title: Pliocene Te Aute limestones, New Zealand: Expanding concepts for cool-water shelf carbonates

authors: Nelson, Campbell S.

subjects: limestone

abstract: Acceptance of a spectrum of warm- through cold-water shallow-marine carbonate facies has become of fundamental importance for correctly interpreting the origin and significance of all ancient platform limestones. Among other attributes, properties that have become a hallmark for characterising many Cenozoic non-tropical occurrences include: (1) the presence of common bryozoan and epifaunal bivalve skeletons; (2) a calcite-dominated mineralogy; (3) relatively thin deposits exhibiting low rates of sediment accumulation; (4) an overall destructive early diagenetic regime; and (5) that major porosity destruction and lithification occur mainly in response to chemical compaction of calcitic skeletons during moderate to deep burial. The Pliocene Te Aute limestones are non-tropical skeletal carbonates formed at paleolatitudes near 40-42°S under the influence of commonly strong tidal flows along the margins of an actively deforming and differentially uplifting forearc basin seaway, immediately inboard of the convergent Pacific-Australian plate boundary off eastern North Island, New Zealand. This dynamic depositional and tectonic setting strongly influenced both the style and subsequent diagenetic evolution of the limestones. Some of the Te Aute limestones exhibit the above kinds of "normal" non-tropical characteristics, but others do not. For example, many are barnacle and/or bivalve dominated, and several include attributes that at least superficially resemble properties of certain tropical carbonates. In this regard, a number of the limestones are infaunal bivalve rich and dominated by an aragonite over a calcite primary mineralogy, with consequently relatively high diagenetic potential. Individual limestone units are also often rather thick (e.g., up to 50-300 m), with accumulation rates from 0.2 to 0.5 m/ka, and locally as high as 1 m/ka. Moreover, there can be a remarkable array of diagenetic features in the limestones, involving grain alteration and/or cementation to widely varying extents within any, or some combination of, the marine phreatic, burial, and meteoric diagenetic environments, including locally widespread development of meteoric cement sourced from aragonite dissolution. The message is that non-tropical shelf carbonates include a more diverse array of geological settings, of skeletal and mineralogical facies, and of diagenetic features than current sedimentary models mainly advocate. While several attributes positively distinguish tropical from non-tropical limestones, continued detailed documentation of the wide spectrum of shallow-marine carbonate deposits formed outside tropical regions remains an important challenge in carbonate sedimentology.

text: Pliocene Te Aute limestones, New Zealand: Expanding concepts for cool-water shelf carbonates Acceptance of a spectrum of warm- through cold-water shallow-marine carbonate facies has become of fundamental importance for correctly interpreting the origin and significance of all ancient platform limestones. Among other attributes, properties that have become a hallmark for characterising many Cenozoic non-tropical occurrences include: (1) the presence of common bryozoan and epifaunal bivalve skeletons; (2) a calcite-dominated mineralogy; (3) relatively thin deposits exhibiting low rates of sediment accumulation; (4) an overall destructive early diagenetic regime; and (5) that major porosity destruction and lithification occur mainly in response to chemical compaction of calcitic skeletons during moderate to deep burial. The Pliocene Te Aute limestones are non-tropical skeletal carbonates formed at paleolatitudes near 40-42°S under the influence of commonly strong tidal flows along the margins of an actively deforming and differentially uplifting forearc basin seaway, immediately inboard of the convergent Pacific-Australian plate boundary off eastern North Island, New Zealand. This dynamic depositional and tectonic setting strongly influenced both the style and subsequent diagenetic evolution of the limestones. Some of the Te Aute limestones exhibit the above kinds of "normal" non-tropical characteristics, but others do not. For example, many are barnacle and/or bivalve dominated, and several include attributes that at least superficially resemble properties of certain tropical carbonates. In this regard, a number of the limestones are infaunal bivalve rich and dominated by an aragonite over a calcite primary mineralogy, with consequently relatively high diagenetic potential. Individual limestone units are also often rather thick (e.g., up to 50-300 m), with accumulation rates from 0.2 to 0.5 m/ka, and locally as high as 1 m/ka. Moreover, there can be a remarkable array of diagenetic features in the limestones, involving grain alteration and/or cementation to widely varying extents within any, or some combination of, the marine phreatic, burial, and meteoric diagenetic environments, including locally widespread development of meteoric cement sourced from aragonite dissolution. The message is that non-tropical shelf carbonates include a more diverse array of geological settings, of skeletal and mineralogical facies, and of diagenetic features than current sedimentary models mainly advocate. While several attributes positively distinguish tropical from non-tropical limestones, continued detailed documentation of the wide spectrum of shallow-marine carbonate deposits formed outside tropical regions remains an important challenge in carbonate sedimentology.

