C—9

32

.\iitun nf tlie Work carried out.

Maps compiled on a scale of 20 chains to 1 in., from information obtained from the bands and Survey Department, have been prepared and supplied by the draughting staff of the Department for use as a basis for the plotting of Held work. Since the watercourses afford by- far the best sections of the rocks in which their valleys have been eroded, and at the same time contain specimens of rocks and mineral-deposits, which have gravitated from the ridges or have been transported by water, the greater part of the work consists in the examination and survey of the stream beds. An examination of the ridges and spurs is also undertaken, but these do not as a rule shoxv good rock outcrops The disposition ami lithological character of all exposures of strata have been noted and mapped with a view to indicating the anticlines of the area, so important in connection with a petroliferous area. General Geology. The following classification of the formations occurring within the area already examined, is tentatively submitted pending further pabeontological and petrographioal xvork on the numerous specimens collected : — Formation. Age. (a.) Whatatutu Series ... ... Probably Miocene (lower beds possibly older). (b.) Waipaoa Beds ... ... Pliocene. (c.) River and terrace gravels ... Pleistocene and Recent. Mr. Alexander McKay, who has traversed a much larger area than that now being described, gives a more detailed classification in a report ''On the Pel i oleum-bearing Rocks of the Poverty Bay and East Cape Districts."* The following table, indicating the various formations mapped by Mr. McKay as occurring xvithin the Whatatutu Subdivision, together with (heir lithological character and typical localities of occurrence, has been compiled from the above report: —

(a.). Whatatutu Series. — Almost the whole of the formations occurring in (he aria examined up to the present time have been classed under this head, for the reason that stratigraphical unconformities arc by no means apparent, and such paheontological evidence as is at present available does not appear to wan ant their being referred to more than one series. Mr. Alexander McKay, however, considers the lower beds to be iinconformably older, and of probable Cretaceous age. Certain beds, from their general mode of occurrence, appear to be associated, and thus the series admits of subdivision in ascending order as follows: — (1.) Chalky limestones; glauconitic sandstones. (2.1 Coralline limestone. (3.) Claystones, with calcareous concretions; argillaceous limestone. (4.) Argillaceous sandstones, coarse conglomerates, sandstones, and claystones; ooncre tionary bands; hue shelly conglomerates; sandstone. (1.) Chalk)/ Limestones and Glauconitic Sandstones. The chalky limestones occur in broken outcrops along a line extending in a north eas! direction frmn :i point in the WaipaoH River about a mile above the confluence with the Mangatu. across the M atigataikapua to the heads of the Wai tang! and Makara streams. The chalky limestone formation is for the most part of xvhitish appearance, but is often tinged pale green or brown, probably by ferruginous minerals The rock frequently breaks into small fragments, but where numerous veinlets of calcite occur is more compact. In places it is highly friable and even slickensided. The glauconitic sandstone is a fairly well-compacted rock, green in colour, appearing duncoloured on weathered surfaces. It occurs in the vicinity of the main oil-spring, in branches of the Te Hau-o-te-Atua and Mangataikapua streams and elsewheif

* Mines Report, 1901, C.-10, pp. 21-25.

Age. Petrological Character. Typical Localities of Occurrence. Middle Cretaceous Sandstones, dark shales, and cal- Upper Waitangi Stream, careous concretions. Bands of limestone of yellow tint Upper Cretaceous... Green sandstones, siliceous shales. Waitangi River to oil-springs. Along Indurated chalky limestones alter- Oilspring Creek to near its junction nating with greensands. Marly- with the Waipaoa. From Oilspring limestones or calcareous sandstone Creek to Mangatu River. Lower Tertiary ... Coarse conglomerate or breccia. Waipaoa River Valley. Oilspring Sandy marly clays, with beds of j Creek, Waipaoa River. Eastern brown sandstone, including fora- j basin of Upper Waingaromia River, miniferal limestone Pliocene ... ... Sandy clay. Pumiceous sands, lime- Terraces east side of Waipaoa River stones above Te Karaka, Recent ... ... Beach-deposits; blown sands; alluvial (river) deposits.