Black Hills Research Articles

MONITORING WITH A MODIFIED ROBEL POLE ON MEADOWS IN THE CENTRAL BLACK HILLS OF SOUTH DAKOTA

Abstract This study using a modified Robel pole was conducted in the central Black Hills, South Dakota. The objectives were to test the relationship between visual obstruction readings and standing herbage, develop guidelines for monitoring, and estimate sample size. The relationship between visual obstruction and standing herbage was linear with 2 segments in a piecewise model. Regression coefficients were highly significant (P ≤ 0.001). Standard error of the estimate for a single mean was 373 kg · ha−1. Herbage ranged from 89 to 3821 kg · ha−1 with a mean of 1416 kg · ha−1. The average number of visually obstructed bands was 6.4 and ranged from 0.21 to 20.4. Cluster analyses grouped the visual obstruction readings into 3 management categories: short, medium, and tall. A minimum of 3 transects (20 stations per transect) is recommended for monitoring areas ≤259 ha (1 section) to be within 20% of the mean at 80% confidence. The protocol developed to monitor standing herbage is accurate, precise, and easy t...

Sedimentology of the Whiteclay Gravel Beds (Ogallala Group) in northwestern Nebraska, USA: Structurally controlled drainage promoted by Early Miocene uplift of the Black Hills Dome

The newly recognized Whiteclay Gravel Beds (WGB) of the Miocene Ogallala Group crop out as a narrow, discontinuous ribbon of sands and gravels in Dawes and Sheridan Counties, northwestern Nebraska, USA. The WGB are exposed in a series of municipal gravel quarries and natural exposures that define a linear trench in underlying strata at least 20 m deep and up to 300 m wide, with short, southeast-trending reaches separating generally longer east-trending sections. This gravel-filled trench can be recognized from the Nebraska–South Dakota border near Whiteclay, Nebraska southeastward to east of Gordon, Nebraska, a distance of ∼ 30 km. The outcrop belt of the WGB is coincident in location and trend with the Whiteclay Fault Zone. Where exposed in quarries, the walls of the trench are steep-sided, vertical, or locally overhanging. Polished surfaces, slickensides, and parallel joint sets are common in the walls of the trench near Whiteclay, but uncommon in those to the east. The narrow belt defined by this trench is filled by stratified gravel (< 2.0 m, typically < 0.3 m) of sedimentary lithologies derived from various Cenozoic units (but principally Anderson Ranch Formation), and sand. Relatively small amounts of unrounded granitic, volcanic, and quartz gravel are preserved in places. Cross-bedding and clast imbrication indicate palaeoflow towards the east. The WGB are interpreted to have formed in response to tectonic upheaval associated with uplift of the Black Hills of South Dakota in Early Miocene times. Fault rupture topography facilitated formation of a steep-sided canyon, or valley, up to 20 m deep, being virtually straight with sharp bends at intervals of several km. An alluvial channel belt developed in the floor of the valley, filling the available accommodation space with coarse sand and gravel via aggradational stacking of the deposits of successive channels and channel belts. Channel belts were probably braided, with individual channels up to 4 m deep and a few tens of metres wide. The multi-storey character of the deposit indicates multiple episodes of cutting and filling. The coarse grain-size of the fill suggests energetic discharge with frequent bankfull flows, even though the system had a relatively low gradient (0.004). An abundance of reworked fossil debris is derived from several stratigraphic units, clasts of which have been identified in the fill. The presence of a contemporary merychippine horse and a primitive species of the oreodont Brachycrus constrain formation of the WGB to a short interval within the Early Miocene (c. 17.5 Ma). The mammal fauna suggests that this stream was a valuable source of water, while fragments of aquatic organisms such as turtles and fish indicate perennial discharge. The WGB provides a crucial window into a pluvial period in the Miocene that is largely unpreserved elsewhere in the basin, facilitated in part by fault rupture topography.

