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Geological Survey of Part of New Plymouth Subdivision. Introductory. Introduction.—From the 22nd November, 1909, to the 18th February, 1910, the writer was occupied in making a geological survey of a portion of the New Plymouth Subdivision. The following report deals mainly with the eastern portion of the subdivision, the survey in this part having been practically completed. Reference, however, will sometimes be made to some of the salient features of the uncompleted portion of the area. Ai;i:a dealt with in Report.—The New Plymouth Subdivision of the Taranaki Division covers an area of about 220 square miles, and consists of the survey districts of Waitara and Paritutu. It is bounded on the north by the coast-line of the North Taranaki Bight from a point about three miles and a half south-west of the New Plymouth Breakwater to a point about one mile and a quarter north-east of the mouth of the Mimi Stream. On the east it is bounded by a zigzag line running southwards for a distance of about twelve miles from the last-mentioned point on the coast-line. The southern boundary is also a zigzag line that runs westward for a distance of about twenty-five miles, where it meets the zigzag western boundary-line that runs southward from the western termination of the northern coast-line-. The Waitara Survey District, with which this report mainly deals, covers an area of about 125 square miles, and makes up the western half of the subdivision, being separated from the Paritutu Survey District by a zigzag line running southward from the Town of Waitara. Object of Survey, and Plan of Conducting Work.—The sole object of the survey being the ascertaining of the pet coliferoufl possibilities of the area, great attention was given to any " indications " in the shape of oil-seepages or gas-vents, and at the same time every effort was made to determine the geological structure of the area with a view to locating the position of anticlines and synclines, which, according to one widely accepted theory of the origin of petroleum-reservoirs, exert a preponderating influence on the occurrence of oil. As in t In- case of t he other geological surveys carried out under the present direction, all streams, ndges, roads, and other natural or artificial features that seemed likely to afford outcrops were carefully examined. Owing to the abundance of data on the maps supplied bythe Lands and Survey Department, it was not found necessary to make chained traverses of any part of the area, the positions of outcrops bem<; located with sufficient accuracy from the existing maps. The results were plotted on plans reduced to a scale ol -id chains to the inch from the original maps m the Lands Office at New Plymouth. In order to ascertain as exactly as possible the stratigraphical arrangement of the sedimentary rocks, strikes and dips wet, observed with great care ; and with the same object a great number of barometric heights were recorded. Numerous supposed gas-vents and oil-seepages, of which information was given locally, were visited, and their positions carefully noted. Previous Investigations. The occurrence of petroleum at Moturoa is said to have been known to the Maoris prior to the advent of Europeans to the district.* In 1839 Dr. E. Dieffenbach visited the Taranaki I )tst rid . and made various observations of a geological character. He noted the character of the rocks composing the " Sugar Loaves " and the adjacent mainland, and recorded also the occurrence of "sulphuretted hydrogen " gas-escapes in the sea near Moturoa.f It is said that a member of Dieffenbach's exploring party found an exceedingly rich specimen of auriferous quartz, the value of which was not known lor many years. The locality of this find is unknown, but is almost certainly east of the area at present under consideration. In 1867 Dr. (Sir .lames) Hector reported on the Taranaki District.f In his report, which seems to form the basis ol all subsequent papers, Hector distinguished four different formations, and emphasized the absence at the surface of the alternating beds of sand and clay that are found in the chid oil districts of the world. In 1899 Mr. Alex. McKay, m a " Report on Petroleum at New Plymouth, Taranaki "§ gave a history ot the search for oil in the district. He concluded that, while- some of the surface indications of oil may be due to the decomposition of carbonaceous material in the more superficial strata, the boring operations have proved the existence of oil-beajring strata at a greater depth. Whether or not these are the continuation of the Mokau coal-beds he considered to be impossible of proof. Towards the end of 1909 Dr. J. M. Bell issued a " Preliminary Report on the Taranaki Oilfield "f This report, while dealing mainly with present boring operations near New Plymouth, also gives a brief summary of the geology and physiography of the whole subdivision. Physiography and General Geology. Physiography.—The New Plymouth Subdivision exhibits a subdued topography, which may be said to be expressed by two general types-one seen in the western part of the area, the other in the eastern part. The western type—that of the Paritutu Survey District—presents an undulating country traversed by rather shallow, fairly rectilinear valleys. The eastern type, as seen in the Waitara Survey District (with which this report chiefly deals) exhibits a series of steep-sided even-crested ridges separated by sinuous flat-bottomed valleys, through which flow sluggish streams. In the Waitara type of topography the trend of the ridges is in general parallel to the intervening streams. A striking exception to this rule is the Tarata Ridge, which has a general west-south-west

+aw , ili ß es Re P ol ;t' 18 " 9 > c --9> P- 3. t"N«* Zealand," 1843, Vol. i, pp. 134-35. % Abstract Report ot the Progress of the Geological Survey of New Zealand during 1866-67. § Mines Report, I 0.1.1, \ . J. pp. o —lU. ( .—l4.