The paleoecologic significance of Paleocene palynomorph assemblages from the Ludow, Slope, and Cannonball formations, southwestern North Dakota

Paleoenvironment exerted control on the distribution of 133 palynomorph taxa from the Ludlow and Slope Formations and Boyce and Three V Tongues of the Cannonball Formation (Fort Union Group, I Paleocene) of southwestern North Dakota. The strata represent fluvial deltaic systems that prograded eastward into the Cannonball Sea. Depositional environments include distributary channels, crevasse splays, crevasse-splay feeder channels, lignite-producing swamps and/or marshes, lakes, brackish to slightly brackish bays, lake and bay fills, and marshes Paleoenvironmentally sensitive palynomorph taxa were identified by subjective examination of pollen diagrams and objective analysis using detrended correspondence analysis. Two paleoenvironmentally restricted palynomorph associations were recognized. The Acritarch association, composed of Ovoidites cf. O. ligneolus, Micrhystridium Type-2, Psiloschizosporis cf. S. spriggii, Cymatiosphaera sp., and three unidentified acritarch taxa, is restricted to slightly brackish to lacustrine paleoenvironments. The Pediastrum association is dominated by Pediastrum, but contains additional algal taxa including Psilainaperturites sp. 2, Ovoidites cf. 0. ligneolus, Botryococcus sp., Micrhystridium Type-1, and several species of dinoflagellates. The Pediastrum association occurs in lacustrine strata and in the basal portions of brackish-water strata, indicating that brackish-water conditions were preceded by less saline environments. Palynornorph assemblages within lignite beds are characterized by sphagnaceous spores (Stereisporites spp.), Gleicheniidites spp., Toroisporis sp., Reticuloidosporites pseudomurii, Fraxinoipollenites variabilis, Rousea cf. R. parvicolpata, Rousea sp. 1, Rousea sp. 2, Retitrescolpites anguluminosus, Cyrillaceaepollenites cf. c. exactus, and Myrtipites? sp. 2. A possible early successional association also occurs in lignites, characterized by Nyssapollenites sp., Quercoidites cf. Q. spissus, Wilsonipites sp., Foveotricolporites pachyexinous, Cranwellia subtilis, Triatriopollenites subtriangulus, Dicotetradites rallus, Cricotriporites plektosus, Sparganiaceaepollenites? sp., and Biretisporites furcosus. Kurtzipites spp., Syncolporites cf. S. minimus, and Wilsonipites sp. are typical of the progradational marsh deposits. Rossipollis scabratus, Corollina sp., Sparganiaceaepollenites cf. s. globipites, Jarzenipollenites trinus, Triporopollenites granilabratus, Rousea sp. 4, and Striatopollis cf. S. trochuensis may represent members of salt marsh floral communities. Dinoflagellate cysts, especially Deflandrea cf. D. flounderensis are typical of brackish-water strata, although some taxa have wider paleoenvironmental tolerance

Unconformities and Age Relationships, Tongue River and Older Members of the Fort Union Formation (Paleocene), Western Williston Basin, U.S.A.

