2008 Joint Annual Meeting (5-9 Oct. 2008): Paleolimnologic Study of Redpath Lake, North Island, New Zealand

151-14 Paleolimnologic Study of Redpath Lake, North Island, New Zealand



Sunday, 5 October 2008
George R. Brown Convention Center, Exhibit Hall E
Joseph E. Carrasco Jr1, Kathleen M. Marsaglia1, Mike Marden1, Matthew E. Kirby2 and Wayne G. Henderson2, (1)Geological Sciences, California State University, Northridge, 18111 Nordhoff Street, Northridge, CA 91330-8266
(2)Geological Sciences, California State University, Fullerton, P.O. Box 6850, Fullerton, CA 92834-6850
In June of 2007, a Landcare Research New Zealand terrace drilling program discovered a potential paleolake deposit (Redpath Paleolake) within the upper Waipaoa River catchment of North Island, New Zealand. This lake formed behind a local landslide dam that when breached resulted in the downcutting and exposure of lake sediments in a single stream bank. In January of 2008, eight meters of section along this bank (Redpath 1A) and a ten meter core (Redpath 3) from the original discovery well bore ~20 m northwest of the stream bank were measured, described, and photographed. Descriptions included color, sedimentary structures, bedding characteristics, organic matter content, grain size, and diagenetic features. These sections were sub-sampled at 1 cm to 2 cm intervals for laboratory analyses such as grain size analysis, mass magnetic susceptibility, loss on ignition 550� and 950�C, and smear slide petrography. Both stratigraphic sections are dominated by mud (~75%), locally laminated, and medium to thin sandy interbeds (~25%); these variations in sediment input perhaps reflect climatic, volcanic and/or tectonic events. Wood fragments yield maximum 14C ages of approximately 15,000 years B.P. for the sequence suggesting that the sediments fill a gap that has not been documented within the region, and is of importance to MARGINS Source-to-Sink modeling.