The uranium series diagenesis and the morphology of drowned Barbadian paleo-reefs.
Item
-
Title
-
The uranium series diagenesis and the morphology of drowned Barbadian paleo-reefs.
-
Identifier
-
AAI3312925
-
identifier
-
3312925
-
Creator
-
Mey, Jacob Louis, IV.
-
Contributor
-
Advisers: R. G. Fairbanks | N. G. Hemming
-
Date
-
2008
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Geochemistry | Physical Oceanography | Geology
-
Abstract
-
Paleoclimatologists rely on precise age determinations of natural materials, such as ice cores, deep ocean sediments, speleothems, and corals. Especially carbonate materials are used as proxies for past climate changes, but only if they are well preserved as closed system samples in their natural environment, and thus present ideal material for radiometric dating. It is important to understand and recognize the symptoms of diagenesis as it enables one to avoid dealing with the thus affected samples altogether. Major challenges arise, however, in that several well-established strict criteria for a priori sample selection fail to identify all affected samples, making some diagenetic effects hard to detect. In many cases, the 'hidden' effects go undetected until the end of costly and timeconsuming analysis, only to yield the inconclusive open system results improper for dating corals.;The present work deals with two central questions: (i) Where do the diagenetic effects occur, and: (ii) What are the mechanisms that set their signatures? In order to answer the first question, it is necessary to understand the second. Barbadian corals that have been exposed to fresh water diagenesis commonly show a positive correlation between 230Th/ 238U and 234U/238U activities in samples with elevated delta234Uinitial. These trends have led authors to develop corrections to open system ages, based on the interpretation that the systematic trends are set by predictable progressive addition of excess 234U and 230Th. The new model developed in this study disavows the progressive addition models, and instead, contends that the trends were set early during the first freshwater exposure and that they have been preserved ever since. The model has been refined to successfully estimate 'marine residence times' for seven Barbadian paleoreefs.;In the present study, several new geospatial techniques, using GIS and 3-dimensional bathymetric digital terrain models, have been developed to improve our understanding of the sea floor morphology around Barbados and other locations with the desired paleoreefs. Our two-pronged approach, viz., unraveling the off-shore drowned paleoreefs and understanding their internal distribution of diagenetic effects, is thought to improve the possibilities for future prospecting for closed system samples to be used in paleoclimate research.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
