Pub Date : 2022-05-18DOI: 10.1080/00288306.2022.2076700
S. Ellis, S. Barker, C. Wilson, I. Hamling, S. Hreinsdóttir, F. Illsley‐Kemp, E. Mestel, J. Muirhead, Bubs Smith, G. Leonard, M. Savage, P. Villamor, P. Otway
ABSTRACT Lake Taupō (Taupō-nui-a-Tia) infills the composite caldera above an active rhyolitic magmatic system in the central Taupō Volcanic Zone (TVZ). Ground deformation is a key unrest indicator at Taupō volcano. We present a spreadsheet tool, TaupōInflate, to calculate and plot ground deformation from magmatic inflation at depth beneath Taupō caldera. Examples show detection limits for inflating magma bodies and their ascent through the crust beneath Lake Taupō. Source locations where it is challenging to detect even substantial volumes of inflating magma bodies are as large as 20 km3, with volume changes up to 0.01 km3, owing to the restricted station placement around the lake, although a dike propagating from shallow crustal depths towards the surface is likely to be detectable. For a magma overpressure of 10 MPa, the sizes of detectable inflating bodies at depths of 5–8 km using the present monitoring system are larger than the volumes of many past eruptions, illustrating the importance of future improvements to the geodetic network. We discuss the potential for future equipment installation, including lakebed instrumentation that would require approval of local iwi Ngāti Tūwharetoa through the Tūwharetoa Māori Trust Board who oversee the health and wellbeing of Lake Taupō.
{"title":"Taupōinflate: illustrating detection limits of magmatic inflation below Lake Taupō","authors":"S. Ellis, S. Barker, C. Wilson, I. Hamling, S. Hreinsdóttir, F. Illsley‐Kemp, E. Mestel, J. Muirhead, Bubs Smith, G. Leonard, M. Savage, P. Villamor, P. Otway","doi":"10.1080/00288306.2022.2076700","DOIUrl":"https://doi.org/10.1080/00288306.2022.2076700","url":null,"abstract":"ABSTRACT Lake Taupō (Taupō-nui-a-Tia) infills the composite caldera above an active rhyolitic magmatic system in the central Taupō Volcanic Zone (TVZ). Ground deformation is a key unrest indicator at Taupō volcano. We present a spreadsheet tool, TaupōInflate, to calculate and plot ground deformation from magmatic inflation at depth beneath Taupō caldera. Examples show detection limits for inflating magma bodies and their ascent through the crust beneath Lake Taupō. Source locations where it is challenging to detect even substantial volumes of inflating magma bodies are as large as 20 km3, with volume changes up to 0.01 km3, owing to the restricted station placement around the lake, although a dike propagating from shallow crustal depths towards the surface is likely to be detectable. For a magma overpressure of 10 MPa, the sizes of detectable inflating bodies at depths of 5–8 km using the present monitoring system are larger than the volumes of many past eruptions, illustrating the importance of future improvements to the geodetic network. We discuss the potential for future equipment installation, including lakebed instrumentation that would require approval of local iwi Ngāti Tūwharetoa through the Tūwharetoa Māori Trust Board who oversee the health and wellbeing of Lake Taupō.","PeriodicalId":49752,"journal":{"name":"New Zealand Journal of Geology and Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48359939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-05DOI: 10.1080/00288306.2022.2063347
C. Adams, J. Bradshaw
ABSTRACT Detrital zircon ages from sandstones in isolated plant-bearing, probably fluviatile sedimentary successions at Milan Rock and Mount Murphy, Marie Byrd Land, West Antarctica indicate probable mid-Cretaceous (95--105 Ma) depositional ages. Rocks of similar age reported from the Amundsen Sea have indicated warm, humid environments and the new data reported here for plant-bearing rocks would now place such conditions close (>80°S) to the contemporary mid-Cretaceous South Pole
