Early Paleogene environmental turnover in the southern Tethys as recorded by foraminiferal and organic-walled dinoflagellate cysts assemblages
Elisa Guasti
Europrox
This research investigates the environmental change of the marine ecosystem
on the continental margin of the Southern Tethys during the early Paleogene.
In particular, my project portrayed how the marine ecosystem reacted to
the Paleocene Eocene thermal maximum (~55 Ma) and explored a possible
hyperthermal event during the middle Paleocene, across the Danian-Selandian
transition (61-59 Ma). Several localities located along paleobathymetric
transects (from middle neritic to upper bathyal) in Jordan, Egypt and
Tunisia have been investigated. Considering that a multi-proxy approach
is preferable for a most reliable reconstruction, I evaluated different
microbiotic groups from the surface water (organic dinocysts and planktic
foraminifera) and from the sea floor (benthic foraminifera); in addition
to geochemical proxies (oxygen and carbon stable isotopes and carbonate
content). Considering multi-proxy observations, climatic and environmental
changes across these intervals of biotic turnover are investigated, unravelling
possible similarities between these two events.
These topics are summarized in six chapters.
In Chapter II, an integrated paleoecological analysis of quantitative
distribution patterns of Paleocene (Planktic foraminiferal Zones P1b-P4)
organic dinocysts and benthic foraminifera from the El Kef section (NW
Tunisia) is proposed.
In Chapter III, the NW Tunisia area has again been the focus, and the
Danian-Selandian transition has been studied in detail by combining foraminifera
and organic dinocysts. From an oligotrophic open marine setting in planktic
foraminifera Zones P2-P3a, a shallower phase toward rich-nutrient environment
is evidenced starting at the base of Subzone P3b.
In Chapter IV, the Danian-Selandian transition Middle East is on focus.
A partially laminated dark-bed rich in fish remains is associated to anomalous
planktic and benthic foraminifera and calcareous nannofossils assemblages
during a brief interval, named as “Neo-duwi event”.
In Chapter V, the uppermost Paleocene is investigated in the Middle East.
In particular, the planktic foraminiferal turnover and the diversification
of new taxa across the Paleocene-Eocene thermal maximum (PETM) are evaluated.
Well diversified planktic foraminiferal assemblages of Subzone P5a abruptly
change into oligotaxic assemblages dominated by Acarinina during the PETM.
Among this group, A. multicamerata sp. nov. is proposed as biozonal marker
of Subzone P5b.
In Chapter VI, the impact of the PETM on planktic and benthic foraminiferal
assemblages at Dababiya (GSSP of the Paleocene/Eocene boundary, Egypt)
has been evaluated.
In Chapter VII, a synthesis of this work is proposed. Correlation across
the Danian-Selandian transition between the Middle East and Tunisia is
investigated. Additionally, a comparison with Zumaya (northern Spain)
is provided. Furthermore, a comparison between the Danian-Selandian transition
and the Paleocene-Eocene thermal maximum is also evaluated trying to underline
similarities and differences.