New Zealand: A Continent in the Ocean
Book 1 of Paleontology
Language: English
38.15.00=Lithology 38.21.00=Regional geology 38.29.00=Stratigraphy 38.31.00=Paleontology ENCYCLOPEDIA Paleontology acoustic impedance alamo impactor america anabar shield arc area arenas asphaltic concrete baker ballance bally baltic shield base basin bed boundary boundy brenchley brook street calder cambrian carbonate carboniferous cartoon illustrating case chaloner change chukchi seas circum-pacific council cleal coarser grained coiled ribbon commonly complex condition continental craton crowther current data delta deposit deposition development devonian dillon dobs linn doolittle dow early earth east environment erwin evandavia aureola event evidence evolution exon exploits subzone facies fault fern-like foliage field fixed stock flood flow form formation formed fossil gas gensel geological geology graciansky grand banks group harris high hogan ice international commission island journal juneaugust units jupiter saturn kirwans dolerite lacey lagersta tten lake lane late level lewry life london major margin marine material mcelwain mckerrow menlo park microfossils conodonts mid-ocean ridges middle model moldowan myrow national academy national aeronautics national museum nature north north america northern notre dame nova scotia novaya zemlya occur ocean ocoee supergroup oil ordovician oxford palaeovaucheria clavata palaeozoic palmer pathological molar paull pefferkorn peptide bond percival permian petroleum physiographic province plants invade plate poag port moresby porter press process processes protoarenicola baiguashanensis range rate rattey record reef region reproduced reservoir result rickards river robert loveridge rock rotational symmetry san andreas sand santa isabel scale schopf science scotese sea sediment sedimentary sequence shelf shuiyousphaeridium macroreticulatum sierra nevada sinospongia typica slope society source south southern sparks rsj structure submarine resources surface tectonic terranes tetagoucheexploits back-arc tianzhushania spinosa time tooth bud treptichnus pedum type university valeria lophostriata vanua levu vice versa viti levu volcanic water wave wernecke supergroup western whalen wong xanthophyte alga year york zhuravlev zone
Published: Dec 31, 2004
Description:
"NEW ZEALAND", "N Mortimer, Institute of Geological and Nuclear Sciences, Dunedin, New Zealand 2005, Elsevier Ltd. All Rights Reserved. Introduction The south-west Pacific Ocean is a region of isolated islands and submerged plateaus and ridges (Figure 1). The three main islands of New Zealand (North, South, and Stewart) make up the largest landmass group in the region. Schists, greywackes, and granitoids are exposed on the Challenger Plateau and Chatham Rise and have been sampled by dredges on the Campbell Plateau and Norfolk Ridge, thus demonstrating their continental geological character. Abyssal Pacific oceanic-crustal floor typically lies at water depths of about 5000 m, and the boundary between continental crust and oceanic crust is marked by a generally pronounced slope break at about 2500 m water depth. The wider area of continental crust in the New Zealand region (Figure 1) is about one-third the area of on-land Australia and is commonly referred to as Zealandia. On-land New Zealand contains a wide variety of Phanerozoic rocks (Figure 2), which preserve a detailed record of the Cambrian to early Early Cretaceous convergent margin of southern Gondwana, late Early Cretaceous rifting, a Late Cretaceous-Palaeogene passive margin, and the Neogene-Holocene active convergent and strike-slip margin. So much of continental Zealandia is submerged because of the widespread Cretaceous extension and rifting. It was only with the development of the Neogene-Holocene convergent plate boundary that about 10% of Zealandia emerged above sea-level. A distinction is generally drawn in New Zealand between pre-late Early Cretaceous (more than 105 Ma) basement rocks, which are commonly metamorphosed and generally highly deformed, and cover rocks, which are younger than 105 Ma, poorly indurated, well stratified, and less deformed. Palaeogeographical Reconstructions The shape of the continental crust of Zealandia has changed throughout the Phanerozoic. From the Cambrian to the Early Cretaceous, the New Zealand part of the Gondwanan margin grew by the magmatic and tectonic addition of batholiths and terranes. In the last 100 Ma this continental crust has been thinned, rotated, and translated in response to multiple tectonic events. Reconstructions (Figure 3) involve subtracting the 480 km Neogene dextral strike-slip movement on the Alpine Fault, the 45 Oligocene-Miocene rotation between the Pacific and Australian plates, and 4000 km of northwards drift. Small crustal blocks within 100 km of the Alpine Fault (i.e., most of on-land New Zealand) have undergone strong Cenozoic deformation. In the pre-rift (100 Ma) palaeogeography (Figure 3A), Zealandia is in a near-polar position and contiguous with Tasmania and Antarctica. By 10 Ma, some movement on the Alpine Fault had taken place, and modern-day New Zealand had been isolated by seafloor spreading. Geological Basement At a regional scale, the volcanic, sedimentary, plutonic, and metamorphic basement rocks of New Zealand can be described in terms of a number of western and eastern tectonostratigraphic terranes, composite regional batholiths intruding these terranes, and schist, gneiss, and mélange overprints on the terranes and batholiths (Figure 4). Figure 5 shows the names, age ranges, and mutual geometric relationships of the constituent basement units on an Early Cretaceous reconstruction (Figure 3A). No Precambrian rocks are exposed; New Zealand has been near a continent-ocean margin throughout the Phanerozoic. Western Province Terranes The Western Province terranes lie west of the Median Batholith and comprise the Early Palaeozoic Buller and Takaka terranes. The Buller Terrane consists of variably metamorphosed siliciclastic