Age and synchronicity of planktonic foraminiferal bioevents across the Cenomanian–Turonian boundary interval (Late Cretaceous)
Articolo
Data di Pubblicazione:
2018
Citazione:
Age and synchronicity of planktonic foraminiferal bioevents across the Cenomanian–Turonian boundary interval (Late Cretaceous) / F. Falzoni, M.R. Petrizzo, M. Caron, R.M. Leckie, K. Elderbak. - In: NEWSLETTERS ON STRATIGRAPHY. - ISSN 0078-0421. - 51:3(2018 Jun), pp. 343-380. [10.1127/nos/2018/0416]
Abstract:
The upper Cenomanian – lower Turonian is a key-stratigraphic interval, as it encompasses the
Late Cretaceous supergreenhouse and a major perturbation of the global carbon cycle (i. e., Oceanic Anoxic
Event 2) as evidenced by a global positive carbon isotope excursion and by the nearly world-wide deposition
of organic-rich marine facies. A turnover in planktonic foraminiferal assemblages and in other marine organisms
is documented across this stratigraphic interval, but reconstruction of the timing and identification of
the cause and effect relationships between environmental perturbations and organism response require a highly-
resolved stratigraphic framework. The appearance and extinction levels of planktonic foraminiferal species
generally allow accurate intra- and supra-basinal correlations. However, bioevents cannot be assumed to be
globally synchronous, because the stratigraphic and geographic distribution of species is modulated by ecological
preferences exhibited by each taxon and controlled by oceanic circulation, often resulting in earlier
or delayed events in certain geographic areas (i. e., diachronous datums). The aim of this study is to test the
synchronicity of the planktonic foraminiferal bioevents recognized across the C/T boundary and to provide
the most reliable sequence of events for correlation of low to mid-latitude localities. For this purpose, we have
compiled a highly-resolved biostratigraphic analysis of the European reference section for the C/T boundary
at Eastbourne, Gun Gardens (UK), and core S57 (Tarfaya, Morocco), and correlated the sequence of bioevents
identified with those recorded in other coeval sections available in the literature, including the GSSP section
for the base of the Turonian Stage at Rock Canyon, Pueblo (Colorado), where we calculated reliable estimates
of planktonic foraminiferal events that are well-constrained by radioisotopically and astrochronologically
dated bentonite layers. Results indicate that the extinctions of Thalmanninella deeckei, Thalmanninella
greenhornensis, Rotalipora cushmani and “Globigerinelloides” bentonensis in the latest Cenomanian are
reliable bioevents for correlation. In addition, our analysis highlights other promising lowest occurrences
(LOs) that need to be better constrained by bio- and chemostratigraphy, including the LO of Marginotruncana
schneegansi falling close to the C/T boundary. By contrast, the appearance of Helvetoglobotruncana helvetica
and of some Dicarinella species, the extinction of anaticinellids and the onset of the “Heterohelix” shift are
likely diachronous across low to mid-latitude localities. Finally, our study suggests that different species concepts
among authors, different sample size and sampling resolution, as well as species paleoecology are important
factors that control the stratigraphic position at which bioevents are identified.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Cenomanian–Turonian; stratigraphy; mid-low latitude correlations; planktonic foraminifera; Pueblo; Eastbourne
Elenco autori:
F. Falzoni, M.R. Petrizzo, M. Caron, R.M. Leckie, K. Elderbak
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