Black Hills Corporation

AbstractElectricity (MIC: 7.1 SIC: 4911 NAIC: 221121)Black Hills is a diversified energy company operating in two primary operating groups: retail services and wholesale energy. Co.'s retail services include public utility electric operations and public utility electric and gas operations, while its wholesale energy businesses are being operated through its direct and indirect subsidiaries: Wyodak Resources related to coal, Black Hills Exploration and Production related to oil and natural gas production, Enserco Energy related to natural gas marketing and Black Hills Generation and its subsidiaries and Black Hills Wyoming related to independent power activities.

View angle effects on relationships between MISR vegetation indices and leaf area index in a recently burned ponderosa pine forest

While nadir-viewing passive multispectral sensors have limited utility for characterizing the full dimensionality of forest canopies, multi-angle remote sensors such as the Multi-angle Imaging SpectroRadiometer (MISR) may improve detection of canopy architecture, canopy cover, and leaf area index (LAI) of forest canopy versus understory vegetation. Our objective was to determine whether data from the MISR sensor could improve estimates of LAI across a post-fire ponderosa pine forest located in the Black Hills of South Dakota. We measured LAI during the 2002 and 2003 growing seasons and created continuous LAI maps using Landsat TM and ETM+ data (mean R 2 = 0.81). We fit linear regression models of total and canopy LAI, using a series of MISR at-nadir and off-nadir or anisotropic vegetation indices as predictor variables, for each of five sampling periods. We found the best LAI model fits using either a new hotspot-adjusted normalized difference vegetation index, NDVI HS, NDVI calculated from the − 60° view angle, or NDVI at-nadir and either the Hotspot–DarkSpot Index (HDS) or the normalized difference anisotrophic index (NDAX) ( R 2 = 0.56–0.91). However, differences in fits of these best models and those including NDVI at-nadir ranged from only 1 to 8%. Reflectance anisotropy patterns related strongly to understory vegetation phenology. We found that the relationships among NDVI or the enhanced vegetation index (EVI) and canopy or total LAI showed little variation across view angles when the understory vegetation was senesced and significant anisotropy when understory green LAI was greatest. These findings demonstrate the value of multi-temporal measurements during periods of understory phenological change, even if the overstory LAI is relatively stable. We also evaluated the performance of the MISR LAI product and found moderate fits between the MISR LAI and our field- and Landsat-derived canopy LAI ( R 2 = 0.21–0.44).

Predation of late Marjuman (Cambrian) linguliformean brachiopods from the Deadwood Formation of South Dakota, USA

One hundred and twenty-five linguliformean brachiopods of late Marjuman (Cambrian) age with shell perforations, presumably caused by predation, were recovered from shallow-water limestones at two localities of the Deadwood Formation in the Black Hills of South Dakota, USA. Three-quarters of the perforated valves belonged to taxa in the order Acrotretida, while one-quarter of the specimens belonged to those of the order Lingulida. This is the first report of predation of fossil lingulids. In both orders there was a marked selection for valve type. Ninety-five per cent of all perforations of acrotretids were in the ventral valve, while 87% of all perforations of lingulids were in the dorsal valve. The highest rate of predation of collected acrotretids, at any stratigraphic horizon, was 22%, while the rate of predation of collected lingulids, at any given stratigraphic horizon, was as high as 9%. Half of the perforated valves had round holes with a sharp, non-beveled exterior edge, and half had irregularly shaped holes with chipped interior edges. The former type is attributed to either boring or a swift, piercing percussive strike, while the latter is attributed to a smashing percussive strike with a blunt appendage. A third type of perforation consisting of minute, roughly circular holes is thought to be too small to be the work of predators, and is assumed to be the result of an encrusting organism or parasite. The different types of perforation seen in the brachiopod valves indicate that there was more than one type of predator attacking them, including possibly one of the earliest durophages. Various hypothetical predators are suggested as potential candidates for causing the shell perforations. The criteria for their selection as possible linguliformean predators include possessing the ability to produce one of the two types of shell perforation, and being small enough to warrant preying on small (< 2 mm) brachiopods.

