scholarly journals Towards characterising rhyolitic tephra layers from New Zealand with rapid, non-destructive μ-XRF core scanning

2019 ◽  
Vol 514 ◽  
pp. 161-172 ◽  
Author(s):  
Leonie Peti ◽  
Paul C. Augustinus ◽  
Patricia S. Gadd ◽  
Sarah J. Davies
Keyword(s):  
New Zealand ◽  
Xrf Core Scanning ◽  
Tephra Layers ◽  
Non Destructive ◽  
Rhyolitic Tephra

scholarly journals Development of non-destructive age indices for three New Zealand loranthaceous mistletoes

1997 ◽  
Vol 35 (3) ◽  
pp. 337-343 ◽  
Author(s):  
David A. Norton ◽  
Jenny J. Ladley ◽  
Ashley D. Sparrow
Keyword(s):  
New Zealand ◽  
Non Destructive

scholarly journals Discovery of halloysite books in altered silicic Quaternary tephras, northern New Zealand

Clay Minerals ◽  
2016 ◽  
Vol 51 (3) ◽  
pp. 351-372 ◽  
Author(s):  
M.J. Cunningham ◽  
D.J. Lowe ◽  
J.B. Wyatt ◽  
V.G. Moon ◽  
G. Jock Churchman
Keyword(s):  
New Zealand ◽  
Volcanic Glass ◽  
Low Permeability ◽  
Tephra Deposits ◽  
Highly Porous ◽  
Rhyolitic Tephra

AbstractHydrated halloysite was discovered in books, a morphology previously associated exclusively with kaolinite. From ∼1.5 to ∼1500 μm in length, the books showed significantly greater mean Fe contents (Fe2O3= 5.2 wt.%) than tubes (Fe2O3= 3.2 wt.%), and expanded rapidly with formamide. They occurred, along with halloysite tubes, spheroids and plates, in highly porous yet poorly permeable, silt-dominated, Si-rich, pumiceous rhyolitic tephra deposits aged ∼0.93 Ma (Te Puna tephra) and ∼0.27 Ma (Te Ranga tephra) at three sites ∼10–20 m stratigraphically below the modern landsurface in the Tauranga area, eastern North Island, New Zealand. The book-bearing tephras were at or near saturation, but have experienced intermittent partial drying, favouring the proposed changes: solubilized volcanic glass + plagioclase→halloysite spheroids→halloysite tubes→halloysite plates→ halloysite books. Unlike parallel studies elsewhere involving both halloysite and kaolinite, kaolinite has not formed in Tauranga presumably because the low permeability ensures that the sites largely remain locally wet so that the halloysite books are metastable. An implication of the discovery is that some halloysite books in similar settings may have been misidentified previously as kaolinite.

A two-stage model for the formation of clay minerals from tephra-derived volcanic glass

Clay Minerals ◽  
1990 ◽  
Vol 25 (3) ◽  
pp. 313-327 ◽  
Author(s):  
A. P. W. Hodder ◽  
B. E. Green ◽  
D. J. Lowe
Keyword(s):  
Clay Minerals ◽  
Late Quaternary ◽  
Volcanic Glass ◽  
Chemical Processes ◽  
Diffusion Controlled ◽  
Tephra Layers ◽  
Clay Formation ◽  
Kinetics Of ◽  
Calculated Activation ◽  
Rhyolitic Tephra

AbstractThe kinetics of clay formation in buried paleosols developed from late Quaternary rhyolitic tephra layers near Rotorua, New Zealand, can be described in terms of a combination of parabolic and linear kinetics, reflecting the hydration of glass, and the formation of clay minerals, respectively. Such a model is consistent with the formation of clay minerals showing an Arrhenian temperature dependence and suggests, on the basis of calculated activation energies, that the process of formation of Al-rich allophane (imogolite) is diffusion controlled, whereas the rate of formation of Si-rich allophane is controlled by the chemical processes at the site of reaction.

Halloysite in late pleistocene rhyolitic tephra beds near Opotiki, coastal Bay of Plenty, North Island, New Zealand

Soil Research ◽  
1978 ◽  
Vol 16 (1) ◽  
pp. 1 ◽  
Author(s):  
JH Kirkman ◽  
WA Pullar
Keyword(s):  
New Zealand ◽  
Late Pleistocene ◽  
Clay Mineralogy ◽  
Time Period ◽  
Cylindrical Form ◽  
Long Time ◽  
Coastal Bay ◽  
Tephra Beds ◽  
Rhyolitic Tephra

Investigation of the clay mineralogy of 14 rhyolitic tephra beds with a suggested age of 125000 to 220000 years revealed that the squat cylindrical form of halloysite is the dominant crystalline mineral. This mineral has probably crystallized from allophane over a long time period, excess silica being precipitated as a weakly hydrated phase. The squat cylindrical crystals perhaps characterize halloysite formation in rhyolitic tephras.

