Brent Alloway - Academia.edu (original) (raw)
Papers by Brent Alloway
New Zealand Journal of Geology and Geophysics, 2002
New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 3... more New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 365-385 0028-8306/02/4503-0365 $7.00/0 © The Royal Society of New Zealand 2002 ... Growth of contractional structures during the last 10 my at the southern end of the emergent Hikurangi forearc basin, New ...
Tectonics, 1994
Analysis of the geometry and ages of faulted and tilted late Quaternary fluvial terraces and thei... more Analysis of the geometry and ages of faulted and tilted late Quaternary fluvial terraces and their associated cover beds provide evidence of active folding at three localities in the Waipara area of North Canterbury, New Zealand. Terrace survey data, the occurrence of the approximately 22.6kyr-old Aokautere Ash, and examination of soil profiles indicate that folding has continued into the late Holocene but that the amounts and rates of deformation are locally variable. Rates of uplift in the Waipara area are compared with those derived from marine terraces preserved at the Pacific coast, east of the study area. Results indicate that rates of measurable deformation reach a maximum along the Waipara range front, where bedrock deformation is most intense and shortening rates of up to 5.57 + 0.69%/100 kyr occur. Across the coastal ranges the average rate of shortening is 0.8 + 0.4%/100 kyr, which corresponds with an absolute shortening rate of 1.4 + 0.6 m/kyr and represents only a small proportion of the predicted plate motion vector in this region. Uplift rates range from 0-1.83 m/kyr for a late last glacial fluvial terrace and from 1.36-2.16 m/kyr for three marine terraces. Fluvial and marine terrace uplift rates vary in accord with the geometries of the folds in bedrock, and the spatial pattern of uplift directly reflects fold growth. The structure contour pattern of folded surfaces provides a first approximation to the spatial pattern of uplift. Differential uplift due to folding accounts for up to approximately 55-75% of the total uplift and has produced folds with structural relief of about 1300 m (i.e., amplitudes of 600-700 m). These folds have formed over the Paper number 94TC01502. 0278-7407/94/94TC-01502510.00 last 0.8 + 0.4 m.y. since the onset of Quaternary deformation in the Waipara region. lected from three different localities across the Waipara Syncline, near the township of Waipara . Fold geometry data, principally derived from altitudinal surveying, include disrupted cover bed stratigraphy and deformed fluvial terrace surfaces. Geometric data are complemented by age determinations provided by the radiometrically dated and laterally extensive Aokautere Ash, a radiocarbon date and detailed analysis of soil profile morphologies. The study has allowed conclusions to be drawn about the rates of shortening and uplift associated with folding, the age of cover beds, fluvial terrace surfaces and their deformation, and the relation-
Geological Society of America Bulletin, 2006
Holocene marginal-marine sedimentary sequences provide information on vertical tectonic deformati... more Holocene marginal-marine sedimentary sequences provide information on vertical tectonic deformation in a transect across the forearc basin adjacent to the Hikurangi subduction zone, New Zealand. The elevation of maximum postglacial sea level indicators at Te Paeroa Lagoon and Opoho is between 4 and 6 m below present mean sea level, indicating net subsidence since 7200 yr B.P. Opoutama is closer to the Hikurangi Trench and appears to lie near the edge of the zone of subsidence, as evidence for vertical movement there is equivocal. Some of the subsidence at Te Paeroa Lagoon and Opoho is likely to be a result of compaction. However, a component of subsidence probably happened coseismically in two events at ca. 7100 and 5550 yr B.P. Event signatures consist of tsunami deposits overlain by chaotically mixed, reworked sediment that appears to have fi lled rapidly created accommodation space at marine inlet sites 10 km apart. Large offshore earthquakes are suggested by the coincidence of tsunami inundation with sudden subsidence. Forward elastic-dislocation models indicate that the observed subsidence could be achieved in ~M w 7.9 earthquakes on either the subduction interface or the Lachlan Fault, which would involve synchronous uplift of Mahia Peninsula. Combined rupture of the interface and the Lachlan Fault, either simultaneously in a ~M w 8.1 earthquake, or consecutively, could explain larger amounts (>1.5 m) of coastal subsidence.
New Zealand Journal of Geology and Geophysics, 2002
Page 1. New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 467-479 0... more Page 1. New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 467-479 0028-8306/02/4504-0467 $7.00/0 © The Royal Society of New Zealand 2002 467 Foraminiferal and molluscan evidence for the Holocene marine ...
Journal of The Royal Society of New Zealand, 2002
This article was downloaded by: [66.249.67.15] On: 08 July 2011, At: 11:56 Publisher: Taylor &... more This article was downloaded by: [66.249.67.15] On: 08 July 2011, At: 11:56 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Quaternary Science, 2007
Auckland occupies a climatically sensitive position close to a major biogeographic boundary in th... more Auckland occupies a climatically sensitive position close to a major biogeographic boundary in the southern mid-latitudes. A new pollen record from Kohuora maar crater, Auckland, displays vegetation and climatic changes for the past ca. 32 000 years. Of particular interest are the inferred climatic patterns for the first part of the interval, encompassing the Last Glacial Maximum (LGM). The Kohuora record corresponds closely with pollen records from other Auckland sites indicating that the patterns observed are at least regional in extent. It is also broadly consistent with a variety of palaeoenvironmental evidence from across New Zealand, including the glacial record from Westland, other palynological records from North Island, other palaeoecological records from the South Island, and aeolian quartz sequences from western North Island. These records show that glacial conditions prevailed across most, if not all, of New Zealand during the interval ca. 29–19 k cal. yr BP, longer and earlier than the LGM sensu stricto. We suggest that the term extended LGM (eLGM) may be more appropriate for the New Zealand region. Within this predominantly cold interval, the Auckland pollen records indicate a climatic amelioration for the interval ca. 26–24 k cal. yr BP, also consistent with other palaeocological data from Canterbury, that fall within a period of climate amelioration recognised between the first two eLGM glacial advances in Westland. We refer to this warming interval as the eLGM Interstadial. The ca. 27 k cal. yr BP Kawakawa/Oruanui tephra is instrumental in most of these inter-site comparisons and occurs after the first peak of eLGM cooling in a short-lived comparatively mild phase. A subsequent return to apparently colder climate in the Auckland records may indicate a volcanic cooling effect or, more likely, widespread landscape disturbance following this major eruption event. Strong correspondence between biotic responses, glacial fluctuations and aeolian quartz deposition linked to major shifts in strength and latitudinal extent of the southern westerlies suggest that both the eLGM and eLGM Interstadial may be more widely registered, at least across the Southern Ocean. Support for this assertion comes from parallel investigations in western and southernmost South America and isotopic and palaeoecological records from Southern Ocean marine cores. Recent reconstructions of the globally averaged ice-equivalent sea-level history are in line with this evidence from the Southern Hemisphere, suggesting that the eLGM may have a global registration. In light of these observations, we suggest a re-examination of the defined timing of the LGM along with renewed effort to establish climatic patterns during this period and understand their causes. Copyright © 2007 John Wiley & Sons, Ltd.