Wall friction measurement and compaction characteristics of bentonite powders

This paper presents a new method (referred to as direct method) for measuring wall friction during powder compaction and ejection. The accuracy for wall friction force measurement by both new and conventional methods (referred to as indirect method) were first studied according to the theory of error propagation. The error sources for compact density measurement in both methods were also examined. Based on the accuracy in the measurement of wall friction force and compact density, the direct method is compared favorably to the indirect method. Two bentonites, Black Hills bentonite and Zhi-Hsing bentonite which were considered as the candidate buffer materials for the geological disposal of high-level radioactive wastes were adopted to conduct a series of compaction and ejection tests. The compaction characteristics of bentonite blocks were expressed in terms of compressibility curve, wall friction ratio and friction index. The Gurnham's equation was used to describe the compressibility curve. The effects of the aspect ratio of block on the friction ratio and friction index are discussed from both experimental and theoretical point of views. Ejection profiles of the compacted bentonite blocks during ejection phase were presented. The proposed measuring method is validated by comparing the readings of ejection force recorded by both upper load cell and ring-type load cell.

Tree Diseases, Canopy Structure, and Bird Distributions in Ponderosa Pine Forests

We examined how canopy patterns at the landscape scale can influence bird community composition, abundance, or distribution. Our long-term goal is to determine how diseases and other small-scale disturbances that change canopy patterns influence bird distribution. Little is known about these relationships, partly because most measures of disturbance are based on timber production metrics. We developed a spatially dependent metric referred to as canopy closure roughness, which was significantly correlated to bird diversity on 4 ha sample plots, and used it to generate a spatial model showing the distribution of bird diversity at a resolution of 30 mover an area of 1 million acres (the entire Black Hills National Forest). Number of bird species per stand varied between 2 and 16. Number of species and bird diversity were positively related to intensity of tree cutting. Most common bird species were yellow-rumped warbler, dark-eyed junco, Townsend's solitaire, black-capped chickadee and red-breasted nuthatch. The spatial model of bird diversity showed clusters of high diversity at different locations within the forest. These methods may help lead to better tools for managing the linkages between specific disturbances and bird usage and enable more effective disturbance management by offering a platform for spatial planning.

Fort Randall on the Missouri, 1856-1892

Jerome A. Greene, a research historian with the National Park Service in Denver, has written a comprehensive history of Fort Randall, one of the many Missouri River military forts that served the imperial interests of the United States during its continental expansion era. Greene begins by providing context for the establishment of Fort Randall in 1856 through a brief sketch of U.S. expansion into the Great Plains region from the Lewis and Clark expedition into the 1840s and 1850s. From there, the book develops three concerns: to show how the fort's physical layout and condition changed over time; to provide a social history of the soldiers' lives at the fort; and to illuminate the role of the fort in the U.S. conquest and colonization of the region. Though Fort Randall was usually not at the center of events, it provides a useful vantage point from which to view broader developments in the region. Through a history of the fort, Greene provides perspective on the northern Plains during the Civil War, the gold rush to the Black Hills, the Great Sioux War, the settlement of prairie lands east of the river, and the confinement of the region's Indian people to reservations. Although the fort was “effectually circumscribed as a major force in the unfolding drama of the West” by 1880, Fort Randall received a brief moment of attention when Sitting Bull's people, having returned to the United States from Canada in 1881, were confined there for several months before being transferred upriver to the Standing Rock Agency (p. 124). Greene provides a useful appendix containing a complete list of names of those imprisoned as well as a series of valuable photographs of Sitting Bull's people and their living conditions at Fort Randall. Greene chronicles the post's “last days” after that episode until it closed in 1892 (p. 165).

