Correlation of Physical, Mineralogical, and Organic Properties of Upper Pleistocene Lacustrine Deposits from Redpath Paleolake, North Island, New Zealand
J. E. Carrasco1, K. M. Marsaglia1, M. Marden2, and M. E. Kirby3
1California State University, Northridge, CA, ([email protected]), ([email protected])
2Landcare Research, Gisborne, New Zealand, [email protected]
3California State University, Fullerton, CA, [email protected]
Redpath Paleolake is located within the Waipaoa Catchment ~48 km northwest of Gisborne and is situated adjacent to the Waikohu River, which has exposed the lake sediments due to cut-bank erosion. A 10-m core (Redpath 3) from a well-bore and an ~8-m section from a nearby stream-bank outcrop (Redpath 1A) were measured, described, and photographed. The core and bank section were respectively sub-sampled at 2 and 1 cm contiguous intervals for laboratory analyses that included mass magnetic susceptibility (CHI) and loss on ignition at 550°C for total organic matter (TOM) and at 950°C for total carbonate (TC). Facies of both lacustrine and non-lacustrine deposits were identified within sections composed of similar facies and similar 14C ages (maximum of ~14,300 years B.P. and minimum of ~13,300 years B.P.), however, distinctive patterns in sedimentation and structure are not apparent and do not directly correlate. These rapid, short-lived facies changes could be linked to rapid marginal facies changes in a small lake. Both the core and bank section show similar ranges and mean values for both CHI and TOM. However, values for TC differ in their mean values and overall downsection patterns. Redpath deposits were compared with nearby modern Lake Tutira sediments in order to determine any particular climatic fluctuations (i.e., ‘sediment storm pulses’); sandy ‘storm pulses’ are found throughout both Redpath sections, indicating a rather dynamic climate at the time. CHI value parameters from Redpath do not mirror those from Lake Tutira, possibly owing to the fact that the values for Tutira reflect a time of increased sedimentation from anthropogenic activity (post-European arrival).
AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009