Journal of Quaternary Science, 2007
It is widely recognised that the acquisition of high-resolution palaeoclimate records from southe... more It is widely recognised that the acquisition of high-resolution palaeoclimate records from southern mid-latitude sites is essential for establishing a coherent picture of inter-hemispheric climate change and for better understanding of the role of Antarctic climate dynamics in the global climate system. New Zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the Southern Hemisphere westerly circulation zone, a critical transition zone between subtropical and Antarctic influences. New Zealand has mountainous axial ranges that amplify the climate signals and, consequently, the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions. Since 1995, INTIMATE has, through a series of international workshops, sought ways to improve procedures for establishing the precise ages of climate events, and to correlate them with high precision, for the last 30 000 calendar years. The NZ-INTIMATE project commenced in late 2003, and has involved virtually the entire New Zealand palaeoclimate community. Its aim is to develop an event stratigraphy for the New Zealand region over the past 30 000 years, and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from Northern Hemisphere records (e.g. Last Glacial Maximum (LGM), Termination I, Younger Dryas). An initial outcome of NZ-INTIMATE has been the identification of a series of well-dated, high-resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal. yr BP to the present day. High-resolution records for the last glacial coldest period (LGCP) (including the LGM sensu stricto) and last glacial–interglacial transition (LGIT) from Auckland maars, Kaipo and Otamangakau wetlands on eastern and central North Island, marine core MD97-2121 east of southern North Island, speleothems on northwest South Island, Okarito wetland on southwestern South Island, are presented. Discontinuous (fragmentary) records comprising compilations of glacial sequences, fluvial sequences, loess accumulation, and aeolian quartz accumulation in an andesitic terrain are described. Comparisons with ice-core records from Antarctica (EPICA Dome C) and Greenland (GISP2) are discussed. A major advantage immediately evident from these records apart from the speleothem record, is that they are linked precisely by one or more tephra layers. Based on these New Zealand terrestrial and marine records, a reasonably coherent, regionally applicable, sequence of climatically linked stratigraphic events over the past 30 000 cal. yr is emerging. Three major climate events are recognised: (1) LGCP beginning at ca. 28 000 cal. yr BP, ending at Termination I, ca. 18 000 cal. yr BP, and including a warmer and more variable phase between ca. 27 000 and 21 000 cal. yr BP, (2) LGIT between ca. 18 000 and 11 600 cal. yr BP, including a Lateglacial warm period from ca. 14 800 to 13 500 cal. yr BP and a Lateglacial climate reversal between ca. 13 500 and 11 600 cal. yr BP, and (3) Holocene interglacial conditions, with two phases of greatest warmth between ca. 11 600 and 10 800 cal. yr BP and from ca. 6 800 to 6 500 cal. yr BP. Some key boundaries coincide with volcanic tephras. Copyright © 2007 John Wiley & Sons, Ltd.
Quaternary Science Reviews, 2008
The role of tephras in the NZ-INTIMATE project is a critical one because most high-resolution pal... more The role of tephras in the NZ-INTIMATE project is a critical one because most high-resolution palaeoclimatic records are linked and dated by one or more tephra layers. In this review, first we document eruptive, distributional, and compositional fingerprinting data, both mineralogical and geochemical, for 22 key marker tephras erupted since 30,000 years ago to facilitate their identification and correlation. We include new glass compositional data. The selected marker tephras comprise 10 from Taupo and nine from Okataina volcanoes (rhyolitic), one from Tuhua volcano (peralkaline rhyolitic), and one each from Tongariro and Egmont volcanoes (andesitic). Second, we use four approaches to develop 2s-age models for the tephras (youngest to oldest): (1) calendar ages for Kaharoa and Taupo/Y were obtained by wiggle-matching log-derived tree-ring sequences dated by 14 C; (2) Whakaipo/V was dated using an age-depth model from peat; (3) 14 tephras in the montane Kaipo peat sequence (Waimihia/S, Unit K, Whakatane, Tuhua, Mamaku, Rotoma, Opepe/E, Poronui/C, Karapiti/B, Okupata, Konini, Waiohau, Rotorua, Rerewhakaaitu) were dated by simultaneously wiggle-matching stratigraphic position and 51 independent 14 C-age points against IntCal04 using Bayesian probability methods via both OxCal and Bpeat; and (4) the five oldest tephras, erupted before ca 18,000 cal. yr BP, were dated by calibrating limited numbers of 14 C ages using IntCal04 (Okareka) or comparison curves of the expanded Cariaco Basin sequence (Te Rere, Kawakawa/Oruanui, Poihipi, Okaia). Kawakawa/Oruanui tephra, the most widely distributed marker tephra, was erupted probably ca 27,0977957 cal. yr BP. Potential dating approaches for the older tephras include their identification in Antarctic ice cores (if present) or annually laminated sediments for which robust calendar-age models have been constructed, high-precision AMS 14 C dating on appropriate material from environmentally stable sites, systematic luminescence dating, or new radiometric techniques (e.g. U-Th/He) if suitable minerals are available and errors markedly reduced. Further application of Bayesian age-modelling to stratigraphic sequences of 14 C ages, possibly augmented with luminescence ages, may help refine age models for pre-Holocene tephras with the largest errors. Finally, we discuss the critical role these marker tephras play in the ongoing construction of an event stratigraphy for the New Zealand region, which is a key objective of Australasian and Southern Hemisphere INTIMATE projects. r
Journal of Quaternary Science, 2004
The precise sequence of events during the Last Termination (18 000–9000 ka 14C yr BP), and the ex... more The precise sequence of events during the Last Termination (18 000–9000 ka 14C yr BP), and the extent to which major environmental changes were synchronous, are difficult to establish using the radiocarbon method alone because of serious distortions of the radiocarbon time-scale, as well as the influences of site-specific errors that can affect the materials dated. Attention has therefore turned to other methods that can provide independent tests of the chronology and correlation of events during the Last Termination. With emphasis on European sequences, we summarise here the potential of tephrostratigraphy and tephrochronology to fulfil this role. Recent advances in the detection and analysis of ‘hidden’ tephra layers (cryptotephra) indicate that some tephras of Last Termination age are much more widespread in Europe than appreciated hitherto, and a number of new tephra deposits have also been identified. There is much potential for developing an integrated tephrochronological framework for Europe, which can help to underpin the overall chronology of events during the Last Termination. For that potential to be realised, however, there needs to be a more systematic and robust analysis of tephra layers than has been the practice in the past. We propose a protocol for improving analytical and reporting procedures, as well as the establishment of a centralised data base of the results, which will provide an important geochronological tool to support a diverse range of stratigraphical studies, including opportunities to reassess volcanic hazards. Although aimed primarily at Europe, the protocol proposed here is of equal relevance to other regions and periods of interest. Copyright © 2004 John Wiley & Sons, Ltd.
