Report for the Cheyenne River Range Allotment Management Plan Environmental Analysis

Report for the Cheyenne River Range Allotment Management Plan Environmental Analysis Effects on Paleontological Resources November 18, 2015 Barbara A. Beasley Nebraska National Forests and Grasslands Supervisor’s Office 125 N. Main Street Chadron, NE 69337 (308) 432-0333 Introduction This report discloses the effects of proposed activities to paleontological (fossil) resources within the boundaries of the Cheyenne River Range Allotment Management Plan. The spatial boundary used to evaluate direct and indirect consequences was the plan boundary, since no paleontological resources outside of this area will be affected by proposed project activities. Information and data collected per Special Use Permit reports and paleontological resource inventory survey Passport in Time Project in July 2014 was used to determine the extent of the richness of paleontological resources within in the Cheyenne River Range Allotment Management Plan project area (CRPAMP). Paleontological resources differ from other resources as the fossils are preserved throughout the geological unit in which they are preserved. All geological units in this project area are very fossiliferous. The Paleontology PIT findings reinforced the richness of the fossil resources within the Indian Creek area. The No Action Alternative (Alternative 1) proposes that no management activities take place within the project area. The Action Alternatives (Alternatives 2 and 3) propose various activities in the pastures noted in the Cheyenne River Range Allotment Management Plan. With respect to this project, the alternatives are very similar in the activities proposed. The action alternatives only differ in the placement and construction of several as yet unidentified range improvements. The Determination of Effects presented in this report takes into consideration the effect of the activities proposed in all action alternatives on the paleontological resources. Affected Environment/Existing Condition In order to address paleontological resources the geologic units are discussed as well. The geologic units are listed stratigraphically (oldest to youngest). The northern portion of the project area is underlain by Late Cretaceous Pierre Shale; this unit is marine and ranges in age from 95 to 65 million years ago (mya). This formation is the remainder of the Western Interior Seaway that extended from present Canada to the Gulf of Mexico. There is a hiatus of deposition, while the Black Hills are forced upwards, draining the Western Interior Seaway. Moving south in the project area toward the Badlands National Park north boundary, the Tertiary Chadron Formation forms grayish-green haystack- shaped mounds. This formation is terrestrial (48 to 36 mya) preserving a humid subtropical environment. Located at the very south end of the project, are the Tertiary Brule and Sharps formations (36 to 26 mya). The Brule and Sharps formations form the steep sloped spires seen near Sheep Mountain Table and southern boundary of the CR RAMP. These formations preserve the continuing drying climate and change in biota to accommodate the changing environment. Figure 1. Looking South from the entrance of Indian Creek Proposed Wilderness Area and Cheyenne River RAMP project area. Foreground is Pierre Shale covered by grasses and brush; middle ground is the Chadron Fm., and the steep slopes in the background are the Brule and Sharps formations. Photo by B.A. Beasley. Figure 1, shows the landscape of the CRRAMP project, looking south toward Sheep Mountain Table, located on Badlands National Park. This view alone encompasses over 95 million years of sedimentary deposits and natural history that occurred in this area of the Buffalo Gap National Grassland. Environments changed from a deep marine interior seaway, preserving marine reptiles, turtles, some the size of squashed Volkswagens, fish up to 17 feet long, flying reptiles, invertebrates, sharks, and flying and diving toothed birds. The reptiles are not dinosaurs; present evidence indicates that dinosaurs were terrestrial. Sometime around 65 mya, volcanos erupted along what we know as the Pacific coast. These volcanos belched volcanic ash. Silica (volcanic glass shards) is a major component of volcanic ash. The ash that blanketed the landscape is a paleontologically bitter-sweet situation. The glass shards literally choked the life out of the fauna and flora, causing death; however, it is due to the high silica concentration that has also preserved the Tertiary life. The Black Hills began to raise around 65 mya, as magma from deep below the surface (caused by volcanoes in the west), forced its way upward. Evidence suggests that the Black Hills are still rising, as the area stream and rivers are cutting into their western banks. During