Geology of the Kaikoura Area - GNS Science

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volatile bituminous coal. The conglomerate clasts, up to0.4 m across, include felsic igneous intrusives, intermediateto mafic volcanic and igneous rocks, and induratedsedimentary rocks. Plant fossils are locally present andmicrofloras indicate an early Late Cretaceous (RaukumaraSeries) age. The formation has been weaklymetamorphosed to zeolite facies. It is interpreted as part ofan extensive braided and locally meandering river depositthat accumulated in a fault-angle depression or half-grabenunder a warm oxidising climate (Johnston 1990).Cretaceous igneous rocksA northeast-southwest aligned belt of isolated igneousbodies extends for over 150 km through Marlborough andnorthern Canterbury (the Central Marlborough igneousprovince of Nicol 1977). Undifferentiated Cretaceousigneous rocks (Ki) include an alkaline ultramafic gabbroring complex and associated hornfels zone preserved atthe summit of Blue Mountain (Grapes 1975), and basaltflows and breccia preserved at Hungry Hill north of theWaima River. Neither of these occurrences has been dateddirectly, but Hungry Hill basalt rests unconformably uponCretaceous Pahau terrane and is overlain by LateCretaceous (Piripauan) Paton Formation (Waters 1988).carbonatite (Fig. 36a). The upper part is intruded by syenitesills and dikes (Baker & others 1994). Magnetite andilmenite, largely within the anorthosite, are responsible fora major magnetic anomaly centred on the Inland KaikouraRange (Reilly 1970). The intrusion is surrounded by acontact-metamorphosed hornfels zone (Kth) up to 400 mwide in the surrounding Pahau terrane rocks (Baker &others 1994). A radial suite of basanitic dikes (Fig 36b,c)extends outwards from the main body for a distance ofmore than 10 km, and the top of the intrusion was probablyemplaced at a depth of 3–4 km. A 96 Ma intrusion age forthe Tapuaenuku Igneous Complex, based on U-Pb dating(Baker & Seward 1996), is supported by K-Ar ages ofcogenetic dike intrusion between 100 and 60 Ma (Grapes& others 1992). The complex is genetically related to the96 Ma Gridiron Formation (Crampton & others 2004) andthe Lookout Formation (Challis 1966; Nicol 1977; Reay1993), but has a greater age range.The Mandamus Igneous Complex (Kim) is exposed in thehills at the northwestern edge of the Culverden Basin. Thecomplex is generally erosion-resistant compared with itsPahau host-rock and is the southernmost of the alkalinegabbro intrusives in the map area. It is composed principallyThe Tapuaenuku Igneous Complex (Kit; Nicol 1977) cropsout as a sub-circular intrusion, 7 km in diameter.Approximately 600 m of vertical section is exposed on Mt.Tapuae-o-Uenuku. The complex is composed of layeredpyroxenite, peridotite, anorthosite, gabbro and minor(b) Basanite dike intruding gabbro and earlier dikeintrusions, Hodder River headwaters.Figure 36 The Tapuaenuku Igneous Complex.(a) Boulders of gabbro, syenite and basanite in theHodder River.34(c) Aerial view (200 m wide) of dikes intruding poorlybedded Pahau terrane in the Inland Kaikoura Range.Photo CN25914/2: D.L. Homer.
of feldspar-clinopyroxene-biotite-amphibole syenite andclinopyroxene-labradorite-olivine-biotite gabbro. Volcanicflow rocks are predominantly trachytic with minor basalt,including possible vent-lavas/breccias around HurunuiPeak. The Mandamus Igneous Complex has been Rb-Srdated at 97 Ma (Weaver & Pankhurst 1991).Paleocene to Eocene sedimentary rocksIn the south of the Kaikoura map area, deposition of theEyre Group including Conway Formation and LoburnMudstone (see above) continued through into thePaleocene. The upper part of the Eyre Group is commonlytoo thin to differentiate from lower parts and is mapped asundifferentiated (KEe; Fig. 28). Paleogene Eyre Group (PEe)includes the Paleocene to Early Eocene Waipara Greensand,consisting of fine- to medium-grained, glauconiticsandstone that becomes increasingly muddy up section(Browne & Field 1985). The overlying Early to MiddleEocene Ashley Mudstone consists of glauconitic,calcareous sandy