Geological Society of America Bulletin, 2007
Journal of The Royal Society of New Zealand, 2005
Abstract Late Pliocene to mid‐Pleistocene (c. 2.1–0.4 Ma) strata exposed in the, now classical, N... more Abstract Late Pliocene to mid‐Pleistocene (c. 2.1–0.4 Ma) strata exposed in the, now classical, Nukumaru and Castlecliff coastal cliff sections north‐west of Wanganui comprise 25, 6th (41 ka) order and 5th (100 ka) order, shallow‐marine to marginal marine ...
Quaternary International, 2008
The trace element composition of individual glass shards from twelve distinct mid-Pleistocene sil... more The trace element composition of individual glass shards from twelve distinct mid-Pleistocene silicic tephra beds from the Auckland region, New Zealand, has been determined by laser ablation (LA) ICP-MS analysis. This is the first application of such data to tephra correlation studies in New Zealand. These analyses support earlier major-element based correlations between three surface sections (Oruarangi and Okariha at Port Waikato, and St Kentigern's at east Auckland) and a long core (Patiki Road, west Auckland). The correlations provide a higher resolution record of Taupo Volcanic Zone (TVZ) activity than is preserved in more proximal deposits, where burial and erosion obscure much of the volcanic record. A combination of major and trace element analysis enables the correlation of three units exposed in the Auckland region with their proximal equivalents (ignimbrites) from the TVZ, namely deposits associated with (1) the Ongatiti ignimbrite (1.2170.04 Ma), (2) an un-named, post-Ahuroa/pre-Unit E ignimbrite (sample UT1274) from the Rocky Hill section, King Country and (3) the Unit E ignimbrite ($1 Ma). Combined major and trace element data show a marked evolution in magma chemistry, with the large Ongatiti and Unit E ignimbrite eruptions occurring after a change in composition caused by replenishment/reactivation of the magma chamber. Changes in magma chemistry between these deposits resulted from a combination of assimilation of metasedimentary country rocks and periods of fractional crystallisation of a plagioclase-dominated assemblage. Trace element data and the wider dispersal of the silicic tephras in the Auckland region suggests that they are all sourced from the Mangakino Volcanic Centre (MVC) in the TVZ. This study illustrates for the first time in a New Zealand context the potential for correlating tephra deposits using single glass shard trace element chemistry. r
New Zealand Journal of Geology and Geophysics, 1994
Tephrostratigraphic and chronologic studies in
Palaeogeography Palaeoclimatology Palaeoecology, 2003
... Anna Sandiford E-mail The Corresponding Author , a , Rewi Newnham Corresponding Author Contac... more ... Anna Sandiford E-mail The Corresponding Author , a , Rewi Newnham Corresponding Author Contact Information , E-mail The Corresponding Author , b , Brent Alloway E-mail The Corresponding ... Mean high sea level is 3.67 m below the current crater floor ( [Coomber, 1998]). ...
New Zealand Journal of Geology and Geophysics, 2001
ABSTRACT An open access copy of this article is available from the publishers website. A 52.5 m c... more ABSTRACT An open access copy of this article is available from the publishers website. A 52.5 m core was extracted from Pukaki Crater, an infilled basaltic explosion crater in the Auckland Volcanic Field, for detailed tephra and palynological analysis. The core consists of a lower 6 m of finely laminated lacustrine sediments representing the interval c. 28 000-6600 cal yr overlain by 46.5 m of homogeneous marine silts deposited between c. 7600 and 6600 cal yr. Favourable conditions have preserved at least 40 tephra layers in the sediments. These have been derived from one local and five distal sources and were deposited within the crater lake between c. 28 000 and c. 7600 cal yr. The tephra beds were identified by stratigraphic position, geochemical analyses, and ferromagnesian mineral assemblage. This tephrostratigraphic framework is underpinned by three distinctive tephra beds, namely Tuhua (c. 6950 cal yr), Rotoma (c. 9500 cal yr), and Kawakawa (c. 26 500 cal yr). Of the 40 tephra beds, 7 are sourced from the rhyolitic Okataina Volcanic Centre (Mamaku c. 8200 cal yr; Rotoma c. 9500 cal yr; Waiohau c. 13 800 cal yr; Rotorua c. 15 800 cal yr; Rerewhakaaitu c. 17 700 cal yr; Okareka c. 21 400 cal yr; Te Rere c. 25 000 cal yr), 3 from the rhyolitic Taupo Volcanic Centre (Opepe c. 10 200 cal yr; Kawakawa c. 26 500 cal yr; Poihipi c. 27 500 cal yr), 5 from the andesitic Tongariro Volcanic Centre, 14 from the andesitic Taranaki Volcano, 1 from Mayor Island (Tuhua c. 6950 cal yr), and 8 from the basaltic Auckland Volcanic Field. In addition, two previously unidentified rhyolitic tephra (c. 17 100 cal yr and c. 20 720 cal yr) are recorded. The occurrence of numerous andesitic and rhyolitic tephra beds in the Auckland region extends the known dispersal of the units and has implications for the assessment of volcanic hazards from distal sources. Many of the Taranaki-derived tephra beds do not stratigraphically match those recorded in the Waikato lakes region and this suggests that Taranaki Volcano produced more ash than previously estimated. The distal tephra record preserved at Pukaki provides age constraints for Auckland Volcanic Field basaltic tephra that are otherwise poorly dated. Basaltic fall events are recorded at c. 14 450 cal yr, 15 750 cal yr, 19 380 cal yr, 19 420 cal yr, 23 825 cal yr, 24 175 cal yr, 25 200 cal yr, and 25 700 cal yr. Fresh glass in the basaltic tephra allows them to be chemically fingerprinted and discriminated, and this will open a new avenue to development of a regional basaltic tephrostratigraphy.