{"title":"Cover successions on early Paleozoic basement in Marie Byrd Land, West Antarctica – evidence for Cretaceous plant-bearing rocks at South Polar latitudes","authors":"C. Adams, J. Bradshaw","doi":"10.1080/00288306.2022.2063347","DOIUrl":"https://doi.org/10.1080/00288306.2022.2063347","url":null,"abstract":"ABSTRACT Detrital zircon ages from sandstones in isolated plant-bearing, probably fluviatile sedimentary successions at Milan Rock and Mount Murphy, Marie Byrd Land, West Antarctica indicate probable mid-Cretaceous (95--105 Ma) depositional ages. Rocks of similar age reported from the Amundsen Sea have indicated warm, humid environments and the new data reported here for plant-bearing rocks would now place such conditions close (>80°S) to the contemporary mid-Cretaceous South Pole","PeriodicalId":49752,"journal":{"name":"New Zealand Journal of Geology and Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45729956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-20DOI: 10.1080/00288306.2022.2059766
Philip Morris, T. Little, R. V. Van Dissen, M. Hemphill-Haley, J. Kearse, M. Hill, Jessica L. Vermeer, K. Norton
ABSTRACT The Mw 7.8 Kaikōura earthquake of November 14th, 2016 provided rare opportunities to evaluate ground deformation during a large strike-slip earthquake. Following the earthquake, both halves of a displaced paleoseismic trench were re-excavated and extended to test, refine, and extend the known late Holocene chronology of surface rupturing earthquakes on the Kekerengu Fault. 28 organic-bearing samples were collected during these excavations. Of these, six samples provided new 14C ages that could be superimposed on the preferred age model of (Little VDR, Kearse J, Norton K, Benson A, Wang N. 2018. Kekerengu fault, New Zealand: Timing and size of Late Holocene surface ruptures. Bulletin of the Seismological Society of America. 108(3B):1556–1572) to derive an expanded, updated age model of earthquake events on the fault that is now based on 16 dated samples. Including the 2016 earthquake, we recognise six surface rupturing earthquakes on the Kekerengu Fault since ∼2000 cal. B.P. Based on the last five events, our analysis yields an updated estimate of the mean recurrence interval for surface rupturing on the fault of 375 ± 32 yrs (1σ) since ∼1650 cal. B.P. An older, sixth event (E5) was not included in the preferred age model due to uncertainties in interpretation; however, incorporating this event into an alternative, six-event age model would adjust the recurrence interval estimate to 433 ± 22 yrs (1σ) since ∼2000 cal. B.P.
{"title":"A revised paleoseismological record of late Holocene ruptures on the Kekerengu Fault following the 2016 Kaikōura earthquake","authors":"Philip Morris, T. Little, R. V. Van Dissen, M. Hemphill-Haley, J. Kearse, M. Hill, Jessica L. Vermeer, K. Norton","doi":"10.1080/00288306.2022.2059766","DOIUrl":"https://doi.org/10.1080/00288306.2022.2059766","url":null,"abstract":"ABSTRACT\u0000 The Mw 7.8 Kaikōura earthquake of November 14th, 2016 provided rare opportunities to evaluate ground deformation during a large strike-slip earthquake. Following the earthquake, both halves of a displaced paleoseismic trench were re-excavated and extended to test, refine, and extend the known late Holocene chronology of surface rupturing earthquakes on the Kekerengu Fault. 28 organic-bearing samples were collected during these excavations. Of these, six samples provided new 14C ages that could be superimposed on the preferred age model of (Little VDR, Kearse J, Norton K, Benson A, Wang N. 2018. Kekerengu fault, New Zealand: Timing and size of Late Holocene surface ruptures. Bulletin of the Seismological Society of America. 108(3B):1556–1572) to derive an expanded, updated age model of earthquake events on the fault that is now based on 16 dated samples. Including the 2016 earthquake, we recognise six surface rupturing earthquakes on the Kekerengu Fault since ∼2000 cal. B.P. Based on the last five events, our analysis yields an updated estimate of the mean recurrence interval for surface rupturing on the fault of 375 ± 32 yrs (1σ) since ∼1650 cal. B.P. An older, sixth event (E5) was not included in the preferred age model due to uncertainties in interpretation; however, incorporating this event into an alternative, six-event age model would adjust the recurrence interval estimate to 433 ± 22 yrs (1σ) since ∼2000 cal. B.P.","PeriodicalId":49752,"journal":{"name":"New Zealand Journal of Geology and Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48674758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-27DOI: 10.1080/00288306.2022.2054828
M. Crundwell, A. Woodhouse
