Go to  Advanced Search

Reconstruction of holocene environmental changes in northern British Columbia using fossil midges

Show full item record

Files in this item

Files Size Format Description   View
ubc_2008_fall_fleming_erin.pdf 2.549Mb Adobe Portable Document Format   View/Open
Title: Reconstruction of holocene environmental changes in northern British Columbia using fossil midges
Author: Fleming, Erin Mattea
Degree Master of Science - MSc
Program Environmental Sciences
Copyright Date: 2008
Publicly Available in cIRcle 2008-11-25
Subject Keywords Chironomidae; Chaoboridae; Pyramid Lake; Bullwinkle Lake; Cassiar Mountains British Columbia; Midge; Palaeoecology; Holocene; Palaeotemperature; Palaeoclimate; Milankovitch thermal maximum
Abstract: Lake sediments contain the remains of midge communities that may be used as biological proxies for inferring past environmental changes. Freshwater midges, including Chironomidae and Chaoboridae, from two alpine tarns (Pyramid Lake and Bullwinkle Lake) in the Cassiar Mountains of northern British Columbia were used to estimate Holocene palaeotemperature changes, and more specifically, to test for the presence of the Milankovitch thermal maximum, an early Holocene warm interval coinciding with peak Holocene summer solar insolation. Mean July air temperatures were reconstructed using midge-inference models developed via weighted averaging-partial least squares (WA-PLS) regression. Cold-tolerant midge taxa dominate the stratigraphies from both Pyramid and Bullwinkle Lakes; however, warm-adapted species are more common in Bullwinkle Lake. Early Holocene warming is apparent at both lakes, however it is unclear whether this is indicative of the Milankovitch thermal maximum. A decrease in temperature occurs from 8,700-7,900 cal. yr BP at Pyramid Lake, around the same time that the 8,200 cal. yr BP cooling event occurred in the northern hemisphere. During the middle Holocene, records from Pyramid Lake indicate an overall decrease in temperature, with a short period of warmer temperatures that peak at 5,100 cal. yr BP. Temperatures fluctuate little during this time at Bullwinkle Lake. A short warming phase is apparent at both lakes during the late Holocene. July temperatures are highest at 2,000 cal. yr BP (10.5°C) in Pyramid Lake and at 1,200 cal. yr BP (13°C) in Bullwinkle Lake. Thereafter, temperatures return to what they were before the warming occurred, and at Bullwinkle Lake, vary little throughout the remainder of the Holocene.
URI: http://hdl.handle.net/2429/2811
Scholarly Level: Graduate

This item appears in the following Collection(s)

Show full item record

All items in cIRcle are protected by copyright, with all rights reserved.

UBC Library
1961 East Mall
Vancouver, B.C.
Canada V6T 1Z1
Tel: 604-822-6375
Fax: 604-822-3893