Earth and Planetary Science Letters, 2004
Paroxysmal pyroclastic flow deposits sourced from Maninjau caldera in west-central Sumatra are da... more Paroxysmal pyroclastic flow deposits sourced from Maninjau caldera in west-central Sumatra are dated at 50±3 ka (n=3) using the isothermal plateau and diameter corrected fission-track (ITPFT and DCFT, respectively) techniques on glass shard constituents. In addition, charcoal obtained from tall trees in position of growth within the paroxysmal flow deposit on the upper flanks for the caldera are also dated at 52.3±2 14C ka (n=2) and 51.1±3.2 14C ka (n=1) using an acid–base, wet oxidation, stepped combustion (ABOX-SC) and standard acid–base–acid (ABA) 14C techniques, respectively. The close correspondence in 14C ages of charcoal sample splits analysed at two laboratories (Australian National University, Australia and Waikato University, New Zealand) verifies the reliability of these 14C techniques up to at least 50 ka.Based on concordant ages derived from glass-FT and 14C techniques, an age of 52±3 ka is assigned to the latest silicic eruptive activity at Maninjau caldera. This chronology is further confirmed by the occurrence of a silicic tephra bed that closely underlies paroxysmal Maninjau deposits at two sections and is correlated with Youngest (75 ka) Toba Tephra (YTT) erupted from Toba caldera in north-central Sumatra. This study not only provides a much needed regional chronological reference point for Quaternary deposits in west-central Sumatra but also extends the minimum age range of the glass-FT technique from 75 ka down to c. 50 ka that is now for the first time within the extended maximum age range of the 14C technique.
Geological Society of America Bulletin, 1996
Thick volcaniclastic sequences of early to middle Pleistocene age in southern North Island, New Z... more Thick volcaniclastic sequences of early to middle Pleistocene age in southern North Island, New Zealand, contain rhyolitic tephra beds that record the early history of the Taupo volcanic zone (TVZ). At least 54 different tephra beds are recorded, and their chronology ...
Quaternary Science Reviews, 2005
Taupo Volcanic Zone (TVZ), in the North Island, New Zealand, is arguably the most active Quaterna... more Taupo Volcanic Zone (TVZ), in the North Island, New Zealand, is arguably the most active Quaternary rhyolitic system in the world. Numerous and widespread rhyolitic tephra layers, sourced from the TVZ, form valuable chronostratigraphic markers in onshore and offshore sedimentary sequences. In deep-sea cores from Ocean Drilling Program (ODP) Leg 181 Sites 1125, 1124, 1123 and 1122, located east of New Zealand, ca 100 tephra beds are recognised post-dating the Plio-Pleistocene boundary at 1.81 Ma. These tephras have been dated by a combination of magnetostratigraphy, orbitally tuned stable-isotope data and isothermal plateau fission track ages. The widespread occurrence of ash offshore to the east of New Zealand is favoured by the small size of New Zealand, the explosivity of the mainly plinian and ignimbritic eruptions and the prevailing westerly wind field.Although some tephras can be directly attributed to known TVZ eruptions, there are many more tephras represented within ODP-cores that have yet to be recognised in near-source on-land sequences. This is due to proximal source area erosion and/or deep burial as well as the adverse effect of vapour phase alteration and devitrification within near-source welded ignimbrites. Despite these difficulties, a number of key deep-sea tephras can be reliably correlated to equivalent-aged tephra exposed in uplifted marine back-arc successions of Wanganui Basin where an excellent chronology has been developed based on magnetostratigraphy, orbitally calibrated sedimentary cycles and isothermal plateau fission track ages on tephra. Significant Pleistocene tephra markers include: the Kawakawa, Omataroa, Rangitawa/Onepuhi, Kaukatea, Kidnappers-B, Potaka, Unit D/Ahuroa, Ongatiti, Rewa, Sub-Rewa, Pakihikura, Ototoka and Table Flat Tephras. Six other tephra layers are correlated between ODP-core sites but have yet to be recognised within onshore records.The identification of Pleistocene TVZ-sourced tephras within the ODP record, and their correlation to Wanganui Basin and other onshore sites is a significant advance as it provides: (1) an even more detailed history of the TVZ than can be currently achieved from the near-source record, (2) a high-resolution tephrochronologic framework for future onshore-offshore paleoenvironmental reconstructions, and (3) well-dated tephra beds correlated from the offshore ODP sites with astronomically tuned timescales provide an opportunity to critically evaluate the chronostratigraphic framework for onshore Plio-Pleistocene sedimentary sequences (e.g. Wanganui Basin, cf. Naish et al. [1998. Quaternary Science Reviews 17 695–710].
Geology, 2003
Ocean Drilling Program Sites 1123 and 1124 provide an unprecedented 12 my record of major rhyolit... more Ocean Drilling Program Sites 1123 and 1124 provide an unprecedented 12 my record of major rhyolitic eruptions from the Coromandel and Taupo volcanic zones of New Zealand. Macroscopic tephras (n = 197) were dated using magnetostratigraphy, supplemented by geochemical ...
Sedimentary Geology, 1993
... in the Wanganui Basin, New Zealand, based on the isothermal plateau fission-track dating of t... more ... in the Wanganui Basin, New Zealand, based on the isothermal plateau fission-track dating of tephra horizons Brent V. Alloway a, Brad J. Pillans b, Amanjit S. Sandhu a and John A. Westgate aa Department of Geology, University of Toronto, Scarborough Campus, 1265 Military ...