this upwards movement, the Western Interior Sea began to drain while deposition of sediments, in western South Dakota halted. This was a 17 mya hiatus of deposition and acceleration of erosion, while the Black Hills reached their current height. The presence of the Black Hills changed the weather and wind patterns. The western volcanoes continued to erupt and volcanic ash continued to rain down on the landscape. After the valleys west of the Black Hills filled with ash; the eruptions continued, falling on the landscape immediately east of the Black Hills, forming the Tertiary geologic units on the Buffalo Gap National Grassland. Tertiary Volcanic Province Both from White River Badlands, Benton et.al, 2015 Generalized Stratigraphic Column of the Indian Creek Allotment and CR CRAMP 30-28 mya 30 mya 34-30 mya 37-34 mya Black Hills Uplift & Erosion 75-69 mya Pierre Shale, late Cretaceous, is a dark gray to black marine shale with stringers of bentonite (decomposed volcanic ash) and layers of nodules that are recognizable over long distances. This formation records the last major transgression of the epicontinental Western Interior Seaway. Fossils include ammonites, snails, clams, crabs, mosasaurs, plesiosaurs, fish (including sharks), turtles, pterosaurs, and flightless and flying toothed birds are common in the Sharon Springs member, even occasional dinosaur bones have been found. Counties for Nebraska National Forests and Grasslands: In South Dakota: Pennington, Fall River, Shannon, and Jackson counties. (Bryant, Laurie and Secord, Ross, Forest Service Paleontological Resource Broadscale Assessment and Classification, Agreement No. 1102-0002-96-032). Pierre Shale, Western Interior Seaway location during the Late Cretaceous, created the deposits of the Pierre Shale Formation. Archelon, Courtesy of the Peabody Museum of Natural History, Yale University extinct giant sea turtle known from fossilized remains found in North American rocks of the Late Cretaceous epoch. Archelon, protected by a shell similar to that found in modern sea turtles, reached a length of about 3.5 m (12 feet). The front feet evolved into powerful structures that could efficiently propel the great bulk of Archelon through the water. Chadron Formation Late Eocene has been mapped in North and South Dakota, and Nebraska. The Ahearn, Crazy Johnson, and Peanut Peak members, named in the Big Badlands of South Dakota, are recognizable only in the area of Indian and Battle Creeks, Pennington Co., SD. Titanotheres (Brontotheres), huge rhinoceros-like animals (eight feet at shoulders) occur and are common in the Chadron Formation (Fm), but had become extinct by the time of the overlying Brule Fm. was deposited. The greyish Chadron Formation was deposited between 34 and 37 million years ago by rivers across a flood plain. Each time the rivers flooded, they deposited a new layer on the plain. Alligator fossils indicate that a lush, subtropical forest covered the land. Most fossils found in this formation are from early mammals like the three-toed horse and the large titanothere. Brontothere Brule Formation Middle-Late Oligocene is primarily pinkish siltstones and claystones, with some greenish channels sandstones. Where is best exposed in Nebraska and South Dakota, the Brule Fm. is divided into a lower Scenic Member, and an upper Poleslide Member. Weathering produces steep, tread-and-riser exposures, which may be nearly vertical in the upper member. The Scenic Member contains abundant nodular concretions and includes the Metamynodon Channels, named for the aquatic rhinoceros found in them. Near the top of the Poleslide Member are the coarse-grained Protoceras Channels, the primary source for these small, horned artiodactyls. Protoceras, an extinct artiodactyl Sharps Formation Late Oligocene, massive pinkish volcaniclastic siltstones and mudstones as much as 350 feet thick. Calcareous concretions are prominent and often contain vertebrate fossils. The Sharps Fm. is distributed in southwestern South Dakota and northwestern Nebraska. The High potential areas includes South Dakota counties include Pennington, Shannon, Washabaugh, Bennett, Jackson, and Todd. Many kinds of vertebrates found in the White River Group persist at least into the lower Sharps Formation. Among those that first appear in the Sharps Fm. are a diminutive sabertooth cat about the size of a bobcat, the last North American primate Ekgmowechashala, hedgehogs, true moles, mountain beavers, and aplodontid rodents. The uncommonly good preservation and relative abundance of vertebrates in the Sharps Fm. make this unit significant. Its position immediately overlying the White River Group makes possible detailed studies of successional faunas between those very well-known geologic units. Ekgmowechashala, “Little

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