title: Geophysical characterisation of the Onewhero and Kellyville volcanic complexes, South Auckland Volcanic Field

authors: Mullane, Kevin Joseph Chase

subjects: South Auckland Volcanic Field

abstract: The Quaternary-aged (1.59 – 0.51 Ma) intraplate, monogenetic, basaltic South Auckland Volcanic Field consists of at least 82 volcanic centres that span an area of 300 km². This study focusses on the volcanic and sedimentary histories of the Onewhero and Kellyville maars, interpreted from additional geological observations, which build upon previous geological studies, and gravimetric and magnetic surveys.
New geological observations of the Onewhero maar reveal the presence of diatomaceous sediment, and at least one lava flow, that probably originated from the nearby Klondyke cone to the south, and which occupies a significant area of the crater floor. A geological investigation of the Kellyville maar reveals a crater that has been partially filled by a thick accumulation of basalt and scoria and overlain by Karapiro Formation sediments and diatomite. Available borehole stratigraphy suggests that the Glass Hill basalt cone present in the Kellyville maar was an early-stage volcanic product rather than a late-stage product as previously thought.
Gravimetric surveys in the Onewhero and Kellyville maars revealed contrasting crater fill deposits. Raw gravity data was acquired in the field, corrected for drift and then reduced to a Bouguer anomaly. The Onewhero maar is characterised by an anomaly of -5.8 mGal that has a concave profile. The post-eruption geological body present at Onewhero is two-dimensionally modelled with a density of 1.3 g/cm³, and has a maximum thickness of 100 m in the northwest of the crater. The Kellyville maar is characterised by an anomaly of +2.5 mGal that has a convex profile. The dominant geological body present in the crater is a lava-lake deposit that is two-dimensionally modelled with a density of 2.9 g/cm³, and has a maximum thickness of 60 m.
The total magnetic field strength of the Onewhero and Kellyville maars was recorded with a proton magnetometer and the values were mapped in ArcMap. In the Onewhero maar, two subdued anomalies were outliers. A positive magnetic anomaly (213 nT) with a broad crescent shape was identified in the middle of the crater and interpreted to be either an extrusive feeder dyke or an accumulation of highly magnetic volcanic sediment deposited in a topographic trough. A circular negative anomaly (-1057 nT) in the northwest of the crater is an accumulation of lake sediment with a low magnetic susceptibility. In the Kellyville maar, two contrasting anomalies were observed. The strongly positive anomaly (1275 nT) corresponds to the geographical position of Glass Hill, a basaltic cone. A strong negative anomaly (-3315 nT) in the middle of the crater corresponds to a known deposit of diatomite.
Overall, the structure of the Onewhero maar, as inferred by this investigation, is similar to many other maars globally and its sedimentary fill is remarkably similar to the Dottingen maar in Germany. The Kellyville maar has a more unique structure but can be compared to the Domain maar in the nearby Auckland Volcanic Field.

text: Geophysical characterisation of the Onewhero and Kellyville volcanic complexes, South Auckland Volcanic Field The Quaternary-aged (1.59 – 0.51 Ma) intraplate, monogenetic, basaltic South Auckland Volcanic Field consists of at least 82 volcanic centres that span an area of 300 km². This study focusses on the volcanic and sedimentary histories of the Onewhero and Kellyville maars, interpreted from additional geological observations, which build upon previous geological studies, and gravimetric and magnetic surveys.
New geological observations of the Onewhero maar reveal the presence of diatomaceous sediment, and at least one lava flow, that probably originated from the nearby Klondyke cone to the south, and which occupies a significant area of the crater floor. A geological investigation of the Kellyville maar reveals a crater that has been partially filled by a thick accumulation of basalt and scoria and overlain by Karapiro Formation sediments and diatomite. Available borehole stratigraphy suggests that the Glass Hill basalt cone present in the Kellyville maar was an early-stage volcanic product rather than a late-stage product as previously thought.
Gravimetric surveys in the Onewhero and Kellyville maars revealed contrasting crater fill deposits. Raw gravity data was acquired in the field, corrected for drift and then reduced to a Bouguer anomaly. The Onewhero maar is characterised by an anomaly of -5.8 mGal that has a concave profile. The post-eruption geological body present at Onewhero is two-dimensionally modelled with a density of 1.3 g/cm³, and has a maximum thickness of 100 m in the northwest of the crater. The Kellyville maar is characterised by an anomaly of +2.5 mGal that has a convex profile. The dominant geological body present in the crater is a lava-lake deposit that is two-dimensionally modelled with a density of 2.9 g/cm³, and has a maximum thickness of 60 m.
The total magnetic field strength of the Onewhero and Kellyville maars was recorded with a proton magnetometer and the values were mapped in ArcMap. In the Onewhero maar, two subdued anomalies were outliers. A positive magnetic anomaly (213 nT) with a broad crescent shape was identified in the middle of the crater and interpreted to be either an extrusive feeder dyke or an accumulation of highly magnetic volcanic sediment deposited in a topographic trough. A circular negative anomaly (-1057 nT) in the northwest of the crater is an accumulation of lake sediment with a low magnetic susceptibility. In the Kellyville maar, two contrasting anomalies were observed. The strongly positive anomaly (1275 nT) corresponds to the geographical position of Glass Hill, a basaltic cone. A strong negative anomaly (-3315 nT) in the middle of the crater corresponds to a known deposit of diatomite.
Overall, the structure of the Onewhero maar, as inferred by this investigation, is similar to many other maars globally and its sedimentary fill is remarkably similar to the Dottingen maar in Germany. The Kellyville maar has a more unique structure but can be compared to the Domain maar in the nearby Auckland Volcanic Field.