Using borehole gamma-ray spectroscopy to detect tephra layers in lacustrine deposits: An example from Lake Chalco, central Mexico 

2021 ◽  
Author(s):  
Mehrdad Sardar Abadi ◽  
Christian Zeeden ◽  
Arne Ulfers ◽  
Katja Hesse ◽  
Thomas Wonik
Keyword(s):  
Gamma Ray ◽  
Lacustrine Sediments ◽  
Central Mexico ◽  
Stratigraphic Correlation ◽  
Gamma Ray Spectroscopy ◽  
Tephra Layers ◽  
Core Descriptions ◽  
Core Description ◽  
Lake Deposits ◽  
Non Destructive

<p>Lacustrine sediments are archives of past environmental conditions. In recent decades, multinational ICDP efforts have conducted lake drilling projects to encode the potential of paleoclimate signals. Gamma-ray spectroscopy is a particularly useful tool as it is non-destructive, fast, and affordable even in cased boreholes. Gamma radiation can be used to identify elemental isotopes in the geological record, which is used for stratigraphic correlation and paleoclimatic investigations. </p><p>However, some lake sediments contain tephra layers with specific gamma-ray signatures, presenting a challenge for extracting the primary signals caused by environmental and climatic agents. Here, we use the sediments of Lake Chalco in central Mexico to propose a protocol to identify tephra layers embedded in other sediments using high-resolution spectral gamma-ray spectroscopy. This facilitates dividing the overall sediment column into representative horizons of tephra and non-tephra.</p><p>Among the upper 300 m of the lake deposit, our index detected 363 tephra layers, while 388 total tephra layers (≥1 mm in thickness) were reported from the core description of the same borehole, predicting 92% of tephra layers documented in the lake deposits from core descriptions. We suggest that not only the strength of the gamma-ray signal but also the composition of its constituent energy channels can be used to detect embedded tephra layers.</p>

Clump structure, population structure and non-destructive biomass estimation of the New Zealand carrageenophyte Sarcothalia lanceata (Gigartinaceae, Rhodophyta)

2016 ◽  
Vol 59 (5) ◽  
Author(s):  
Kate F. Neill ◽  
Wendy A. Nelson ◽  
Ruth Falshaw ◽  
Catriona L. Hurd
Keyword(s):  
New Zealand ◽  
Total Population ◽  
Natural Populations ◽  
Biomass Estimation ◽  
Suitable Candidate ◽  
Regression Methods ◽  
Fundamental Information ◽  
Clump Size ◽  
Non Destructive ◽  
Two Populations

Abstractis a New Zealand carrageenophyte with tetrasporophytic thalli that produce carrageenan very close to the idealised structure of lambda-carrageenan. As such there is interest in its potential for commercial utilisation. There is no information on the biology and ecology of natural populations of this species, but this knowledge is critical for determining whether a species is a suitable candidate for sustainable wild harvest or for aquaculture. Population studies were conducted at two sites in New Zealand’s South Island in order to provide fundamental information on this species. The structure (abundance and composition of male, female, tetrasporophytic and non-reproductive clumps) of the two populations was assessed monthly over a year, and population biomass estimated using regression methods. Seasonal variation was not evident in most of the parameters measured, but differences between sites were found in total population density, the density of different life-history phases, and clump size and structure. The turnover in biomass occurs more frequently at the blade level than at the clump level and the presence of a basal crust in this species promotes population stability.

scholarly journals The use of diagnostic radiology to detect shell irregularities in the New Zealand paua (abalone) Haliotis iris

2001 ◽  
Vol 35 (2) ◽  
pp. 167-171 ◽  
Author(s):  
John C. Schofield ◽  
Roseanne M. Grindley ◽  
Jonathan A. Keogh
Keyword(s):  
New Zealand ◽  
Diagnostic Radiology ◽  
Video Display ◽  
Ray Method ◽  
Marine Gastropods ◽  
X Ray ◽  
Non Invasive ◽  
Display Unit ◽  
Non Destructive ◽  
Video Display Unit

A method is described for the non-destructive, non-invasive, detection of shell lesions in the New Zealand paua, a marine gastropod Haliotis iris using diagnostic radiology. The X-ray method reliably detected the presence of shell lesions in 96% of the cases examined once lesion dimensions exceeded 6.2 × 7.1 mm. The extent of lesions above this size can be reliably and accurately determined from X-ray images viewed on a video display unit (VDU). Biofouling on the outside of the shell can cause misdiagnoses. This method is a significant animal welfare refinement in the identification of marine gastropods with shell lesions, when compared with traditional techniques which kill the animals.

Miocene tephra beds in the Cypress Hills of Saskatchewan, Canada

1992 ◽  
Vol 29 (1) ◽  
pp. 48-51 ◽  
Author(s):  
Willem J. Vreeken ◽  
John A. Westgate
Keyword(s):  
Middle Miocene ◽  
Volcanic Eruptions ◽  
Snake River Plain ◽  
Snake River ◽  
Weighted Mean ◽  
Tephra Layers ◽  
Tephra Beds ◽  
River Plain ◽  
Erosion Surface ◽  
Rhyolitic Tephra

Six rhyolitic tephra layers from ancient loess and related detritus in the Cypress Hills, Saskatchewan, represent separate volcanic eruptions from the Snake River Plain. Idaho, U.S.A. The weighted mean age and uncertainty of the youngest tephra bed is 8.3 ± 0.2 Ma, using the isothermal plateau fissiontrack technique on its hydrated glass shards. The loess that hosts five of these tephra beds extends across the Cypress Plain, which is the oldest (Middle Miocene) and highest depositional surface in the Interior Plains, and also occurs on four juxtaposed erosion surfaces. It appears that the first and maybe the second erosion surface began forming before 10 Ma, and that formation of the second, third, and fourth erosion surfaces was completed between 10 and 8.3 Ma.

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