317 Stratigraphy (Posters)

Wednesday, 4 November 2015
9:00 AM - 6:30 PM
Exhibit Hall

HIGH RESOLUTION ANALYSIS OF DEPOSITIONAL VARIATION WITHIN THE UPPER KOPE FORMATION (CINCINNATIAN, ORDOVICIAN) OF NORTHERN KENTUCKY USING FOSSILS AND RARE EARTH ELEMENT COMPOSITION

Paper number: 317-4
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The Ordovician strata of the Cincinnatian was deposited on a shallow platform of the Cincinnati Arch within the Appalachian Basin approximately 450 million years ago. Sediments of the Cincinnatian consist of interbedded limestone and shale in a cyclic deposition. Sediments and fossils of the upper Kope Formation were analyzed to evaluate changes in depositional environment and ocean chemistry through the sequences. Fossil samples of limestone units were collected for the upper five sequences of the Kope Formation and conodont specimens were collected for the uppermost sequence of the Kope Formation in Northern Kentucky. Fossils in the limestone layers were counted and compared. Sowerbyella was inversely proportional to Oneilla while Batastoma was inversely proportional to Parvohallopora. Sowerbyella and Batastoma became more abundant towards the top of the Kope Formation, indicating a shallowing of the environment overall.

Conodonts were collected from the uppermost sequence of the Kope Formation with ten samples collected. Conodonts were separated from the shale by soaking in water and then sieving, while samples of the calcsilicates were dissolved in dilute acetic acid, then sieved with a 125 micron sieve. Material captured by the sieve was then separated using bromoform to concentrate the conodonts. The conodonts are composed of apatite and absorb rare earth elements (REE) from the pore waters during early diagenesis, recording the water chemistry and depositional environment. Rare earth elements were analyzed using laser ablation ICP-MS at the U.S. Geological Survey. While crowns and bases had different absolute concentrations of REE, the ratios of the REE were the same within a single specimen. Ratios of light, medium and heavy REE can be used to determine water depth and possible fluvial input.