguous, separation occurred by c. 700–800 Ma.

No abstract

No abstract

No abstract

U-Pb analyses of detrital zircons from various allochthonous assemblages of Paleozoic and early Mesozoic age in western Nevada and northern California yield new constraints on the sediment dispersal patterns and tectonic evolution of western North America. During early Paleozoic time, a large submarine fan system formed in slope, rise, basinal, and perhaps trench settings near the continental margin, west of continental shelf deposits of the Cordilleran miogeocline. Our detrital zircon data suggest that most of the detritus in this fan system along the western U.S