title: Hydrocarbon seep-carbonates of a Miocene forearc (East Coast Basin), North Island, New Zealand

authors: Campbell, Kathleen A.

subjects: hydrocarbon seep-carbonate

abstract: An ancient hydrocarbon seep province of 14 isolated, authigenic carbonate deposits has been identified in fine-grained, deep-marine siliciclastic strata of the Miocene East Coast Basin, North Island, New Zealand. These forearc sediments have been uplifted and complexly deformed into accretionary ridges, adjacent to the still-active Hikurangi convergent margin. Older active and passive margin strata (mid-Cretaceous to Oligocene in age) underlie the Neogene sequence, and contain oil- and gas-prone source rocks. Older Mesozoic meta-sedimentary rocks constitute the backstop against which the current phase of subduction-related sedimentation has accumulated (~ 24 Ma–present). The seep-carbonates (up to 10 m thick, 200 m across) archive methane signatures in their depleted carbon isotopes (to δ13C –51.7‰ PDB), and contain chemosynthesis-based paleocommunities (e.g. worm tubes, bathymodioline mussels, and vesicomyid, lucinid and thyasirid bivalves) typical of other Cenozoic and modern seeps. Northern and southern sites are geographically separated, and exhibit distinct lithological and faunal differences. Structural settings are variable. Seep-associated lithologies also are varied, and suggest carbonate development in sub-seafloor, seafloor and physically reworked (diapiric expansion, gas explosion, gravity slide or debris flow) settings, similar to Italian Apennine seep deposits of overlapping ages.
Peculiar attributes of the New Zealand Miocene seep deposits are several, including digitate thrombolites of clotted microbial micrite encased in thick, isopachous horizons and botryoids of aragonite. Seep plumbing features are also well-exposed at some sites, displaying probable gas-explosion breccias filled with aragonite, tubular concretions (fluid conduits), and carbonate-cemented, thin sandstone beds and burrows within otherwise impermeable mudstones. A few seeps were large enough to develop talus-debris piles on their flanks, which were populated by lucinid bivalves and terebratulid brachiopods. Firmgrounds and hardgrounds were common, as evidenced by trace fossil associations or caryophyllid coral thickets atop some seep-carbonate deposits. Thus, the New Zealand examples show strong evidence of formation in sediments at or just beneath the seafloor, but some were clearly exhumed by erosion to sustain later non-seep, epifaunal and boring paleocommunities.

text: Hydrocarbon seep-carbonates of a Miocene forearc (East Coast Basin), North Island, New Zealand An ancient hydrocarbon seep province of 14 isolated, authigenic carbonate deposits has been identified in fine-grained, deep-marine siliciclastic strata of the Miocene East Coast Basin, North Island, New Zealand. These forearc sediments have been uplifted and complexly deformed into accretionary ridges, adjacent to the still-active Hikurangi convergent margin. Older active and passive margin strata (mid-Cretaceous to Oligocene in age) underlie the Neogene sequence, and contain oil- and gas-prone source rocks. Older Mesozoic meta-sedimentary rocks constitute the backstop against which the current phase of subduction-related sedimentation has accumulated (~ 24 Ma–present). The seep-carbonates (up to 10 m thick, 200 m across) archive methane signatures in their depleted carbon isotopes (to δ13C –51.7‰ PDB), and contain chemosynthesis-based paleocommunities (e.g. worm tubes, bathymodioline mussels, and vesicomyid, lucinid and thyasirid bivalves) typical of other Cenozoic and modern seeps. Northern and southern sites are geographically separated, and exhibit distinct lithological and faunal differences. Structural settings are variable. Seep-associated lithologies also are varied, and suggest carbonate development in sub-seafloor, seafloor and physically reworked (diapiric expansion, gas explosion, gravity slide or debris flow) settings, similar to Italian Apennine seep deposits of overlapping ages.
Peculiar attributes of the New Zealand Miocene seep deposits are several, including digitate thrombolites of clotted microbial micrite encased in thick, isopachous horizons and botryoids of aragonite. Seep plumbing features are also well-exposed at some sites, displaying probable gas-explosion breccias filled with aragonite, tubular concretions (fluid conduits), and carbonate-cemented, thin sandstone beds and burrows within otherwise impermeable mudstones. A few seeps were large enough to develop talus-debris piles on their flanks, which were populated by lucinid bivalves and terebratulid brachiopods. Firmgrounds and hardgrounds were common, as evidenced by trace fossil associations or caryophyllid coral thickets atop some seep-carbonate deposits. Thus, the New Zealand examples show strong evidence of formation in sediments at or just beneath the seafloor, but some were clearly exhumed by erosion to sustain later non-seep, epifaunal and boring paleocommunities.

