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

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Abstract Non-technical: The Cretaceous period (145 to 66 myr ago) is characterized by an interval when the Earth experienced unusually warm temperatures and high carbon dioxide levels. To understand how the Earth might behave during greenhouse conditions it is imperative to study these unique times in the Earth's past. In an effort to examine this time period, the International Continental Scientific Drilling Program launched a project entitled 'Continental Scientific Drilling Project of Cretaceous Songliao Basin: Continuous High-resolution Terrestrial Archives and Greenhouse Climate Change,'. This project will provide ~10 km of nearly continuous core through the entire Cretaceous that is preserved as ancient lake sediments in northeast China. PIs will take advantage of this unprecedented opportunity to study the Cretaceous hothouse by collecting isotopic and sedimentologic data specifically focusing on intervals (e.g. ~93 myr ago) in the Cretaceous when the Earth experienced extreme warmth and the oceans became anoxic. They have assembled a team of scientists (Stanford Univ., Univ. of Wisconsin, and Northwestern Univ.) with unique and complimentary skill sets to address the problem of how Earth's mid-latitudes behave during extreme warmth. PIs are particularly interested in examining the links and feedbacks between the Earth's hydrologic and carbon cycles and time-scales that these cycles are operative over. Their study will provide one of the most detailed and constrained isotopic data sets for a terrestrial setting. These data will provide the basis for their modeling studies that will give quantitative bounds on the temperature and precipitation changes associated with hyperthermal events.Technical: This one-year study focuses on the Cretaceous terrestrial record of climate change in the Songliao Basin of northeastern China, a long-lived, internally drained rift basin. PIs understanding of the terrestrial responses to global climate change are informed in part, by paleoclimate studies of times when the Earth experienced greenhouse and hothouse conditions. They have a unique opportunity to address questions concerning the links and feedbacks between global warming, the carbon cycle and the hydrologic cycle in a terrestrial setting through the examination of core material collected in ICDP coring of the Cretaceous Songliao Basin. Their initial studies of the Upper Cretaceous core (SK-I) from this basin show that the carbon isotopic values of ostracods reflect the global perturbations of the carbon cycle as observed in marine records (Chamberlain et al., 2013). With the collection of the new drill core from SK-II (May 2014), PIs are positioned to extend this record through the Lower Cretaceous. In their study of the Cretaceous drill-core they will address two related hypotheses, which are: 1) SK-II core will record the temperature history of the Lower Cretaceous observed in marine settings, particularly the hyperthermals and their carbon isotopic changes; and 2) the Songliao drill core contains carbon isotopic evidence for the Ocean Anoxic Event (OAE) 2 at the Cenomanian/Turonian boundary, and this boundary will record evidence for the increased chemical and physical weathering that may be responsible for OAE 2. To test these two related hypotheses will require oxygen, carbon and strontium isotopic and trace/REE element studies set within a rigorous sedimentologic and geochronologic framework. The latter will be supported by field investigations of volcanic and sedimentary rocks exposed near the basin margins. Driven by their earlier studies, PIs recognize that the isotopic values record both global climate changes and regional basin evolution. Unraveling these basin responses is not trivial, thus they have assembled scientists with unique yet complimentary expertise involving sedimentology, geochemistry, and modeling. Since this is a one-year study PIs will focus on existing core material (SK-I) and the upper portion of planned core (SK-II) that span the Cenomanian/Turonian boundary and OAE 2.