--> --> The Effect of Volcanism on Proximal and Distal Marine Environments during the Triassic-Jurassic Transition (TJT; latest Rhaetian-Sinemurian), Northern Israel, Levant Basin

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The Effect of Volcanism on Proximal and Distal Marine Environments during the Triassic-Jurassic Transition (TJT; latest Rhaetian-Sinemurian), Northern Israel, Levant Basin

Abstract

This study explores the relationship between types of major volcanism, trends of warming/cooling, sedimentation patterns, and ecological crises across the Triassic-Jurassic transition (TJT). This interval was studied in three adjacent boreholes, two with volcanics (Asher Atlit 1, Elijah 3) and one volcanic-free (Ga'ash 2). Locally, these boreholes are located on the transition zone to the open Tethyan sea northwest of the Judea Graben structure. Their TJT successions characterize this transition in the Levant region, corresponding also to major East Mediterranean volcanism and to part of the Central Atlantic Magmatic Province (CAMP). Dating is derived from foraminifera-based stratigraphy, Sr stratigraphy and published radiometric data, and the TJ boundary interval and four out of five reported events of global δ13Ccarb negative excursions (CIE) were identified. A Norian warming trend linked to submarine volcanism type is well demonstrated at Asher Atlit 1. It continued into the early Rhaetian, identified at Ga’ash 2 and Elijah 3 as well. This warming trend correlates to increase of terrestrially derived siliciclastic influx in the proximal algal mat – ooidal carbonate setting at Ga’ash 2, but in the distal marine volcanic site (Asher Atlit 1) reefs free of siliciclastics prevailed. The change in volcanism type in the latest Rhaetian to subaerial volcanic eruptions corresponded to low-latitude cooling in the Levant and in many other localities in the East Mediterranean region. This cooling trend became enhanced toward the TJB when massive eruptive volcanism of the Central Atlantic Magmatic Province (CAMP) became dominant. In the latest Rhaetian – Hettangian, the cooling is associated with a dramatically reduced in rate of carbonate sedimentation and absence of reef-building organisms over a 4-5 My time interval. The TJT cooling was followed by gradual recovery of the carbonate depositional system, localized increase in sedimentation rate in dolomitic shallow marine environments, and the global recovery from the TJT global biotic crisis, demonstrated by two CIE events of the Sinemurian.