year: 2008

title: Concurrent schedule performance of possums: a comparison of two models

authors: Bron, Angela

abstract: These experiments examined the behaviour of brushtail possums (Trichosurus vulpecula) under concurrent variable-interval schedules of reinforcement. In the first experiment the lever pressing of six possums resulted in intermittent access to a barley/carob mixture under four pairs of variable-interval schedules. In most respects, the behaviour of the possums was similar to that observed with other species. However, the degree of undermatching of the response ratios to the obtained reinforcement-rate ratios was greater than is normally observed with these schedules. Both the Generalised Matching Law and the Contingency-Discriminability model described the data well, although, where overmatching was obtained, the parameter values given by the Contingency-Discriminability model did not make sense in terms of the original assumptions of the model. The second experiment examined the possibility that the undermatching related to the length of the changeover delay used. Six possums were exposed to five different pairs of concurrent schedules at each of four different changeover-delay lengths (ranging from 0 to 6 s). Time allocation and post-changeover delay responses more closely approximated matching with a 2-s changeover delay than with a 0-s delay, but no further changes in sensitivity were observed with further increases in changeover-delay length. Overmatching was consistently observed in the post changeover delay data, resulting in un-interpretable parameter values from Contingency-Discriminability analyses. The addition of the punishment parameter (w) to the Contingency-Discriminability model, suggested to deal with such data, did not generally result in more sensible parameter estimates. The third experiment attempted to bias possums responding using qualitatively different reinforcers. Equal variable-interval schedules were used with the barley/carob mixture available on one schedule and Cocopopsᵀᴹ or coconut on the other. Possums’ behaviour was biased by these foods, with a small bias away from the barley/carob mixture resulting from the Cocopops and a large bias towards the barley/carob mixture resulting from the coconut. In the fourth experiment, graded point estimates of bias were obtained by presenting four different concentrations of salted barley/carob mixture (ranging from 0% to 6%) on one schedule and plain barley/carob mixture on the other schedule. Small biases were found with 0% and 2% salt, and large biases were found towards the barley/carob mixture with 4% and 6% salt. To assess whether bias remains constant with changes in the reinforcer-rate ratio, further conditions were conducted with 4% and 6% salt, with four pairs of unequal concurrent variable-interval schedules. Analyses of these data with both the Generalised Matching Law and the Contingency-Discriminability Model revealed an interaction between bias and the reinforcement-rate ratio. This interaction may be due to an improvement in discriminability due to the different reinforcers. The behaviour of the possums was generally well described by both the Generalised Matching Law and the Contingency-Discriminability model. Overall, neither model was better at describing behaviour under the above conditions, although several problems were found with the application of the Contingency-Discriminability model.