sandstones and mudstones, of continental Gondwanan provenance, and is the westernmost recognized terrane in New Zealand (i.e., the terrane closest to the Gondwanan cratonic core). Rare fossils are of Ordovician age, but a Buller Terrane paragneiss contains detrital zircons as old as 3400 Ma (Archean; New Zealand's oldest known geological material). Intercalated volcanics are absent. The Takaka Terrane consists of siliciclastic, carbonate, and volcanic rocks. Middle Cambrian trilobites in the Takaka Terrane are New Zealand's oldest known fossils. The Takaka Terrane is generally well stratified and lithologically diverse, and includes Cambrian ultramafics and boninites, Ordovician limestones, and Silurian orthoquartzites. The Buller and Takaka Terranes were accreted to Gondwana by the Devonian. Eastern Province Terranes The Eastern Province terranes lie east of the Median Batholith and comprise the Brook Street, Murihiku, Maitai, Caples, Rakaia, and Pahau terranes. Carboniferous conodonts are known from a limestone in the Rakaia Terrane, but the age range of clastic rocks in Eastern Province terranes is from Permian to Early Cretaceous (Figure 5). The Eastern Province terranes are thus entirely younger than the Western Province terranes and represent accretion of material to Gondwana in the Mesozoic. The Brook Street Terrane is a Permian subduction-related isotopically primitive pyroxene-rich basalt-dominated volcanic pile and volcaniclastic apron, in places up to 14 km thick, which is intruded by Permian layered gabbros and trondhjemite plutons that are now part of the Median Batholith. New Zealand's only known Glossopteris, a Gondwanan leaf fossil, occurs in the Brook Street Terrane. The Murihiku Terrane comprises a 9-13 km Late Permian to Late Jurassic volcaniclastic marine succession of sandstone with lesser conglomerates, mudstones, and tuffs. It has the simplest internal structure of all the Mesozoic New Zealand terranes, a broad synclinorium that is traceable for 450 km through the North and South Islands. The Maitai Terrane consists of the eastern Early Permian (285-275 Ma, according to uranium-lead dating of zircon) Dun Mountain Ophiolite Belt, which is unconformably overlain by 6 km of well-stratified Late Permian to Middle Triassic volcaniclastic sedimentary rocks. The ophiolite originated in a near-arc setting. The Brook Street, Murihiku and Maitai terranes are adjacent to each other as a Permian-Triassic arc, fore-arc, and exhumed near-arc ophiolite, respectively. The Caples, Bay of Islands, and Rakaia terranes contrast with the aforementioned Eastern Province terranes in that their Permian-Jurassic clastic sequences are tectonically imbricated with ocean-floor basalt, chert, and limestone associations; all three terranes grade into the pumpellyite-actinolite to amphibolite facies Haast Schist. Deposition occurred as submarine-fan deposits in lower trench-slope basins, before juxtaposition in an accretionary prism. Compositional and provenance differences are used to discriminate the three terranes: Rakaia sandstones are quartz rich, plutoniclastic, and of average rhyodacitic composition and are thus compositionally distinct from the more dacitic to andesitic volcaniclastic-dominated sandstones in Caples and the Bay of Islands. The Pahau Terrane has a similar lithology and structure to the Rakaia Terrane, but its depositional ages extend into the Late Jurassic and Early Cretaceous and it contains tuffs. Much of the Pahau clastic detritus is probably recycled from Rakaia rocks, but a volcanic input, probably from the Median Batholith, is also required. The Pahau Terrane probably represents trench deposits that" Ключевые слова: circum-pacific council, protoarenicola baiguashanensis, lane, permian, ga, south, carbonate, bally, schopf, process, exon, evolution, volcanic, continental, san andreas, physiographic province, vanua levu, type, ballance, complex, level, geological, erwin, sand, gensel, london, devonian, york, international commission, percival, journal, island, harris, notre dame, sedimentary, deposition, paull, rate, science, gas, time, press, craton, scotese, whalen, myrow, ma, microfossils conodonts, evandavia aureola, boundary, region, lewry, coiled ribbon, margin, occur, year, field, life, chukchi seas, hogan, facies, middle, fixed stock, scale, result, rickards, river, fern-like foliage, bed, geology, palaeozoic, nova scotia, lacey, cleal, jupiter saturn, slope, cambrian, north, marine, novaya zemlya, fossil, calder, formation, lagersta tten, case, large, record, america, brenchley, santa isabel, nature, carboniferous, palmer, wernecke supergroup, peptide bond, acoustic impedance, development, baker, sediment, palaeovaucheria clavata, reef, oxford, juneaugust units, treptichnus pedum, porter, formed, tectonic, exploits subzone, sequence, pathological molar, east, sparks rsj, xanthophyte alga, dillon, submarine resources, group, late, north america, shelf, northern, viti levu, port moresby, dow, vice versa, area, rotational symmetry, reservoir, ice, western, doolittle, high, ga ga, mid-ocean ridges, national academy, sierra nevada, environment, southern, plate, fault, chaloner, national aeronautics, rock, robert loveridge, event, grand banks, national museum, university, mckerrow, tianzhushania spinosa, cartoon illustrating, range, earth, source, arenas, poag, kirwans dolerite, base, terranes, commonly, pefferkorn, boundy, lake, ha, arc, tetagoucheexploits back-arc, graciansky, oil, menlo park, wave, shuiyousphaeridium macroreticulatum, structure, brook street, plants invade, sinospongia typica, water, basin, ocean, sea, crowther, data, major, flow, mcelwain, flood, wong, ordovician, material, deposit, valeria lophostriata, model, coarser grained, anabar shield, surface, zone, small, reproduced, baltic shield, zhuravlev, early, alamo impactor, asphaltic concrete, rattey, moldowan, wa, dobs linn, society, processes, change, evidence, delta, condition, tooth bud, ocoee supergroup, current, petroleum, form