50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...

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2 National Institute of Water and Atmosphere Ltd, PO Box 8602, Christchurch, New Zealand. (a.wells*gns.cri.nz) A study of five shore-parallel dune ridge sequences in southwest New Zealand shows that tectonic activity has been the primary controlling influence in their formation since at least AD 1450. The timing of dune building episodes at the mouths of the Haast, Okuru, Waiatoto, Arawhata and Awarua Rivers was determined using the ages of colonizing trees. Episodic dune formation was indicated by clear discontinuities in tree ages, with distinct cohorts having colonized successive, newlyformed, dune ridge-swale units. At Haast and Okuru, four dune ridge-swale units have formed since AD 1460, with each unit closely post-dating an Alpine fault rupture (c. AD 1490, c. AD 1615, AD 1717, AD 1826). At Waiatoto, Arawhata and Awarua, three dune-swale units have formed since AD 1490 and each of these also closely post-dates an Alpine fault rupture (c. AD 1490, AD 1717, AD 1826). Colonizing cohorts of trees started growing within 17-47 years after an earthquake, and at all five sites all known major regional earthquakes that affected each site since AD 1460 had resulted in a dune building episode at that site. No other dunes are present at any site. Progradational coastal dune systems have potential as a tool for paleoseismic studies. In regions with high background levels of sediment delivery to limit erosion/burial of dunes and with little coseismic subsidence, dune systems may offer a near-complete, spatially discrete record of earthquake-induced sedimentation events over the last 6500 years or so. Earthquakes are a key driver of paleoenvironmental change and coastal plain development in this tectonically active region. ORAL MECHANISMS OF LATE QUATERNARY FOREARC UPLIFT: A CASE STUDY OF THE NORTHEASTERN RAUKUMARA PENINSULA, NEW ZEALAND Kate Wilson 1 , Kelvin Berryman 2 , Tim Little 1 , Nicola Litchfield 2 & Ursula Cochran 2 . 1 Victoria University of Wellington, PO Box 600, Wellington. 2 Institute of Geological and Nuclear Sciences, PO Box 30368, Lower Hutt. (K.Wilson*gns.cri.nz) On the northeastern Raukumara Peninsula at Hicks Bay and Te Araroa, we have investigated Holocene landforms and coastal stratigraphy with the aim of documenting coastal uplift mechanisms. Drill cores of incised-valley infill sediments at Hicks Bay show apparently continuous estuarine sedimentation at intertidal elevations throughout the early Holocene. Radiocarbon ages allow comparisons between the thickness of sediment preserved and the amount of accommodation space expected to have been created within the estuary due to eustatic sea level rise. Accommodation space deficits indicate tectonic uplift did take place during deposition of the sequence, yet the continuity of estuarine sedimentation implies this tectonic uplift was relatively gradual and continuous as opposed to the sudden and infrequent uplift characteristic of earthquakes. Raised beach ridges at Te Araroa, ~ 8 km southeast of Hicks Bay, display a seaward-sloping, stepped morphology. The seaward slope indicates that gradual tectonic uplift continued through the midlate Holocene. The beach ridge steps have an amplitude of
TECTONIC AND NON-TECTONIC CAUSES OF EARLY HOLOCENE RELATIVE SEA LEVELCHANGEWITHINA TRANSGRESSIVE ESTUARY ON A SUBDUCTION MARGIN, PAKARAE RIVER, NORTH ISLAND, NEW ZEALAND. Kate Wilson 1 , Kelvin Berryman 2 , Tim Little 1 , Ursula Cochran 2 & Nicola Litchfield 2 . 1 Victoria University of Wellington, PO Box 600, Wellington. 2 Institute of Geological and Nuclear Sciences, PO Box 30368, Lower Hutt. (K.Wilson*gns.cri.nz) The highest Holocene marine terrace at Pakarae, North Island, New Zealand, corresponds with the maximum Holocene marine flooding surface. This terrace is underlain by a sequence of estuarine, fluvial and marine sediments that were deposited under rising eustatic sea level (SL) conditions. These sediments are presently exposed at elevations up to 20 m above modern mean SL as a result of tectonic uplift. This sedimentary sequence provides an opportunity to study the paleoenvironmental development of incised valleys under conditions of rising SL and tectonic uplift. The stratigraphy is valuable for comparison with traditional facies models of incised valley infills, which were developed exclusively from studies on stable coasts. We use sedimentology, macropaleontology and micropaleontology (benthic foraminifera) to reconstruct the paleoenvironments that accompanied infilling of Pakarae valley and to estimate the frequency, magnitude and timing of uplift events that occurred during the depositional period (c. 10,500 – c. 7,000 cal. yrs BP). We divide the Pakarae valley infill sequence into eight bio-lithofacies, each relates to a particular paleoenvironment. These are grouped into four paleoenvironmental facies: barrier, estuarine, estuary-head delta and fluvial. The basal fluvial facies, the immediately overlying estuary-head delta facies, and the capping barrier facies correlate well with models of incised valley infill from stable coasts and indicate that the complete sequence of valley infill is probably present within the Pakarae outcrops. However the middle section of the Pakarae stratigraphy displays alternations of estuarine and fluvial facies. This contrasts both with models of incised valley infill and with individual estuary infill studies; which