Document Type
Thesis
Abstract
The Cambrian Elbrook Formation contains oolitic limestones with both intact and broken ooids. Thin sections of samples from an outcrop in Swoope, Virginia were analyzed to determine factors that affect the condition in which ooids preserved. The ooids occur in layers with varying proportions of intact to broken ooids, micrite to sparry cement in the matrix, and ooid density. A total of 185 ooids were counted: 80 intact and 105 broken. Three factors affecting the condition in which ooids were preserved were tested: the presence of micrite in the matrix surrounding ooids, contact between ooids, and micritization of ooids cortices. Micrite in the matrix ranged from 0 — 75% of the matrix in a layer and an inverse relationship exists between the percent of micrite in the matrix and the percent of broken ooids. This is statistically significant. Micrite in the matrix allows force to act isotropically on the ooids, resulting in more intact ooids. Contact between ooids also affected ooid condition, whereby ooids in contact with other ooids were more likely to be broken and intact ooids were more likely to not be in contact with other ooids. However, the difference is not statistically significant. Micritization of ooid cortices did not affect ooid condition. The orientation of breakage planes within ooids was inhomogeneous showing a range of orientations, suggesting ooids broke after deposition but before lithification.
Date Awarded
2012
Department
Geology
Advisor 1
Heather MacDonald
Advisor 2
Rowan Lockwood
Recommended Citation
Cuker, Lydia P. G., "Characteristics of Ooids in the Middle to Late Cambrian Elbrook Formation, Virginia" (2012). Geology Senior Theses. William & Mary. Paper 267.
https://scholarworks.wm.edu/geologyseniors/267
