Quantitative estimates of increased heat transfer by atmospheric H 2 O vapor during the Albian greenhouse warming suggest that the intensified hydrologic cycle played a greater role in warming high latitudes than at present and thus represents a viable alternative to oceanic heat transport. Sphaerosiderite ␦ 18 O values in paleosols of the North American Cretaceous Western Interior Basin are a proxy for meteoric ␦ 18 O values, and massbalance modeling results suggest that Albian precipitation rates exceeded modern rates at both mid and high latitudes. Comparison of modeled Albian and modern precipitation minus evaporation values suggests amplification of the Albian moisture deficit in the tropics and moisture surplus in the mid to high latitudes. The tropical moisture deficit represents an average heat loss of ϳ75 W/m 2 at 10؇N paleolatitude (at present, 21 W/m 2). The increased precipitation at higher latitudes implies an average heat gain of ϳ83 W/ m 2 at 45؇N (at present, 23 W/m 2) and of 19 W/m 2 at 75؇N (at present, 4 W/m 2). These estimates of increased poleward heat transfer by H 2 O vapor during the Albian may help to explain the reduced equator-to-pole temperature gradients.
Figure 1. Two overlapping stratigraphic sections were combined in this study of Rose Creek Pit (RCP), Nebraska. Stars represent sample positions for palynological analysis. Arrow points to the D 2 sequence boundary identified by this study in carbon isotopes; cclay, s-silt, fmc-fine, medium, and coarse sand.
The goal of this study was to evaluate methanogen diversity in animal hosts to develop a swine-specific archaeal molecular marker for fecal source tracking in surface waters. Phylogenetic analysis of swine mcrA sequences compared to mcrA sequences from the feces of five animals (cow, deer, sheep, horse, and chicken) and sewage showed four distinct swine clusters, with three swine-specific clades. From this analysis, six sequences were chosen for molecular marker development and initial testing. Only one mcrA sequence (P23-2) showed specificity for swine and therefore was used for environmental testing. PCR primers for the P23-2 clone mcrA sequence were developed and evaluated for swine specificity. The P23-2 primers amplified products in P23-2 plasmid DNA (100%), pig feces (84%), and swine waste lagoon surface water samples (100%) but did not amplify a product in 47 bacterial and archaeal stock cultures and 477 environmental bacterial isolates and sewage and water samples from a bovine waste lagoon and a polluted creek. Amplification was observed in only one sheep sample out of 260 human and nonswine animal fecal samples. Sequencing of PCR products from pig feces demonstrated 100% similarity to pig mcrA sequence from clone P23-2. The minimal amount of DNA required for the detection was 1 pg for P23-2 plasmid, 1 ng for pig feces, 50 ng for swine waste lagoon surface water, 1 ng for sow waste influent, and 10 ng for lagoon sludge samples. Lower detection limits of 10 ؊6 g of wet pig feces in 500 ml of phosphate-buffered saline and 10 ؊4 g of lagoon waste in estuarine water were established for the P23-2 marker. This study was the first to utilize methanogens for the development of a swine-specific fecal contamination marker.
Siderite-bearing pedogenic horizons of the Nanushuk Formation of the North Slope, Alaska, provide a critical high paleolatitude oxygen isotopic proxy record of paleoprecipitation, supplying important empirical data needed for paleoclimatic reconstructions and models of ''greenhouseworld'' precipitation rates. Siderite ␦ 18 O values were determined from four paleosol horizons in the National Petroleum Reserve Alaska (NPR-A) Grandstand # 1 Core, and the values range between ؊17.6‰ and ؊14.3‰ Peedee belemnite (PDB) with standard deviations generally less than 0.6‰ within individual horizons. The ␦ 13 C values are much more variable, ranging from ؊4.6‰ to ؉10.8‰ PDB. A covariant ␦ 18 O versus ␦ 13 C trend in one horizon probably resulted from mixing between modified marine and meteoric phreatic fluids during siderite precipitation.Groundwater values calculated from siderite oxygen isotopic values and paleobotanical temperature estimates range from † ؊23.0‰ to ؊19.5‰ standard mean ocean water (SMOW). Minor element analyses show that the siderites are impure, having enrichments in Ca, Mg, Mn, and Sr. Minor element substitutions and Mg/Fe and Mg/ (Ca ؉ Mg) ratios also suggest the influence of marine fluids upon siderite precipitation.The pedogenic horizons are characterized by gleyed colors, rare root traces, abundant siderite, abundant organic matter, rare clay and silty clay coatings and infillings, some preservation of primary sedimentary stratification, and a lack of ferruginous oxides and mottles. The pedogenic features suggest that these were poorly drained, reducing, hydromorphic soils that developed in coal-bearing delta plain facies and are similar to modern Inceptisols.Model-derived estimates of precipitation rates for the Late Albian of the North Slope, Alaska (485-626 mm/yr), are consistent with precipitation rates necessary to maintain modern peat-forming environments. This information reinforces the mutual consistency between empirical paleotemperature estimates and isotope mass balance models of the hydrologic cycle and can be used in future global circulation modeling (GCM) experiments of ''greenhouseworld'' climates to constrain high latitude precipitation rates in simulations of ancient worlds with decreased equator-to-pole temperature gradients.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.