central montana
Recently Published Documents

Estimates of dead and down woody material (DWM) biomass are important for nutrient cycling, wildlife habitat assessment, fire effects and climate change science. Most methods used to sample woody material initially assess volume then estimates of wood density are used to convert volume to biomass. To assess initial wood density and decomposition rate, this study examined in situ wood density of lodgepole pine logs at the Tenderfoot Creek Experimental Forest (TCEF), central Montana, United States, 1, 11, and 22 years after felling. Mean wood density decreased from 0.39 to 0.27 g cm–3 over 22 years and the single exponential decay rate was k = 0.012 yr–1 1 and 11-years post-felling and 0.022 yr–1 11 and 22 years post-felling. A common 5-category decay classification system was evaluated for estimating wood density by decay class, which identified significant difference in three of four observed classes.

Abstract Few bryozoans have been described from the Cretaceous Western Interior Seaway (WIS), which is consistent with the low diversity of other typically stenohaline groups in this large expanse of relatively shallow marine water. Here we describe a new cheilostome bryozoan, Conopeum flumineum n. sp., based on well-preserved material from the Campanian Judith River Formation of the Upper Missouri River Breaks National Monument in north-central Montana. The new species shows strong morphological similarities with Conopeum seurati, a Recent species that is often categorized as brackish, but which is euryhaline and can also be found in marine and stenohaline environments. The new Campanian bryozoan species was found in a locality also containing fragmentary remains of dinosaurs and other terrestrial vertebrates, as well freshwater mollusks and terrestrial plant debris. The sedimentology and facies associations of the fossil-bearing site suggest that the depositional setting was a swamp or tidally influenced fluvial backwater on the Judith River coastal plain. The proximity of the site to the western shoreline of the WIS presumably made it susceptible to occasional marine flooding during storms or extreme tides. Previous occurrences of Conopeum in the Cretaceous of the Western Interior have also been associated with dinosaur remains, corroborating the very nearshore and at times even ‘upstream’ distribution of this euryhaline genus. UUID: http://zoobank.org/bb1fdc8a-5017-44c5-9251-9e24ef3995e3.

The following is a correction for Lesica (2019) J. Bot. Res. Inst. Texas 13(1):1–6. For Page 4, Figure 2 the captions are reversed and should be as follows.Top: M. glaucescens, Lewis & Clark Co., Montana. Bottom: Musineon vaginatum, Missoula Co., Montana.

Abstract In the Big Snowy Mountains of central Montana, USA, late Visean to Bashkirian strata preserve a nearly complete, but poorly documented, paleotropical stratigraphic succession that straddles the range of current estimates of the onset of the Late Paleozoic Ice Age (LPIA). Sedimentologic and stratigraphic investigation of the Otter (late Visean to Serpukhovian) and Heath (Serpukhovian) formations, with secondary focus on the overlying Tyler (late Serpukhovian to Bashkirian) and Alaska Bench (Bashkirian) formations, facilitated an appraisal of paleotropical environmental change preserved in this succession. Three facies associations reminiscent of environments currently forming in Shark Bay, Australia, were identified in the Otter Formation: shallow semi-restricted littoral platform, intertidal platform, and supratidal plain. Five facies associations broadly comparable to modern environments present in the Sunda Shelf and southern coast of the Persian Gulf were identified in the Heath Formation: offshore outer ramp, mid- to outer ramp, inner ramp, coastal plain, and sabkha. Facies associations preserved in the Heath Formation are here explained in the context of a protected, homoclinal carbonate ramp situated in a partially silled epicontinental embayment. A shift from low-magnitude relative sea-level oscillations preserved in the Otter Formation to a cyclothemic stratigraphic pattern entailing ≥ 6 fourth-order, high-frequency and high-magnitude relative sea-level fluctuations in the Heath Formation is here interpreted to record the main eustatic signal of the LPIA in central Montana. Current published biostratigraphic constraints for the observed stratigraphy estimate the main eustatic signal of the LPIA to have occurred approximately between 331 (base Serpukhovian) and 327 Ma in central Montana. A distinct upward transition from coal and paleosol-bearing depositional sequences in the lower Heath to evaporite and limestone-bearing depositional sequences in the upper Heath preserves a broad humid to arid paleoclimate shift during deposition of this unit, which influenced hydrographic circulation patterns and the resultant distribution of anoxic environments in the Big Snowy Trough during this time interval. Improved depositional and sequence stratigraphic models of the Heath Formation proposed in this study permit new insight into the theoretical distribution of, and water depth necessary to preserve, black, organic-rich claystone and shale in partially silled intracratonic basins, in addition to new temporal constraints on LPIA onset in paleotropical western Laurentia.