Paper No. 1
Presentation Time: 8:00 AM


SUAREZ, Celina1, TRIESCHMANN, Ben1, YOU, Hailu2 and LI, Da-Qing3, (1)Geosciences, University of Arkansas, 216 Ozark Hall, Fayetteville, AR 72701, (2)Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 142 Xizhimenwai Street, Beijing, 100044, China, (3)Third Geology and Mineral Resources Exploration Academy, Gansu Provincial Bureau of Geo-exploration and Mineral Development, 121 Langongping Street, Lanzhou, 730050, China,

Stable isotopic analyses of tooth enamel phosphate and carbonate were collected from a maxillary and dentary tooth of the advanced iguanodontid Lanzhousaurus magnidens from the early Cretaceous Hekou Group, NW China. A long isotopic record representing over a year is available for these teeth, as Lanzhousaurus teeth are the largest herbivorous dinosaur teeth ever discovered (~10cm). O isotopic composition was collected to determine the isotopic composition of drinking water and seasonality of the early Cretaceous Lanzhou-Minhe basin of Northwest China. Tooth carbonate C and O isotopic composition was used to determine Lanzhousaurus diet and therefore dominant plant type. Isotopic composition of tooth phosphate (δ18Op) ranged from +18.72 to +22.64‰ V-SMOW and averaged +20.30‰ for the dentary and +16.79‰ to +23.37‰ and averaged +21.62‰ for the maxilla. Seasonal variability was observed and typically ranged 1 to 2‰, but was as much as ~4‰. A long term increasing trend in isotopic composition was also observed. Isotopic composition of tooth enamel carbonate oxygen (δ18Oco3) currently analyzed on the dentary ranged between +26.01 and +22.59 ‰ V-SMOW. Carbon isotopic composition ranged from -5.39 to -6.57‰ V-PDB. δ18Op and δ18OCO3 of individual samples are linearly correlated (r2 = 0.72) suggesting little diagenetic alteration of enamel carbonate. Based on physiological equations and testing a range of relative humidities from 50 to 70%, isotopic composition of drinking water ranged between an average δ18O value of -9.2‰ for 50% relative humidity to -5.2‰ for 70% relative humidity. Estimated plant diet δ13C values suggest a dry C3 dominated ecosystem and ranged between -24.57‰ and -23.39‰ and averaged -24.00‰. These values will be compared to additional water isotope proxies (turtle δ18Op) as well as bulk and picked organic C from the surrounding sediment. These values will help determine if Lanzhousaurus was consuming meteoric water or high elevation water derived from the nearby mountains, revealing a clearer picture of the terrestrial ecosystem of the early Cretaceous Lanzhou-Minhe Basin.