TY - JOUR
T1 - The duration and magnitude of Cretaceous cool events
T2 - Evidence from the northern high latitudes
AU - Vickers, Madeleine
AU - Price, Gregory
AU - Jerrett, Rhodri
AU - Sutton, Paul
AU - Watkinson, Matthew
AU - FitzPatrick, Meriel
PY - 2019
Y1 - 2019
N2 - 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.
AB - 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.
U2 - 10.1130/B35074.1
DO - 10.1130/B35074.1
M3 - Journal article
SN - 0016-7606
VL - 131
SP - 1979
EP - 1994
JO - Bulletin of the Geological Society of America
JF - Bulletin of the Geological Society of America
IS - 11-12
ER -
