The geology, hydrogeology, and groundwater geochemistry are described for an interface aquifer in Eastern Ontario exhibiting anomalously high proportions of iodine (I) as iodide (I-) and dissolved methane (CH4). The studied area is unique in that it shows a significant marine influence, attributed to the most recent Champlain Sea incursion 10 – 12 ka BP, which has implications for I and CH4 enrichment. I and CH4 in groundwater are found in high proportions in reducing fossil seawaters, which are typically observed in depressions in the bedrock surface that are overlain by thick layers of glaciomarine muds. I is released via microbial decomposition of marine phytoplankton into mud porewaters, where it is then leached to underlying groundwaters. 129I and 14C isotopic signatures of I and C compounds highlight the importance of allochthonous I and C sources in the Champlain Sea basin derived from glacial abrasion of the surrounding terrain and imported via glacial meltwater. CH4 is microbial in origin, with marine phytoplankton from the Champlain Sea incursion and ancient terrestrial organic matter from an Early Wisconsinian interstadial period (60 – 75 ka BP) as the dominant substrates. A thermogenic CH4 component was observed for areas underlain by the Billings shale unit. Both I and CH4 originate at least partially from the same marine phytoplankton source within the muds, demonstrate similar controls on enrichment, and have a Spearman’s rank coefficient of 0.62, indicating that the correlation between I and CH4 in groundwater in the studied area is significant.

Abstract This thesis deals with the Holocene development of palsa mires in continental Europe, especially permafrost dynamics and its consequences on vegetation succession and peat accumulation. Peat deposits of four permafrost mires in boreal and subarctic northeastern European Russia and in northern oroboreal Finland have been studied using plant macrofossil analysis, (AMS) radiocarbon dating, dry bulk density and carbon content measurements. In addition, preliminary results are available from another palsa mire in northeastern European Russia. Modern vegetation has been investigated to support the interpretation of fossil plant assemblages. Earlier literature on vegetation, stratigraphy and dating of permafrost mires in Europe has been reviewed. The vegetation of palsa mires in general is well known. As a rule, palsas are dry ombrotrophic habitats, surrounded by wet flarks of variable trophic levels. There is a lack of information about vegetation in different small-scale habitats within palsa mires, which would have been useful when studying the permafrost-vegetation relationship. Although no functional indicator species of permafrost have been found, permafrost dynamics in peat stratigraphy can often be detected with high degree of probability based on changes in vegetation. Some plant assemblages and vegetation successions are typical on permafrost, while many species rarely grow on or near to permafrost. Relatively sudden changes between dry and wet mire environments and continuously dynamic conditions are good signs of permafrost impact. Also gradual changes towards drier conditions may be caused by permafrost; in these cases the timing of first permafrost aggradation is more difficult to ascertain and can usually be pronounced only in terms of maximum and minimum ages. Changes in peat accumulation rates and even hiatuses in stratigraphy are additional tools to support the interpretation on permafrost history at the studied sites. Dry organic matter and carbon accumulation rates for different developmental stages are calculated for the five studied mires. From earlier studies this information is not available. Accumulation rates in the permafrost environment are very variable: from zero or negative rates in old palsas to as high as 100 gC/m2yr in incipient palsas. On moist plateau palsas, permafrost flarks and in unstable permafrost conditions, accumulation continues at low to moderate rates. Thermokarst processes result in decomposition of former peat deposits with important consequences for the ecosystem carbon balance, especially in plateau palsa mires. Radiocarbon datings are available from 27 permafrost mires in continental Europe; only 5 of these are situated in Russia. Many of the published dates cannot be considered reliable as dating permafrost aggradation. Based on limited material, permafrost started to develop at latest about 3000 BP in mires of northern Russia and 2500 BP in Fennoscandia. Older permafrost formation is suggested for a few sites, but the evidence is insufficient to confirm this interpretation. The oldest preserved palsas are ca. 2500–2000 14C years old. Most of the modern palsas are less than 600 14C years old. Permafrost aggradation follows the major climate development in the Holocene, with formation being most active during the coldest stages. Global warming is expected to greatly affect the Arctic in the near future, which would imply significant changes in ecosystem functioning and carbon balance of permafrost mires. This study contributes to the understanding of the possible impacts of climate change on these ecosystems using paleoecological techniques.

