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Fluvial strata of the Tornillo Group preserve a succession of Late Cretaceous, Paleocene, and early Eocene continental faunas and floras and provide a record of the Laramide orogeny in the southern part of the North American Cordillera. Contacts between units in the Tornillo Group (Javelina, Black Peaks, and Hannold Hill formations) have proven difficult to identify, but minor adjustments to the stratigraphy allow each to be readily mapped and provide a means to assess intraformational thickness variation and syndepositional deformation within the Tornillo Basin. The Javelina Formation is thin in the southwestern part of the basin, and the Black Peaks Formation thins toward both southwestern and northeastern sides, suggesting that development of the monoclines that bound the basin began in latest Cretaceous through Paleocene time. An obscure structure extending southeastward from Grapevine anticline divides the basin into northeastern and southwestern segments. The Javelina Formation thins southwest of this structure and lacks lacustrine facies found to the northeast. The upper half of the Black Peaks Formation is absent southwest of this line, and northeast-facing monoclinal folds that affect the Hannold Hill Formation in the same vicinity are truncated at the base of the overlying Canoe Formation. Depositional limits of the Hannold Hill Formation probably did not extend to the southwest. The middle Eocene Canoe Formation is largely unaffected by contractive deformation that affects the Tornillo Group. Although incipient Laramide-age deformation broadly defined the Tornillo Basin during latest Cretaceous through Paleocene time, deformation here occurred mostly during the early Eocene.

Depositional cycles in fluvial successions are described here as chronostratigraphic packages of strata founded on a laterally extensive, scour-based, amalgamated channel-sand body, overlain by mudrocks, isolated channel fills, avulsion and splay complexes, and paleosols. Ten packages are described from the lower Horseshoe Canyon Formation (Campanian-Maastrichtian), one of a succession of clastic wedges filling the Alberta foreland basin in south-central Alberta. The structure of these packages is consistent with the fall-rise-fall cycle of base-level described in other studies, but the package-bounding scours and internal surfaces are discontinuous and difficult to trace in the mudrock-dominated strata. Terrestrial vertebrate fossils are preserved in relatively fossiliferous, facies-independent horizons 1 to 3 m thick that statistically correlate with the stratigraphic position of package scours and surfaces. Fossiliferous horizons formed as a result of attritional accumulation under an optimum, relatively low, regional deposition rate. Not only do these horizons aid in locating package surfaces, but they also provide insight to the interaction of the packagescale, base-level oscillation with the larger-scale fluctuation in accommodation associated with the formation of the clastic wedge. As such, fossiliferous horizons in the Horseshoe Canyon Formation make better boundary markers than do paleosols, splays, coal seams, or even the surfaces associated with package structure. Therefore, the vertebrate fossil record may supply a means of stratigraphically evaluating sections in other locations in which typical sedimentological and architectural cues for surfaces are absent.

Although previous work has demonstrated that biological phosphates ('biophosphates') record significant changes in delta18O associated with variations in local climate and seasonality, the repeatability of these analyses between laboratories has not previously been tested. We serially sampled enamel on four Cretaceous dinosaur teeth for phosphate delta18O analysis at up to three different facilities. With the exception of one set of unprocessed enamel samples, the material supplied to each laboratory was chemically processed to silver phosphate. Each laboratory analyzed sample sets by pyrolysis (thermochemical decomposition) in a ThermoFinnigan TC/EA attached to a ThermoFinnigan Delta Plus mass spectrometer. Significant interference between phosphate samples and the NIST reference material 8557 barium sulfate (NBS 127) distorts some of the results. Samples analyzed immediately following NBS 127 may be depleted by 6 per thousand isotopically and in instrument peak amplitude response by 80%. Substantial interference can persist over the subsequent 20 silver phosphate samples, and can influence the instrument peak amplitude response from some organic standards. Experiments using reagent-grade silver phosphate link these effects to divalent cations, particularly Ca2+ and Ba2+, which linger in the reactor and scavenge oxygen evolved from pyrolysis of subsequent samples. Unprocessed enamel includes 40 wt% calcium and self-scavenges oxygen, disrupting the isotopic measurements for the first half of a set and depleting subsequent organic standards by up to 9 per thousand. In sets without NBS 127 or calcium, such interference did not occur and an interlaboratory comparison of results from enamel shows reproducible, significantly correlated peaked delta18O patterns with a 2-3 per thousand dynamic range, consistent with previous results from contemporaneous teeth. Whereas both unprocessed enamel and the NBS 127 barium sulfate should be applied to biological phosphate ('biophosphate') stable isotope research with caution, seasonal variations in enamel phosphate delta18O are a paleoecologically valuable, reproducible phenomenon in theropod dinosaur teeth.