Using Laser Altimetry-based Segmentation to Refine Automated Tree Identification in Managed Forests of the Black Hills, South Dakota

The success of a local maximum (LM) tree detection algorithm for detecting individual trees from lidar data depends on stand conditions that are often highly variable. A laser height variance and percent canopy cover (PCC) classification is used to segment the landscape by stand condition prior to stem detection. We test the performance of the LM algorithm using canopy height model (CHM) smoothing decisions and crown width estimation for each stand condition ranging from open savannah to multi-strata stands. Results show that CHM smoothing improves stem predictions for low density stands and no CHM smoothing better detects stems in dense even-aged stands, specifically dominant and co-dominant trees (R 2 � 0.61, RMSE � 20.91 stems with smoothing; R 2 � 0.85, RMSE � 46.02 stems with no-smoothing; combined smoothed CHM for low density and unsmoothed CHM for high density stands R 2 � 0.88, RMSE � 28.59 stems). At a threshold of approximately 2,200 stems ha � 1 , stem detection accuracy is no longer obtainable in any

Black Hill Reserve, Kyneton – 11/11/06

Black Hill Reserve, Kyneton – 11/11/06

Red-Headed Woodpecker Nest-Site Selection and Reproduction in Mixed Ponderosa Pine and Aspen Woodland Following Fire

Abstract Abstract Red-headed Woodpecker (Melanerpeserythrocephalus) populationsare declining at a continental scale, yet little isknown about their nest-site selection and reproductionwithin burned forests. We measured reproductiveparameters and nest-site characteristics at 17Red-headed Woodpecker nests and 17 random sitesbetween 2001 and 2004 in the Black Hills, SouthDakota. The average date the first egg was laid was 17June, and the average clutch size was 5.4 ±0.4. The daily nest survival rate averaged 0.98(overall nest success = 47%), and predation was the major cause ofnest failure. Red-headed Woodpecker nests occurredfarther from grassland edges in large diameter snagswithin severely burned quaking aspen(Populustremuloides) stands.High-severity fire within these aspen stands resultedin a combination of snag and understorycharacteristics that differed from the surroundingpine forest matrix. Interactions between cover typeand burn severity may have important ecologicalconsequences for Red-headed Woodpeckers in a mixedconifer forest.

Combining phylogenetic and ecological niche modeling approaches to determine distribution and historical biogeography of Black Hills mountain snails (Oreohelicidae)

ABSTRACTWe aim to show how a combination of molecular systematics and ecological niche modelling approaches can be used to test historical biogeographical hypotheses for species of conservation concern. We focus on the land snail genus Oreohelix (Oreohelicidae), a group found throughout the Rocky Mountains. In addition to its larger distribution, a group of Oreohelix is also found in the Black Hills of Wyoming and South Dakota, an isolated, easternmost extension of the Rocky Mountains. We determine the number, distribution, and relationships of Black Hills Oreohelicids, which are a current conservation concern due to their fragmented distribution. We compared Black Hills groups to those in the main part of the Rockies to test historical biogeographical patterns that explain current diversity. We collected mtDNA data (COI and 12S sequences) from multiple populations of Oreohelix throughout the Black Hills and in adjacent populations in the Rocky Mountains to construct phylogenetic hypotheses. To determine whether favourable environmental conditions currently exist between the Black Hills and the north‐eastern Rocky Mountains, we used DesktopGARP to generate an ecological niche model for distinct lineages discovered in the molecular phylogenetic analysis. Results show that all Black Hills populations are likely Oreohelix cooperi and that little genetic differentiation exists within this clade. In addition, Black Hills groups are genetically similar or identical to populations found in the Judith Mountains and Bighorn Mountains (north‐eastern Rockies). Ecological niche models show that suitable environmental conditions may exist between eastern Rockies and Black Hills O. cooperi samples. Taken together, the phylogenetic and niche model data, along with the low vagility of the snails, support passive long‐distance dispersal as a likely explanation for current arrangement of biodiversity.

Landscape-Scale Attributes of Elk Centers of Activity in the Central Black Hills of South Dakota

Abstract We researched the environmental attributes (n = 28) associated with elk (n = 50) summer range (1 May–30 Sep) in the central Black Hills of South Dakota, USA, during 1998–2001. We defined high-use areas or centers of activity as landscapes underlying large concentrations of elk locations resulting from the shared fidelity of independently moving animals to specific regions on summer range. We divided the study area into 3-km grid cells to represent the distance elk travel in a 24-hour period. We computed mean elevation and slope, proportion and configuration of overstory canopy cover, proportion and configuration of dominant vegetation type, estimated biomass, road density, traffic rate, and amount of habitat not dissected by improved surface roads for each cell. We used a combination of multiple stepwise regression and likelihood ratio tests to develop spatially adjusted models with total number of elk locations per cell as the dependent variable. Environmental attributes varied in their signific...