Rockshelters are capable of preserving excellent environmental records within their sediments. But the matter of interpreting an environmental record from rockshelter sediments presents a significant hurdle in the form of dating. An “age-depth model” is typically used to estimate the age of environmental information extending through the deposit. An age-depth model calculates the changes in time between direct ages (like a radiocarbon age) and can provide an estimated age for any depth. While radiocarbon dating can provide an age for organic remains, optically stimulated luminescence (OSL) can provide a direct age on quartz sand deposition and is particularly effective when applied to deposits formed by the wind. This study compares radiocarbon and OSL age-depth models from Last Canyon Cave (LCC) in the Pryor Mountains of south-central Montana. While radiocarbon ages are quite frequently used to construct age-depth models, it is possible they fail to provide accurate ages for the environmental material they aim to date. I re-evaluated the stratigraphy at LCC and then collected OSL samples as well as samples for grain-size analysis from three different sedimentary exposures. Radiocarbon ages had already been produced for one of the exposures (Kornfeld et al. 2012). The OSL samples were most reliable when analyzed on a single-grain level. After creating age-depth models and collecting the grain-size data, I applied ages to all of the grain-size samples according to each of the three age-depth models. Ultimately, the single-grain OSL proved to be fundamentally different than the radiocarbon age-depth model, thereby challenging the current paleoenvironmental reconstruction of the site (Minckley et al. 2015). I conclude that the radiocarbon and single-grain OSL age-depth models were not sufficiently similar, and therefore both dating methods should always be used together when investigating deposits in rockshelters in order to understand how they relate to one another and to the site formation. The use of granulometry also proved to be an important part of reconstruction site formation history. Ultimately, both single-grain OSL and granulometry were determined to be essential parts of studying environmental records in sedimentary deposits in rockshelters.

Archaeologists describe the Uinta Fremont (A.D. 0 – 1300) as a mixed foraging-farming society that underwent a dramatic social change from A.D. 700 – 1000. Researchers observe through different architectural styles and subsistence activity a change from large, aggregated settlements to more dispersed and defensively oriented villages and hamlets. The Ideal Free Distribution (IFD) model provides an explanatory framework through which to interpret these changes. IFD predicts the order in which people or animals will occupy habitats based on a habitat’s relative suitability and suggests hypothetical behaviors that people or animals might engage in to improve or maintain the relative suitability of a habitat. One prediction of IFD is that behaviors indicating resource competition will become more frequent when population density increases. I test whether this hypothesis explains changes in storage features by considering storage behavior as a manifestation of resource competition, and I investigate whether storage feature frequency correlates with periods of Fremont population increases and paleoenvironmental degradation. These tests explain aspects of Fremont culture change and suggest future research possibilities. Storage feature frequency, representing resource competition, remains low from A.D. 0 – 700, suggesting that the habitats could absorb growing Fremont populations. After A.D. 700, however, resource competition rose and remained high, a condition that likely spurred the defensive architecture and dispersed settlements that became increasingly common after A.D. 1000. The successes and limitations of applying IFD to the archaeological record point the way toward future uses of the model to investigate settlement spacing and reaffirm the use of radiocarbon data in archaeological science.

I conduct the first comparative analysis of long term human population stability in North America. Questions regarding population stability among animals and plants are fundamental to population ecology, yet no anthropological research has addressed human population stability. This is an important knowledge gap, because a species’ population stability can have implications for its risk of extinction and for the stability of the ecological community in which it lives. I use archaeological and paleoclimatological data to compare long term population stability with subsistence strategy and climate stability over 6,000 years. I conduct my analysis on a large scale to better understand general trends between population stability, subsistence strategy, and climate stability. I found that agricultural sequences fluctuate less than hunter-gatherer sequences in general, but they also experience rare, extreme population swings not seen among hunter-gatherers. I suggest that agriculturalists are more vulnerable to population collapses because of their increased population densities. I found that population stability shows a weak relationship with climate stability. Climate stability may have an indirect effect on long-term population stability.

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No / We present a series of iterative methods to examine the problems associated with summed probability functions (SPFs) based on archaeological radiocarbon data. As a case study we use an SPF generated from a substantial radiocarbon data-set from the Irish Later Bronze and Iron Ages. We use simple numerical methods to show that real patterns can be deciphered from SPFs that can be used to trace and evaluate patterns of change. However, our results suggest that SPFs should not be used as a simple index of past human activity. / This research forms part of the project ‘Mobility, Climate and Culture: Re-modelling the Irish Iron Age’, funded by the British Academy through their BARDA scheme. Preliminary data collection was conducted as part of a pilot project funded by the Heritage Council of Ireland.