Downloaded from http://sp.lyellcollection.org/ by guest on June 17, 2013 Geological Society, London, Special Publications Online First Use of multiple oxygen isotope proxies for elucidating Arctic Cretaceous palaeo-hydrology Celina A. Suarez, G. A. Ludvigson, L. A. Gonzalez, A. R. Fiorillo, P. P. Flaig and P. J. Mccarthy Geological Society, London, Special Publications, first published June 17, 2013; doi 10.1144/SP382.3 Email alerting click here to receive free e-mail alerts when service new articles cite this article Permission click here to seek permission to re-use all or request part of this article Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection How to cite click here for further information about Online First and how to cite articles Notes © The Geological Society of London 2013 Downloaded from http://sp.lyellcollection.org/ by guest on June 17, 2013 Use of multiple oxygen isotope proxies for elucidating Arctic Cretaceous palaeo-hydrology CELINA A. SUAREZ1*, G. A. LUDVIGSON2, L. A. GONZALEZ3, A. R. FIORILLO4, P. P. FLAIG5 &P.J.MCCARTHY6 1Department of Geosciences, University of Arkansas, 346 Arkansas Avenue, Fayetteville, AR 72701, USA 2Kansas Geological Survey, 1930 Constant Avenue, Lawrence, KS 66047-3726, USA 3Department of Geology, University of Kansas, 1475 Jayhawk Boulevard, Lawrence, KS 66045-7594, USA 4Museum of Nature and Science, PO Box 151469, Dallas, TX 75315, USA 5Bureau of Economic Geology, Jackson School of Geosciences, University of Texas, Austin, TX 78758, USA 6Department of Geology & Geophysics, University of Alaska, Fairbanks, AK 99775-5780, USA *Corresponding author (e-mail: [email protected]) Abstract: Stable oxygen isotope analysis of siderite and dinosaur tooth enamel phosphate from the Campanian–Maastrichtian Prince Creek Formation, Alaska, USA, are analysed to determine the palaeohydrology of the ancient Colville Basin north of the Ancestral Brooks Range. d18Oof freshwater siderites relative to V-PDB ranges between 214.86 and 216.21‰. Dinosaur tooth enamel d18O from three different sites (Kikak–Tegoseak, Pediomys Point, Liscomb) range 18 18 between +3.9‰ and +10.2.0‰. d Ometeoric water are calculated from d Osiderite that formed at seasonal temperatures ranging from 22 to 14.5 8C, with a mean annual temperature of 6.3 8C. 18 At 6.3 8C, the d Ow calculated from siderite ranged between 222.23 and 220.89‰ V-SMOW. Ingested water compositions are estimated from dinosaur teeth assuming body temperatures of 37 8C and local relative humidity of 77.5%, resulting in values ranging from 228.7 to 220.4‰ V-SMOW, suggesting consumption of meteoric water and orographically depleted runoff from 18 the Brooks Range. The ranges in calculated d Ometeoric water are compatible between the two proxies, and are mutually corroborating evidence of extremely 18O-depleted precipitation at high latitudes during the Late Cretaceous relative to those generated using general circulation models. This depletion is proposed to result from increased rainout effects from an intensified hydrological cycle, which probably played a role in sustaining polar warmth. Supplementary material: Parameters used for generation of equations compared to Kohn (1996) can be found at http://www.geolsoc.org.uk/SUP18642 Stable isotopic proxies are invaluable tools for (Kiehl 2011) are predicted to approach those (pCO2, understanding past and current climates. Pedogenic temperature) seen in the various greenhouse worlds carbonates (siderite and calcite) are commonly used of the Cretaceous. Several studies on the Cretace- to determine the isotopic composition of meteoric ous climate have revealed shallow equatorial-to- water (Lohmann 1988; Hays & Grossman 1991; pole air and ocean temperature gradients (Wolfe & Ludvigson et al. 1998; Ufnar et al. 2004a; Suarez Upchurch 1987; Amiot et al. 2004; Jenkyns et al. et al. 2011). When analysed over a range of lati- 2004; Puce´at et al. 2007), while others have indi- tudes, the resulting isotopic gradients can be used cated equator-to-pole precipitation d18O gradients to determine global isotopic groundwater gradients. that are steeper than the modern climate system This gradient is related to the isotopic composition (Ludvigson et al. 1998; Ufnar et al. 2002; Suarez of the precipitation, which is itself related to temp- et al. 2011). This steep gradient has been explained erature gradients, humidity and, in some instances, as resulting from increased rainout, thereby increas- orographic effects. ing latent heat transport from the equator to the Isotopic studies of the Cretaceous are of particu- poles during greenhouse conditions (Ufnar et al. lar importance because future climatic conditions 2004b). These conclusions are based on empirical From:Bojar, A.-V., Melinte-Dobrinescu,M.C.&Smit, J. (eds) Isotopic Studies in Cretaceous Research. Geological Society, London, Special Publications, 382, http://dx.doi.org/10.1144/SP382.3 # The Geological Society of London 2013. