Crustal origin of the West Florida Terrane, and detrital zircon provenance and development of accommodation during initial rifting of the southeastern Gulf of Mexico and western Bahamas

Abstract

Well and seismic data were combined with existing radiometric data and 1328 new laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb zircon ages from igneous, sedimentary and volcaniclastic rocks in three wells to determine the origin and evolution of key crustal terranes, and the timing of initial rifting and synrift deposition in the southeastern Gulf of Mexico and western Bahamas. These data reveal that several southeastern Gulf of Mexico crustal terranes, distinguished by their zircon age distributions and geochemistries, were amalgamated into a single terrane of mixed Pan-African and Amazonian crustal affinity (the newly named West Florida Terrane) during the formation of Pangaea. Sinistral offset along the Florida Transfer Zone (FTZ) during the Late Triassic–Middle Jurassic was likely to have been facilitated by crustal heterogeneity at the boundary between the West Florida and Suwannee terranes, a prime area for reactivation during the break-up of Pangaea. Initial extension, igneous activity and synrift deposition in the region began during the Middle Triassic in the western Bahamas and offshore North Florida, and rapidly expanded into the South Florida Basin by the Early Jurassic. Peak igneous activity and accommodation in the region was diachronous from north to south, beginning in the north during the Early Jurassic (Sinemurian–Pliensbachian) before ending in the south in the Early–Middle Jurassic (Sinemurian–Aalenian/early Bajocian). Detrital zircons in sedimentary and volcaniclastic rocks were primarily derived from local erosion of pre-existing crustal terranes. Long-distance transport was likely for pre-Neoproterozoic and post-Cambrian Paleozoic zircons. Middle Jurassic detrital zircons in volcaniclastic rocks of the western Bahamas may have been deposited during ash-fall events from hotspot activity in the southeastern Bahamas.

The Matzitzi Formation in southern Mexico: A record of Pangea final assembly or breakup initiation along inherited suture belts?

“…15 m.y. older than the Middle Triassic age documented by previous work (e.g., Erlich & Pindell, 2021). Interestingly, Permian extension is distributed along orogenic belts and major transform faults (e.g.…”

“…Basaltic to rhyolitic volcanic rocks interbedded with fluvial red beds are ubiquitous in the subsurface of the South Georgia–Florida area of the southeastern USA (Erlich & Pindell, 2021; Heatherington & Mueller, 1999). At present, the oldest known volcanic rocks in this area are of early Middle Triassic age (Erlich & Pindell, 2021). However, these rocks are only known through sparse drilling that does not yet provide an exhaustive chronostratigraphic framework of the entire volcano‐sedimentary record.…”

The petrogenesis of Early–Middle Jurassic magmatism in southern and central Mexico and its role during the break-up of Western Pangaea

“…Based on a multi-stage, global plate-reconstruction model of western equatorial Pangaea, Pindell et al (2020) estimated continental extension in the order of 600 km and 400 km in the western and eastern proto-GM, respectively. Crustal thinning during this time interval favoured the emplacement of syn-rift basaltic, rhyolitic and minor andesitic lava flows, dykes and sills in the South Georgia rift basin (Heatherington & Mueller, 1999;Heffner et al 2012), the Southwest Florida Mesozoic volcanic province (Heatherington & Mueller, 1991, 2003 and the Apalachicola and South Florida basins (Erlich & Pindell, 2021;Fig. 4).…”

“…The progressive break-up of Pangaea between ~195 and ~168 Ma was accommodated by normal to lateral faults with different orientations, mostly following previous zones of weakness between terranes (e.g. Erlich & Pindell, 2021;Fig. 4).…”

“…2a). During this early stage of Pangaea break-up, rift basins were infilled by voluminous, Middle-Upper Triassic fluvial to shallow-marine successions that are locally interbedded with and cut by syn-rift volcanic and intrusive rocks (Klitgord et al 1988;Le Roy & Piqué, 2001;Schlische, 2003;Martin-Rojas et al 2009;Frederick et al 2020;Erlich & Pindell, 2021;Fig. 2b).…”