STRATIGRAPHIC RECORD OF THE EARLY MESOZOIC BREAKUP OF PANGEA IN THE LAURASIA-GONDWANA RIFT SYSTEM

Abstract

▪ Abstract  Rift basins of the Central Atlantic Margins (CAM) of North America and Morocco preserve largely continental sequences of sedimentary strata and less important minor basalt flows spanning much of the early Mesozoic. The best known is the Newark basin of New Jersey, New York, and Pennsylvania where an astronomically calibrated magnetic polarity time scale is developed. Lacustrine cycles of Milankovitch origin are commonly present in CAM basins, with the period changing from 10 ky (paleoequator with coals), to 20 ky (4°–10°N), to perhaps 40 ky northward with evaporites. Cycles of ∼100 ky, 413 ky, and ∼2 my are also important. Four mostly unconformity-bounded tectonostratigraphic sequences are present. The Anisian TS I is fluvial and eolian. TS II–TS IV (Late Triassic to Early Jurassic) consist of “tripartite” lacustrine sequences caused by extension pulses. The Newark basin accumulation rate history allows comparison with quantitative rift basin models. The North American plate's slow northward drift resulted in a relative shift of climate, although the rapid humidification during the latest Triassic and Early Jurassic is associated with a sea-level rise. The Triassic-Jurassic mass extinction is of independent origin, plausibly impact related.