The “Passive” Margin of Eastern North America: Rifting and the Influence of Prerift Orogenic Activity on Postrift Development

Abstract

We have analyzed and synthesized geologic and geophysical data from the onshore Newark rift basin and adjacent onshore and offshore basins to better understand the Mesozoic development of the eastern North American rift system and passive margin. Our work indicates that rifting had three phases: (1) an initial, prolonged phase of extension and subsidence; (2) a short-lived phase with higher rates of extension and subsidence, intrabasin faulting, and intense magmatism; and (3) a final phase with limited subsidence and deposition. Additionally, our work shows that anomalous uplift and erosion, associated with crustal-scale arching/warping subparallel to the prerift and syn-rift crustal fabric not the continent-ocean boundary, affected a region landward of the basement hinge zone. Uplift and erosion began during the final rifting phase and continued into early drifting with erosion locally exceeding 6 km. Subsequent subsidence was minimal. We propose that denudation unloading related to relic, prerift orogenic crustal thickness and elevated topography triggered the anomalous uplift and erosion. After the Paleozoic orogenies, postorogenic denudation unloading (cyclic erosion and isostatic rebound/uplift) significantly thinned the thickened crust and reduced topographic elevation. During rifting, extension stretched and tectonically thinned the crust, promoting widespread subsidence and deposition that dampened the postorogenic cycle of erosion and isostatic rebound/uplift. During the rift-drift transition, with extension focused near the breakup site, denudation unloading resumed landward of the basement hinge zone, producing significant erosion and uplift (related to isostatic rebound), crustal thinning, and topographic decay that left behind only eroded remnants of the once massive rift basins.

High‐Resolution Ps Receiver Function Imaging of the Crust and Mantle Lithosphere Beneath Southern New England and Tectonic Implications

“…The crust beneath rift basins is likely to be thinned more than surrounding regions due to concentrated extension (Bell et al., 1988). It is also possible that overall thinning and extension of Appalachian crust during the breakup of Pangea (e.g., Withjack et al., 2020) smoothed out any preexisting crustal thickness differences between various accreted terranes. This may explain why we do not see dramatic contrasts in Moho depths associated with terrane boundaries east of the Laurentian Moho step (for example, between the Avalon terrane at the eastern end of the SEISConn array and the Putnam‐Nashoba terrane to its west).…”

A Jurassic volcanic passive margin in Iran and Turkey

“…The different types of sediments with similar ages and the absence of Jurassic sediments in some areas suggest that Jurassic basins opened in central, north and southern Iran as well as in northern Turkey. Such distributed extension is common in the early stages of continental breakup, for example, in the Triassic of the eastern USA (Withjack et al, 2020). From this perspective, Jurassic basins may have accompanied the opening of Neotethys.…”

Phanerozoic cooling events in the continental rims of the Central Atlantic Ocean.

“…The uppermost rift-related deposits, together with the CAMP magmatic rocks, are overlain by an important unconformity that is recorded on both sides of the CAO, often put in relation with the CAO opening in regional studies (e.g., Frizon de Tari and Jabour, 2013;Withjack et al, 2020). While this surface has been recognised and studied, the precise timing of the onset for the CAO opening remains, to date, an open question.…”

“…During the Middle Jurassic-Early Cretaceous post-rift period, the onshore NW Africa and NE America are now known to have experienced post-rift uplifts (e.g., in NW Africa: Ghorbal et al, 2008;Saddiqi et al, 2009;Ruiz et al, 2011;Oukassou et al, 2013;Leprêtre et al, 2015Leprêtre et al, , 2017Sehrt et al, 2017Sehrt et al, , 2018Charton et al, 2018;Gouiza et al, 2017aGouiza et al, , b, 2019e.g., in NE America: Wang et al, 1994;Roden-Tice et al, 2000;Spotila et al, 2004;Reed et al, 2005;McKeon et al, 2013;Shorten and Fitzgerald, 2019;Withjack et al, 2020). Post-rift cooling -generally attributed to erosional exhumation and/or uplift -occurred from the Mid-Late Jurassic to the Neocomian (Cretaceous), with varying rates, more or less at the time of sedimentation changes from a carbonate-dominated to siliciclastic-dominated type in the northern CAO.…”