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics Downloaded from http://sp.lyellcollection.org/ by guest on June 17, 2013 C. A. SUAREZ ET AL. data, but general circulation models (GCMs) with of vertebrates and pedogenic carbonates from isotopic capabilities have not been able to repro- other foreland basin settings have been used to duce the steep isotopic gradient (Poulsen et al. identify local orographic effects (Suarez et al. 2007) at high latitudes. The inability of Earth 2012). Therefore, the comparison of vertebrate system models to simulate empirically derived ingested water with local groundwater is carried data has been explained by postulating local orogra- out to determine the range in isotopic compositions phic effects as having confounded the high latitude of surface waters, and to determine if there is a sig- data set. Consequently, additional studies of high- nificant orographic effect on meteoric water from latitude regional climates are important for better the ancestral Brooks Range. Comparisons to esti- understanding the disparity between GCM results mates of the d18O of meteoric water from the under- and empirically derived data. Can the addition lying Nanushuk Formation (Albian–Cenomanian) of vertebrate stable isotope proxies help to better are also made to determine whether the d18Oof understand regional palaeohydrology in the context PCF meteoric waters are as depleted in 18O during of global climate change? the slightly cooler Late Campanian–Early Maas- The sensitivity of the Arctic to climate changes trichtian interval, and from sampling sites much makes it an ideal place to investigate past green- further removed from the ancestral Brooks Range house states of the Earth. The Arctic preserves than those initially studied by Ufnar et al. (2004a). sediments deposited in greenhouse states, including the Palaeocene–Eocene thermal maximum (PETM) and the Cretaceous (the focus of this study) (Ufnar Stable isotopes in vertebrate bioapatite et al. 2004a; Pagani et al. 2006; Jahren et al. 2009). Investigation of these past climates suggests The isotopic composition of continental vertebrates that during exceptional warmth, the Arctic was is primarily controlled by ingested surface water/ devoid of ice caps and sustained considerable bio- living water and relative humidity (Kohn 1996). 18 diversity atypical of high latitudes today (e.g. lush Offsets in d Ow across the landscape can be deciduous forests in the middle Eocene (Jahren recorded in bioapatites of the taxa that live in or et al. 2010) and champsosaurs in the Cenoma- consume it. As a result, the isotopic composition nian–Turonian (Tarduno et al. 1998; Vandermark of vertebrate tooth enamel can be used to determine et al. 2007)). The lack of ice caps, which decreases the range of the isotopic composition of surface albedo, and the presence of dark-coloured veget- water. Pedogenic calcite and siderite are known to ation, which increases insolation, acted as a positive record the average or slightly 18O-enriched end- feedback that helped sustain these warm climates member (in the case of calcite) isotopic composi- of the Arctic (Hay & DeConto 1999). As current tion of meteoric water (Lohmann 1988; Cerling & pCO2 and temperatures increase, the not-too-distant Quade 1993; Cojan et al. 2003; Breecker et al. future of the Arctic may become increasingly 2009; Suarez et al. 2009). Because pedogenic car- similar to the Arctic of the Cretaceous (Kiehl 2011). bonates form in one location, they are less likely The use of vertebrate remains as proxy data has to record a wide range in the surface water isotopic some advantages over other palaeo proxies. Phos- composition, for example, from river water draining phate tends to be more resistant to diagenesis mountainous regions v. precipitation. Large-bodied (Kolodny et al. 1996; Sharp et al. 2000) and may thermoregulating terrestrial animals (non-aquatic) be a reliable proxy for water d18O. Also, thermore- all demonstrate a similar relationship between ing- gulating animals that grow their phosphate at a con- ested surface water and the d18O of tooth phos- stant or near-constant body temperature can be phate (Kohn 1996), with the dominant influences 18 analysed without having to determine temperature for d Op being surface water, diet and relative independently. As land-dwelling animals get their humidity. Terrestrial animal body water tends to water from a variety of sources, they can also sam- be enriched compared to local drinking water as a ple the full spectrum of freshwater isotopic compo- result of water loss by panting or transcutaneous sitions of a particular region (Barrick et al. 1999). water loss (evaporative enrichment). This trend, This study uses the vertebrate remains of dino- however, is highly dependent on humidity. Herbi- saurs from the Arctic Prince Creek Formation vore enamel tends to be enriched relative to carni- (PCF, late Campanian to early Maastrichthian) as vores because of the consumption of isotopically an additional proxy for surface-water isotopic com- 18O-enriched plant leaves. Leaf water tends to be positions to augment data from pedogenic sideri- 18O-enriched due to evaporation of water during tes (Ufnar et al.