An unconformable relationship is observed within the Paleocene Fort Union Formation in the western Williston Basin at the contact between the Tongue River Member and the underlying Lebo and Ludlow Members. Isotopic dates and pollen biozone data reported here are integrated with previously published data. A new correlation of these facies results in a revised history of localized depositional and tectonic events. One unconformity occurs at this lithological contact in the Pine Hills (PH), Terry Badlands (TB), and Ekalaka (E) areas west of the Cedar Creek anticline (CCA), and another unconformity occurs at the same lithological contact in the Little Missouri River (LMR) area east of the CCA. The two unconformities differ in age by about two million years. The older is the U2 and the younger is the U3 , which initially were recognized in the Ekalaka area of southeastern Montana (Belt et al., 2002). The U2 crops out in the TB, PH, and E areas, where at least 85 m of Tongue River strata bearing palynomorphs characteristic of biozone P-3 are found above the unconformity. Radiometric dates from strata (bearing palynomorphs characteristic of biozone P-2) below the U2 range in age from 64.0 to 64.73 Ma. The U2 unconformity west of the CCA thus occurs in strata near the base of the lower P-3 biozone. The U3 crops out in the LMR area (east of the CCA), where only 13 m of strata characterized by the P-3 pollen biozone occur above it. Radiometric dates from an ash \u3c1 m above the U3 in that area range in age from 61.03 to 61.23 Ma, and the P-3/P-4 pollen biozone boundary is located 13 m above the ashes. The U3 thus occurs in strata characterized by upper parts of the P-3 pollen biozone east of the CCA. The U3 is also identifiable in the middle of the ca. 200 m-thick Tongue River Member west of the CCA, where mammal sites 40 to 80 m above it are Tiffanian-3 in age. The strata below this unconformity are tilted gently to the northwest; strata above the unconformity are flat lying. This mid Tongue River unconformity probably correlates with the unconformity at the base of the Tongue River Member in the LMR area east of the CCA, where a Ti-2 mammal site (the “X-X” locality) occurs \u3c10 m above it. Depositional and tectonic events can be summarized using North American Mammal Age nomenclature as a relative time scale. From latest Cretaceous through Puercan time, paleodrainage was toward the east or southeast, in the direction of the Cannonball Sea. The Black Hills did not serve as an obstruction at that time. During early Torrejonian time, the Miles City arch (MCA) and Black Hills were uplifted and partially eroded, leading to the U2 unconformity. When deposition resumed, paleodrainages shifted to a northeasterly course. During middle and late Torrejonian time, facies of the lower Tongue River (“Dominy”) sequence and the Ekalaka Member of the Fort Union Formation were deposited in the middle of a subbasin between the MCA and the CCA. Simultaneously, smectite-rich components of the Ludlow Member were being deposited east of the CCA. During latest Torrejonian time, uplift of the Black Hills tilted the “Dominy” sequence toward the northwest and local erosion led to the U3 unconformity. Following this tilting, during Tiffanian time, deposition of the upper Tongue River (“Knobloch”) sequence shows continuity from western North Dakota across eastern Montana and into the northern Powder River Basin

Evidence for Marine Influence on a Low-Gradient Coastal Plain: Ichnology and Invertebrate Paleontology of the Lower Tongue River Member (Fort Union Formation, Middle Paleocene), Western Williston Basin, U.S.A.

The Paleocene Tongue River Member of the Fort Union Formation contains trace-fossil associations indicative of marine influence in otherwise freshwater facies. The identified ichnogenera include: Arenicolites, Diplocraterion, Monocraterion, Ophiomorpha, Rhizocorallium, Skolithos linearis, Teichichnus, Thalassinoides, and one form of uncertain affinity. Two species of the marine diatom Coscinodiscus occur a few meters above the base of the member. The burrows occur in at least five discrete, thin, rippled, fine-grained sandstone beds within the lower 85 m of the member west of the Cedar Creek anticline (CCA) in the Signal Butte, Terry Badlands, and Pine Hills areas. Two discrete burrowed beds are found in the lower 10 m of the member east of the CCA in the little Missouri River area. Abundant freshwater ostracodes include Bisulcocypridea arvadensis, Candona, and Cypridopsis. Freshwater bivalves include Plesielliptio and Pachydon mactriformis. We recognize four fossil assemblages that represent fluvio-lacustrine, proximal estuarine, central estuarine, and distal estuarine environments. Biostratal alternations between fresh- and brackish-water assemblages indicate that the Tongue River Member was deposited along a low-gradient coastal plain that was repeatedly inundated from the east by the Cannonball Sea. The existence of marine-influenced beds in the Tongue River Member invalidates the basis for the Slope Formation

Natural climate solutions for the United States

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science Advances 4 (2018): eaat1869, doi:10.1126/sciadv.aat1869.Limiting climate warming to <2°C requires increased mitigation efforts, including land stewardship, whose potential in the United States is poorly understood. We quantified the potential of natural climate solutions (NCS)—21 conservation, restoration, and improved land management interventions on natural and agricultural lands—to increase carbon storage and avoid greenhouse gas emissions in the United States. We found a maximum potential of 1.2 (0.9 to 1.6) Pg CO2e year−1, the equivalent of 21% of current net annual emissions of the United States. At current carbon market prices (USD 10 per Mg CO2e), 299 Tg CO2e year−1 could be achieved. NCS would also provide air and water filtration, flood control, soil health, wildlife habitat, and climate resilience benefits.This study was made possible by funding from the Doris Duke Charitable Foundation. C.A.W. and H.G. acknowledge financial support from NASA’s Carbon Monitoring System program (NNH14ZDA001N-CMS) under award NNX14AR39G. S.D.B. acknowledges support from the DOE’s Office of Biological and Environmental Research Program under the award DE-SC0014416. J.W.F. acknowledges financial support from the Florida Coastal Everglades Long-Term Ecological Research program under National Science Foundation grant no. DEB-1237517