Changes in CO2 during ocean anoxic event 1d indicate similarities to other carbon cycle perturbations

Past greenhouse intervals of the Mesozoic were repeatedly punctuated by Ocean Anoxic Events (OAEs), major perturbations to the global carbon cycle and abrupt climate changes that may serve as relevant analogs for Earth’s greenhouse gas-forced climate future. The key to better understanding these transient climate disruptions and possible CO2 forced tipping-points resides in high-resolution, precise, and accurate estimates of atmospheric CO2 for individual OAEs. Here we present a high-temporal resolution, multi-proxy pCO2 reconstruction for the onset of mid-Cretaceous (Albian-Cenomanian Boundary) OAE1d. Coupling of pCO2 estimates with carbon isotopic compositions (δ13C) of charcoal, vitrain, and cuticle from the Rose Creek Pit (RCP), Nebraska, reveals complex phasing, including a lag between the well-documented negative δ13C excursion defining the onset of OAE1d and the CO2 increase. This lag indicates that increased CO2 or other C-based greenhouse gases may not have been the primary cause of the negative excursion. Our study reveals a pCO2 increase within the interval of the negative δ13C excursion, reaching a maximum of up to ~840 ppm (95% confidence interval -307 ppm/+167 ppm) toward its end. The reconstructed magnitude of CO2 increase (~357 ppm) is similar to that of Late Cretaceous OAE2 but of smaller magnitude than that of other major carbon cycle perturbations of the Mesozoic assessed via stomatal methods (e.g., the Toarcian OAE [TOAE], Triassic-Jurassic boundary event, Cretaceous-Paleogene Boundary event). Furthermore, our results indicate a possible shared causal or developmental mechanism with OAE1a and the TOAE

Data for Cenozoic paleoclimate on land in North America

These three datasets (in .csv and .xlsx formats) are the data used for the article: Retallack, G.J., 2007, Cenozoic paleoclimate on land in North America. Journal of Geology 115, 271-294.Paleotemperature and paleoprecipitation over the past 40 m.yr. can be inferred from the degree of chemical weathering and depth of carbonate nodules in paleosols of Oregon, Montana, and Nebraska. Paleosol records show that late Eocene (35 Ma), middle Miocene (16 Ma), late Miocene (7 Ma), and early Pliocene (4 Ma) warm climatic episodes were also times of a wet climate in Oregon, Montana, and Nebraska. Oregon and Nebraska were humid during warmwet times, but Montana was no wetter than subhumid within the rain shadow of intermontane basins. Global warmwet paleoclimatic spikes steepened rather than flattened geographic gradients of Rocky Mountain rain shadows. Longlived mountain barriers created dusty dry basins with sedimentation rates high enough to preserve Milankovitch-scale (100–41 kyr) global paleoclimatic variation in some sequences of paleosols. Greenhouse warm-wet climates indicated by paleosols were also peaks of diversity for North American plants and animals and coincided with advances in coevolution of grasses and grazers. Paleosol records differ from global compilations of marine foraminiferal oxygen and carbon isotopic composition, due to competing influences of global ice volume and C4 grass expansion. Paleosol records support links between global warming and high atmospheric CO2

Paleosol data from Kenya.

These data were collected to evaluate the changing vegetation and paleoclimate of Kenya over the past 20 million years, and its relevance for human evolution. Data was collected in several areas of Kenya with Cenozoic deposits well known for fossil mammals, including islands and shores of Lake Victoria, the central and southern Gregory Rift, and the basin of Lake Turkana. data are largely measurements of key characteristics of fossil soils (paleosols) in the field: depth to the carbonate (Bk) horizon, thickness of the carbonate (Bk) horizon and size of the carbonate nodules.Data collected in several areas of Kenya with Cenozoic deposits well known for fossil mammals, including islands and shores of Lake Victoria, the central and southern Gregory Rift, and the basin of Lake Turkana. Data are largely measurements of key characteristics of fossil soils (paleosols) in the field: depth to the carbonate (Bk) horizon, thickness of the carbonate (Bk) horizon and size of the carbonate nodules.Wenner-Gren Foundation and the Paleoanthropology Division of the U.S. National Science Foundation; NSF grants EAR8206183, EAR85023232, SBR951317

Paleosol data from Pennsylvania, New York, Maryland, Ohio, Tennessee, West Virginia, and Quebec.

Data were collected to establish a paleoclimatic time series for Devonian and Early Carboniferous rocks with evidence of fossils transitional between fish and amphibians. Data was collected in Pennsylvania, New York, Maryland, Ohio, Tennessee, West Virginia, and Quebec.Data on depth to calcic horizon in paleosols of the northern Appalachians for tetrapod bones and trackways, as well as fossil tree remains. These data were collected to establish a paleoclimatic time series for Devonian and Early Carboniferous rocks with evidence of fossils transitional between fish and amphibians