text: Concurrent schedule performance of possums: a comparison of two models These experiments examined the behaviour of brushtail possums (Trichosurus vulpecula) under concurrent variable-interval schedules of reinforcement. In the first experiment the lever pressing of six possums resulted in intermittent access to a barley/carob mixture under four pairs of variable-interval schedules. In most respects, the behaviour of the possums was similar to that observed with other species. However, the degree of undermatching of the response ratios to the obtained reinforcement-rate ratios was greater than is normally observed with these schedules. Both the Generalised Matching Law and the Contingency-Discriminability model described the data well, although, where overmatching was obtained, the parameter values given by the Contingency-Discriminability model did not make sense in terms of the original assumptions of the model. The second experiment examined the possibility that the undermatching related to the length of the changeover delay used. Six possums were exposed to five different pairs of concurrent schedules at each of four different changeover-delay lengths (ranging from 0 to 6 s). Time allocation and post-changeover delay responses more closely approximated matching with a 2-s changeover delay than with a 0-s delay, but no further changes in sensitivity were observed with further increases in changeover-delay length. Overmatching was consistently observed in the post changeover delay data, resulting in un-interpretable parameter values from Contingency-Discriminability analyses. The addition of the punishment parameter (w) to the Contingency-Discriminability model, suggested to deal with such data, did not generally result in more sensible parameter estimates. The third experiment attempted to bias possums responding using qualitatively different reinforcers. Equal variable-interval schedules were used with the barley/carob mixture available on one schedule and Cocopopsᵀᴹ or coconut on the other. Possums’ behaviour was biased by these foods, with a small bias away from the barley/carob mixture resulting from the Cocopops and a large bias towards the barley/carob mixture resulting from the coconut. In the fourth experiment, graded point estimates of bias were obtained by presenting four different concentrations of salted barley/carob mixture (ranging from 0% to 6%) on one schedule and plain barley/carob mixture on the other schedule. Small biases were found with 0% and 2% salt, and large biases were found towards the barley/carob mixture with 4% and 6% salt. To assess whether bias remains constant with changes in the reinforcer-rate ratio, further conditions were conducted with 4% and 6% salt, with four pairs of unequal concurrent variable-interval schedules. Analyses of these data with both the Generalised Matching Law and the Contingency-Discriminability Model revealed an interaction between bias and the reinforcement-rate ratio. This interaction may be due to an improvement in discriminability due to the different reinforcers. The behaviour of the possums was generally well described by both the Generalised Matching Law and the Contingency-Discriminability model. Overall, neither model was better at describing behaviour under the above conditions, although several problems were found with the application of the Contingency-Discriminability model.

year: 2001

title: Water Quality Modelling of Te Waihora/Lake Ellesmere

authors: Hamilton, David P.

abstract: As a component of work to contribute towards the management of water quality of Te Waihora/Lake Ellesmere, the University of Waikato was subcontracted by University of Otago to apply a coupled hydrodynamic-water quality model to the lake. The primary funder for this work was Environment Canterbury (ECAN), Whakaora Te Waihora and the Central Government Freshwater Cleanup Fund. The main modelling tool used in the study to simulate the dynamics of Te Waihora/Lake Ellesmere was the one‐dimensional (1‐D) hydrodynamic-water quality model DYRESM-CAEDYM. The model was used to reproduce observed water column data for a mid-lake station over the period 2011 to 2015. Once a satisfactory level of reproduction of these data had been achieved, an assessment was carried out with the model to examine the impact of various management scenarios on lake water quality. These scenarios involved: (i) projected changes to external nutrient loads to the lake that could be associated with future land management in the catchment and (ii) different lake water level management regimes based around opening of the barrier separating the lake from the ocean. The scenarios are intended here to be a catalyst for further hui and consultations that may adapt and refine additional scenarios, some of which may involve testing of multiple management options. The quantitative output from the model provides a component of the input required to inform strategies for lake management, alongside historical and expert knowledge, as well as analysis of measured data.

text: Water Quality Modelling of Te Waihora/Lake Ellesmere As a component of work to contribute towards the management of water quality of Te Waihora/Lake Ellesmere, the University of Waikato was subcontracted by University of Otago to apply a coupled hydrodynamic-water quality model to the lake. The primary funder for this work was Environment Canterbury (ECAN), Whakaora Te Waihora and the Central Government Freshwater Cleanup Fund. The main modelling tool used in the study to simulate the dynamics of Te Waihora/Lake Ellesmere was the one‐dimensional (1‐D) hydrodynamic-water quality model DYRESM-CAEDYM. The model was used to reproduce observed water column data for a mid-lake station over the period 2011 to 2015. Once a satisfactory level of reproduction of these data had been achieved, an assessment was carried out with the model to examine the impact of various management scenarios on lake water quality. These scenarios involved: (i) projected changes to external nutrient loads to the lake that could be associated with future land management in the catchment and (ii) different lake water level management regimes based around opening of the barrier separating the lake from the ocean. The scenarios are intended here to be a catalyst for further hui and consultations that may adapt and refine additional scenarios, some of which may involve testing of multiple management options. The quantitative output from the model provides a component of the input required to inform strategies for lake management, alongside historical and expert knowledge, as well as analysis of measured data.

year: 2017