mudstone, siltstone and sandstone. Ingeneral the Ashley Formation rests disconformably onWaipara Greensand (commonly with a burrowed,phosphatised contact) but, locally, around the lowerHurunui River-Culverden area, it is unconformable onPahau terrane (Fig. 28). In the far south of the Kaikouramap area, the Middle to Late Eocene Homebush Sandstoneoverlies the Ashley Mudstone. It is a massive, glauconitic,unfossiliferous, well-sorted, quartzose sandstone, that mayhave become remobilised or intruded into underlying andoverlying units since deposition (Browne & Field 1985).The environment of deposition of upper Eyre Group rocksincludes shallow marine, low energy outer shelf (bathyal),and relatively high-energy near-shore beach settings.The Muzzle Group (Reay 1993) consists of mainly stronglyindurated micritic limestone and calcareous mudstone,chert, and minor greensand and volcanic rocks. The groupcontains two formations, the Mead Hill Formation and theAmuri Limestone, and in areas where both formations arethin the Muzzle Group is undifferentiated (KPz) on themap. The Mead Hill Formation (Kzm; Webb 1971) istypically a greenish-grey, chert-rich, micritic limestone,weathering to white and black (Fig. 37), with calcareousmudstone and nodular chert. The formation is limited tothe northeastern part of the map area and varies greatly inthickness. In Branch Stream it is about 120 m thick but itpinches out in the middle Clarence valley and is absent inSeymour Stream (Reay 1993); it reaches its greatestthickness in Mead Stream, where it is over 250 m thick(Strong & others 1995). In the northern Clarence valleyand in coastal eastern Marlborough, the formation containsthe Cretaceous-Paleogene boundary, which is particularlywell exposed in Mead Stream (Fig. 38) and is marked bymajor changes in microfossil assemblages (see text box).At Mead Stream the top of the formation is as young asLate Paleocene (Strong & others 1995; Hollis & others2005a).Figure 37 The Mead Hill Formation, MuzzleGroup, is a well-bedded siliceous limestone,shown here in Mead Stream.Figure 38 The Cretaceous-Paleogeneboundary occurs within the Mead HillFormation in Mead Stream. The hammerhandle rests on the thin bed marking theboundary.35
Page 1: 1 : 2 5 0 0 0 0 G e o l o g i c a l
Page 7: ABSTRACTThe Kaikoura 1:250 000 geol
Page 10 and 11: 27 10722181725814362333322621243128
Page 12 and 13: ProvinceSEDIMENTARY AND VOLCANIC RO
Page 14 and 15: Main Divide rangesGEOMORPHOLOGYThe
Page 16 and 17: Figure 9 Basin and range topography
Page 18 and 19: Figure 12 The active Alpine (Wairau
Page 20 and 21: 290PermianCarboniferous354Late Devo
Page 22 and 23: iotite granite, locally with megacr
Page 24: interlayered with the Rotoroa Compl
Page 28 and 29: Figure 19 Maitai Group sedimentary
Page 30 and 31: Torlesse composite terraneThe Torle
Page 32 and 33: Permian to Late Triassic semischist
Page 34: Zones of intra-Pahau mélange, char
Page 37 and 38: CRETACEOUS TO PLIOCENEFollowing ama
Page 39 and 40: Figure 31 Interbedded sandstone and
Page 41: Figure 34 The Seymour Group include
Page 45 and 46: The Amuri Limestone (Pza, Eza) is w
Page 47 and 48: overlies older rocks (Carter & Land
Page 49 and 50: Late Miocene to earliest Late Plioc
Page 51 and 52: QUATERNARYThe tectonic regime initi
Page 53 and 54: Figure 52 Screes on the southern fl
Page 55 and 56: Marine depositsMarine sand and grav
Page 57 and 58: and/or non-deposition (including th
Page 59 and 60: hydrous mica clay are widespread as
Page 61 and 62: Dunite boulders are sporadically co
Page 63 and 64: GEOLOGICAL HAZARDSParts of the Kaik
Page 65 and 66: The Modified Mercalli Intensity sca
Page 67 and 68: Table 2. Mean return periods for ea
Page 69 and 70: REFERENCESAdams, C.J. 2003: K-Ar ge
Page 71 and 72: Childerhouse, S.J.; Dawson, S.M.; S
Page 73 and 74: Holdaway, R.N.; Worthy, T.H. 1997:
Page 75 and 76: McPherson, R.I. 1988: Experimental
Page 77 and 78: Stewart, R.B. 1974: Geology of Mt M
Page 79: This map and text illustrate the ge

Geology of the Kaikoura Area - GNS Science

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