Sea-level changes and black shales associated with the late Paleocene thermal maximum: Organic-geochemical and micropaleontologic evidence from the southern Tethyan margin (Egypt-Israel)

摘要

Organic geochemistry and microfossil contents of six sections spanning the late Paleocene thermal maximum are investigated. The sections are arranged along a depth transect (~50–600 m) across an epicontinental basin covering Egypt and Israel. This study is aimed at unraveling paleoceanographic changes associated with the late Paleocene thermal maximum. In three sections (~200–600 m paleodepth), black shales, consisting of dark brown laminated marls with as much as 2.7% total organic carbon (TOC), mark the late Paleocene thermal maximum. The black shales of the deeper sites correlate with pink to gray fissile marls in the shallowest section. In the two remaining sections, this stratigraphic interval is missing. A relative sea-level fall (~30 m) immediately preceded the late Paleocene thermal maximum, during which sea-level rose again by ~20 m. This rise may have been eustatically controlled, possibly through a combination of thermal expansion of the oceanic water column and melting of unknown sources of high-altitude or polar ice caps in response to global warming. During the late Paleocene thermal maximum, the upwelling of low-oxygen intermediate Tethyan water into the epicontinental basin led to enhanced biological productivity and anoxia at the seafloor. Before and after the late Paleocene thermal maximum, upwelling and biological productivity were less intense, and seafloor dysoxia was restricted to neritic parts of the basin. The presence of similar TOC-rich beds in extensive areas in southern Asia indicates that the Tethyan continental margins may have acted as significant carbon sinks during the late Paleocene thermal maximum.