The colloquially named leopard rock of the Holder and Laborcita formations (Late Pennsylvanian-Early Permian) is an algal/foraminiferal boundstone that occurs within a cyclic, interfingered, carbonate siliciclastic system in the Sacramento Mountains of southeastern New Mexico) and often accompanies phylloid algal mounds. This project is the first to fully characterize and evaluate the evidence that leopard rock is microbial in origin and assess the potential influence of methane seeps and deltaic organics on its genesis. Characterization of the algal-foraminiferal boundstone revealed a highly variable expression in outcrop based on geolocated photo imagery, hand samples, optical microscopy, and scanning electron microscopy (SEM) data. Leopard rock is interpreted as microbial in origin based upon all features observed in aggregate, particularly upward-oriented concentric gradational laminae and striking clusters of segmented curvilinear cylinders (~1000 nm long). Leopard rock is best described as thrombolytic. A comprehensive categorization into thrombolite types was conducted and field and analytical data were used in creating a geospatial data base. The data was evaluated spatially in ArcMap for co-occurrence, trends, and possible associations within, and between, categorizations and formations. Distribution and associations of dome (1-3 m), small coniform (< 1 m), and planar outcrop structures and thrombolite types reflect a hierarchy of complexity and prevalence that would be expected from a microbial system. An extensive multi-scale feature comparison of potential modern analogues from Australia, the Bahamas, and Canada, in conjunction with contiguous paleo-analogues, support the interpretation of a highly adaptable complex microbial ecosystem. Results were also consistent within the global chemical, biologic, and physical context at the time of deposition. Evidence for methane seep contribution support the plausibility of supplemental microbial energy sources based on modern examples and limited paleo-analogues. Stratigraphic position and a paucity of data do not support a significant role for deltaic bathymetry or organic influx in leopard rock genesis. The results of this study provide robust evidence that leopard rock is a multi-faceted complex microbial thrombolite that displays a continuum of expression not represented by one all-encompassing term and illustrates the value of multi-parameter analyses augmented across time and space using analogues and geospatial software.

This research employs a modern analogue approach to examine relationships between pollen, vegetation change, and land use in the tropical environments of Island Southeast Asia over the past ~5000 years. Interpretation of fossil pollen data relies upon uniformitarian principles. Few modern pollen- vegetation studies from the region exist, and those that do have focused on climatic or ecological aims. Main contributions of this study are: the collection and analysis of modern botanical data and pollen assemblages from various human-modified and ‘natural’ vegetation types; and the comparison of this modern dataset with fossil pollen sequences in order to test hypotheses relating to signatures of past land use. Some fossil assemblages showed statistical similarity with those from modern ‘cultured’ landscapes, whilst others aligned more closely with those from natural vegetation. Cores from the northern Kelabit Highlands of Sarawak, Malaysian Borneo, contain assemblages from 1700 cal BP onwards that are similar to those produced by modern arboriculture; a core from the southern Highlands contains fossil assemblages as old as 2000 cal BP that align with those from modern wet rice paddies. These ages coincide with the earliest archaeological dates from nearby sites. Earlier vegetation changes appear to relate to edaphic development and climatic fluctuations. In northern Palawan, western Philippines, the first fossil pollen sequence from the island records post-5000 cal BP marine regression, hydrological fluctuations that are likely related to ENSO cyclicities, and persistence of open landscapes with minor evidence of closed forest after 2750 cal BP. This contrasts with existing proxy data that imply increasingly closed forest through the Holocene. In a region where direct archaeobotanical evidence is sparse, and little modern pollen- vegetation work has been done, this research contributes to clarifying modes and timings of changes in subsistence-related disturbance, as well as bolstering recent interpretations from other palaeoclimatic proxies for ENSO intensification from ~4000 cal BP. These results, and those from similar future studies, can provide baseline data for long-term monitoring and conservation initiatives.