New Zealand Journal of Geology and Geophysics, 2002
New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 3... more New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 365-385 0028-8306/02/4503-0365 $7.00/0 © The Royal Society of New Zealand 2002 ... Growth of contractional structures during the last 10 my at the southern end of the emergent Hikurangi forearc basin, New ...
Tectonics, 1994
Analysis of the geometry and ages of faulted and tilted late Quaternary fluvial terraces and thei... more Analysis of the geometry and ages of faulted and tilted late Quaternary fluvial terraces and their associated cover beds provide evidence of active folding at three localities in the Waipara area of North Canterbury, New Zealand. Terrace survey data, the occurrence of the approximately 22.6kyr-old Aokautere Ash, and examination of soil profiles indicate that folding has continued into the late Holocene but that the amounts and rates of deformation are locally variable. Rates of uplift in the Waipara area are compared with those derived from marine terraces preserved at the Pacific coast, east of the study area. Results indicate that rates of measurable deformation reach a maximum along the Waipara range front, where bedrock deformation is most intense and shortening rates of up to 5.57 + 0.69%/100 kyr occur. Across the coastal ranges the average rate of shortening is 0.8 + 0.4%/100 kyr, which corresponds with an absolute shortening rate of 1.4 + 0.6 m/kyr and represents only a small proportion of the predicted plate motion vector in this region. Uplift rates range from 0-1.83 m/kyr for a late last glacial fluvial terrace and from 1.36-2.16 m/kyr for three marine terraces. Fluvial and marine terrace uplift rates vary in accord with the geometries of the folds in bedrock, and the spatial pattern of uplift directly reflects fold growth. The structure contour pattern of folded surfaces provides a first approximation to the spatial pattern of uplift. Differential uplift due to folding accounts for up to approximately 55-75% of the total uplift and has produced folds with structural relief of about 1300 m (i.e., amplitudes of 600-700 m). These folds have formed over the Paper number 94TC01502. 0278-7407/94/94TC-01502510.00 last 0.8 + 0.4 m.y. since the onset of Quaternary deformation in the Waipara region. lected from three different localities across the Waipara Syncline, near the township of Waipara . Fold geometry data, principally derived from altitudinal surveying, include disrupted cover bed stratigraphy and deformed fluvial terrace surfaces. Geometric data are complemented by age determinations provided by the radiometrically dated and laterally extensive Aokautere Ash, a radiocarbon date and detailed analysis of soil profile morphologies. The study has allowed conclusions to be drawn about the rates of shortening and uplift associated with folding, the age of cover beds, fluvial terrace surfaces and their deformation, and the relation-
Geological Society of America Bulletin, 2006
Holocene marginal-marine sedimentary sequences provide information on vertical tectonic deformati... more Holocene marginal-marine sedimentary sequences provide information on vertical tectonic deformation in a transect across the forearc basin adjacent to the Hikurangi subduction zone, New Zealand. The elevation of maximum postglacial sea level indicators at Te Paeroa Lagoon and Opoho is between 4 and 6 m below present mean sea level, indicating net subsidence since 7200 yr B.P. Opoutama is closer to the Hikurangi Trench and appears to lie near the edge of the zone of subsidence, as evidence for vertical movement there is equivocal. Some of the subsidence at Te Paeroa Lagoon and Opoho is likely to be a result of compaction. However, a component of subsidence probably happened coseismically in two events at ca. 7100 and 5550 yr B.P. Event signatures consist of tsunami deposits overlain by chaotically mixed, reworked sediment that appears to have fi lled rapidly created accommodation space at marine inlet sites 10 km apart. Large offshore earthquakes are suggested by the coincidence of tsunami inundation with sudden subsidence. Forward elastic-dislocation models indicate that the observed subsidence could be achieved in ~M w 7.9 earthquakes on either the subduction interface or the Lachlan Fault, which would involve synchronous uplift of Mahia Peninsula. Combined rupture of the interface and the Lachlan Fault, either simultaneously in a ~M w 8.1 earthquake, or consecutively, could explain larger amounts (>1.5 m) of coastal subsidence.
New Zealand Journal of Geology and Geophysics, 2002
Page 1. New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 467-479 0... more Page 1. New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 467-479 0028-8306/02/4504-0467 $7.00/0 © The Royal Society of New Zealand 2002 467 Foraminiferal and molluscan evidence for the Holocene marine ...
Journal of The Royal Society of New Zealand, 2002
This article was downloaded by: [66.249.67.15] On: 08 July 2011, At: 11:56 Publisher: Taylor &... more This article was downloaded by: [66.249.67.15] On: 08 July 2011, At: 11:56 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Quaternary Science, 2007
Auckland occupies a climatically sensitive position close to a major biogeographic boundary in th... more Auckland occupies a climatically sensitive position close to a major biogeographic boundary in the southern mid-latitudes. A new pollen record from Kohuora maar crater, Auckland, displays vegetation and climatic changes for the past ca. 32 000 years. Of particular interest are the inferred climatic patterns for the first part of the interval, encompassing the Last Glacial Maximum (LGM). The Kohuora record corresponds closely with pollen records from other Auckland sites indicating that the patterns observed are at least regional in extent. It is also broadly consistent with a variety of palaeoenvironmental evidence from across New Zealand, including the glacial record from Westland, other palynological records from North Island, other palaeoecological records from the South Island, and aeolian quartz sequences from western North Island. These records show that glacial conditions prevailed across most, if not all, of New Zealand during the interval ca. 29–19 k cal. yr BP, longer and earlier than the LGM sensu stricto. We suggest that the term extended LGM (eLGM) may be more appropriate for the New Zealand region. Within this predominantly cold interval, the Auckland pollen records indicate a climatic amelioration for the interval ca. 26–24 k cal. yr BP, also consistent with other palaeocological data from Canterbury, that fall within a period of climate amelioration recognised between the first two eLGM glacial advances in Westland. We refer to this warming interval as the eLGM Interstadial. The ca. 27 k cal. yr BP Kawakawa/Oruanui tephra is instrumental in most of these inter-site comparisons and occurs after the first peak of eLGM cooling in a short-lived comparatively mild phase. A subsequent return to apparently colder climate in the Auckland records may indicate a volcanic cooling effect or, more likely, widespread landscape disturbance following this major eruption event. Strong correspondence between biotic responses, glacial fluctuations and aeolian quartz deposition linked to major shifts in strength and latitudinal extent of the southern westerlies suggest that both the eLGM and eLGM Interstadial may be more widely registered, at least across the Southern Ocean. Support for this assertion comes from parallel investigations in western and southernmost South America and isotopic and palaeoecological records from Southern Ocean marine cores. Recent reconstructions of the globally averaged ice-equivalent sea-level history are in line with this evidence from the Southern Hemisphere, suggesting that the eLGM may have a global registration. In light of these observations, we suggest a re-examination of the defined timing of the LGM along with renewed effort to establish climatic patterns during this period and understand their causes. Copyright © 2007 John Wiley & Sons, Ltd.
