Abstract An evaluation of the potential geodynamic connections between the evolution of Paleozoic oceans in NW Gondwana and NE Gondwana is challenging. Until recently, most syntheses emphasized only two Paleozoic oceans (the Proto-Tethys and the Palaeo-Tethys) in the east Tethys realm. However, the discovery of early Paleozoic ophiolites along Palaeo-Tethys sutures located south of Proto-Tethys sutures challenges these traditional views. After a comprehensive review of relevant early Paleozoic tectonomagmatic events, we herein recognize and propose a model for the tectonic evolution of a hitherto unrecognized early Paleozoic ocean, which we call the Proto-Qiangtang Ocean. This ocean was short lived; it opened in the late Cambrian, began to subduct in the Middle Ordovician, and closed diachronously westwards between the Late Ordovician and the middle Silurian. Its closure by middle Silurian time indicates that was a spatially and temporally distinct ocean from the Palaeo-Tethys Ocean. The early tectonic evolution of the Proto-Qiangtang Ocean shares many characteristics with that of the Rheic Ocean. Both opened in the late Cambrian in the back-arc region of the Iapetus–Proto-Tethys Ocean, and the Proto-Qiangtang Ocean is considered to represent the eastern extension of the Rheic Ocean. This correlation has important implications for the Paleozoic tectonic evolution and palaeogeography of northern Gondwana.

At the Shell Creek stratigraphic section, Wilcox County, Alabama, a 35–75-cm-thick, Cretaceous-Tertiary (K-T) boundary sand body crops out over an area of ∼200 m 2 . This sand body consists of (1) a basal impact spherule-bearing, coarse to medium sand and (2) an overlying fine sand with hummocky-type cross-lamination. This K-T boundary sand body probably represents postimpact, shelf sedimentation events involving (1) gravity-driven resedimentation of reworked impact spherule-bearing sands and (2) energetic wave reworking of the impact spherule-bearing, gravity-driven deposits or other subsequently deposited sands. Most impact spherules from Shell Creek are spherically shaped grains (∼1 mm in diameter) that are now hollow, or were hollow prior to secondary calcite filling. Most impact spherules from Shell Creek consist of an outer shell, which is composed of smectitic clays, and an inner region of open space or sparry calcite. Most of these impact spherules still retain vesicles that attest to their former molten condition. This stratigraphic section represents the most easterly U.S. Gulf Coastal Plain occurrence of abundant impact spherules in a Cretaceous-Tertiary boundary sand body.