Fossil midge remains from a sediment core from Lake Stowell, Saltspring Island (48°46’54”N, 123°26’38”W) were used to produce quantitative estimates of mean July air temperature over the last 14,000 years. Chironomid and Chaoborus remains were identified, and multiple models of past temperatures based on transfer functions of northern North American calibration datasets were evaluated. The selected model was used to create the first quantitative paleotemperature estimates for the Gulf Islands region. Inferred paleotemperatures at Lake Stowell varied between 12.1 °C and 18.6 °C over the last 14,000 calendar years. Several major climate phases were identified based on changes in paleotemperature. The base of the record is characterised by a cool lateglacial interval with a minimum inferred July temperature of 12.1 °C. Inferred temperatures generally increased by ~4 °C between ~14,200 and 10,300 cal yr BP but this warming was interrupted by cooling, coincident with the Younger Dryas Chronozone, when inferred temperatures drop ~2 °C from the temperatures immediately preceding this interval. A warm early Holocene extends from ~10,300 to 8100 cal yr BP with temperatures regularly exceeding 16 °C. Following the early Holocene, inferred temperatures decreased to approximately 14.9 °C in the mid-Holocene. After a brief warm peak in the late Holocene, inferred temperatures cooled towards the present. Inferred changes in paleotemperature from Lake Stowell are consistent with other paleoenvironmental studies conducted in southern British Columbia and throughout much of the Northern Hemisphere. Temperature changes at Lake Stowell are muted in comparison to continental sites, which may be due to the influence of marine conditions. This research provides context for other studies in the region, and contributes to our understanding of environmental change since the last glacial maximum. / Graduate / 2017-08-17 / 0426 / 0793 / 0353 / jillian.lemmen@gmail.com

O objetivo do presente estudo foi investigar a resposta da assembleia de foraminíferos planctônicos frente às variações paleoceanográficas superficiais na porção oeste do Atlântico Sul, o qual desempenha um papel fundamental na Célula de Revolvimento Meridional do Atlântico (AMOC, Meridional Overturning Circulation). Para esta finalidade, foi analisado um registro sedimentar marinho contínuo desde o Último Máximo Glacial até o presente, com base na assembleia de foraminíferos planctônicos, isótopos de oxigênio e na razão Mg/Ca. Adicionalmente, foram avaliadas as variações na ocorrência e na geoquímica dos dois morfotipos de G. ruber (branca), principal espécie utilizada em estudos paleoceanográficos de regiões tropicais e subtropicais. Os resultados mostraram que as diferenças geoquímicas e de abundância relativa dos morfotipos de G. ruber branca evidenciam dois grupos de espécimes ecologicamente distintos, confirmando que o morfotipo sensu stricto calcifica em menores profundidades com relação ao morfotipo sensu lato e que reconstituições paleoceanográficas baseadas no uso não-seletivo dos morfotipos poderiam ser tendenciosas. A Análise Fatorial realizada nos dados de abundância relativa dos foraminíferos planctônicos identificou 4 fatores principais: o Fator 1, representado pelas espécies G. tenella, G. calida, e G. rubescens e relacionado com a temperatura subsuperficial; o Fator 2, representado pelas espécies N. incompta, N. dutertrei e G. truncatulinoides, relacionado com a profundidade da termoclina; o Fator 3, representado pela espécie G. bulloides, associado com o processo de ressurgência e o Fator 4, representado pelas espécies G. ruber e G. glutinata, associado com a intensidade da Corrente do Brasil. As variações mais expressivas de paleotemperatura e paleosalinidade da superfície do mar e da fauna de foraminíferos planctônicos estão relacionadas com os eventos climáticos abruptos do Hemisfério Norte ocorridos durante a deglaciação, tendo sido moduladas pelas variações de arranjo e intensidade da AMOC. Durante os eventos frios Heinrich 1 e Younger Dryas, relacionados a um enfraquecimento da AMOC, foi observado um aumento das paleotemperatura e paleosalinidade e da intensidade da Corrente do Brasil (Fator 4). Contrariamente, durante o evento quente Bolling-Allerod, a paleotemperatura e a paleosalinidade diminuíram expressivamente, como