year: 2003-09-01

title: Improvement of mechanical performance of industrial hemp fibre reinforced polylactide biocomposites

authors: Sawpan, Moyeenuddin Ahmad

subjects: polymer–matrix composites

abstract: In this work, mechanical properties of chemically treated random short fibre and aligned long hemp fibre reinforced PLA composites were investigated over a range of fibre content (0–40 wt.%). It was found that tensile strength, Young’s modulus and impact strength of short hemp fibre reinforced PLA composites increased with increased fibre content. Alkali and silane fibre treatments were found to improve tensile and impact properties which appears to be due to good fibre/matrix adhesion and increased matrix crystallinity. A 30 wt.% alkali treated fibre reinforced PLA composite (PLA/ALK) with a tensile strength of 75.5 MPa, Young’s modulus of 8.18 GPa and impact strength of 2.64 kJ/m2 was found to be the best. However, plane-strain fracture toughness and strain energy release rate decreased with increased fibre content. The mechanical properties of the PLA/ALK composites were increased further due to alignment of long fibres.

text: Improvement of mechanical performance of industrial hemp fibre reinforced polylactide biocomposites In this work, mechanical properties of chemically treated random short fibre and aligned long hemp fibre reinforced PLA composites were investigated over a range of fibre content (0–40 wt.%). It was found that tensile strength, Young’s modulus and impact strength of short hemp fibre reinforced PLA composites increased with increased fibre content. Alkali and silane fibre treatments were found to improve tensile and impact properties which appears to be due to good fibre/matrix adhesion and increased matrix crystallinity. A 30 wt.% alkali treated fibre reinforced PLA composite (PLA/ALK) with a tensile strength of 75.5 MPa, Young’s modulus of 8.18 GPa and impact strength of 2.64 kJ/m2 was found to be the best. However, plane-strain fracture toughness and strain energy release rate decreased with increased fibre content. The mechanical properties of the PLA/ALK composites were increased further due to alignment of long fibres.

year: 2011-03

title: Environmental aspects of storm runoff discharge from a timber port, Tauranga, New Zealand

authors: Tian, Fengming

subjects: storm runoff water

abstract: An investigation was undertaken into storm runoff water quantity and quality, contaminant input to the receiving tidal waters from the Mt. Maunganui wharf, accumulation of potentially toxic resin acids in adjacent sediments, and the dilution of the wharf runoff in the receiving tidal waters, in order to assess the possible adverse environmental impact associated with the log operation at the Port of Tauranga Ltd.
Based upon field data and rainfall records, about a half of the annual precipitation over the log handling areas is converted to surface runoff (117,000 m³a⁻¹). Annual runoff volume per hectare of wharf surface is estimated as 7,500 m³ha⁻¹a⁻¹ for the sealed area and 3,700 m³ha⁻¹a⁻¹ for the gravelled area.
The optical quality of the wharf runoff is degraded due to addition of bark and soil particles. The black disk visual clarity (0.01-0.02 m) was only 0.5-1.0% of that in the receiving tidal waters. The wharf runoff appears very dark gray to yellowish brown in apparent colour (10YR1/3 to 10YR5/6 Munsell colour chart) and has a soluble yellow substance concentration of about 25 m⁻¹. Power relationships between the traditionally used parameters, for example, suspended solids and turbidity, were identified. The wharf surface pavement types had a significant influence on visual clarity, but little influence on yellow substance concentration.
The potentially toxic resin acids in the wharf runoff have been determined with SIM GC-MS. The average total resin acid level (1,030 ppb) is comparable to that of 1,000 ppb reported at which acute toxicity is likely to be exhibited. A relationship of resin acids against volatile suspended solids was established. Tests undertaken suggest that conventional treatment methods of natural sedimentation and flocculation-sedimentation are able to remove the resin acids effectively.
The levels of biological oxygen demand (BOD), total phosphorus and nitrogen in the wharf runoff are considerably higher than those of common urban runoff. However, the wharf runoff contributes little nitrate nitrogen and oil and grease to the receiving environment.
About 87,500 kg of suspended solids, 43,000 kg of volatile suspended solids, 14,200 kg of BOD, 500 kg of phosphorus, and 103 kg of resin acids are discharged to the Tauranga Harbour annually from runoff from the Mt. Maunganui wharf.
Analyses show that the impact on adjacent sediments from the storm runoff is limited to a distance of about 100 m from the discharge points and the resin acid levels in the sediments within this distance are not significantly higher compared to that of the storm runoff. The net resin acid accumulation rate in the shipping channel (Stella Passage) beside the log handling areas was estimated to be in the range of 300 to 370 ppb per year.
Based on field investigation and numerical simulations, the findings on dispersion and dilution of the wharf runoff in the receiving tidal waters are as follows: (i) the sea water around Stella Passage experiences an obvious natural salinity stratification, the extent of which depends greatly on the weather conditions; (ii) the wind drag stress and the pressure gradient caused by the addition of runoff had the greatest influence on the plume dynamics during the flood tide. The plumes basically remain within the top 2-3 m of the water column under different winds; (iii) the plume is unlikely to advect to the Whareroa Marae under strong (30-40 knots) easterly or northeasterly winds for a storm with a 5-year return period. However, there is an obvious influence on the Whareroa Marae under 30- 40 knot northerly winds; and (iv) the short duration and restricted region of the low dilution pulse of effluent around slack water may explain why there has been no reports of acute toxic events.
Sealing the gravel covered wharf area, improving the sweeping efficiency, and extending the present outfalls to the sea floor might be potential options for mitigating the environmental impact associated with discharge of the wharf runoff.