Journal of Quaternary Science, 2007
It is widely recognised that the acquisition of high-resolution palaeoclimate records from southe... more It is widely recognised that the acquisition of high-resolution palaeoclimate records from southern mid-latitude sites is essential for establishing a coherent picture of inter-hemispheric climate change and for better understanding of the role of Antarctic climate dynamics in the global climate system. New Zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the Southern Hemisphere westerly circulation zone, a critical transition zone between subtropical and Antarctic influences. New Zealand has mountainous axial ranges that amplify the climate signals and, consequently, the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions. Since 1995, INTIMATE has, through a series of international workshops, sought ways to improve procedures for establishing the precise ages of climate events, and to correlate them with high precision, for the last 30 000 calendar years. The NZ-INTIMATE project commenced in late 2003, and has involved virtually the entire New Zealand palaeoclimate community. Its aim is to develop an event stratigraphy for the New Zealand region over the past 30 000 years, and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from Northern Hemisphere records (e.g. Last Glacial Maximum (LGM), Termination I, Younger Dryas). An initial outcome of NZ-INTIMATE has been the identification of a series of well-dated, high-resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal. yr BP to the present day. High-resolution records for the last glacial coldest period (LGCP) (including the LGM sensu stricto) and last glacial–interglacial transition (LGIT) from Auckland maars, Kaipo and Otamangakau wetlands on eastern and central North Island, marine core MD97-2121 east of southern North Island, speleothems on northwest South Island, Okarito wetland on southwestern South Island, are presented. Discontinuous (fragmentary) records comprising compilations of glacial sequences, fluvial sequences, loess accumulation, and aeolian quartz accumulation in an andesitic terrain are described. Comparisons with ice-core records from Antarctica (EPICA Dome C) and Greenland (GISP2) are discussed. A major advantage immediately evident from these records apart from the speleothem record, is that they are linked precisely by one or more tephra layers. Based on these New Zealand terrestrial and marine records, a reasonably coherent, regionally applicable, sequence of climatically linked stratigraphic events over the past 30 000 cal. yr is emerging. Three major climate events are recognised: (1) LGCP beginning at ca. 28 000 cal. yr BP, ending at Termination I, ca. 18 000 cal. yr BP, and including a warmer and more variable phase between ca. 27 000 and 21 000 cal. yr BP, (2) LGIT between ca. 18 000 and 11 600 cal. yr BP, including a Lateglacial warm period from ca. 14 800 to 13 500 cal. yr BP and a Lateglacial climate reversal between ca. 13 500 and 11 600 cal. yr BP, and (3) Holocene interglacial conditions, with two phases of greatest warmth between ca. 11 600 and 10 800 cal. yr BP and from ca. 6 800 to 6 500 cal. yr BP. Some key boundaries coincide with volcanic tephras. Copyright © 2007 John Wiley & Sons, Ltd.
Quaternary Science Reviews, 2008
The role of tephras in the NZ-INTIMATE project is a critical one because most high-resolution pal... more The role of tephras in the NZ-INTIMATE project is a critical one because most high-resolution palaeoclimatic records are linked and dated by one or more tephra layers. In this review, first we document eruptive, distributional, and compositional fingerprinting data, both mineralogical and geochemical, for 22 key marker tephras erupted since 30,000 years ago to facilitate their identification and correlation. We include new glass compositional data. The selected marker tephras comprise 10 from Taupo and nine from Okataina volcanoes (rhyolitic), one from Tuhua volcano (peralkaline rhyolitic), and one each from Tongariro and Egmont volcanoes (andesitic). Second, we use four approaches to develop 2s-age models for the tephras (youngest to oldest): (1) calendar ages for Kaharoa and Taupo/Y were obtained by wiggle-matching log-derived tree-ring sequences dated by 14 C; (2) Whakaipo/V was dated using an age-depth model from peat; (3) 14 tephras in the montane Kaipo peat sequence (Waimihia/S, Unit K, Whakatane, Tuhua, Mamaku, Rotoma, Opepe/E, Poronui/C, Karapiti/B, Okupata, Konini, Waiohau, Rotorua, Rerewhakaaitu) were dated by simultaneously wiggle-matching stratigraphic position and 51 independent 14 C-age points against IntCal04 using Bayesian probability methods via both OxCal and Bpeat; and (4) the five oldest tephras, erupted before ca 18,000 cal. yr BP, were dated by calibrating limited numbers of 14 C ages using IntCal04 (Okareka) or comparison curves of the expanded Cariaco Basin sequence (Te Rere, Kawakawa/Oruanui, Poihipi, Okaia). Kawakawa/Oruanui tephra, the most widely distributed marker tephra, was erupted probably ca 27,0977957 cal. yr BP. Potential dating approaches for the older tephras include their identification in Antarctic ice cores (if present) or annually laminated sediments for which robust calendar-age models have been constructed, high-precision AMS 14 C dating on appropriate material from environmentally stable sites, systematic luminescence dating, or new radiometric techniques (e.g. U-Th/He) if suitable minerals are available and errors markedly reduced. Further application of Bayesian age-modelling to stratigraphic sequences of 14 C ages, possibly augmented with luminescence ages, may help refine age models for pre-Holocene tephras with the largest errors. Finally, we discuss the critical role these marker tephras play in the ongoing construction of an event stratigraphy for the New Zealand region, which is a key objective of Australasian and Southern Hemisphere INTIMATE projects. r
Journal of Quaternary Science, 2004
The precise sequence of events during the Last Termination (18 000–9000 ka 14C yr BP), and the ex... more The precise sequence of events during the Last Termination (18 000–9000 ka 14C yr BP), and the extent to which major environmental changes were synchronous, are difficult to establish using the radiocarbon method alone because of serious distortions of the radiocarbon time-scale, as well as the influences of site-specific errors that can affect the materials dated. Attention has therefore turned to other methods that can provide independent tests of the chronology and correlation of events during the Last Termination. With emphasis on European sequences, we summarise here the potential of tephrostratigraphy and tephrochronology to fulfil this role. Recent advances in the detection and analysis of ‘hidden’ tephra layers (cryptotephra) indicate that some tephras of Last Termination age are much more widespread in Europe than appreciated hitherto, and a number of new tephra deposits have also been identified. There is much potential for developing an integrated tephrochronological framework for Europe, which can help to underpin the overall chronology of events during the Last Termination. For that potential to be realised, however, there needs to be a more systematic and robust analysis of tephra layers than has been the practice in the past. We propose a protocol for improving analytical and reporting procedures, as well as the establishment of a centralised data base of the results, which will provide an important geochronological tool to support a diverse range of stratigraphical studies, including opportunities to reassess volcanic hazards. Although aimed primarily at Europe, the protocol proposed here is of equal relevance to other regions and periods of interest. Copyright © 2004 John Wiley & Sons, Ltd.