year: 2015

title: Geomorphological context and formation history of Cloggs Cave: What was the cave like when people inhabited it?

authors: Delannoy, Jean-Jacques

subjects: archaeomorphology

abstract: New research undertaken at Cloggs Cave, in the foothills of the Australian Alps, employed an integrated geological-geomorphological-archaeological approach with manifold dating methods and fine resolution LiDAR 3D mapping. Long-standing questions about the site’s chronostratigraphy (e.g. the exact relationship between basal megafaunal deposits and archaeological layers), sedimentation processes and geomorphic changes were resolved. The cave’s formation history was reconstructed to understand its changing morphology and morphogenic processes, and to clarify how these processes shaped the cave’s deposits. Key findings include the identification of: 1) the geomorphological processes that caused the lateral juxtaposition of 52,000 year-old megafaunal and later occupational layers; 2) the existence of one and possibly two (now-buried) palaeo-entrance(s) that enabled now-extinct megafauna and extant large fauna to enter the cave, most likely via a free-roaming passage rather than a pit drop; 3) morphological changes to the cave during the time of the Old People, including the timing of changes to the inclination of palaeo-surfaces; and 4) modifications to stalactites, crushing of calcite formations for the manufacture of powder, construction of a stone arrangement, and movement of large limestone blocks by the Old People. Ultimately, these findings demonstrate that to properly understand what Cloggs Cave was like when the Old People visited the site requires the construction of a narrative that spans some 400 million years and the development of an approach capable of integrating the many scales and processes (e.g. geological, geomorphological, archaeological) that configured to shape the site.

text: Geomorphological context and formation history of Cloggs Cave: What was the cave like when people inhabited it? New research undertaken at Cloggs Cave, in the foothills of the Australian Alps, employed an integrated geological-geomorphological-archaeological approach with manifold dating methods and fine resolution LiDAR 3D mapping. Long-standing questions about the site’s chronostratigraphy (e.g. the exact relationship between basal megafaunal deposits and archaeological layers), sedimentation processes and geomorphic changes were resolved. The cave’s formation history was reconstructed to understand its changing morphology and morphogenic processes, and to clarify how these processes shaped the cave’s deposits. Key findings include the identification of: 1) the geomorphological processes that caused the lateral juxtaposition of 52,000 year-old megafaunal and later occupational layers; 2) the existence of one and possibly two (now-buried) palaeo-entrance(s) that enabled now-extinct megafauna and extant large fauna to enter the cave, most likely via a free-roaming passage rather than a pit drop; 3) morphological changes to the cave during the time of the Old People, including the timing of changes to the inclination of palaeo-surfaces; and 4) modifications to stalactites, crushing of calcite formations for the manufacture of powder, construction of a stone arrangement, and movement of large limestone blocks by the Old People. Ultimately, these findings demonstrate that to properly understand what Cloggs Cave was like when the Old People visited the site requires the construction of a narrative that spans some 400 million years and the development of an approach capable of integrating the many scales and processes (e.g. geological, geomorphological, archaeological) that configured to shape the site.

year: 2020

title: The Proceedings of the National Māori Graduates of Psychology Symposium 2002: Making a difference

authors: Nikora, Linda Waimarie

subjects: Maori

abstract: This is the full proceedings of the National Māori Graduates of Psychology Symposium 2002. The proceeding include the following themes: Kia matāra - negotiating the challenges in Māori development, kia mau – recruitment and retention, Tuhia mai, whiua atu – research and methodology, tinia mai – interventions and treatment, taitaia i te ahi manuka – pride upon the skin.

text: The Proceedings of the National Māori Graduates of Psychology Symposium 2002: Making a difference This is the full proceedings of the National Māori Graduates of Psychology Symposium 2002. The proceeding include the following themes: Kia matāra - negotiating the challenges in Māori development, kia mau – recruitment and retention, Tuhia mai, whiua atu – research and methodology, tinia mai – interventions and treatment, taitaia i te ahi manuka – pride upon the skin.

year: 2003