ANALYSIS OF THE ENVIRONMENTAL CONDITIONS FOLLOWING THE LATE CAMBRIAN REEF ECLIPSE IN THE NOTCH PEAK FORMATION AND EASTERN NEVADA

In the middle to late Cambrian, evidence exhibits a lull of biodiversity within metazoan-reef systems, prior to the Ordovician Radiation. This lull can be defined as a point in time when little biological activity occurred. Archaeocyaths were one of the dominant framework-builders during the early Cambrian that supported skeletal reef ecosystems. Although, archaeocyathan sponges could provide the framework to make reefs that quickly led to diversity, they were relatively short-lived. As a result, this became a cumulative event that resulted in a loss of reef-building activity, referred to as a reef eclipse. For that reason, the metazoan reefs diminished following the archaeocyathan extinction and microbial-reefs began to increase in the late Cambrian. Later, lithistid sponge-microbial reefs established a newer framework that was composed of bowl-shaped sponges. While other lithistid-microbial reefs were found in high-energy subtidal conditions with different structures, this adaptation is consistent with a low-energy subtidal environment from the Arrow Canyon region during this period.

The objective of this research is to examine the post-extinction interval during this biodiversity lull. The first goal of this project is to create meter-scaled outcrop descriptions of carbonate rocks in the Arrow Canyon and Eureka regions of eastern Nevada. Stratigraphic analysis of various sites from the Notch Peak Formation can provide a perspective of the energy level from these shallow water environments. Secondly, samples taken for thin sections will be used to investigate the abundance of organisms throughout this reef eclipse. Point count analysis will give a detailed, quantifiable account of biological material found within the sediment. By analyzing the previous environments, this project aims to highlight the variable nature within these ecosystems in order to gain a better understanding of long-term effects of climate change and framework builder extinction upon reef environments.