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The beds of the syncline are gently folded, and eight miles north-west of Tinui near its west edge turn over to form an anticline. South-westward along the belt continuing the syncline the rocks have a complex structure. Generally, the Tertiary beds are regular ; but in one place—that is, in the narrow strip near Castle Point—they are closely bent into many short twists. The Cretaceous beds, on the contrary, are nearly everywhere intricately contorted and badly shattered. Again, while in the broad sense both the Cretaceous and the Tertiary structures tiend north-north-east, the Cretaceous structures are in places transverse to the Tertiary, in some places oblique, and in others perpendicular. As already mentioned, the country is built of major units bounded by faults. In no place can the actual faults be seen, not even where the Cretaceous-Tertiary contact runs out to the coast. Generally, one set of beds is followed for miles by means of scattered outcrops till after crossing an interval without any outcrop the observer finds himself in a different set. Then, after returning over the blank space to trace down the contact, he finds a low slip of crushed rock, a gently swelling mound, or an open valley with no rock exposed. After trying out several of these, he gets familiar with their habits, and recognizes them, as a matter of course, as the indications of fault contacts. The main Cretaceous block is faulted along both sides. On the east side of it on the coast five miles north of Castle Point a rock platform 20 to 30 chains wide, formed of contorted and brecciated white Cretaceous argil lite dipping westward at 80° or standing vertical is interrupted by a gap 15 chains across, east of which regular beds of Tertiary brown sandstone dip east at 80°. To the south the rocks on the west continue unchanged, but the sandstone beds on the east dip less and less steeply for the next 60 chains, and past that all dip to the west. This is a typical CretaceousTertiary fault contact. The break appears to be a steep or vertical thrust with the beds generally parallel to the fault. In many places the margins of the Tertiary are splintered and form jagged salients and narrow outliers. Within the Cretaceous horst the Jurassic core is bounded by steep pug or shatter belts. On the east side of the Jurassic in Pakowhai River the Cretaceous beds of fine light argillite and siltstone dip 30° westward for half a mile, and next steepen to 80° in 10 chains and end at a narrow gully with a mudflow at the mouth. Across this the rocks are hard, nearly black, polished and slickensided, twisted, shattered, and pugged argillites, sandstone, greywacke, and conglomerate, dipping 80° westward. In other places the rocks are crushed or minutely shattered and slickensided through thousands of feet. In Mangapakeha Survey District a Jurassic-Tertiary contact is well exposed. The soft Tertiary brown sandstone striking east of north dips 20° to the west. West of the Tertiary is a 2,000 ft. range of crushed and pugged dark argillite, greywacke, and conglomerate. Generally, throughout the Jurassic and Cretaceous wherever a hard and soft bed are in contact the soft bed is crushed and the hard one slickensided ; and where the hard bed is thick the adjoining soft beds are finely shattered and crushed. Within the Tertiary, also, faults have moved the beds 5,000 ft. to 10,000 ft. past one another. Erosion has in places left no fault scarps ; and, indeed, at Tinui has gone so far as to remove all the upthrown Tertiary and crushed Cretaceous rocks and to expose obsequent scarps, 1,000 ft. high on the downthrown Tertiary sandstone. Again at Castle Point the mudstone under the Te Aute limestone at the "Castle" has in the late Tertiary been dropped 10,000 ft. past the sandstone of the mainland. The surface was afterwards smoothed down by erosion ; but renewed movement on the same faults later on twisted and overturned the limestone. Stratigraphy. The Jurassic rocks nowhere crop out in a continuous section. They form ranges two miles and a half wide in the south of Mangapakeha Survey District, and one mile and a half wide in the upper Mangapakeha Stream. The beds are vertical or steep and twisted. They are thick, probably tens of thousands of feet, but underlying rocks are nowhere exposed. In the big masses of these supposed Jurassic beds no fossil was found. Among similar rocks in the upper Makirikiri Stream, west of Manawa Trig., Mangapakeha Survey District, two loose blocks of limestone contain numerous specimens of a shell identified by Dr. Marwick as Buchia (Aucella), a Jurassic form. Only one good section of Cretaceous beds is exposed in the district, that along Mataikona River. Here the beds lying between two strong faults dip continuously at 70° for two miles, and contain fossils characteristic of the Raukumara and Tapuwacroa Series of the East Cape district. Overlying them are fine light-coloured strata resembling the Mangatu Series of the same region. In Waipaua Stream the Raukumara Series of alternating greywacke and argillite with Inoceramus bicorrugatus is 7,000 ft. thick. Above it is conglomerate with the Tapuwaeroa fossil Ostrea lapillicola and alternating beds of argillite, greywacke, and many beds of fine conglomerate, totalling 5,000 ft. thick. Above this, unfossiliferous, finer, and lighter-coloured beds 2,500 ft. thick are assigned to the Mangatu. They are cut off above by a fault. Among the fine beds of the Mangatu occur thick beds of black shale several hundred feet thick. In other places the Mangatu beds are thicker ; 6,000 ft. is exposed in a continuous section in the upper Castlepoint Stream. In many places wide stretches of country are occupied by Mangatu rocks, but the structure is not evident and does not allow the thickness to be estimated. Cretaceous-Tertiary boundaries are in most places along faults. At sedimentary contact's in some places the Cretaceous beds have the same attitude as the Tertiary ; in others there is marked discordance. Parallel Cretaceous and Tertiary beds can be seen in Angle Stream, two miles east of Tinui; unconformable Cretaceous and Tertiary sets almost perpendicular to each other are exposed

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