Taphonomy of a Petrified Forest in the Two Medicine Formation (Campanian), Northwest Montana: Implications for Palinspastic Restoration of the Boulder Batholith and Elkhorn Mountains Volcanics

Roberts, Eric M.; Hendrix, Marc S.

doi:10.1669/0883-1351(2000)015<0476:toapfi>2.0.co;2

Cited by 23 publications

(8 citation statements)

References 25 publications

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“…The presence of such soil forming features as slickensides, colour mottling and banding, minor Fe-oxide staining, small CaCO 3 concretions, and the common presence of bioturbation and root traces all diagnose these deposits as weakly developed paleosols, fitting the classification of 'protosols' (Brown and Kraus, 1987;Retallack, 1997). FA3 units with distinct haystack and popcorn weathering features are interpreted as swelling bentonitic mudstones that imply the presence of devitrified volcanic ashes (Roberts and Hendrix, 2000). However, several of these units were collected and separated to obtain volcanic phenocrysts for radioisotopic dating.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Investigating the stratigraphy and palaeoenvironments for a suite of newly discovered mid-Cretaceous vertebrate fossil-localities in the Winton Formation, Queensland, Australia

Tucker

Roberts

Darlington

et al. 2017

Sedimentary Geology

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Please cite this article as: Tucker, Ryan T., Roberts, Eric M., Darlington, Vikie, Salisbury, Steven W., Investigating the stratigraphy and palaeoenvironments for a suite of newly discovered mid-Cretaceous vertebrate fossil-localities in the Winton Formation, Queensland, Australia, Sedimentary Geology (2017), doi:10.1016/j.sedgeo.2017 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT

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Section: Accepted M Manuscriptmentioning

confidence: 99%

Investigating the stratigraphy and palaeoenvironments for a suite of newly discovered mid-Cretaceous vertebrate fossil-localities in the Winton Formation, Queensland, Australia

Tucker

Roberts

Darlington

et al. 2017

Sedimentary Geology

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“…1; Gill and Cobban 1973;Rogers 1998;Rogers et al 1993). This 600-m-thick, nonmarine sequence consists of sediment derived from erosion of the Cordilleran fold and thrust belt and volcaniclastic materials from the Elkhorn Mountains volcanic center (Mudge 1970;Gill and Cobban 1973;Lorenz and Gavin 1984;Rogers et al 1993;Lageson et al 2001;Roberts and Hendrix 2000). Lithologies comprising the Two Medicine Formation include primarily lenticular meandering and anastomosed fluvial channel sandstone beds with associated floodplain mudstone successions (Lorenz and Gavin 1984;Lorenz 1981).…”

Section: Geologic Settingmentioning

confidence: 99%

A Theropod Nesting Trace With Eggs From the Upper Cretaceous (Campanian) Two Medicine Formation of Montana

Jackson

Schaff²,

Varricchio

et al. 2015

PALAIOS

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A nesting trace preserved in alluvial floodplain deposits in the Upper Cretaceous Two Medicine Formation at the Willow Creek anticline in north-central Montana contains four crushed theropod eggs referable to the oospecies Continuoolithus canadensis. These eggs immediately overlie the lower surface of a 35-cm-long 3 7cm-thick, dark-green mudstone lens, surrounded by reddish-purple mudstone. The long axes of three eggs are parallel to one another and to the lower boundary of the lens, whereas the fourth egg lies at a 30u angle to the others. A thin, 1-cm-thick organic horizon overlies the eggs, suggesting they were buried with some vegetation. Geometric modeling of the slightly asymmetrical C. canadensis eggs yields a volume and mass of approximately 194 cm 3 and 205 g for each egg. This method provides a more accurate estimation for the surface area than allometric equations that are based on modern bird eggs because of the elongate shape of many non-avian theropod eggs. Pore density and water vapor conductance (G H2O) calculated from one egg in the trace and five additional C. canadensis eggs from the Willow Creek anticline vary across three regions. High, moderate, and very low G H2O characterize the equatorial zone, blunt, and tapering poles, respectively. The average G H2O for all eggs exceeds that of an avian egg of similar mass by 3.93, thus supporting sedimentologic evidence of substrate burial during incubation.

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“…Available Pb isotopic data from approximately KPB‐aged igneous sources are plotted in Figure . Some previous workers have suggested that they can be traced to the Elkhorn Mountains volcanics [ Cherven and Jacob , ], but these rocks are probably too old, as geological constraints make them older than the (largely) 80–74 Ma Boulder Batholith [ Tilling et al ., ; Rutland et al ., ; Thomas et al ., ; Rogers et al ., ; Roberts and Hendrix , ; Lund et al ., ]. Other plausible sources include the poorly dated Judith Mountains volcanics [ Zhang and Spry , ] and more distally, any volcanism associated with the latest stages of the Boulder Batholith [ Lund et al ., ] or the earliest stages of the Bitterroot lobe of the Idaho Batholith [ Gaschnig et al ., , 2012], which temporally straddles the KPB.…”

Section: Resultsmentioning

confidence: 99%

Chemical and Pb isotope composition of phenocrysts from bentonites constrains the chronostratigraphy around the Cretaceous‐Paleogene boundary in the Hell Creek region, Montana

Ickert

Mulcahy

Sprain

et al. 2015

Geochem Geophys Geosyst

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An excellent record of environmental and paleobiological change around the CretaceousPaleogene boundary is preserved in the Hell Creek and Fort Union Formations in the western Williston Basin of northeastern Montana. These records are present in fluvial deposits whose lateral discontinuity hampers long-distance correlation. Geochronology has been focused on bentonite beds that are often present in lignites. To better identify unique bentonites for correlation across the region, the chemical and Pb isotopic composition of feldspar and titanite has been measured on 46 samples. Many of these samples have been dated by 40 Ar/ 39 Ar. The combination of chemical and isotopic compositions of phenocrysts has enabled the identification of several unique bentonite beds. In particular, three horizons located at and above the Cretaceous-Paleogene boundary can now be traced-based on their unique compositions-across the region, clarifying previously ambiguous stratigraphic relationships. Other bentonites show unusual features, such as Pb isotope variations consistent with magma mixing or assimilation, that will make them easy to recognize in future studies. This technique is limited in some cases by more than one bentonite having compositions that cannot be distinguished, or bentonites with abundant xenocrysts. The Pb isotopes are consistent with a derivation from the Bitterroot Batholith, whose age range overlaps that of the tephra. These data provide an improved stratigraphic framework for the Hell Creek region and provide a basis for more focused tephrostratigraphic work, and more generally demonstrate that the combination of mineral chemistry and Pb isotope compositions is an effective technique for tephra correlation.

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Taphonomy of a Petrified Forest in the Two Medicine Formation (Campanian), Northwest Montana: Implications for Palinspastic Restoration of the Boulder Batholith and Elkhorn Mountains Volcanics

Cited by 23 publications

References 25 publications

Investigating the stratigraphy and palaeoenvironments for a suite of newly discovered mid-Cretaceous vertebrate fossil-localities in the Winton Formation, Queensland, Australia

Investigating the stratigraphy and palaeoenvironments for a suite of newly discovered mid-Cretaceous vertebrate fossil-localities in the Winton Formation, Queensland, Australia

A Theropod Nesting Trace With Eggs From the Upper Cretaceous (Campanian) Two Medicine Formation of Montana

Chemical and Pb isotope composition of phenocrysts from bentonites constrains the chronostratigraphy around the Cretaceous‐Paleogene boundary in the Hell Creek region, Montana

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