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Climatic significance of Holocene beachrock sites along shorelines of the Red Sea: Discussion

¹ Department of Earth and Environmental Sciences, New Mexico Tech, Socorro, New Mexico 87801; mozley@nmt.edu
² Department of Geosciences, University of Massachusetts Amhurst, Amhurst, Massachusetts 01003; sburns@geo.umass.edu

The first 20% of the full text of this article appears below.

The geologic record of climate change is currently a very active area of research. The results of such studies have the potential to greatly improve our understanding of the different factors that influence climate and, consequently, may help to guide policy initiatives regarding global warming. Given the importance of such studies, it is imperative that they be scientifically rigorous and thorough. Friedman (2005) falls short on both counts. In this article, Friedman attempted to use the oxygen isotopic composition of a series of ¹⁴C-dated beachrock samples to infer past changes in temperature. On the basis of increasing ¹⁸O values for beachrock with decreasing age, he concluded that global temperature has decreased dramatically during much of the Holocene. The conclusions of the study regarding changing temperature are not supported by the data presented. Alternative hypotheses, not considered in the study, are far more likely explanations for the observed isotopic trend than decreasing temperature.

The principal problems with the article are that (1) critical assumptions are unsupported, and there is no discussion of alternative hypotheses; (2) there is no description of the petrographic characteristics of the samples; (3) no information on methodology is included; (4) the existing literature on beachrock, much directly relevant to the study, is completely ignored; and (5) the conclusions are contradicted by a large number of paleoclimate studies for the same period. These problems are discussed in detail below.

Friedman makes several important assumptions without adequately justifying them. The first assumption is that cements in the beachrock precipitated from unaltered seawater. He acknowledges that ground-water discharge, mixing with river water, and evaporation effects (particularly significant in the Gulf of Aqaba; Friedman, 1968) can alter the isotopic composition of local seawater, but proceeds to assume, for the purpose of the . . . [Full Text of this Article]

This article has been cited by other articles:

				G. M. Friedman Climatic significance of Holocene beachrock sites along shorelines of the Red Sea: Reply AAPG Bulletin, June 1, 2006; 90(6): 975 - 982. [Full Text] [PDF]