{"title":"A detailed biostratigraphic framework for 0–1.2 Ma Quaternary sediments of north-eastern Zealandia","authors":"M. Crundwell, A. Woodhouse","doi":"10.1080/00288306.2022.2054828","DOIUrl":"https://doi.org/10.1080/00288306.2022.2054828","url":null,"abstract":"","PeriodicalId":49752,"journal":{"name":"New Zealand Journal of Geology and Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44478267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-16DOI: 10.1080/00288306.2022.2050771
A. Cooper
ABSTRACT Diopside-rich rocks (diopsidites) are interlaminated with nephrite in boulders derived from metasomatic contacts developed between Pounamu Ultramafic meta-serpentinite and country rock Alpine Schist, Westland, New Zealand. Petrographic textures indicate that parental tremolite rock, formed by metasomatic diffusion during metamorphism, has been intensely deformed and recrystallised to alternating semi-nephrite and nephrite domains during development of a secondary crenulation cleavage. Nephrites are subsequently sequentially overprinted by porphyroblastic tremolite, diopside, then further tremolite. Crystallisation is controlled by fluctuating activities of SiO2, CaO and H2O in associated fluids. Pervasive dissolution of nephritic tremolite and crystallisation of diopside generates diopsidites containing accessory epidote, uvarovite and zincian chromite formed in equilibrium with H2O-rich fluids. Diopsidites are in turn overgrown by coarse grained (in places > 50 cm long) diopside crystals, interpreted to have infilled an extension fracture that formed during ongoing uplift of the Southern Alps.
{"title":"Origin and evolution of nephrites, diopsidites and giant diopside crystals from the contact zones of the Pounamu Ultramafics, Westland, New Zealand","authors":"A. Cooper","doi":"10.1080/00288306.2022.2050771","DOIUrl":"https://doi.org/10.1080/00288306.2022.2050771","url":null,"abstract":"ABSTRACT Diopside-rich rocks (diopsidites) are interlaminated with nephrite in boulders derived from metasomatic contacts developed between Pounamu Ultramafic meta-serpentinite and country rock Alpine Schist, Westland, New Zealand. Petrographic textures indicate that parental tremolite rock, formed by metasomatic diffusion during metamorphism, has been intensely deformed and recrystallised to alternating semi-nephrite and nephrite domains during development of a secondary crenulation cleavage. Nephrites are subsequently sequentially overprinted by porphyroblastic tremolite, diopside, then further tremolite. Crystallisation is controlled by fluctuating activities of SiO2, CaO and H2O in associated fluids. Pervasive dissolution of nephritic tremolite and crystallisation of diopside generates diopsidites containing accessory epidote, uvarovite and zincian chromite formed in equilibrium with H2O-rich fluids. Diopsidites are in turn overgrown by coarse grained (in places > 50 cm long) diopside crystals, interpreted to have infilled an extension fracture that formed during ongoing uplift of the Southern Alps.","PeriodicalId":49752,"journal":{"name":"New Zealand Journal of Geology and Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48029952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-23DOI: 10.1080/00288306.2022.2039223
D. Craw, N. Mortimer
ABSTRACT The non-marine Blue Spur Conglomerate in southeast Otago hosts the largest gold paleoplacer in New Zealand, but its formal stratigraphic relationships have thus far not been clear. The name reflects the extensive formation of ferrous iron-bearing diagenetic clay. We present a reference section for the unit, which is in part late Haumurian in age (c. 81–66 Ma). The unit is defined as a formal Member of the nearby, but not contiguous, Late Cretaceous Taratu Formation, Onekakara Group, Haerenga Supergroup. The Blue Spur Conglomerate contains three principal clast types: proximal schist debris, quartz pebbles and recycled distal greywacke cobbles, whereas the wider Taratu Formation is dominated by quartz pebble conglomerate with subordinate lithic clasts. Rare clasts of silicified quartz pebble conglomerate (silcrete) in both units attest to the recycling of older mature quartz sediments. The Blue Spur Conglomerate formed locally at the base of active normal fault scarps that controlled a broad valley in which the regionally extensive Taratu Formation accumulated. Detrital gold in the Blue Spur Conglomerate had both proximal and distal sources, whereas the Taratu Formation elsewhere received only distal gold.