Fluid-mediated polymetamorphism related to Proterozoic collision of Archean Wyoming and Superior provinces in the Black Hills, South Dakota

Late Archean and Early Proterozoic continental margin pelites, graywackes, and quartzites in today’s Black Hills were regionally metamorphosed during the collision of the Archean Wyoming and Superior provinces beginning at ~1755 Ma. During east-west regional compression, metamorphism reached incipient garnet-biotite grade conditions at ~400 °C. Unzoned garnet (Sps44Alm44Pyr3Grs9) characterizes the mineral assemblage in graphitic metapelites. The low-temperature onset of the garnet-biotite assemblage is attributed to high Mn concentrations and low aH2O due to the presence of CH4 and CO2. During late stages of the collision, the rocks were intruded by the Harney Peak leucogranite (HPG). Vigorous fl uid fl ow, evidenced by abundant quartz veins, metasomatism, and consumption of graphite from metapelites, occurred in the granite aureole. The lowest-grade aureole assemblage includes chlorite that overgrows the early regional foliation and new, clear, almandine rims on garnet. Higher-grade facies include staurolite, then sillimanite, and fi nally second-sillimanite. The prograde mineral assemblages are consistent with calculated pseudosection assemblages for the average metapelite. Beginning with the sillimanite zone, almandine garnet is mostly inclusion-free. Textures suggest that this new garnet grew after dissolution of the old garnet, for which the only remaining evidence are remnant inclusions or coarse quartz-biotite clots. The new garnet grew in response to more elevated temperatures. Garnet compositions projected onto the pseudosection indicate nearly isobaric heating between 3.5–4.5 kbar during prograde metamorphism. Occasional replacements of staurolite by muscovite and biotite are attributed to infi ltration of the rocks by K-bearing magmatic fl uids. Andalusite occurs as euhedral crystals in quartz veins or as late poikiloblasts along foliations planes, where it appears to have grown while Si-rich fl uids passed through the rocks. Typically, it replaces earlier muscovite, suggesting that the fl uids had low aH2O. The andalusite indicates decompression of the still hot, buoyant, fault-bounded block that included the HPG magma, relative to surrounding blocks in the terrane. This decompression contributed to the high-T/low-P conditions that existed in this portion of the thickened orogen and suggests that the various fault-bounded blocks in the Black Hills may have had different P-T histories.

Modeling Postfire Mortality of Ponderosa Pine following a Mixed-Severity Wildfire in the Black Hills: The Role of Tree Morphology and Direct Fire Effects

Abstract We examined the relationship among tree size, crown and stem damage, and 5 years of postfire mortality of ponderosa pine (Pinus ponderosa Dougl. ex. P. &amp; C. Laws.) in the Black Hills following a large, mixed-severity wildfire. We measured tree morphology and direct fire effects on 963 trees and assessed individual tree mortality annually from 2001 to 2005. We used logistic regression to model tree mortality as a function of tree morphology (dbh) and bark thickness (BARK) and direct fire effects [percentage of the live crown scorched (PSCOR) and basal char measured as the percentage of the bole charred below 30 cm (CHAR)]. Models using dbh and BARK were modeled separately due to correlation between the variables. In all models, mortality decreased with increasing dbh and BARK and increased with increasing PSCOR and CHAR. Basal char contributed to the mortality of trees less than 40 cm but became less influential as dbh and BARK increased. Overall, probability of mortality modeled as a function of dbh, PSCOR, and CHAR correctly predicted the status of 78% of trees, whereas the model predicting mortality as a function of BARK, PSCOR, and CHAR had an increase in prediction accuracy of only 1%.

