The duration and magnitude of Cretaceous cool events: Evidence from the northern high latitudes

Abstract

The Early Cretaceous (145–100 Ma) was characterized by long-term greenhouse climates, with a reduced equatorial to polar temperature gradient, although an increasingly large body of evidence suggests that this period was punctuated by episodic global “cold snaps.” Understanding climate dynamics during this high-atmospheric CO2 period of Earth’s history may have significant impact on how we understand climatic feedbacks and predict future global climate changes under an anthropogenically-driven high-pCO2 atmosphere. This study utilizes facies analysis to constrain the paleobathymetry of Lower Cretaceous glendonites—a pseudomorph after ikaite, a mineral that forms naturally at 7 °C or lower—from two paleo-high-latitude (60–70°N) sites in Svalbard, Arctic Norway, to infer global climatic changes during the Early Cretaceous. The original ikaite formed in the offshore transition zone of a shallow marine shelf at water depths of <100 m, suggesting mean annual water temperatures of ≤7 °C at these depths at 60–70°N. We correlate glendonite-bearing horizons from Lower Cretaceous successions around the globe using carbon isotope stratigraphy, in conjunction with the pre-existing biostratigraphic framework, in order to infer northern hemispheric to global climatic cooling. A distinct interval of glendonites in the Northern Hemisphere, from sites >60°N, spans the late Berriasian to earliest Barremian (at least 8.6 m.y.), significantly prolonging the duration of the previously hypothesized Valanginian cold snap (associated with the “Weissert Event”). Widespread glendonites occur again in late Aptian and extend to the early Albian, in both hemispheres, corroborating other proxy evidence for late Aptian cooling. The glendonites from Svalbard suggest that Cretaceous cold episodes were characterized with high latitude (>60°N) shallow water temperatures that are consistent with the existence of a small northern polar ice cap at this time.

Carbon isotope and sequence stratigraphy of the upper Isachsen Formation on Axel Heiberg Island (Nunavut, Canada): High Arctic expression of oceanic anoxic event 1a in a deltaic environment

“…A similar shift from terrestrial to marine conditions has been reported from early Aptian strata on High Arctic Svalbard, where inner shelf deposits of the Carolinefjellet Formation replaced fluvial and marginal marine sandstone of the Helvetiafjellet Formation ( Fig. 8B; Midtkandal et al, 2016;Vickers et al, 2016Vickers et al, , 2019. Chemostratigraphy places this transition into the negative carbon isotope excursion at the onset of OAE 1a (Midtkandal et al, 2016;Vickers et al, 2016Vickers et al, , 2019, indicating a similar age for the basinal Carolinefjellet Formation and the Rondon Member at Glacier Fiord (Fig.…”

“…To date, most research on OAE 1a has focused on sedimentary archives from low and mid-latitudes, while studies from high-latitude environments are scarce due to their remoteness (Herrle et al, 2015;Midtkandal et al, 2016;Vickers et al, 2016Vickers et al, , 2019. Recent studies of outcrops on Axel Heiberg Island (Nunavut, Canada; Fig.…”

Aptian-Albian clumped isotopes from northwest China: Cool temperatures, variable atmospheric <i>p</i>CO<sub>2</sub> and regional shifts in hydrologic cycle

“…interval (potentially associated with the "cold snap"; Mutterlose et al, 2009) may reflect on a shift in climate and Hadley cell circulation, driven by a decrease in atmospheric pCO2 (e.g., Hasegawa et al, 2012). Indeed, other sedimentological evidence (e.g., glendonites) provide further support for relatively cold conditions at high northern latitudes associated with this interval (Vickers et al, 2019). For our records,, atmospheric pCO2 drops during the C10 interval from pre-and post-segment values within error of 1000 ppmv, to < 350 ppmv in the C10 interval ( Fig.…”

“…Multiple climate events (including OAEs) have been identified during the late Early Cretaceous (Vickers et al, 2019;Jenkyns, 2018) oftentimes referred to as the mid-Cretaceous (i.e., here, our records span the Aptian-Albian; 125 to 100.5 Ma). While limited, available temperature records (e.g., Jenkyns, 2018) and high latitude sedimentological evidence (Vickers et al, 2019) suggest a relatively cool interval (following warmth during OAE 1a) associated with a global carbon isotope maximum (i.e., "C10"; Bralower et al, 1999;Menegatti et al, 1998;Mutterlose et al, 2009) at the Aptian-Albian boundary prior to OAE 1b (Bottini et al, 2015).…”

“…Multiple climate events (including OAEs) have been identified during the late Early Cretaceous (Vickers et al, 2019;Jenkyns, 2018) oftentimes referred to as the mid-Cretaceous (i.e., here, our records span the Aptian-Albian; 125 to 100.5 Ma). While limited, available temperature records (e.g., Jenkyns, 2018) and high latitude sedimentological evidence (Vickers et al, 2019) suggest a relatively cool interval (following warmth during OAE 1a) associated with a global carbon isotope maximum (i.e., "C10"; Bralower et al, 1999;Menegatti et al, 1998;Mutterlose et al, 2009) at the Aptian-Albian boundary prior to OAE 1b (Bottini et al, 2015). Estimates of Aptian-Albian atmospheric paleo-pCO2, while highly uncertain, tend to suggest low (less than 1000 to 1500 ppmv background greenhouse climate conditions; Franks et al, 2014) concentrations at the Aptian-Albian consistent with a cooler climate (Du et al, 2018;Passalia, 2009;Haworth et al, 2010;Aucour et al, 2008;Ekart et al, 1999;Wallmann, 2001;Fletcher et al, 2005).…”