The early Toarcian (early Jurassic) ostracod extinction events in the Iberian Range: The effect of temperature changes and prolonged exposure to low dissolved oxygen concentrations

Abstract

ABSTRAeT Keywords:Early Jurassic Metacopine Mass extinctions OstracodaThe early Toarcian extinction event, once regarded as spanning in the late Pliensbachian-early Toarcian boundary period, actually occurred in two distinct phases in the early Toarcian of the Iberian Range. The first episode occurred in the Mirabile Subzone, Tenuicostatum Zone and is characterised by the disappearance of abaut 12% of ostracod species and one suborder, the Metacopina (Superfamily Healdioidea). Ihis study shows that this suborder disappears during stratigraphical intervals that are considered to be representative of low oxygen conditions in the Iberian Range. The collapse of marine ecosystems (affecting up to 40% of ostracod species) in the Elegantulum Subzone, Serpentinum Zone was most likely triggered by a sudden and widespread lethal increase in seawater temperature. These combined processes of oxygenation and temperature change are considered to be responsible for the profound changes in marine environments that resulted in the early Toarcian ostracod extinction in the Iberian Range.Low oxygen episodes Water temperature

Stratigraphic and environmental control on marine benthic community change through the early Toarcian extinction event (Iberian Range, Spain)

“…Anoxia has been considered the main cause of the marine extinction, as the event was firstly recognised in settings characterised by the deposition of widespread organic rich black shales (e.g., Little and Benton 1995). However, this hypothesis has been questioned following discovery that the extinction event is also recorded in localities that remained fully oxygenated throughout the lower Toarcian (Gómez and Goy 2011;García Joral et al 2011;Arias 2013). In particular, the absence of black shale deposition in most of northern and central Spain has been used to support the hypothesis that temperature rise, and not anoxia, was the main trigger of extinction on a global scale (Gómez et al 2008; Gómez and Goy 2011).…”

Microfossil assemblages and geochemistry for interpreting the incidence of the Jenkyns Event (early Toarcian) in the south-eastern Iberian Palaeomargin (External Subbetic, SE Spain)

“…The genus Bairdia is a shallow infaunal to epifaunal form (Sohn, 1960) interpreted as an opportunist (Fohrer and Samankassou, 2005;Reolid, 2014a). Metacopina (Healdiidae) are not recorded after the biotic crisis as widely as in other Tethys localities (Boomer and Whatley, 1992;Whatley et al, 1994;Arias and Whatley, 2004;Boomer et al, 2008;Arias, 2013;Cabral et al, 2013;Soulimane et al, 2017aSoulimane et al, , 2020. The Jenkyns Event marks the global extinction of Metacopina (e.g.…”

“…The Jenkyns Event marks the global extinction of Metacopina (e.g. Boomer et al, 2008;Arias, 2013). Families Healdiidae, Bythocytheridae, and Polycopidae are not recovered after the barren interval.…”

“…Some authors propose that the early Toarcian ostracod turnover is a consequence of global warming (Arias and Whatley, 2004;Gómez and Arias, 2010;Arias, 2013). Boomer et al (2008) and Arias and Whatley (2009) put forth the possible existence of competition among the different ostracod groups after extinction of the metacopines.…”

Análisis de elementos traza en braquiópodos del Jurásico Inferior del Paleomargen Sud-Ibérico (SE de España). Correlación con las señales bióticas e implicaciones ambientales en torno al Evento de Extinción Masiva del Toarciense inferior

“…This phase took place just before the well-known early Toarcian mass extinction event often correlated with the Toarcian Oceanic Anoxic Event (T-OAE), also called Jenkyns Event (Müller et al, 2017;Reolid et al, 2020). This event represented one of the most critical ecological crisis in the whole Mesozoic, implying extinction and significant faunal turnovers in the nektonic/planktic and benthic biota (Hallam, 1986(Hallam, , 1987Vörös, 1993Vörös, , 2002Little & Benton, 1995;Aberhan & Fürsich, 1997;Harries & Little, 1999;Macchioni & Cecca, 2002;Wignall et al, 2005;Wignall & Bond, 2008;Arias, 2009Arias, , 2013Dera et al, 2010;Caruthers et al, 2013;Reolid et al, , 2019Baeza-Carratalá et al, 2015. The Jenkyns Event is worldwide characterized by the record of a negative carbon isotopic excursion (CIE) also recorded in the South-Iberian Palaeomargin Rodrigues et al, 2019;Ruebsam et al, 2020) (Fig.…”