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Journal of the Royal Society of New Zealand abstractsMcLeod Fault: associated monocline and Pliocene angular unconformity, Point Range and Mangaopari Stream, Wairarapa, New ZealandP. Vella, J.D. Collen*The NNE-trending McLeod Fault, here named, displaces Torlesse (Mesozoic) basement rocks and the unconformably overlying Sunnyside Conglomerate (Upper Miocene), upthrown on the east side, against Upper Miocene marine mudstone and sandstone from Mangaopari Stream northward to a few hundred metres beyond McLeod Creek. Farther northwards, basement and Sunnyside Conglomerate plunge under Upper Miocene, Pliocene and early Quaternary strata which are draped over the fault to form a monocline. The steep limb of the monocline strikes at 021deg., contains Upper Miocene and Lower Pliocene strata dipping 65deg. to 90deg. WNW, and extends more than 2 km NNE from McLeod Stream. Identifiable beds in the monocline are not attenuated, indicating a reversed attitude of the underlying McLeod Fault and shortening of the basement. In the steep limb dips up to 70deg. in early Pliocene strata contrast with dips up to 47deg. in adjacent late Pliocene and early Quaternary strata, indicating two episodes of active movement: between approx. 3.4 and 2.4 Ma beds were tilted up to 21deg. to WNW, and from 1 Ma they were tilted up to a further 47deg.. Submarine erosion during the earlier episode is represented by a late Pliocene unconformity which has implications regarding biostratigraphic, paleomagnetic and oxygen isotope studies made at Mangaopari Stream.Keywords: McLeod Fault, monocline, Mangaopari Mudstone Formation, Mangaopari Stream section, NZMS S27, Upper Miocene-Quaternary, unconformity, Wairarapa
(c) Journal of The Royal Society of New Zealand, Volume 28, Number 1, March 1998, pp 157-164
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