title: Grand Canyon landslide-dam and paleolake triggered by the Meteor Crater impact at 56 ka

authors: Karlstrom, KE

abstract: This paper hypothesizes that the Meteor Crater impact in Arizona, USA, 56,000 years ago triggered landslides in Grand Canyon that dammed the Colorado River and formed Nankoweap paleolake. This is compatible with shock and earthquake physics for the impact that infer a M5.4 seismic event, attenuated to an effective magnitude of M3.5 at Grand Canyon. Results that support the hypothesis include radiocarbon dating of driftwood and luminescence dating of associated slack-water lake sediments that are preserved in caves up to 60 m above the modern Colorado River. Radiocarbon ages from two locations, including Stanton’s Cave, date the driftwood as 55.25 ± 2.44 ka (n = 4). Sediments associated with the driftwood gave a luminescence age of 56.00 ± 6.39 ka (n = 2). These six Grand Canyon dates, and three published ages for the Meteor Crater impact, show statistically indistinguishable results that support the hypothesis for a geologically instantaneous series of events with a mean age of 55.60 ± 1.30 ka. This work highlights the value of radiocarbon dating near the limits of the technique, integration of multiple dating methods, and seismic and landslide hazards associated with meteorite impacts in regions of extreme topography like Grand Canyon.

text: Grand Canyon landslide-dam and paleolake triggered by the Meteor Crater impact at 56 ka This paper hypothesizes that the Meteor Crater impact in Arizona, USA, 56,000 years ago triggered landslides in Grand Canyon that dammed the Colorado River and formed Nankoweap paleolake. This is compatible with shock and earthquake physics for the impact that infer a M5.4 seismic event, attenuated to an effective magnitude of M3.5 at Grand Canyon. Results that support the hypothesis include radiocarbon dating of driftwood and luminescence dating of associated slack-water lake sediments that are preserved in caves up to 60 m above the modern Colorado River. Radiocarbon ages from two locations, including Stanton’s Cave, date the driftwood as 55.25 ± 2.44 ka (n = 4). Sediments associated with the driftwood gave a luminescence age of 56.00 ± 6.39 ka (n = 2). These six Grand Canyon dates, and three published ages for the Meteor Crater impact, show statistically indistinguishable results that support the hypothesis for a geologically instantaneous series of events with a mean age of 55.60 ± 1.30 ka. This work highlights the value of radiocarbon dating near the limits of the technique, integration of multiple dating methods, and seismic and landslide hazards associated with meteorite impacts in regions of extreme topography like Grand Canyon.

year: 2025

title: The effects of delay to reinforcement and inter-trial interval on fixed-ratio schedule performance

authors: Stuart, Stacey Louisa

abstract: A delay to reinforcement has been found in previous studies to influence the effectiveness of a reinforcer. As the delay duration increases, response rates decrease and post reinforcement pause durations increase. The present study tested whether it was the increase in time between the effective response and delivery of reinforcement, or, the increases in intervals between reinforcers that devalue the reinforcer. This study also compared the ability of two demand equations and MPR to predict response rates when effort required was changed. The effects of varying delay to reinforcement and intertrial interval on behaviour was examined while the time available for responding was kept constant. 
	There were four conditions; 4-s ITI, 4-s delay, 16-s ITI and 16-s delay, and 6 hens responded under each of these conditions in an ascending geometric series of fixed ratio (FR) values. It was shown that hens generally responded at a faster rate in the ITI conditions than the equivalent delay conditions and peak response rates were seen highest in the 16-s ITI condition in accordance with the demand data.  The data was described well by both the demand equations and the MPR equation. While there were inconsistencies among the parameters, there was a moderately strong positive relationships between the parameter values of as and α in the 16-s ITI (r = .51, p = 0.29) and delay (r = .44, p = .44) conditions.

