Date of Award

5-2009

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Sandra Passchier

Committee Member

Duke Ophori

Committee Member

Matthew Gorring

Abstract

The Squantum Tillite has been studied in order to ascertain its depositional history. The Squantum Tillite is part of the Neoproterozoic Boston Bay Group, located in the Boston Basin. Researchers have proposed contradicting hypotheses about the origin of the rocks in the area for over a century. While some believe that the rocks were deposited by glaciers along a prograding submarine margin, others believe the rocks are of volcanic or tectonic origin. Many scientists are inclined to believe the rocks are of tectonic origin because the Squantum Tillite is located in a tectonic Basin (the Boston Basin).

Field logging was used to determine the characteristic sedimentary facies in the area. The sedimentary facies observed in the Boston Tillite includes diamictites, mudstones, fine to medium grained sandstones and little amount of volcanic sandstone. Field observations show sandstones and mudstones fining up when moving in the upward direction along the cliff. A total of thirty (30) samples were also collected in situ from the outcrops and these were taken to the lab for further chemical analysis. Rock samples and twelve (12) USGS rock standards were analyzed for major and trace elements via Inductively-Coupled Plasma Optical Emission Spectrometry (ICPOES).

Chemical index of alteration (CIA), a major element ratio, was used to deduce the degree of chemical weathering in this Neoproterozoic sequence. CIA values from analyzed data fall within the range of 61 and 75 indicating that the rocks in the Squantum Tillite have significant chemical alteration. Sample to average crust for each element was also plotted on a spider diagram. Silica, titanium, aluminum, potassium, barium and yttrium were abundant since they show a ratio of 1 or higher. Calcium appears to be the most depleted element and this indicates glacial conditions. The high CIA values could also be accounted for by the calcium depletion, because calcium is a denominator in the CIA formula. The field data were further interpreted and results compared with other data from similar studies along the Polar Regions and in various locations including, the late Precambrian Gaskiers Formation in Newfoundland, Canada, the Neoproterozoic Mirbat formation in South Oman, the Neoproterozoic Port Askaig Formation in Scotland and the Fork Tillite of Utah. Field and laboratory results were used to draw conclusions on the actual mode of deposition of the Squantum Tillite and to test the snowball earth hypothesis so as to determine whether or not data collected from chemical analysis supports the snowball earth theory.

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