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At least 22 tridactyl dinosaur tracks, poorly preserved in various degrees of expression, have recently been found at an exposure in the Dakota Formation (Lower Cretaceous, Albian) in Jefferson County, Nebraska. These tracks generally have broad, blunt digits and a broad posterior margin. The largest of the tracks measures 57 cm in length and 58 cm in width. All of the tracks lie within a stratigraphic horizon of 40 cm or less, but they do not form a single trackway. We interpret the trackmakers to have been ornithopods. The Jefferson County tracks are in a well-cemented sandstone with oscillation ripples, at a stratigraphic level between two wellestablished sequence boundaries. Channel forms and lateral accretion units are common in the stratigraphic interval enclosing the tracks, and the site is interpreted as a bar or sand flat in a tidally influenced river. The Jefferson County tracks are only the second known occurrence of large Mesozoic tetrapod tracks east of the Rocky Mountain Front-High Plains Margin, including the Black Hills of South Dakota, west of the Atlantic Coastal Plain, and north of the Gulf Coastal Plain. Further, this paper is the first documentation of in situ dinosaur fossils from the Nebraska-Iowa area.

The Cretaceous Dakota Formation in the areas of Kansas, Nebraska, and Iowa contains a rich and well-preserved microflora of fossil palynomorphs. A comprehensive listing of these taxa is presented in this publication as part of a continuing effort to develop a refined biostratigraphic scheme for mid-Cretaceous terrestrial deposits in North America. The Dakota Formation in this region contains four distinctive Albian-Cenomanian palynostratigraphic zones that are used to partition the unit into successive depositional cycles, and each zone records deposition in fluvial-estuarine environments. The late Albian Kiowa-Skull Creek depositional cycle at the base of the Dakota Formation is recognized throughout the study area, and is also recognized in other parts of the Cretaceous North American Western Interior basin. The overlying newly recognized latest Albian "Muddy-Mowry Cycle" is formally defined for the first time in this paper and correlates with depositional cycles recognized by other workers in other parts of the Western Interior basin. The Cenomanian lower Greenhorn Cycle is already widely recognized by many other workers throughout the Western Interior basin. Laterally extensive thin zones of pervasive carbonate mineral cementation are noted in fluvial-estuarine deposits in the Dakota Formation. They are believed to have formed as synsedimentary cements that precipitated below estuarine marine-flooding surfaces in settings related to discharging paleoground waters. The existence of these early diagenetic cementation zones has important implications for the recognition of diagenetic barriers and baffles to modern fluid flow in the Dakota Formation. New stable isotopic data on these authigenic cements are reported in this paper and add to a body of published data on the δ18O of mid-Cretaceous paleoprecipitation in North America.