predict that only central estuary basin sediments should be present between the transgressive estuary-head delta and the barrier facies. The whole Pakarae sequence is compressed relative to the amount of accommodation space estimated to have been created by eustatic SL rise during the depositional period. Only a small proportion of this can be explained by compaction, most of this important difference is the result of tectonic uplift during deposition. Supplemented by detailed microfossil studies and radiocarbon dates, we identify which facies transitions within the middle section are tectonic and non-tectonic in origin. One uplift event of at least 2 m occurred between 8695 – 8376 cal. yrs B.P. One or two uplift events occurred after deposition of the Rotoma tephra at ~ 9500 cal. yrs B.P and before 9255 – 8990 cal. yrs. B.P. Our data extends the paleoseismic history of this important location which has one of the highest uplift rates along a subduction margin without an historical record of subduction earthquakes. ORAL IMPACTS OF TEPHRA FALL ON A DAIRY FARMING OPERATION AT REREWHAKAAITU, EASTERN TAUPO VOLCANIC ZONE, NEW ZEALAND T.M. Wilson 1 &J.W.Cole 1 1 Natural Hazards Research Centre, Department of Geological Sciences, University of Canterbury, Christchurch, New Zealand (tmw42*student.canterbury.ac.nz) Much of New Zealand’s dairy farming industry, central to New Zealand’s economy, is based in the central North Island, in or near the Taupo Volcanic Zone, and is highly vulnerable to tephra fall. A vulnerability analysis was undertaken of, ‘Tulachard’ a study farm at Rerewhakaaitu, eastern Taupo Volcanic Zone, to assess the susceptibility of dairy farm’s infrastructure and operational processes to tephra fall. ‘Tulachard’ was particularly appropriate as it is close to Tarawera Volcano. Power supply, water supply and ability to use the tractor were identified as the most vulnerable elements to ‘Tulachard’s’ ability to respond and recover from tephra fall. One of the most vulnerable components of a milking shed is the condenser used for cooling milk because of its exposed nature and requirement for circulating outside air. An air conditioning condenser, similar to condensers used in milk cooling systems, was laboratory tested where it performed moderately well when inundated with dry tephra, but rapidly failed with wet tephra. A telephone survey of the Rerewhakaaitu dairy farming community established their perceptions of the risks faced from volcanic hazards. Although all respondents were aware of volcanic hazards, over half did not believe their farm would be affected by a volcanic eruption in their lifetime. None had prepared for a future volcanic eruption. This has important education implications for key organisations that would be affected if dairy farms were affected by eruptions. 50 th Kaikoura05 -95- Kaikoura 2005
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CHARACTERISATION OF NEW ZEALAND NEP
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myrtaceous. One 20 mm diameter flow
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ange of lower resolution or fragmen
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CRETACEOUS-EOCENE TRANSGRESSION MAR
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consists of a well-developed canyon
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model. The relative position of the
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converts to plate theory. Thus, the
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and on the following morning the mi
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the LGM grass peak. This period of
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offshore west coast to offshore eas
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4 Institut de Recherche pour le Dé
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VEGETATION AND CLIMATE CHANGE AT TH
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wider range. The youngest layer has
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few normal faults visible especiall
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TRACKING CRUSTAL DIFFERENTIATION AN
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EMPIRICAL SCALING RELATIONS FOR SEI
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hydrovolcanic eruptions then took p
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and that the MTL marks a Late Carbo
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faunal changes within these cores w
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material at subsurface depths of se
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survived through in low numbers in
Page 43 and 44: in the TVZ and southern Havre Troug
Page 45 and 46: Tephra beds are commonly used to ai
Page 47 and 48: The MCC is bounded by deep-seated t
Page 49 and 50: distal alluvial plains where large
Page 51 and 52: Many of the molluscs in the highly
Page 53 and 54: incremental slip history and paleoe
Page 55 and 56: This paper explores what we know of
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Page 59 and 60: These areas are also described in
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Page 69 and 70: with 63.8%, and then [3] with 49.9%
Page 71 and 72: U-Th-Ra disequilibria data. In part
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Page 85 and 86: The new era of commercial viability
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