No abstract

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.

The MD 80-08 coal exploration core from the Albian Boulder Creek Formation of northeastern British Columbia contains 90 m of alluvial strata that underwent extensive pedogenic modification. Gleyed colors, pedogenic slickensides, clay coatings, mottling, sphaerosiderite, and sedimentary pyrite characterize the paleosols. The isotopic compositions of 30 sphaerosiderite-bearing horizons commonly show trends of invariant ␦ 18 O and variable ␦ 13 C values. Equal-area plots of ␦ 18 O vs. ␦ 13 C were used to construct meteoric sphaerosiderite lines (MSLs). The MSLs indicate that meteoric groundwater compositions ranged from approximately Ϫ11‰ to Ϫ16‰ (SMOW). The sphaerosiderite ␦ 18 O values indicate formation in shallow groundwaters predominantly recharged by local precipitation. The sphaerosiderite isotopic compositions are a proxy record of mid-Cretaceous precipitation, and are useful for quantifying changes in the hydrologic cycle during humid ''greenhouse'' periods. Micromorphology of a 1.15 meter interval (69.75-68.6 m), with a ؉1.31‰ increase in the average ␦ 18 O values, records a polygenetic history of paleosol development. The pedocomplex has a four-stage developmental history characterized by: (1) an initial well-drained phase, with wet-dry cycles and relatively low baselevel; (2) erosion, baselevel rise and coarser-grained sedimentation; (3) saturated, reducing soil conditions, high baselevel, with some marine influence on pedogenesis; and (4) meteoric-water-dominated hydromorphic soil conditions, high baselevel, and sphaerosiderite precipitation. The ␦ 18 O excursion recorded through this interval reflects minor mixing of marine and meteoric groundwaters. The modal abundance of pyrite, and increased Mg/(Ca ؉ Mg) and Mg/Fe cation ratios in the sphaerosiderites further substantiate marine influence on pedogenesis. The alluvial section of the Boulder Creek Formation is aggradational, and several changes in baselevel recorded in the paleosols are interpreted to have been driven by minor (parasequence-scale) changes in relative sea level.

Meteoric sphaerosiderite lines (MSLs), defined by invariant δ18O and variable δ13C values, are obtained from ancient wetland palaeosol sphaerosiderites (millimetre‐scale FeCO3 nodules), and are a stable isotope proxy record of terrestrial meteoric isotopic compositions. The palaeoclimatic utility of sphaerosiderite has been well tested; however, diagenetically altered horizons that do not yield simple MSLs have been encountered. Well‐preserved sphaerosiderites typically exhibit smooth exteriors, spherulitic crystalline microstructures and relatively pure (> 95 mol% FeCO3) compositions. Diagenetically altered sphaerosiderites typically exhibit corroded margins, replacement textures and increased crystal lattice substitution of Ca2+, Mg2+ and Mn2+ for Fe2+. Examples of diagenetically altered Cretaceous sphaerosiderite‐bearing palaeosols from the Dakota Formation (Kansas), the Swan River Formation (Saskatchewan) and the Success S2 Formation (Saskatchewan) were examined in this study to determine the extent to which original, early diagenetic δ18O and δ13C values are preserved. All three units contain poikilotopic calcite cements with significantly different δ18O and δ13C values from the co‐occurring sphaerosiderites. The complete isolation of all carbonate phases is necessary to ensure that inadvertent physical mixing does not affect the isotopic analyses. The Dakota and Swan River samples ultimately yield distinct MSLs for the sphaerosiderites, and MCLs (meteoric calcite lines) for the calcite cements. The Success S2 sample yields a covariant δ18O vs. δ13C trend resulting from precipitation in pore fluids that were mixtures between meteoric and modified marine phreatic waters. The calcite cements in the Success S2 Formation yield meteoric δ18O and δ13C values. A stable isotope mass balance model was used to produce hyperbolic fluid mixing trends between meteoric and modified marine end‐member compositions. Modelled hyperbolic fluid mixing curves for the Success S2 Formation suggest precipitation from fluids that were < 25% sea water.

No abstract