Geological Society of America Bulletin, 2007
Journal of The Royal Society of New Zealand, 2005
Abstract Late Pliocene to mid‐Pleistocene (c. 2.1–0.4 Ma) strata exposed in the, now classical, N... more Abstract Late Pliocene to mid‐Pleistocene (c. 2.1–0.4 Ma) strata exposed in the, now classical, Nukumaru and Castlecliff coastal cliff sections north‐west of Wanganui comprise 25, 6th (41 ka) order and 5th (100 ka) order, shallow‐marine to marginal marine ...
Quaternary International, 2008
The trace element composition of individual glass shards from twelve distinct mid-Pleistocene sil... more The trace element composition of individual glass shards from twelve distinct mid-Pleistocene silicic tephra beds from the Auckland region, New Zealand, has been determined by laser ablation (LA) ICP-MS analysis. This is the first application of such data to tephra correlation studies in New Zealand. These analyses support earlier major-element based correlations between three surface sections (Oruarangi and Okariha at Port Waikato, and St Kentigern's at east Auckland) and a long core (Patiki Road, west Auckland). The correlations provide a higher resolution record of Taupo Volcanic Zone (TVZ) activity than is preserved in more proximal deposits, where burial and erosion obscure much of the volcanic record. A combination of major and trace element analysis enables the correlation of three units exposed in the Auckland region with their proximal equivalents (ignimbrites) from the TVZ, namely deposits associated with (1) the Ongatiti ignimbrite (1.2170.04 Ma), (2) an un-named, post-Ahuroa/pre-Unit E ignimbrite (sample UT1274) from the Rocky Hill section, King Country and (3) the Unit E ignimbrite ($1 Ma). Combined major and trace element data show a marked evolution in magma chemistry, with the large Ongatiti and Unit E ignimbrite eruptions occurring after a change in composition caused by replenishment/reactivation of the magma chamber. Changes in magma chemistry between these deposits resulted from a combination of assimilation of metasedimentary country rocks and periods of fractional crystallisation of a plagioclase-dominated assemblage. Trace element data and the wider dispersal of the silicic tephras in the Auckland region suggests that they are all sourced from the Mangakino Volcanic Centre (MVC) in the TVZ. This study illustrates for the first time in a New Zealand context the potential for correlating tephra deposits using single glass shard trace element chemistry. r
New Zealand Journal of Geology and Geophysics, 1994
Tephrostratigraphic and chronologic studies in
Palaeogeography Palaeoclimatology Palaeoecology, 2003
... Anna Sandiford E-mail The Corresponding Author , a , Rewi Newnham Corresponding Author Contac... more ... Anna Sandiford E-mail The Corresponding Author , a , Rewi Newnham Corresponding Author Contact Information , E-mail The Corresponding Author , b , Brent Alloway E-mail The Corresponding ... Mean high sea level is 3.67 m below the current crater floor ( [Coomber, 1998]). ...
New Zealand Journal of Geology and Geophysics, 2001
ABSTRACT An open access copy of this article is available from the publishers website. A 52.5 m c... more ABSTRACT An open access copy of this article is available from the publishers website. A 52.5 m core was extracted from Pukaki Crater, an infilled basaltic explosion crater in the Auckland Volcanic Field, for detailed tephra and palynological analysis. The core consists of a lower 6 m of finely laminated lacustrine sediments representing the interval c. 28 000-6600 cal yr overlain by 46.5 m of homogeneous marine silts deposited between c. 7600 and 6600 cal yr. Favourable conditions have preserved at least 40 tephra layers in the sediments. These have been derived from one local and five distal sources and were deposited within the crater lake between c. 28 000 and c. 7600 cal yr. The tephra beds were identified by stratigraphic position, geochemical analyses, and ferromagnesian mineral assemblage. This tephrostratigraphic framework is underpinned by three distinctive tephra beds, namely Tuhua (c. 6950 cal yr), Rotoma (c. 9500 cal yr), and Kawakawa (c. 26 500 cal yr). Of the 40 tephra beds, 7 are sourced from the rhyolitic Okataina Volcanic Centre (Mamaku c. 8200 cal yr; Rotoma c. 9500 cal yr; Waiohau c. 13 800 cal yr; Rotorua c. 15 800 cal yr; Rerewhakaaitu c. 17 700 cal yr; Okareka c. 21 400 cal yr; Te Rere c. 25 000 cal yr), 3 from the rhyolitic Taupo Volcanic Centre (Opepe c. 10 200 cal yr; Kawakawa c. 26 500 cal yr; Poihipi c. 27 500 cal yr), 5 from the andesitic Tongariro Volcanic Centre, 14 from the andesitic Taranaki Volcano, 1 from Mayor Island (Tuhua c. 6950 cal yr), and 8 from the basaltic Auckland Volcanic Field. In addition, two previously unidentified rhyolitic tephra (c. 17 100 cal yr and c. 20 720 cal yr) are recorded. The occurrence of numerous andesitic and rhyolitic tephra beds in the Auckland region extends the known dispersal of the units and has implications for the assessment of volcanic hazards from distal sources. Many of the Taranaki-derived tephra beds do not stratigraphically match those recorded in the Waikato lakes region and this suggests that Taranaki Volcano produced more ash than previously estimated. The distal tephra record preserved at Pukaki provides age constraints for Auckland Volcanic Field basaltic tephra that are otherwise poorly dated. Basaltic fall events are recorded at c. 14 450 cal yr, 15 750 cal yr, 19 380 cal yr, 19 420 cal yr, 23 825 cal yr, 24 175 cal yr, 25 200 cal yr, and 25 700 cal yr. Fresh glass in the basaltic tephra allows them to be chemically fingerprinted and discriminated, and this will open a new avenue to development of a regional basaltic tephrostratigraphy.