text: The effects of delay to reinforcement and inter-trial interval on fixed-ratio schedule performance A delay to reinforcement has been found in previous studies to influence the effectiveness of a reinforcer. As the delay duration increases, response rates decrease and post reinforcement pause durations increase. The present study tested whether it was the increase in time between the effective response and delivery of reinforcement, or, the increases in intervals between reinforcers that devalue the reinforcer. This study also compared the ability of two demand equations and MPR to predict response rates when effort required was changed. The effects of varying delay to reinforcement and intertrial interval on behaviour was examined while the time available for responding was kept constant. 
	There were four conditions; 4-s ITI, 4-s delay, 16-s ITI and 16-s delay, and 6 hens responded under each of these conditions in an ascending geometric series of fixed ratio (FR) values. It was shown that hens generally responded at a faster rate in the ITI conditions than the equivalent delay conditions and peak response rates were seen highest in the 16-s ITI condition in accordance with the demand data.  The data was described well by both the demand equations and the MPR equation. While there were inconsistencies among the parameters, there was a moderately strong positive relationships between the parameter values of as and α in the 16-s ITI (r = .51, p = 0.29) and delay (r = .44, p = .44) conditions.

year: 2013

title: The biology and general ecology of the Koaro (Galaxias brevipinnis) in some tributary streams of Lake Taupo

authors: Kusabs, Ian Andrew

abstract: The ecology and general biology of Galaxias brevipinnis were studied in three tributary streams of Lake Taupo between May 1988 and April 1989. Adult koaro were found in relatively high densities in the Waipehi and Omori streams but in low densities in the larger Waiotaka stream. The results of population estimation studies suggest that the distribution and abundance of koaro is negatively correlated with that of trout. There was a general decline in the population density of stream-resident koaro in the winter months. Juvenile koaro were found to migrate into the tributaries from August to December, with migrations being at a peak in October and November.

Population length-frequency distributions and otoliths used to age koaro indicated that there were up to 5 age classes. Growth was allometric and was adequately described by the von Bertalanffy equation after the first year of life. Koaro were found to be in best condition in the Spring and lowest in Winter.

Spawning appeared to occur from December through to April peaking in late Summer to early in the Waipehi Stream was Autumn. The mean fecundity of koaro approximately 5500. A sex-ratio of approximately 1:1 (males: females) were found in the koaro populations in the Omori and Waipehi streams, but during spawning there were always more ripe males than gravid females.

There was considerable overlap in the diets of both koaro and juvenile rainbow trout in the Waipehi and Omori streams, with invertebrates being consumed according to their relative abundance in the benthos. Ephemeroptera larvae were numerically the most important food item in the diet of both species. However, by weight, fish (juvenile koaro) were the most important food · item in the diet of koaro and rainbow trout in the Waipehi stream. In the Omori stream in Winter, trout eggs were the most important food item in terms of weight. Terrestrial prey was found to be of relatively minor importance in the diets of koaro and rainbow trout in the Waipehi and Omori streams.

text: The biology and general ecology of the Koaro (Galaxias brevipinnis) in some tributary streams of Lake Taupo The ecology and general biology of Galaxias brevipinnis were studied in three tributary streams of Lake Taupo between May 1988 and April 1989. Adult koaro were found in relatively high densities in the Waipehi and Omori streams but in low densities in the larger Waiotaka stream. The results of population estimation studies suggest that the distribution and abundance of koaro is negatively correlated with that of trout. There was a general decline in the population density of stream-resident koaro in the winter months. Juvenile koaro were found to migrate into the tributaries from August to December, with migrations being at a peak in October and November.

Population length-frequency distributions and otoliths used to age koaro indicated that there were up to 5 age classes. Growth was allometric and was adequately described by the von Bertalanffy equation after the first year of life. Koaro were found to be in best condition in the Spring and lowest in Winter.

Spawning appeared to occur from December through to April peaking in late Summer to early in the Waipehi Stream was Autumn. The mean fecundity of koaro approximately 5500. A sex-ratio of approximately 1:1 (males: females) were found in the koaro populations in the Omori and Waipehi streams, but during spawning there were always more ripe males than gravid females.

There was considerable overlap in the diets of both koaro and juvenile rainbow trout in the Waipehi and Omori streams, with invertebrates being consumed according to their relative abundance in the benthos. Ephemeroptera larvae were numerically the most important food item in the diet of both species. However, by weight, fish (juvenile koaro) were the most important food · item in the diet of koaro and rainbow trout in the Waipehi stream. In the Omori stream in Winter, trout eggs were the most important food item in terms of weight. Terrestrial prey was found to be of relatively minor importance in the diets of koaro and rainbow trout in the Waipehi and Omori streams.

year: 1989