text: Environmental aspects of storm runoff discharge from a timber port, Tauranga, New Zealand An investigation was undertaken into storm runoff water quantity and quality, contaminant input to the receiving tidal waters from the Mt. Maunganui wharf, accumulation of potentially toxic resin acids in adjacent sediments, and the dilution of the wharf runoff in the receiving tidal waters, in order to assess the possible adverse environmental impact associated with the log operation at the Port of Tauranga Ltd.
Based upon field data and rainfall records, about a half of the annual precipitation over the log handling areas is converted to surface runoff (117,000 m³a⁻¹). Annual runoff volume per hectare of wharf surface is estimated as 7,500 m³ha⁻¹a⁻¹ for the sealed area and 3,700 m³ha⁻¹a⁻¹ for the gravelled area.
The optical quality of the wharf runoff is degraded due to addition of bark and soil particles. The black disk visual clarity (0.01-0.02 m) was only 0.5-1.0% of that in the receiving tidal waters. The wharf runoff appears very dark gray to yellowish brown in apparent colour (10YR1/3 to 10YR5/6 Munsell colour chart) and has a soluble yellow substance concentration of about 25 m⁻¹. Power relationships between the traditionally used parameters, for example, suspended solids and turbidity, were identified. The wharf surface pavement types had a significant influence on visual clarity, but little influence on yellow substance concentration.
The potentially toxic resin acids in the wharf runoff have been determined with SIM GC-MS. The average total resin acid level (1,030 ppb) is comparable to that of 1,000 ppb reported at which acute toxicity is likely to be exhibited. A relationship of resin acids against volatile suspended solids was established. Tests undertaken suggest that conventional treatment methods of natural sedimentation and flocculation-sedimentation are able to remove the resin acids effectively.
The levels of biological oxygen demand (BOD), total phosphorus and nitrogen in the wharf runoff are considerably higher than those of common urban runoff. However, the wharf runoff contributes little nitrate nitrogen and oil and grease to the receiving environment.
About 87,500 kg of suspended solids, 43,000 kg of volatile suspended solids, 14,200 kg of BOD, 500 kg of phosphorus, and 103 kg of resin acids are discharged to the Tauranga Harbour annually from runoff from the Mt. Maunganui wharf.
Analyses show that the impact on adjacent sediments from the storm runoff is limited to a distance of about 100 m from the discharge points and the resin acid levels in the sediments within this distance are not significantly higher compared to that of the storm runoff. The net resin acid accumulation rate in the shipping channel (Stella Passage) beside the log handling areas was estimated to be in the range of 300 to 370 ppb per year.
Based on field investigation and numerical simulations, the findings on dispersion and dilution of the wharf runoff in the receiving tidal waters are as follows: (i) the sea water around Stella Passage experiences an obvious natural salinity stratification, the extent of which depends greatly on the weather conditions; (ii) the wind drag stress and the pressure gradient caused by the addition of runoff had the greatest influence on the plume dynamics during the flood tide. The plumes basically remain within the top 2-3 m of the water column under different winds; (iii) the plume is unlikely to advect to the Whareroa Marae under strong (30-40 knots) easterly or northeasterly winds for a storm with a 5-year return period. However, there is an obvious influence on the Whareroa Marae under 30- 40 knot northerly winds; and (iv) the short duration and restricted region of the low dilution pulse of effluent around slack water may explain why there has been no reports of acute toxic events.
Sealing the gravel covered wharf area, improving the sweeping efficiency, and extending the present outfalls to the sea floor might be potential options for mitigating the environmental impact associated with discharge of the wharf runoff.

year: 1997