Earth and Planetary Science Letters, 2004
Paroxysmal pyroclastic flow deposits sourced from Maninjau caldera in west-central Sumatra are da... more Paroxysmal pyroclastic flow deposits sourced from Maninjau caldera in west-central Sumatra are dated at 50±3 ka (n=3) using the isothermal plateau and diameter corrected fission-track (ITPFT and DCFT, respectively) techniques on glass shard constituents. In addition, charcoal obtained from tall trees in position of growth within the paroxysmal flow deposit on the upper flanks for the caldera are also dated at 52.3±2 14C ka (n=2) and 51.1±3.2 14C ka (n=1) using an acid–base, wet oxidation, stepped combustion (ABOX-SC) and standard acid–base–acid (ABA) 14C techniques, respectively. The close correspondence in 14C ages of charcoal sample splits analysed at two laboratories (Australian National University, Australia and Waikato University, New Zealand) verifies the reliability of these 14C techniques up to at least 50 ka.Based on concordant ages derived from glass-FT and 14C techniques, an age of 52±3 ka is assigned to the latest silicic eruptive activity at Maninjau caldera. This chronology is further confirmed by the occurrence of a silicic tephra bed that closely underlies paroxysmal Maninjau deposits at two sections and is correlated with Youngest (75 ka) Toba Tephra (YTT) erupted from Toba caldera in north-central Sumatra. This study not only provides a much needed regional chronological reference point for Quaternary deposits in west-central Sumatra but also extends the minimum age range of the glass-FT technique from 75 ka down to c. 50 ka that is now for the first time within the extended maximum age range of the 14C technique.
Geological Society of America Bulletin, 1996
Thick volcaniclastic sequences of early to middle Pleistocene age in southern North Island, New Z... more Thick volcaniclastic sequences of early to middle Pleistocene age in southern North Island, New Zealand, contain rhyolitic tephra beds that record the early history of the Taupo volcanic zone (TVZ). At least 54 different tephra beds are recorded, and their chronology ...
Quaternary Science Reviews, 2005
Taupo Volcanic Zone (TVZ), in the North Island, New Zealand, is arguably the most active Quaterna... more Taupo Volcanic Zone (TVZ), in the North Island, New Zealand, is arguably the most active Quaternary rhyolitic system in the world. Numerous and widespread rhyolitic tephra layers, sourced from the TVZ, form valuable chronostratigraphic markers in onshore and offshore sedimentary sequences. In deep-sea cores from Ocean Drilling Program (ODP) Leg 181 Sites 1125, 1124, 1123 and 1122, located east of New Zealand, ca 100 tephra beds are recognised post-dating the Plio-Pleistocene boundary at 1.81 Ma. These tephras have been dated by a combination of magnetostratigraphy, orbitally tuned stable-isotope data and isothermal plateau fission track ages. The widespread occurrence of ash offshore to the east of New Zealand is favoured by the small size of New Zealand, the explosivity of the mainly plinian and ignimbritic eruptions and the prevailing westerly wind field.Although some tephras can be directly attributed to known TVZ eruptions, there are many more tephras represented within ODP-cores that have yet to be recognised in near-source on-land sequences. This is due to proximal source area erosion and/or deep burial as well as the adverse effect of vapour phase alteration and devitrification within near-source welded ignimbrites. Despite these difficulties, a number of key deep-sea tephras can be reliably correlated to equivalent-aged tephra exposed in uplifted marine back-arc successions of Wanganui Basin where an excellent chronology has been developed based on magnetostratigraphy, orbitally calibrated sedimentary cycles and isothermal plateau fission track ages on tephra. Significant Pleistocene tephra markers include: the Kawakawa, Omataroa, Rangitawa/Onepuhi, Kaukatea, Kidnappers-B, Potaka, Unit D/Ahuroa, Ongatiti, Rewa, Sub-Rewa, Pakihikura, Ototoka and Table Flat Tephras. Six other tephra layers are correlated between ODP-core sites but have yet to be recognised within onshore records.The identification of Pleistocene TVZ-sourced tephras within the ODP record, and their correlation to Wanganui Basin and other onshore sites is a significant advance as it provides: (1) an even more detailed history of the TVZ than can be currently achieved from the near-source record, (2) a high-resolution tephrochronologic framework for future onshore-offshore paleoenvironmental reconstructions, and (3) well-dated tephra beds correlated from the offshore ODP sites with astronomically tuned timescales provide an opportunity to critically evaluate the chronostratigraphic framework for onshore Plio-Pleistocene sedimentary sequences (e.g. Wanganui Basin, cf. Naish et al. [1998. Quaternary Science Reviews 17 695–710].
Geology, 2003
Ocean Drilling Program Sites 1123 and 1124 provide an unprecedented 12 my record of major rhyolit... more Ocean Drilling Program Sites 1123 and 1124 provide an unprecedented 12 my record of major rhyolitic eruptions from the Coromandel and Taupo volcanic zones of New Zealand. Macroscopic tephras (n = 197) were dated using magnetostratigraphy, supplemented by geochemical ...
Sedimentary Geology, 1993
... in the Wanganui Basin, New Zealand, based on the isothermal plateau fission-track dating of t... more ... in the Wanganui Basin, New Zealand, based on the isothermal plateau fission-track dating of tephra horizons Brent V. Alloway a, Brad J. Pillans b, Amanjit S. Sandhu a and John A. Westgate aa Department of Geology, University of Toronto, Scarborough Campus, 1265 Military ...
Enviroments associated to the Friasian fauna (middle Miocene) at Alto Río Cisnes, Aysén, Chile