ELEMENTAL ANALYSIS OF THE NORTHVIEW FORMATION CONSTRAINS DEPOSITIONAL CONDITIONS

Paleoenvironments can be reconstructed from basic stratigraphic conditions. In this study, the Early Mississippian Northview Formation of southwest Missouri, USA was examined to obtain further information on the paleogeographic conditions that led to its deposition. The Northview Formation is a marine deposit composed of dark gray to light green shale with bioturbated tan sandstones and siltstones interbedded near the top. Body fossils are scarce within the Northview, but ichnofossils within the siltstones indicate that it was most likely deposited in an oxygenated shallow marine environment. For this study, an elemental analysis was completed to further constrain the depositional environment in southwest Missouri using an Agilent 7900 Quadrupole Inductively Coupled Plasma Mass Spectrometer.

Using this ICP-MS, Sr and Ba ppm ratios of 0.593+ were found that suggest the basal Northview was deposited under open marine conditions with normal salinity. The upper Northview, however, had Sr and Ba ppm ratios of 0.141-0.384, which suggest deposition in an environment that had mixtures of fresh and brackish water. The inputs of fresh water imply a large regression period, probably a deltaic environment. Future ratio measurements between B and Ga as well as S and Total Organic Carbon are going to be measured in order to strengthen these interpretations. Additionally, the deltaic interpretation implies that further work is needed on the source area and local tectonic conditions, along with the bathymetry of the Early Mississippian carbonate platform in Missouri and adjacent states.