Dissertations and Theses @ UNI

Availability

Open Access Thesis

Keywords

Palynology--Iowa; Pollen, Fossil--Iowa; Palynology; Pollen, Fossil; Iowa;

Abstract

Peat samples from a temporary exposure in the Early Phase High Terrace of the Iowa River near Iowa City, Iowa, were analyzed for pollen. The pollen sequence, dated at 24,570 +/- 200 to 18,620 +/- 140 B.P.·, can be divided into three zones based on pollen percentages. In the basal zone (zone-1), arboreal pollen is dominated by Pinus (pine), with lesser amounts of Picea (spruce), and is interpreted to represent a Pinus-Picea boreal forest. Picea pollen percentages increase through the intermediate zone (zone-2) of the sequence as Pinus pollen percentages decline, indicating a transition to a Picea-dominated boreal forest. A relative decline in Picea pollen and a dramatic increase of Cyperaceae (sedge) pollen occurs in the upper zone (zone-3) of the sequence. This trend in zone-3, when considered with findings and interpretations of others, is consistent with a transition to a tundra environment at about 21,000 B.P. The vegetational transition reflects cooling climatic conditions associated with glacial advance during the six-thousand year interval represented by this particular peat deposit.

Year of Submission

1991

Degree Name

Master of Arts

Department

Department of Earth Science

First Advisor

Lynn Brant

Second Advisor

Wayne I. Anderson

Third Advisor

James Walters

Comments

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Date Original

1991

Object Description

1 PDF file (59 leaves)

Language

en

File Format

application/pdf

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