Lithium isotopic systematics of granites and pegmatites from the Black Hills, South Dakota

To study Li isotopic fractionation during granite differentiation and late-stage pegmatite evolution, Li isotopic compositions and concentrations have been measured for the S-type Harney Peak Granite, the spatially associated Tin Mountain pegmatite, and possible metasedimentary source rocks in the Black Hills, South Dakota. The Harney Peak Granite is isotopically heterogeneous, with δ 7 Li varying from –3.1 to +6.6. The δ 7 Li values of Proterozoic metasedimentary rocks that are possible sources of the Harney Peak Granite range from –3.1 to +2.5 and overlap with post-Archean shales and the Harney Peak Granite. For the granite suite, there is no correlation between δ 7 Li and elements indicative of degrees of granite differentiation (SiO2, Li, Rb, etc.). The Li isotopic composition of the Harney Peak Granite, therefore, appears to res ect the source composition. Minerals from the zoned Tin Mountain pegmatite have extremely high Li contents and heavier Li isotopic compositions than the granite or surrounding Black Hills metasedimentary rocks. The heavier compositions may res ect Li isotopic fractionation resulting from extensive crystal-melt fractionation. Lithium concentrations decrease in the order: spodumene (~3.7 wt%), muscovite (0.2 to 2.0 wt%), plagioclase (100–1100 ppm), quartz (30–140 ppm). Plagioclase, muscovite, and spodumene in all zones display a relatively narrow range in δ 7 Li of +7.9 to +11.4. In contrast, quartz is isotopically heavier and more variable (+14.7 to +21.3), with δ 7 Li showing an inverse correlation with Li concentration. This correlation res ects the mixing of isotopically heavy Li in quartz and lighter Li in s uid inclusions, as documented by s uid inclusion compositions (δ

Glittering Dust, Dormant Treasure: Press, Public Memory and Georgia's “Forgotten” Gold Rush

This article examines nineteenth-century local, regional and national newspaper coverage of the first major American gold rush, which began in 1828 when as many as 20,000 people headed to the hills of northern Georgia to seek their fortunes. So much gold was discovered that a United States Mint was established in Dahlonega, Georgia, a town named for the Cherokee word for gold. The mint produced more than $100,000 during its first year, and more than one-and-a-half million coins by the time it closed in 1861. Accounts of this gold rush are “as fascinating as any fiction,” yet unlike the storied gold stampedes in California, Colorado, Alaska and the Black Hills, the Georgia rush has been lost to American collective memory. The purpose of this article is to seek to understand why. Despite boosterism and increasing nostalgia in coverage, the story was overshadowed by the Civil War, the exploitation of the Cherokee, the hardships of Reconstruction and the sensationalized gold rushes in the American West.

CLIMATE EFFECTS ON FIRE REGIMES AND TREE RECRUITMENT IN BLACK HILLS PONDEROSA PINE FORESTS

Climate influences forest structure through effects on both species demography (recruitment and mortality) and disturbance regimes. Here, I compare multi-century chronologies of regional fire years and tree recruitment from ponderosa pine forests in the Black Hills of southwestern South Dakota and northeastern Wyoming to reconstructions of precipitation and global circulation indices. Regional fire years were affected by droughts and variations in both Pacific and Atlantic sea surface temperatures. Fires were synchronous with La Niñas, cool phases of the Pacific Decadal Oscillation (PDO), and warm phases of the Atlantic Multidecadal Oscillation (AMO). These quasi-periodic circulation features are associated with drought conditions over much of the western United States. The opposite pattern (El Niño, warm PDO, cool AMO) was associated with fewer fires than expected. Regional tree recruitment largely occurred during wet periods in precipitation reconstructions, with the most abundant recruitment coeval with an extended pluvial from the late 1700s to early 1800s. Widespread even-aged cohorts likely were not the result of large crown fires causing overstory mortality, but rather were caused by optimal climate conditions that contributed to synchronous regional recruitment and longer intervals between surface fires. Synchronous recruitment driven by climate is an example of the Moran effect. The presence of abundant fire-scarred trees in multi-aged stands supports a prevailing historical model for ponderosa pine forests in which recurrent surface fires affected heterogenous forest structure, although the Black Hills apparently had a greater range of fire behavior and resulting forest structure over multi-decadal time scales than ponderosa pine forests of the Southwest that burned more often.

