New Zealand Journal of Geology and Geophysics abstracts
Timing of normal faulting in the Waikato Coal Measures, New
Zealand, and its implications for coal-seam geometry
Steven L. Hall1
Andrew Nicol2
Tim A. Moore1,3*
Kari N. Bassett1
1Department of Geological
Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
2GNS Science
P.O. Box 30 368
Lower Hutt, New Zealand
3Solid Energy New Zealand
P.O. Box 1303
Christchurch, New Zealand
*Corresponding author.
Abstract Coal seams within the Waikato Coal
Measures can vary significantly (>50%) in thickness over short
lateral distances (<500 m). Normal faulting during coal-measure
deposition could produce the observed variations in seam thicknesses,
but the timing of faulting has not been determined precisely. To
constrain the timing of faulting, and its potential impact on coal seam
geometry, we have analysed displacements for nine normal faults
striking both NNW to N and NNE to NE. Displacements were derived from
drillholes, mine workings, and seismic reflection lines. The data
indicate that normal faulting occurred after peat accumulation in the
coal measures, in some cases perhaps commencing in the latest Eocene to
early Oligocene (i.e., c. 33–36 Ma). Normal faulting had
little or no impact on the accumulation of peat in the Waikato Coal
Measures. Variations in coal-seam thickness were controlled by basement
paleotopography and fluctuations in sediment supply.
Keywords normal faults; Waikato Coal Measures;
coal-seam geometry
G05004; Received 25 January 2005; accepted 17 November 2005; Online
publication date 28 February 2006
New Zealand Journal of Geology & Geophysics, 2006, Vol. 49:
101–113
0028–8306/06/4901–0101 © The Royal Society of New Zealand 2006
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