Abstract: Recognition of a modern sediment oscillation in Loon Lake, Halifax County, Nova Scotia: implications for paleoclimate and environmental research
Bibliographic record
Abstract
In this study the physical properties of Loon Lake near Halifax were studied with the intent of understanding the processes that influence sedimentation and sediment mobility in small, shallow, organic-dominated lakes. Organic Jakes are o(interest as productivity shifts resulting from climate change events are often preserved within the lake sediments. As well, remediation of contaminated organic lakes is often hampered by a lack of understanding of the physical processes that govern sedimentation and sediment mobility. Loon Lake was chosen for this study on the basis of size, shape, depth and location. Loon Lake is located along the path of a recent hurricane. We hypothesised that hurricanes may be significant in the mobilization of lake bottom and watershed sediments. Sonar profiling was carried out to determine basin stratigraphy, using a King 1570 sonar unit. Lake sediment sampling was accomplished with a Glew gravity sediment corer. Sediment traps and thermistor strings were employed to ascertain the lakes present trophic state. 3-D reconstruction of sediment distribution was accomplished using the Rockworks 99 program. Loss on ignition and thin section analyses were carried out on core sediment. Wind speed and precipitation data were used to model basin and watershed dynamics. Loon Lake is highly productive and exhibited very high organic sedimentation rates and much of the organic sediment is algae. A elastic sediment oscillation was evident near the top of all cores recovered. The sediment oscillation is characterized by an increase in the clay content within the lake sediment core and a decrease in L.0.1. The elastic oscillation is asymmetrically distributed, with thickest accumulations in the north end of the lake. The lack of any ice rafted silt or sand within the oscillation indicates that the sediment was deposited during ice-free conditions. Wind speeds associated with recent hurricanes were sufficient enough to produce turbulent conditions and re-suspend previously deposited organic sediment within the lake basin. Rainfall amounts were sufficient and of short enough duration · that saturated conditions and overland flow likely existed. We conclude that the oscillation is a product of the transfer of surface sediment (made available in part by physical disturbance) into the lake basin and the transfer within the basin of this sediment by turbulent suspension. These results indicate that shallow organic lakes are susceptible to hurricane induced mixing and sediment redistribution. They also illustrate that significant sediment oscillations <;an be produced by very short term, catastrophic events and ao not necessarily need to be a product of a period of climate change.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".