Pliocene‐Quaternary sedimentation and Alpine Fault related tectonics in the lower Cascade valley, South Westland, New Zealand

Abstract

Study of Pliocene and Quaternary sediments west of the Alpine Fault in the Cascade valley, South Westland, New Zealand, has allowed determination of Alpine Fault displacement rate and coastal uplift rate over the last 3.5 m.y. Exposures of the Pliocene Halfway Formation (latest Opoitian-Waipipian) are composed of marine sand and conglomerate deposited in c. 200-1000 m water depth. Beds are gently dipping and weakly deformed, with the direction of principal shortening oriented at a high angle to the Alpine Fault and plunging gently northwest (c. 107340°). Fiordland-derived clasts indicate a minimum of 95-100 km of lateral offset on the Alpine Fault since deposition of Halfway Formation. Paleogeographic evidence suggests that first-order features of the drainage were similar in Pliocene time to those of the present day.Quaternary moraines and fluvioglacial sediments are subdivided on the basis of composition and morphology into five groups: Cl (oldest) to C5 (youngest). The Cl deposits have a provenance consistent with a glacier flowing from the Pyke valley. The C2 and C3 deposits are c. 95% ultramafic and 5% Haast Schist derived, whereas the C4 and C5 deposits are c. 75% ultramafic and 25% Haast Schist Teer Formation (new) is composed of shallow-marine fossiliferous glacial silts, which lie unconformably above Halfway Formation and beneath C3 and C4 moraines. Clast compositions indicate that source regions to the east of the Alpine Fault were in the vicinity of the Pyke valley and that Teer Formation may be a fiord correlative of the C1 morainic deposits. Based on an offset of c. 18-32 km and an Alpine Fault displacement rate of 27 ± 6 mm/yr, an age for the Teer Formation and C1 deposits of 0.9 ± 0.4 Ma is interpolated. Uplift rate estimates based on Halfway and Teer Formation coastal outcrops are in the range 0.1-0.5 mm/yr.

A historical perspective of the genus Mytilus (Bivalvia: Mollusca) in New Zealand: multivariate morphometric analyses of fossil, midden and contemporary blue mussels

“…The fossil record for Mytilus in NZ dates back a little over 1.0 Mya, to the early Castlecliffian (Sutherland, Nathan & Turnbull, 1995 with an appendix by A. G. Beu), and supports a Pleistocene (1.5–2.5 Mya) origin of Mytilus spp. in the southern hemisphere (Hilbish et al ., 2000).…”

“…E38/f15, collected by A. G. Beu, S. Nathan and I. M. Turnbull from the large boulders of Teer Formation in Whiskey Creek, north coast of Cascade Point, south Westland, between Teer Creek and the ‘giant slip’, grid ref. E38/448788 (Sutherland et al ., 1995).…”

The Alpine Fault biogeographic hypothesis revisited

“…That movement occurred largely in the late Neogene is supported by extensive evidence (e.g. Cutten, 1979; Johnston, 1990; Sutherland et al., 1995), and 230 km of dextral strike‐slip since 6.4 Ma (latest Miocene) has been proposed (Walcott, 1998) and 100 km of strike‐slip motion since Mid‐Pliocene demonstrated (Sutherland, 1999). North‐west South Island and southern South Island were thus juxtaposed very closely as recently as Late Miocene to Miocene/Pliocene boundary.…”

Torlesse greywacke and Haast Schist source for Pliocene conglomerates near Reefton, New Zealand

“…significant quantities of non-local Eastern Province detritus, which has been interpreted in terms of progressive dip-slip and strike-slip movement on the Alpine Fault and other faults in the Neogene (Cutten 1979;Smale 1991;Sutherland et al 1995;Sutherland 1994Sutherland , 1996Rose 1996).…”

“…The Buller Terrane provenance of the Rotokohu Coal Measures requires that the Inangahua region was isolated from this Caples Terrane source, and suggests a source area in the north, west, or southwest. Sutherland (1996) showed that in central Westland (Waiho-1 borehole) a major change in provenance from Nathan (1978), Cutten (1979), Suggate (1984), Nathan et al (1986), Smale (1991), Turnbull et al (1993), Sutherland (1994Sutherland ( , 1996, Sutherland et al (1995), and Rose (1996). Time-scale of Crampton et al (1995).…”