{"title":"Stratigraphy and palaeogeography of the Cretaceous Blue Spur Conglomerate, Otago, New Zealand","authors":"D. Craw, N. Mortimer","doi":"10.1080/00288306.2022.2039223","DOIUrl":"https://doi.org/10.1080/00288306.2022.2039223","url":null,"abstract":"ABSTRACT\u0000 The non-marine Blue Spur Conglomerate in southeast Otago hosts the largest gold paleoplacer in New Zealand, but its formal stratigraphic relationships have thus far not been clear. The name reflects the extensive formation of ferrous iron-bearing diagenetic clay. We present a reference section for the unit, which is in part late Haumurian in age (c. 81–66 Ma). The unit is defined as a formal Member of the nearby, but not contiguous, Late Cretaceous Taratu Formation, Onekakara Group, Haerenga Supergroup. The Blue Spur Conglomerate contains three principal clast types: proximal schist debris, quartz pebbles and recycled distal greywacke cobbles, whereas the wider Taratu Formation is dominated by quartz pebble conglomerate with subordinate lithic clasts. Rare clasts of silicified quartz pebble conglomerate (silcrete) in both units attest to the recycling of older mature quartz sediments. The Blue Spur Conglomerate formed locally at the base of active normal fault scarps that controlled a broad valley in which the regionally extensive Taratu Formation accumulated. Detrital gold in the Blue Spur Conglomerate had both proximal and distal sources, whereas the Taratu Formation elsewhere received only distal gold.","PeriodicalId":49752,"journal":{"name":"New Zealand Journal of Geology and Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43687985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-02DOI: 10.1080/00288306.2021.2021955
A. Nicol, J. Begg, V. Saltogianni, V. Mouslopoulou, O. Oncken, A. Howell
ABSTRACT The Kaikōura Earthquake uplifted Kaikōura Peninsula by ≤∼1 m. Uplift in 2016 mainly resulted from slip on an offshore thrust fault (OSTF), modelled to splay from the plate-interface, and was further influenced by slip on two newly identified faults (Armers Beach Fault, ABF; Te Taumanu Fault, TTF) mapped onshore from differential lidar (D-lidar). Forward dislocation modelling indicates that 2016 peninsula uplift can be reproduced by mean slip of ∼2.3 m on the OSTF and 0.25–0.5 m on the ABF and TTF. The variable co-seismic uplift recorded during the 2016 earthquake differs from the near-uniform (1.2 ± 0.2°) northwest tilting of MIS5c (96 ± 5 ka) and MIS5e (123 ± 5 ka) marine terraces; these ages are constrained by Optically Stimulated Luminescence (OSL) dating and correlation to sea-level curves. Tilting of Late Quaternary marine terraces can be primarily reproduced by slip rates of ∼0.8–2.7 mm/yr on the OSTF and 0.3–0.6 mm/yr on the ABF. Slip on the TTF is not required to produce tilting of the marine terraces, suggesting that it may have ruptured less frequently than the OSTF and ABF in the Late Quaternary. The OSTF links 2016 ruptures north and south of Kaikōura, with the earthquake rupturing an interconnected network of faults.
