New major and trace element data and 40Ar/39Ar plateau ages constrain the timing, duration and time-related
geochemical evolution of the Central Atlantic magmatic province in the U.S.A. (Newark and Culpeper basins)
and refine correlations with basaltic lava flows from other Late Triassic–Early Jurassic circum-Atlantic basins.
The precise, statistically robust 40Ar/39Ar plateau ages were obtained on biotite and on fresh plagioclase and
calculated using the latest 40K decay constants. These ages are supported by a general consistency of the Ca/K
calculated from 37Ar/39Ar of the plateau steps and the Ca/K obtained by detailed electronmicroprobe analyses
on plagioclase phenocrysts. The ages of five analyzed basalt lava flows, from all three lava flow units in the
Newark basins, and the ages of two sill samples are indistinguishable, indicating a brief magmatic peak phase
at 201.8±0.7 Ma. Recalibrated 40Ar/39Ar plateau ages from the entire province indicate a near-synchronous
onset and peak volcanic activity at the Triassic–Jurassic boundary within the circum-Atlantic basins from the
U.S.A., Canada and Morocco. The early erupted magmas (Moroccan Lower to Upper basalts, the Fundy basin
North Mountain Basalt, and Orange Mountain and equivalent U.S.A. flows) yield an enriched geochemical
signature (e.g., with relatively high La/Yb), whereas late magmas in the U.S.A. (Hook Mountain and Hampden
basalts) and Morocco (Recurrent basalt) yield relatively depleted geochemical compositions (low La/Yb). A
slight, but significant age difference for eruption of Hook Mountain and Hampden basalts (200.3±0.9 Ma)
and Recurrent basalts (198.2±1.1 Ma) is interpreted as evidence of a diachronous northward rift–drift
transition during break-up of Pangea. Our data indicate also a prolonged intrusive sequence that continued
until about 195 Ma at the Palisades sill and is consistent with sporadic late CAMP magmatism for dykes from
the south-eastern U.S.A. and for intrusions from Guinea.
