title: Formation of magnetite-enriched zones in and offshore of a mesotidal estuarine lagoon: An environmental magnetic study of Tauranga Harbour and Bay of Plenty, New Zealand

authors: Badesab, Firoz

subjects: environmental magnetism

abstract: Magnetic iron minerals are widespread and indicative sediment constituents in estuarine, coastal and shelf systems. We combine environmental magnetic, sedimentological and numerical methods to identify magnetite-enriched placer-like zones in a complex coastal system and delineate their formation mechanisms. Magnetic susceptibility and remanence measurements on 245 surficial sediment samples collected in and around Tauranga Harbour, the largest barrier-enclosed tidal estuary of New Zealand, reveal several discrete enrichment zones controlled by local hydrodynamic conditions. Active magnetite enrichment takes place in tidal channels, which feed into two coast-parallel nearshore magnetite-enriched belts centered at water depths of 6–10 m and 10–20 m. A close correlation between magnetite content and magnetic grain size was found, where higher susceptibility values are associated within coarser magnetic crystal sizes. Two key mechanisms for magnetite enrichment are identified. First, tide-induced residual currents primarily enable magnetite enrichment within the estuarine channel network. A coast-parallel, fine sand magnetite enrichment belt in water depths of less than 10 m along the barrier island has a strong decrease in magnetite content away from the southern tidal inlet and is apparently related to active coast-parallel transport combined with mobilizing surf zone processes. A second, less pronounced, but more uniform magnetite enrichment belt at 10–20 m water depth is composed of non-mobile, medium-coarse-grained relict sands, which have been reworked during post-glacial sea level transgression. We demonstrate the potential of magnetic methods to reveal and differentiate coastal magnetite enrichment patterns and investigate their formative mechanisms.

text: Formation of magnetite-enriched zones in and offshore of a mesotidal estuarine lagoon: An environmental magnetic study of Tauranga Harbour and Bay of Plenty, New Zealand Magnetic iron minerals are widespread and indicative sediment constituents in estuarine, coastal and shelf systems. We combine environmental magnetic, sedimentological and numerical methods to identify magnetite-enriched placer-like zones in a complex coastal system and delineate their formation mechanisms. Magnetic susceptibility and remanence measurements on 245 surficial sediment samples collected in and around Tauranga Harbour, the largest barrier-enclosed tidal estuary of New Zealand, reveal several discrete enrichment zones controlled by local hydrodynamic conditions. Active magnetite enrichment takes place in tidal channels, which feed into two coast-parallel nearshore magnetite-enriched belts centered at water depths of 6–10 m and 10–20 m. A close correlation between magnetite content and magnetic grain size was found, where higher susceptibility values are associated within coarser magnetic crystal sizes. Two key mechanisms for magnetite enrichment are identified. First, tide-induced residual currents primarily enable magnetite enrichment within the estuarine channel network. A coast-parallel, fine sand magnetite enrichment belt in water depths of less than 10 m along the barrier island has a strong decrease in magnetite content away from the southern tidal inlet and is apparently related to active coast-parallel transport combined with mobilizing surf zone processes. A second, less pronounced, but more uniform magnetite enrichment belt at 10–20 m water depth is composed of non-mobile, medium-coarse-grained relict sands, which have been reworked during post-glacial sea level transgression. We demonstrate the potential of magnetic methods to reveal and differentiate coastal magnetite enrichment patterns and investigate their formative mechanisms.

year: 2012

title: Polarization tunable selective polariton generator

authors: Sedoglavich, Nemanya

subjects: selective polariton generator

abstract: A selective polariton generator (SPG) design, based on surface plasmon antennae principles, is demonstrated to provide a selective light transmission peak. The polarization-sensitive structure selectively generates and transports polaritons of a desired wavelength through a circular subwavelength aperture. By varying the SPG structure around a central nanohole, we are able to control the peak optical transmission wavelengths via the polarization state of the incident photons. We find good agreement between simulations and experimental results.

text: Polarization tunable selective polariton generator A selective polariton generator (SPG) design, based on surface plasmon antennae principles, is demonstrated to provide a selective light transmission peak. The polarization-sensitive structure selectively generates and transports polaritons of a desired wavelength through a circular subwavelength aperture. By varying the SPG structure around a central nanohole, we are able to control the peak optical transmission wavelengths via the polarization state of the incident photons. We find good agreement between simulations and experimental results.

year: 2009-03

title: Telling “Us” in the “Days Destined to You: Response Life-Telling: Indigenous Oral Autobiography and the Performance of Relation

authors: Mahuika, Nepia

subjects: Arts & Humanities

abstract: This “tau-utuutu” (responsive) protocol feels familiar to me.² My turn to speak, to respond, to share in a conversation with Warren Cariou’s stimulating essay on “Life-Telling,” Indigenous autobiography, and Dovie Thomason. It reminds me of how life-telling, orality, and history, interweave and work in my tribal universe. At home, we take turns speaking. We inherit our words, we respond, carve, and weave new narratives—make them ours. Where I come from, lives are frequently “told,” sung, cried, carved, and performed, through tribal conversations, a chorus of textured tones, sometimes in a grand debate within which our personal and collective pasts, presents, and futures converge and diverge.³ I am glad, then, to be invited, to add my voice to this present discussion. It feels natural . . . normal . . . Native.

text: Telling “Us” in the “Days Destined to You: Response Life-Telling: Indigenous Oral Autobiography and the Performance of Relation This “tau-utuutu” (responsive) protocol feels familiar to me.² My turn to speak, to respond, to share in a conversation with Warren Cariou’s stimulating essay on “Life-Telling,” Indigenous autobiography, and Dovie Thomason. It reminds me of how life-telling, orality, and history, interweave and work in my tribal universe. At home, we take turns speaking. We inherit our words, we respond, carve, and weave new narratives—make them ours. Where I come from, lives are frequently “told,” sung, cried, carved, and performed, through tribal conversations, a chorus of textured tones, sometimes in a grand debate within which our personal and collective pasts, presents, and futures converge and diverge.³ I am glad, then, to be invited, to add my voice to this present discussion. It feels natural . . . normal . . . Native.

year: 2016