Geology of the Pareora district

Author:

Croxford, Norton James William.

Year:

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Abstract:

INTRODUCTION
The Limits of the Area Prescribed. The area is rectangular, having its eastern margin situated 9 miles west of Timaru city. The south east corner of the rectangle is li miles south east of Mt. Horrible Trig. at (GRSlll/640500~ with the north east corner situated 5~ miles to the north at (GRS111/6406oq • From the eastern boundary, both the north and south edges of the rectangle extend directly westwards for 12i miles to the western boundary, thereby enclosing 70 sq. miles. General Description of the Area •. Topography. The area may be divided into 4 topographical sections which from east to west are, (1) 1. The Timaru Downs. 2. The Craigmore - Cave Hill. '9 - 3· The Pare ora Intermontane Basin. 4. The Hunters Hills. Westwards from Timaru the elevation of the gently undulating topography gradually increases till a height of 1,272 ft. is reac~ed at Mt. Horrible Trig. (;.. This rising upland constitutes the Timaru Downs and is bordered to the south and west by the escarpments of Mt. Horrible, which are up to 700 ft.high. t •• )0 C1 ol 0\ oT I I) 2. (2) Immediately west of Mt. Horrible the Craigmore -Cave broken anticline forms a narrow ridge, traversing the area from north to south. The highest part is (4) at Trig. H on Cave Hill, 1,780 ft. high. The Pareora intermontane basi~ is bounded in I . the east by the Craigmore-Cave Hill, and in the west by the Hunters Hills. It is occupied by long parallel ~ndulating downs which extend towards the west, increasing gently in height as the Hunters Hills are app,r oached. (. ' These Hills rise steeply from the western margin of the 1ntermontane basin and within the area reach ·a height of 3,486 ft. at Trig. Kl. Drainage. The Pareora River has its source in the Hunters Hills. It pa~ses through the deep Upper Pareora Gorge, then out into the Pareora intermontane basin, where it meets the Motu_~aika and White Rock Rivers before passing through the Low·er Pare ora Gorge. All three ri vera drain the Pareora intermontane basin. Below this gorge at the s.w. corner of Mt. Horrible, the Pareora River is joined by Taiko Stream and Pareora River (South Branch) which drain the Taiko and Maungati areas respectively. (S) (~) itnuH 1 m it · :I.i.'I oH '!0 'I Vegetation. The natural flora of the area is tussock, flax and cabbage trees with a little bush confined to stream valleys in the high country. Climate and Agriculture. The climate is inclined to be dry with an average annual rainfall of 23 ins. Sheep farming is extensive in the uplands but also important in the lowlands. Cattle grazing is largely confined to the low country. Cropping is particularly important upon the low lands where topography and climate are suited to such activity. Previous Ge,ological Investigat,ion.s .• As early as 1848, Mantell, during an exploratory journey from Christchurch to Dunedin, noted certain geological ~eatures at Timaru and wrote (18501 p.322) that, "The superficial deposits of Timaru are of the same nature as those of the plains, and are superposed on a vesicular volcanic rock which reaches a height of fifteen feet, and, gradually dipping to the south, disappears in the course of a few miles." Mantell also mentions a seam of coal 10 ft. thick said to occur, 11 on the bank of a stream inland of Timaru." (l850, P~323). According to Gudex (1918, p.244), 11Haast in l865 examined the country between Mt. Horrible and the banks of the Pareora River, with a view to obtaining a V ta t.Sl r..aq ~.riu te .... l olrl !.:>i:Cl d water-supply for Timaru. 11 Gudex also states that, (p.254) "In 1875 Hutton, in his Catalogue of Tertiary Mollusca, &c., introduced the Pareora Formation as one of the four chief divisions of the Tertiary, dividing it into an upper and lower group, but he identified no fossils from Pareora, and was uncertain whether this locality should be referred to the Upper or Lower Group." In 1877, McKay visited the area whilst on a geological traverse between Waipara and North Otago. McKay (1877 pp.49-66) gives an account of the sequence observed. Park (l904, P·530) remarks that, "The sections at the lower and upper ends of the Pareora Gorge are so obscure as to be of no value for the determination of relations existing between the beds containing what has ·been known as the Pareora fauna and the Oamaru Stone." -'He goes on to say that, "At White Rock River, higher up the valley, the Oamaru Stone is absent, but the fossiliferous clays and sandstones exposed there rest upon the basement rock of the district." 4. Evidently Park failed to recognize the limestone which dips westwards from the Craigmore anticline to pass beneath the White Rock River area and reappear along the base of the Hunters Hills. McKay (187~pp.50-51) in a section of the Pareora area presents the White Rock River beds in their correct stratigraphical position. H l :I 'I 6~ I) du ['100 bt. t 'lo d .ad '00 Hardcastle in 1890 (pp.406-414) and in 1891 (pp.311-324) published detailed information concerning respectively the loess and drift deposits of South Canterbury, whilst in 1908 (pp.6-6o) he also published a popularized account of the geology of South Canterbury. In 1914 Gudex studied the Tertiary sequence in the Pareora- district and stated {1918,p.246) that, 11My examination of the district shows that the Tertiary beds of the district are all conformable, and not separable ' into two unconformable groups as McKay supposed; that the upper beds with a 11 Pareora fauna" are above the limestone, and not below as Park supposed; and that there is a similar fauna above and below the limestone, as Thomson suggested. (Thomson , l915, pp.l23-124)." In 1917 Thomson visited the area and examined the limestones occupring at Craigmore {Thomson 1926 p.159). Finally the White Rock River 'fossil locality was visited by Laws who described Hutchinsonian-Awamoan faunas collected throughout South Canterbury. (Laws 1 1933, pp.315 - 319). ---------------------- 5·

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iii. 159 p., ill.; 27cm.

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OU geology Identifier:

1954Croxford

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http://download.otagogeology.org.nz/temp/Abstracts/1954Croxford.pdf

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Citation

Croxford, Norton James William., “Geology of the Pareora district,” Otago Geology Theses, accessed December 12, 2018, http://theses.otagogeology.org.nz/items/show/3.