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WHITEHALL GEOGROUP, INC. Whitehall GeoGroup, Inc. utilizes an integrated approach to earth science in a diversity of projects including minerals remoteness work, geological review of properties, geologic mapping, hydrostratigraphy, oil and gas exploration, reservoir characterization, and minerals evaluation. Our continued efforts in research of continental sedimentation/ stratigraphic analysis have enabled WGI to provide cutting-edge expertise in these areas. NEW PUBLICATIONS:
ABSTRACT—Aelurodon montanensis, sp. nov. (Carnivora, Canidae, Borophaginae), is described from a new locality, Aelurodon Cut, near Pipestone Springs in Jefferson County, Montana. The new species is a primitive representative of the previously recognized Aelurodon mcgrewi–A. stirtoni clade, one of the most hypercarnivorous, relatively rare clades in the subfamily Borophaginae. It shares with this clade such derived characters as a broadened posterior cingulum of p3, initial development of a posteriorly expanded M1 internal cingulum, and similarities in dental proportions. Evolutionary trends within this clade include reduction in size, increasingly hypercarnivorous dentition with lengthened shearing blades on the upper and lower carnassials, a more trenchant talonid on m1, a reduced grinding part of upper and lower molars, and a posteriorly expanded M1 internal cingulum. Based on the stage of evolution of the new canid and on an associated metapodial fragment of Aepycamelus, we tentatively assign an early Barstovian age to the Aelurodon Cut locality.
ABSTRACT - Five regional Cenozoic unconformity-bounded sequences in southwestern Montana correlate with five regional Cenozoic unconformity-bounded sequences in central Washington. The strata in both areas are continental. The bounding unconformities are variously marked by extensive paleosol formation, irregular topography developed on erosional surfaces, and/or angular discordance of strata. Sequence identification in southwestern Montana is based largely on paleosols, biostratigraphy, and seismic reflection data. In central Washington, changes in lithology and provenance have been important for sequence identification. The correlation of the five sequences highlights the similarity in the Cenozoic stratigraphic record throughout the northwestern United States. Specifically, interregional unconformities occur at about 55 Ma, 37 Ma, 30 Ma, 20 Ma, and 4 Ma. Minor differences in the ages of the bounding unconformities in southwestern Montana and in central Washington may be due to differences in the timing of geologic events or to insufficient data. The major lithologic difference is that in the approximately 17 to 4 Ma sequence, the Columbia River Basalt dominates the Washington sequence whereas clastic strata, numerous tuffs, and only minor basalt, occur in southwestern Montana. The application of sequence stratigraphy allows the correlation of geographically separate strata, some of which even may have had different source areas. The Cenozoic sequences of southwestern Montana and central Washington extend into the rest of the Pacific Northwest, the Great Plains, and much of the Cordillera. The wide extent of these sequences will elucidate interregional Cenozoic history.
Volume will be published during 1/2007 (pdf is now available from - hanneman@jeffersonvalley.net):
ABSTRACT -Calcic pedocomplexes are associated with regional unconformities in the Great Plains and western USA that have approximate ages of 30 Ma, 20 Ma, and 4 Ma. In southwestern Montana, the calcic pedocomplexes are readily identifiable on the surface with a pedocomplex typically containing several partial soil profiles. In the most complete scenario, an individual profile may contain an argillic or argillic/calcareous (Bt or Btk) horizon, a K horizon, and a C horizon. Often, however, the Bt(k) horizon is truncated or can be entirely absent from an individual profile. The K horizon contains an upper laminated zone that is underlain by an indurated carbonate sheet. Carbonate nodules and chalky micritic matrix material underlie the sheet carbonate. The calcic paleosols display carbonate morphology ranging from Stage IV to Stage VI. The calcic pedocomplexes also possess distinct physical properties that aid in subsurface identification. The combined density and velocity differences between paleosols and non-pedogenic strata result in bright reflections on seismic sections and distinct well log signatures. Although the calcic pedocomplexes /regional unconformity associations were first described within Tertiary strata of southwestern Montana, the same associations exist in numerous localities in the Great Plains and in other parts of the western USA. The extensive occurrence of the calcic paleosols/regional unconformity associations throughout this large area underscores their utility as a regional correlation tool. Moreover, the delineation of regional unconformities that are large-scale sequence boundaries by pedocomplexes has broad implications for continental sequence stratigraphy.
Adobe Acrobat pdf files of the Aelurodon and the 2003 SEPM papers are available upon request from: earthmaps@earthmaps.com
ABSTRACT FOR AAPG/SEPM ANNUAL MEETING (CALGARY, ALTA., CANADA, JUNE, 2005): Calcic
Paleosols - Regional Sequence Boundary Indicators in Cenozoic Strata of
Southwestern Montana
Calcic paleosols delineate regional sequence boundaries in Cenozoic strata of southwestern Montana. The bounding surfaces are recognized by the existence of stacks of calcic paleosols that exhibit advanced stages of carbonate morphology. Because of the nature of soil formation, calcic paleosol stacks may not exist as continuous features over all paleolandscapes. Consequently, laterally equivalent sequence boundaries may also be identified by erosional features, angular stratal relationships, and abrupt changes in provenance or lithologies. The paleosol stacks appear within the subsurface as several relatively thin, high velocity/high density zones. Zone thickness ranges from 1 to 1.5 m; zones are stacked to thicknesses of up to 15 m. Density varies within the zones by as much as 0.6 g/cm3, and differs by as much as 0.9 g/cm3 from material immediately above these zones. Velocity differs by as much as 10 ft/ms from the overlying material. The combined density and velocity differences between paleosols and sediments result in bright reflections on seismic sections. The use of a sequence stratigraphy with calcic paleosols as boundary indicators is a valuable explorationist tool for the deeper Cenozoic basins of southwestern Montana. Prior interpretations for these basins were based upon the assumption that only two units were present in the Cenozoic basin-fill, and that pre-Cenozoic rocks were the cause of reflections beneath these units. The application of a sequence stratigraphy for these basins reconciles basin-fill thicknesses interpreted from regional gravity surveys and seismic data collected from the deeper basins.
Areas of Expertise
Rocker-Ramsey area - WGI has recently completed a geologic map of the Rocker - Ramsey area, southwestern Montana. This map is available at the 1:100,000 scale (metric topographic), and covers part of the upper Clark Fork Superfund area. Sage Creek - Upper Ruby - Blacktail Valleys, Montana - WGI has completed a geologic map of the Sage Creek - Upper Ruby - Blacktail valleys, southwestern Montana. This map is available at the 1:100,000 scale (metric topographic). A report accompanies this map; the report includes unpublished age dates (radiometric/vertebrate land mammal ages) and lithologic descriptions of the Cenozoic strata.
Contact Information:Telephone: 406-287-5408 Mailing Address: 107 Whitetail Road, Whitehall, MT 59759
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