Age and synchronicity of planktonic foraminiferal bioevents across the Cenomanian – Turonian boundary interval (Late Cretaceous)

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 worldwide 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.

Evolutionary trend of Cenomanian alveolinids from Zagros Basin,SWof Iran

“…Five levels were described in the Pyun section which coincide with bioevents. The mentioned levels are certainly controlled by ecological factors (Falzoni, Petrizzo, Caron, Leckie, & Elderbak, 2018). The evolutionary trend initiates with praealveolinids and ovalveolinids and proceeds in the middle of the Late Cenomanian.…”

Chemostratigraphy and stratigraphic distribution of keeled planktonic foraminifera in the Cenomanian of the North German Basin

“…Over the years however, taxonomic revisions of planktonic foraminiferal taxa, especially of the polyphyletic Rotalipora group (Rotalipora, Brotzen 1942;Thalmanninella, Sigal, 1948;Pseudothamanninella, Wonders, 1978;Parathalmanninella, Lipson-Benitah, 2008), have resulted in the re-interpretation of the morphologic plasticity and species variation within the lineages (Robaszynski et al, 1994;Petrizzo and Huber, 2006;Gonzales-Donoso et al, 2007;Lipson-Benitah, 2008), which of course, has influences on the classic planktonic foraminiferal biozonations (e.g. discussions in Ando et al, 2010;Falzoni et al, 2018). In contrast to the Tethys, unkeeled and globular forms, predominately muricohedbergellids (Huber and Leckie, 2011) dominate the lower to lowermost Upper Cretaceous of the Boreal epicontinental basins (Hecht, 1938;Carter and Hart, 1977;Weiss, 1997;Rückheim et al, 2006;Weiss, 2012).…”

Late Cretaceous Paleoceanographic Evolution and the Onset of Cooling in the Santonian at Southern High Latitudes (IODP Site U1513, SE Indian Ocean)

“…The extinction of Marginotruncana in the Santonian might be explained by the stress of cooling combined with likely competition exerted by species of the diversifying Globotruncana lineage which occupied similar depth habitats as species of Marginotruncana , a possibility previously postulated by Falzoni et al. (2018).…”

“…In terms of composition of the planktonic foraminiferal assemblages, the interval of relatively rapid cooling (Figure 12) includes (a) the extinctions of P. papula at 77.60 m CCSF and all species of the genus Marginotruncana (79.75 m CCSF), (b) the appearance of A. cretacea (75.29 m CCSF), and (c) an increase in abundance of G. bulloides. The extinction of Marginotruncana in the Santonian might be explained by the stress of cooling combined with likely competition exerted by species of the diversifying Globotruncana lineage which occupied similar depth habitats as species of Marginotruncana, a possibility previously postulated by Falzoni et al (2018).…”