Long-term Late Cretaceous oxygen- and carbon-isotope trends and planktonic foraminiferal turnover: A new record from the southern midlatitudes

Abstract

The ~35 myr-long Late Cretaceous greenhouse climate has been subjected to a number of studies with emphasis on the Cenomanian-Turonian and late Campanian-Maastrichtian intervals. By contrast, far less information is available for the Turonian-early Campanian interval, even though it encompasses the transition out of the extreme warmth of the Cenomanian-Turonian greenhouse climate optimum and includes a ~3 myr-long mid-Coniacian-mid-Santonian interval when planktonic foraminifera underwent a large-scale, but poorly understood, turnover. This study presents ~1350 δ 18 O and δ 13 C values of well-preserved benthic and planktonic foraminifera and of the <63 μm size fraction from the Exmouth Plateau off Australia (eastern Indian Ocean). These data provide: (i) the most continuous, highly resolved and stratigraphically well-constrained record of long-term trends in Late Cretaceous oxygen-and carbon-isotope ratios from the southern mid-latitudes, and (ii) new information on the paleoecological preferences of planktonic foraminiferal taxa. The results indicate persistent warmth from the early Turonian until the mid-Santonian, cooling from the mid-Santonian through the mid-Campanian, and short-term climatic variability during the late Campanian-Maastrichtian. Moreover, our results suggest the cause of Coniacian-Santonian turnover among planktonic foraminifera may have been the evolution of a temperature/salinity-tolerant genus (Marginotruncana) and the cause of the Santonian-early Campanian extinction of Dicarinella and Marginotruncana may have been surface-ocean cooling and competition with globotruncanids.

Late Cretaceous Temperature Evolution of the Southern High Latitudes: A TEX86 Perspective

“…The absolute values of TEX 86 -SSTs from the Falkland Plateau (using all three calibrations) are close to the maximum SSTs suggested by planktic foraminiferal δ 18 O-SST records from the Southern Atlantic and Southern Tethys (e.g., Falzoni et al, 2016;Huber et al, 1995Huber et al, , 2018 and provide further evidence supporting the existence of extremely warm temperatures at southern paleolatitudes of~55°to 60°S in the Late Cretaceous (e.g., Huber et al, 1995Huber et al, , 2018Falzoni et al, 2016). Nonetheless, the SSTs calculated from TEX 86 at Site 511 are slightly warmer than the corresponding δ 18 O values ( Figure 6).…”

“…All oxygen‐isotope values are reported relative to VPDB. 1 Huber et al (); 2 Huber et al (); 3 Barrera and Savin (); 4 Friedrich et al (); 5 Barrera and Huber (); 6 Falzoni et al (); 7 Clarke and Jenkyns (); 8 Ando et al (); 9 Woelders et al (); 10 Bice et al (); 11 Forster et al (); 12 Schouten et al (); 13 Bornemann et al (); 14 Sinninghe Damsté et al (); 15 Robinson et al (); 16 Alsenz et al (); 17 van Helmond et al (); 18 Linnert et al (); 19 van Helmond et al (); 20 Woelders et al (). All age models from original sources, plotted on the 2016 timescale (Ogg et al, ).…”

“…This event is not seen in other records (including in the TEX 86 record from the same site; Robinson et al, ) and suggests that it might be predominantly a local environmental signal. However, the gentle increase in δ 18 O values from the Turonian to Campanian at Sites 1135 and 1138 shows a strong similarity to planktic foraminiferal, benthic foraminiferal, and bulk carbonate δ 18 O values from the Exmouth Plateau, approximately 10° further north (Clarke & Jenkyns, ; Falzoni et al, ) and is thus interpreted to reflect dominantly bottom‐water temperature trends. These data further suggest slow, steady cooling through the Late Cretaceous.…”

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

“…In fact, OAE 2 is globally recognized as a time of increased sea-surface productivity under greenhouse climate conditions interrupted by a brief cooling episode (i. e., the "Plenus Cold Event", see Gale and Christensen 1996, Forster et al 2007, Sinninghe Damsté et al 2010, Jenkyns et al 2017, Kuhnt et al 2017) that may correspond to rising sea level and to a re-oxygenation event of bottom waters in the Western Interior Seaway (WIS) (i. e., the "Benthonic Zone": Eicher and Worstell 1970, Eicher and Diner 1985, Leckie 1985, Elderbak and Leckie 2016. Across OAE 2, planktonic foraminiferal assemblages underwent a substantial turnover due to the extinction of the single-keeled rotaliporids with umbilical supplementary apertures (genera Rotalipora and Thalmanninella) and to the appearance and progressive diversification of double-keeled taxa (genera Dicarinella and Marginotruncana), that dominated the assemblages until the Santonian (Robaszynski et al 1990, Premoli Silva and Sliter 1999, Leckie et al 2002, Petrizzo 2002, Falzoni et al 2013, 2016a. However, correlating stratigraphic sequences, discriminating global from local signals, and reconstructing the cause and effect relationships between environmental changes and organism response require a reproducible and highlyresolved stratigraphic framework.…”

Did Late Cretaceous cooling trigger the Campanian–Maastrichtian Boundary Event?

“…The Campanian is a key interval in the Late Cretaceous, as it marks the transition between the mid-Cretaceous ʻhot greenhouseʼ and the ʻcool greenhouseʼ of the Maastrichtian and early Paleocene (Clarke and Jenkyns 1999, Zachos et al 2008, Friedrich et al 2012, Ando et al 2013, Linnert et al 2014, Falzoni et al 2016. The cooling was accompanied by changes in global oceanic circulation towards a mode of deepwater formation in high southern latitudes, although the precise timing and geographic influence of these changes is still being revealed , Frank and Arthur 1999, Huber et al 2002, Cramer et al 2009, Robinson et al 2010, MacLeod et al 2011, Friedrich et al 2012, Martin et al 2012, Robinson and Vance 2012, Murphy and Thomas 2012, Jung et al 2013, Voigt et al 2013, Moiroud et al 2013.…”