{"title":"Uplift and fault slip during the 2016 Kaikōura Earthquake and Late Quaternary, Kaikōura Peninsula, New Zealand","authors":"A. Nicol, J. Begg, V. Saltogianni, V. Mouslopoulou, O. Oncken, A. Howell","doi":"10.1080/00288306.2021.2021955","DOIUrl":"https://doi.org/10.1080/00288306.2021.2021955","url":null,"abstract":"ABSTRACT The Kaikōura Earthquake uplifted Kaikōura Peninsula by ≤∼1 m. Uplift in 2016 mainly resulted from slip on an offshore thrust fault (OSTF), modelled to splay from the plate-interface, and was further influenced by slip on two newly identified faults (Armers Beach Fault, ABF; Te Taumanu Fault, TTF) mapped onshore from differential lidar (D-lidar). Forward dislocation modelling indicates that 2016 peninsula uplift can be reproduced by mean slip of ∼2.3 m on the OSTF and 0.25–0.5 m on the ABF and TTF. The variable co-seismic uplift recorded during the 2016 earthquake differs from the near-uniform (1.2 ± 0.2°) northwest tilting of MIS5c (96 ± 5 ka) and MIS5e (123 ± 5 ka) marine terraces; these ages are constrained by Optically Stimulated Luminescence (OSL) dating and correlation to sea-level curves. Tilting of Late Quaternary marine terraces can be primarily reproduced by slip rates of ∼0.8–2.7 mm/yr on the OSTF and 0.3–0.6 mm/yr on the ABF. Slip on the TTF is not required to produce tilting of the marine terraces, suggesting that it may have ruptured less frequently than the OSTF and ABF in the Late Quaternary. The OSTF links 2016 ruptures north and south of Kaikōura, with the earthquake rupturing an interconnected network of faults.","PeriodicalId":49752,"journal":{"name":"New Zealand Journal of Geology and Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45812144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-17DOI: 10.1080/00288306.2021.2021956
Yoshihiro Tanaka, Megan Ortega, R. Fordyce
ABSTRACT The major increase in cetacean brain size happened in the middle Miocene, about 15 million years ago, and involved the modern oceanic dolphin lineage Delphinoidea. In this paper, we describe a new specimen of an archaic dolphin, aff. Prosqualodon davidis, from the Gee Greensand, near Oamaru, New Zealand. The specimen is from the early Miocene, approximately 23–19–18 Ma, and includes an incomplete cranium, endocast, teeth, and some postcranial elements. Comparison of the median sulcus among previously reported endocasts and brains of the Cetacea suggests that the cerebrum was expanded incipiently in the Odontoceti from the early Miocene in the Eurhinodelphinidae + Delphinoidea lineage. Conversely, the olfactory fossa has been reduced in Odontoceti, and completely lost in at least two clades (Delphinoidea and Platanista gangetica), because olfaction was most likely no longer an essential sense for animals spending their life in water. Reduction and loss of the olfactory fossa saved energy, which may be related to the expansion of the cerebrum and cortex in an Odontoceti lineage that led to modern oceanic dolphins. The early Miocene appears to have been a transitional period for archaic and modern-type odontocetes, which were possibly and partly separated by these differences.
{"title":"A new early Miocene archaic dolphin (Odontoceti, Cetacea) from New Zealand, and brain evolution of the Odontoceti","authors":"Yoshihiro Tanaka, Megan Ortega, R. Fordyce","doi":"10.1080/00288306.2021.2021956","DOIUrl":"https://doi.org/10.1080/00288306.2021.2021956","url":null,"abstract":"ABSTRACT The major increase in cetacean brain size happened in the middle Miocene, about 15 million years ago, and involved the modern oceanic dolphin lineage Delphinoidea. In this paper, we describe a new specimen of an archaic dolphin, aff. Prosqualodon davidis, from the Gee Greensand, near Oamaru, New Zealand. The specimen is from the early Miocene, approximately 23–19–18 Ma, and includes an incomplete cranium, endocast, teeth, and some postcranial elements. Comparison of the median sulcus among previously reported endocasts and brains of the Cetacea suggests that the cerebrum was expanded incipiently in the Odontoceti from the early Miocene in the Eurhinodelphinidae + Delphinoidea lineage. Conversely, the olfactory fossa has been reduced in Odontoceti, and completely lost in at least two clades (Delphinoidea and Platanista gangetica), because olfaction was most likely no longer an essential sense for animals spending their life in water. Reduction and loss of the olfactory fossa saved energy, which may be related to the expansion of the cerebrum and cortex in an Odontoceti lineage that led to modern oceanic dolphins. The early Miocene appears to have been a transitional period for archaic and modern-type odontocetes, which were possibly and partly separated by these differences.","PeriodicalId":49752,"journal":{"name":"New Zealand Journal of Geology and Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43746437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-12DOI: 10.1080/00288306.2021.2011328
K. L. Maier, A. Orpin, H. Neil
ABSTRACT Enclosed depressions, termed pockmarks, are widespread seafloor morphologies, commonly associated with fluid seepage. This study provides the first detailed documentation of pockmarks offshore the South Westland margin of the South Island/Te Waipounamu, Aotearoa New Zealand. Pockmarks are identified from multibeam bathymetry (25-m grid) through manual and semi-automated selection in water depths of 100–2600 m. Pockmarks are most concentrated at 400–850 m water depth on continental slope areas between submarine canyons. A continuum of pockmark morphologies includes – (1) large (>0.5 km2 area) and irregularly shaped pockmarks above partially infilled channels; (2) small and circular pockmarks (∼100–200 m diameter; ∼0.008–0.03 km2 area) occurring between canyons; and (3) elongated and intermediate size pockmarks, generally oriented along-slope and often occurring above buried sediment waves. Elongated pockmarks appear to have been modified by near-seafloor oceanographic and/or turbidity current flows. Pockmark features occur across many locations around Aotearoa, including both the eastern and western margins. Some similar pockmark morphologies are identified in these different tectonic, sedimentary, and oceanographic settings, suggesting that there may be some similarity in formative mechanisms, but clear mechanisms leading to their formation remain enigmatic.
