Holocene Records of Nebraska Mammals

A survey of the archeological and paleontological literature allowed a compilation of Holocene records of mammals in Nebraska. This survey identified Holocene records from 338 sites in 62 of the 93 Nebraska counties. These counties were located throughout state, but there was a concentration of sites in southwestern Nebraska where there were 27 fossil sites in Frontier County and 22 in Harlan County. Fossils sites were underrepresented in the Sand Hills region. Records of fossil mammals covered the entire Holocene period from 13,000 years ago until AD 1850. A minimum of 57 species (with eight additional species potentially present) representing six orders of mammals were represented in the compilation—four species of Lagomorpha, four species of Soricomorpha, 17 species of Carnivora (with three additional species potentially present), one species of Perissodactyla, six species of Artiodactyla, and 25 species of Rodentia (with five additional species potentially present). The remains of bison were found at 276 sites, which was more than for any other species in the state. Additional species that formed the main portion of the diet of Native Americans were the next most abundant in the fossil record—deer, pronghorn, and wapiti. That these food species dominated in the Holocene record was to be expected because fossils were recovered primarily from archeological sites.

North Platte River-South Platte River Confluence Area Drainage System History as Determined by Topographic Map Interpretation: Western Nebraska, USA

Detailed topographic maps of the western Nebraska North Platte River-South Platte River confluence area show a low relief and gently sloping southeast-oriented upland surface, asymmetrical drainage divides, nearly adjacent and parallel east-oriented North and South Platte River valley segments, barbed tributaries, and shallow divide crossings (low points along drainage divides) in a region south of the Nebraska Sand Hills and at the Nebraska loess region’s western margin. Published interpretations of North and South Platte River confluence area landforms (referred to as the accepted paradigm) do not explain most drainage features and are compared with a new paradigm’s interpretations to determine which of the two paradigms explains the regional drainage history and related surface features in a simple and consistent manner. New paradigm interpretations require large sheets of slowly-moving southeast-oriented water to have flowed toward what was probably an actively eroding Republican River valley and to have shaped the upland surface while the Platte and North and South Platte River valleys eroded headward into and across the region so as to create the asymmetric drainage divides, barbed tributaries, and shallow divide crossings. These new paradigm interpretations are consistent with each other and with recently published new paradigm interpretations of upstream North and South Platte River drainage system history. New paradigm interpretations also suggest the adjacent Nebraska Sand Hills developed on a large flood deposited delta (typical of sand dune areas on former glacial lake deltas further to the north) and the slowly-moving sheets of water may have been responsible for some or all of Nebraska’s loess deposits, although the new paradigm leads to a fundamentally different middle and late Cenozoic regional geologic and glacial history than what workers using the accepted paradigm have described.

ENHANCED AEOLIAN ACTIVITIES IN THE MIDDLE YANGTZE RIVER BASIN DURING MIS2: EVIDENCE FROM RADIOCARBON DATING OF SAND HILLS AND LOESS SEDIMENTS

ABSTRACTAeolian deposits are widely distributed in the middle Yangtze River Basin (YRB), central China. The formation of those aeolian deposits (including aeolian sands and loess deposits) represented the deterioration of local environment. Previous geochronological studies have shown that both aeolian sands and loess began to be deposited in the last interglacial (~100 ka). In this study, a total of four and six accelerator mass spectrometry radiocarbon (AMS 14C) samples were collected from a sand hill and a loess section, respectively, in the Jiujiang area to refine their chronology. Charcoals extracted from bulk samples were employed for AMS 14C dating. The sand layer at the lower part of the HG-C section is sandwiched by two mud layers dated to 26,670–26,285 and 24,480–24,180 cal BP, respectively. Therefore, we infer that aeolian activities in this region started at ~25 ka BP, which was significantly younger than that of previous studies. Meanwhile, thick loess began to deposit leeward of the sand hills in this region. Based on the AMS14C chronology and provenance tracing, we conclude that the loess was essentially the fine-grained aeolian deposits. Our results suggest that topography and vegetation cover have an important effect on the spatial distribution of aeolian deposits in this region.

H.T.U. Smith (1965) dune morphology and chronology in central and western Nebraska. The Journal of Geology 73(4): 557–578

Climatic geomorphologists, and eolian geomorphologists in particular, have always been interested in studying dunes to understand and construct past climatic conditions. Smith’s 1965 paper presents an excellent example of a reconnaissance piece of scientific work that set the foundation for (1) using aerial photo-interpretation to provide chronological information about dune fields; (2) the use of eolian processes and landforms as climate change indicators; and (3) extraterrestrial or planetary geomorphology. This article briefly describes Smith’s background, background on Nebraska Sand Hills, and the impact and legacy of Smith’s classic paper.