Collaborative Research: High-resolution Cretaceous terrestrial climate records of temperature, weathering and hydrologic response to hyperthermals in Songliao Basin, China

International Continental Scientific Drilling Program project ICDP-2008/03, “Continental Scientific Drilling Project of Cretaceous Songliao Basin: Continuous High-resolution Terrestrial Archives and Greenhouse Climate Change,” offers an unprecedented opportunity to study the Cretaceous greenhouse in a terrestrial setting. This project has and will recover an astonishing 9.5 km of continuous core from the Cretaceous/Paleogene to Cretaceous/Jurassic boundary (Feng et al., 2013), made possible by long-term subsidence and sedimentation in an internally drained rift basin. One of the planned cores (2.5 km of core) through the Upper Cretaceous (SK-I) is already in hand and the other (SK-II) that will extend into the Jurassic (an additional 7 km of core) will commence drilling in early 2014. Initial studies of SK-I demonstrate that the core robustly records the long-term paleoclimate of the Late Cretaceous, including periods of hyperthermia (Wang et al., 2013a,b,c). As part of this effort, the PIs on this proposal conducted an oxygen and carbon isotope study of ostracods collected from SK-I (Chamberlain et al., 2013). Our initial research demonstrates that the stable isotopic record of these ostracods mimic records preserved in marine settings for the Late Cretaceous. With the proposed collection of the new drill core from SK-II we are now poised to: 1) extend our long-term isotopic record through the entire Cretaceous, thereby producing an unprecedented continuous terrestrial record, and 2) address mechanisms proposed for hyperthermal events in the Cretaceous using the existing SK-I and the planned SK-II isotopic records. These two nested goals are discussed below. Goal 1: Long-term isotopic record of the Cretaceous. Our understanding of the links and feedbacks between the long-term carbon cycle and Earth’s climate is a major research focus in Earth Sciences. Of particular relevance to today’s concerns of global change are studies of times in the past when the Earth experienced greenhouse and hothouse conditions – such as the Cretaceous. Working mostly on sediments from either ocean drill cores and marine sediments exposed on the Earth’s surface the Cretaceous is identified as a time of extreme warmth and high climate variability (Huber et al., 2002). Presently, our understanding of the warm Cretaceous is largely based upon well-documented marine records. However, in order to understand how the ocean, atmosphere, and biosphere interact under ancient greenhouse conditions, it is imperative to link marine and terrestrial records. We now have a unique and exciting opportunity to constrain the terrestrial response to greenhouse warming with the collection of the two drill cores (SK-I in-hand and SK-II planned) that will extend through the entire Cretaceous in the Songliao Basin (Fig. 1). Here we plan a three-year study to extend our isotopic record throughout the Cretaceous. This portion of the research plan will test the hypothesis, driven by our previous study (Chamberlain et al., 2013), that the SK-II core will record the temperature history of the Early Cretaceous as observed in nonmarine settings, particularly the hyperthermals and their associated carbon isotope shifts. One of the goals of the ICDP project (Feng et al., 2013) is to document and understand mechanisms for ocean anoxic events. As stated above, we have found that the carbon isotope record of SK-I records two OAEs. The largest of these, OAE 2, occurs at SK-1’s base and will be completely recovered at the top of the new SK-II core. Thus, as we collect our long-term