title: Comparison of a Self-Processed EM3000 Multibeam Echosounder Dataset with a QTC View Habitat Mapping and a Sidescan Sonar Imagery, Tamaki Strait, New Zealand

authors: Schimel, Alexandre Carmelo Gregory

subjects: reflectivity

abstract: A methodology for automatically processing the data files from an EM3000 multibeam echosounder (Kongsberg Maritime, 300 kHz) is presented. Written in MatLab, it includes data extraction, bathymetry processing, computation of seafloor local slope, and a simple correction of the backscatter along-track banding effect. The success of the latter is dependent on operational restrictions, which are also detailed. This processing is applied to a dataset acquired in 2007 in the Tamaki Strait, New Zealand. The resulting maps are compared with a habitat classification obtained with the acoustic ground-discrimination software QTC View linked to a 200-kHz single-beam echosounder and to the imagery from a 100-kHz sidescan sonar survey, both performed in 2002. The multibeam backscatter map was found to be very similar to the sidescan imagery, quite correlated to the QTC View map on one site but mainly uncorrelated on another site. Hypotheses to explain these results are formulated and discussed. The maps and the comparison to prior surveys are used to draw conclusions on the quality of the code for further research on multibeam benthic habitat mapping.

text: Comparison of a Self-Processed EM3000 Multibeam Echosounder Dataset with a QTC View Habitat Mapping and a Sidescan Sonar Imagery, Tamaki Strait, New Zealand A methodology for automatically processing the data files from an EM3000 multibeam echosounder (Kongsberg Maritime, 300 kHz) is presented. Written in MatLab, it includes data extraction, bathymetry processing, computation of seafloor local slope, and a simple correction of the backscatter along-track banding effect. The success of the latter is dependent on operational restrictions, which are also detailed. This processing is applied to a dataset acquired in 2007 in the Tamaki Strait, New Zealand. The resulting maps are compared with a habitat classification obtained with the acoustic ground-discrimination software QTC View linked to a 200-kHz single-beam echosounder and to the imagery from a 100-kHz sidescan sonar survey, both performed in 2002. The multibeam backscatter map was found to be very similar to the sidescan imagery, quite correlated to the QTC View map on one site but mainly uncorrelated on another site. Hypotheses to explain these results are formulated and discussed. The maps and the comparison to prior surveys are used to draw conclusions on the quality of the code for further research on multibeam benthic habitat mapping.

year: 2010

title: Linking proximal ignimbrites and coeval distal tephra deposits to establish a record of voluminous Early Quaternary (2.4–1.9 Ma) volcanism of the Tauranga Volcanic Centre, New Zealand

authors: Prentice, Marlena Lee

subjects: Taupō Volcanic Zone

abstract: The Tauranga Volcanic Centre (TgaVC) of the North Island, New Zealand, was active from 2.95 to 1.9 Ma. It lies temporally and spatially between the currently active Taupō Volcanic Zone, one of the most productive regions of Quaternary silicic volcanism globally, and its predecessor, the Coromandel Volcanic Zone. This study provides an enhanced chronology for pyroclastic volcanism of the TgaVC with four locally widespread units named and defined as follows: Welcome Bay and Wharo ignimbrites (together formerly known as Lower Pāpāmoa Ignimbrite); Otawera Ignimbrite; and Arateka Ignimbrite (formerly known as Upper Pāpāmoa Ignimbrite). These eruptives were followed by the eruption of the large-volume Waiteariki Ignimbrite at 2.1 Ma. In northern Hawke’s Bay (150-170 km southeast of TgaVC), several distal tephra-fall horizons and an ignimbrite (Hikuroa Pumice Member) are preserved in marine-hosted sediments and are stratigraphically equivalent to the five ignimbrites of the TgaVC. Using new major- and trace-element data on glass in conjunction with new zircon-derived U-Pb ages, a correlation between the Hawke’s Bay tephras and the TgaVC ignimbrites is established and the Hikuroa Pumice Member is confirmed as the distal deposit of the Waiteariki Ignimbrite. The integrated proximal and distal records show that at least eight eruptions occurred in the TgaVC between 2.4 and 1.9 Ma and provide a maximum repose period between explosive eruptions of ca. 50 kyrs.

text: Linking proximal ignimbrites and coeval distal tephra deposits to establish a record of voluminous Early Quaternary (2.4–1.9 Ma) volcanism of the Tauranga Volcanic Centre, New Zealand The Tauranga Volcanic Centre (TgaVC) of the North Island, New Zealand, was active from 2.95 to 1.9 Ma. It lies temporally and spatially between the currently active Taupō Volcanic Zone, one of the most productive regions of Quaternary silicic volcanism globally, and its predecessor, the Coromandel Volcanic Zone. This study provides an enhanced chronology for pyroclastic volcanism of the TgaVC with four locally widespread units named and defined as follows: Welcome Bay and Wharo ignimbrites (together formerly known as Lower Pāpāmoa Ignimbrite); Otawera Ignimbrite; and Arateka Ignimbrite (formerly known as Upper Pāpāmoa Ignimbrite). These eruptives were followed by the eruption of the large-volume Waiteariki Ignimbrite at 2.1 Ma. In northern Hawke’s Bay (150-170 km southeast of TgaVC), several distal tephra-fall horizons and an ignimbrite (Hikuroa Pumice Member) are preserved in marine-hosted sediments and are stratigraphically equivalent to the five ignimbrites of the TgaVC. Using new major- and trace-element data on glass in conjunction with new zircon-derived U-Pb ages, a correlation between the Hawke’s Bay tephras and the TgaVC ignimbrites is established and the Hikuroa Pumice Member is confirmed as the distal deposit of the Waiteariki Ignimbrite. The integrated proximal and distal records show that at least eight eruptions occurred in the TgaVC between 2.4 and 1.9 Ma and provide a maximum repose period between explosive eruptions of ca. 50 kyrs.

year: 2022-09

title: [Review of Sociocultural realities: exploring new horizons by Angus Macfarlane, Sonja Macfarlane and Melinda Webber]

authors: McNae, Rachel Elizabeth

abstract: This article reviews the book "Sociocultural realities: exploring new horizons", by Angus Macfarlane, Sonja Macfarlane and Melinda Webber, Christchurch, New Zealand, Canterbury University Press, 2015, 220 pp., $45 (softcover), ISBN 9781927145722

text: [Review of Sociocultural realities: exploring new horizons by Angus Macfarlane, Sonja Macfarlane and Melinda Webber] This article reviews the book "Sociocultural realities: exploring new horizons", by Angus Macfarlane, Sonja Macfarlane and Melinda Webber, Christchurch, New Zealand, Canterbury University Press, 2015, 220 pp., $45 (softcover), ISBN 9781927145722

year: 2017