Re-evaluation of the Albian–Cenomanian boundary in the U.S. Western Interior based on dinoflagellate cysts

The position of the Albian–Cenomanian boundary in the U.S. Western Interior Basin has been the subject of debate because the ammonites and foraminifers that define the boundary are endemic. Traditionally, the boundary, as defined in Europe by planktonic foraminifers and ammonites, is correlated with the last occurrence of the ammonite genus, Neogastroplites [Reeside, J.B., Cobban, W.A., 1960. Studies of the Mowry Shale (Cretaceous) and contemporary formations in the United States and Canada. U.S. Geological Survey Professional Paper 355, 126 pp]. More recently, the boundary was correlated with the first occurrence of Metengonoceras teigenensis [Cobban, W.A., 1951. Colorado shale of central and northwestern Montana and equivalent rocks of Black Hills. American Association of Petroleum Geologists Bulletin 35, 2170–2198]. These ammonites are associated with bentonites, the ages of which have been extrapolated to the type region of France to date the base of the Cenomanian from the Western Interior Basin. However, since cosmopolitan dinoflagellates are common to this region and the European reference sections where the boundary is defined, they can be used to reevaluate the position of the Albian–Cenomanian boundary in the Western Interior Basin. In our study, 224 samples from 29 outcrop sections in Montana, Wyoming, Colorado, Oklahoma and New Mexico were analyzed for dinoflagellate cysts, as well as other palynomorphs, foraminifers, bivalves and ammonites; these fossils were used for graphic correlation. The recovery and preservation of the dinoflagellate cysts varied from poor to good, and diversity varied from low to moderate. Typical Late Albian to Early Cenomanian taxa, including Ovoidinium verrucosum, Ovoidinium scabrosum and Palaeohystrichophora infusorioides, dominate the assemblages; however, dinoflagellate ranges in the five sections in which the neogastroplitid zones are defined (Arrow Creek, Ayers Ranch, Belt Butte, Geyser, Teigen) suggest correlation with the uppermost Albian. Dinoflagellate ranges were confirmed in additional Montana, Wyoming and northern Colorado sections by a few diagnostic taxa ( Aptea polymorpha, Apteodinium grande, Batioladinium jaegeri, Luxadinium propatulum, Chichaouadinium vestitum), and they were graphically correlated with published European ranges. The result is that the Albian–Cenomanian boundary correlates with the 97 million year old Clay Spur Bentonite.

Taxonomy and origin of present-day morphometric variation inPicea glauca(×engelmannii) seed-cone scales in North America

White spruce ( Picea glauca (Moench) Voss) and Engelmann spruce ( Picea engelmannii Parry ex Engelm.) seed-cones from 676 sites in Canada and the northern United States were analyzed to determine the degree and spatial extent of interspecific hybridization. Fifteen cone-scale variables were analyzed, with percent free-scale and scale shape considered best for differentiating these taxa. The results show that putative Engelmann spruce and their hybrids occur mostly in the vicinity of the Rocky Mountains. Putative white spruce occurs across Canada east of the Rocky Mountains, whereas white × Engelmann hybrids occur eastward to Manitoba and northward to 68° latitude in northwest Canada. To explain the occurrence of the latter taxon hundreds of kilometres from an Engelmann spruce pollen source, it is hypothesized that palaeohybridization occurred during the Wisconsinan glacial period, probably in the southern Montana – Wyoming – Black Hills (South Dakota) region, with the resulting hybrids spreading north and northeastward into interior Canada following the retreat of the Laurentide glacier. White and Engelmann spruce have morphologically distinct cone-scales, whereas their hybrids have intermediate characteristics. An emended species ( Picea albertiana ) and two subspecies (P. albertiana subsp. albertiana and P. albertiana subsp. ogilviei) are proposed to account for morphological intermediates between the parent species.