{"title":"Seafloor pockmarks on the South Westland margin of the South Island/Te Waipounamu, Aotearoa New Zealand","authors":"K. L. Maier, A. Orpin, H. Neil","doi":"10.1080/00288306.2021.2011328","DOIUrl":"https://doi.org/10.1080/00288306.2021.2011328","url":null,"abstract":"ABSTRACT Enclosed depressions, termed pockmarks, are widespread seafloor morphologies, commonly associated with fluid seepage. This study provides the first detailed documentation of pockmarks offshore the South Westland margin of the South Island/Te Waipounamu, Aotearoa New Zealand. Pockmarks are identified from multibeam bathymetry (25-m grid) through manual and semi-automated selection in water depths of 100–2600 m. Pockmarks are most concentrated at 400–850 m water depth on continental slope areas between submarine canyons. A continuum of pockmark morphologies includes – (1) large (>0.5 km2 area) and irregularly shaped pockmarks above partially infilled channels; (2) small and circular pockmarks (∼100–200 m diameter; ∼0.008–0.03 km2 area) occurring between canyons; and (3) elongated and intermediate size pockmarks, generally oriented along-slope and often occurring above buried sediment waves. Elongated pockmarks appear to have been modified by near-seafloor oceanographic and/or turbidity current flows. Pockmark features occur across many locations around Aotearoa, including both the eastern and western margins. Some similar pockmark morphologies are identified in these different tectonic, sedimentary, and oceanographic settings, suggesting that there may be some similarity in formative mechanisms, but clear mechanisms leading to their formation remain enigmatic.","PeriodicalId":49752,"journal":{"name":"New Zealand Journal of Geology and Geophysics","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43825933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-02DOI: 10.1080/00288306.2021.2011329
D. Ninis, T. Little, N. Litchfield, Ningsheng Wang, K. Jacobs, C. Henderson
ABSTRACT Along the south coast of the North Island of New Zealand, elevated Pleistocene marine terraces provide evidence for vertical deformation associated with active crustal faults and the westward subduction of the Pacific Plate at the southern Hikurangi margin. We have reassessed the age and elevation of these terraces. Optically Stimulated Luminescence (OSL) data of their cover bed sediments (20 new ages) provide the first numerical ages for most of these terraces. Shore platform elevations have been surveyed using differential Global Navigation Satellite System (GNSS) measurements of the wave-cut bedrock straths underlying these terraces. These new data allow the terraces to be temporally correlated across the margin. Seven different-aged terraces were identified and mapped along the Wellington south coast; these are preserved discontinuously between the westernmost site at Tongue Point, and Ngawi near Cape Palliser, to the east. The OSL data indicate that most of these terraces formed at MIS 5a, 5c, 5e (Last Interglacial) and 7a. The terraces are best preserved within the Hikurangi margin forearc, where they decrease in altitude towards the west, indicating long wavelength, westward tectonic tilting. The terraces are locally offset by a number of active crustal faults, most notably the Wairarapa and Ohariu faults.
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