resposta à retomada da AMOC, e houve aumento da produtividade e presença de uma termoclina mais rasa (Fatores 2 e 3). Sugere-se ainda, que entre 26 e 15 ka houve um deslocamento para norte da Confluência Brasil-Malvinas, possivelmente alcançando a latitude da área de estudo (&#8764;23&#176;S), inferido pela presença da espécie G. inflata. Durante o Holoceno, também foi registrada variação significativa na intensidade da Corrente do Brasil, indicada pelos valores máximos do Fator 4 em torno de 7 ka. O reaparecimento das espécies do plexo G. menardii se deu em 8 ka, assim como o aumento das espécies de foraminíferos planctônicos subsuperficiais, indicado pelo Fator 1. Essas mudanças no Holoceno foram atribuídas à entrada efetiva das águas quentes e salinas do Oceano Índico via vazamento das Agulhas, as quais foram essenciais para o restabelecimento da AMOC moderna. / The objective of the present study was to investigate the response of the planktonic foraminiferaassemblage to the superficial paleoceanographic variations in the western South Atlantic, which plays a key role in the AMOC. For this purpose, a continuous marine sedimentary record was analyzed from the Late Glacial Maximum to the present, based on the planktonic foraminifera assemblage, oxygen isotopes and the Mg/Ca ratio. In addition, variations in the occurrence and geochemistry of the two morphotypes of G. ruber (white) were evaluated. This is the main species used in paleoceanographic studies of tropical and subtropical regions. The results showed that the geochemical and relative abundance differences between the G. ruber morphotypes show two ecologically distinct groups of specimens, confirming that the morphotype sensu stricto calcifies at lower depths with respect to the morphotype and sensu lato, and paleoceanographic and paleoceanographic reconstructions using non-selective mixture of morphotypescould potentially be biased. The Factorial Analysis identified four factors: Factor 1, represented by G. tenella, G. calida, and G. rubescens, is related to the subsurface temperature; Factor 2, represented by N. incompta, N. dutertrei and G. truncatulinoides is related to the depth of the thermocline; Factor 3, represented by G. bulloides, is related toupwelling; and Factor 4, represented by G. ruber and G. glutinata, is related to the intensity of the Brazil Current. The results showed that the most significant variations of paleotemperature and paleosalinity and the planktonic foraminifera assemblage are related to the abrupt climatic events of the Northern Hemisphere occurred during deglaciation and were modulated by variations in AMOC arrangement and intensity. During the cold events Heinrich 1 and Younger Dryas, related to a weakening of the AMOC, an increase of paleotemperature and paleosalinity and intensity of the Brazil Current (Factor 4) in the western portion of the South Atlantic was observed. Conversely, during the hot event Bolli-Allerod, paleotemperature and paleosalinity decreased expressively, as a response to AMOC resumption, with increased productivity and presence of a shallower thermocline (Factors 2 and 3). It is also suggested that between 26 and 15 ka there was a displacement to the north of the Brazil-Malvinas Confluence, possibly reaching the latitude of the study area (&#8764;23&#176;S), inferred by the presence of the G. inflata. Along the Holocene, there was also a significant variation in the intensity of the Brazil Current, indicated by the maximum values of Factor 4 around 7ka. The reappearance of G. menardii plexus occurred in 8ka, as well as the increase of the species of subsurface planktonic foraminifera, indicated by Factor 1. These changes in the Holocene were attributed to the effective entrance of the hot and saline waters from the Indian Ocean via the Agulhas Leakage, which were essential for the reestablishment of the modern AMOC.

O objetivo do presente estudo foi investigar a resposta da assembleia de foraminíferos planctônicos frente às variações paleoceanográficas superficiais na porção oeste do Atlântico Sul, o qual desempenha um papel fundamental na Célula de Revolvimento Meridional do Atlântico (AMOC, Meridional Overturning Circulation). Para esta finalidade, foi analisado um registro sedimentar marinho contínuo desde o Último Máximo Glacial até o presente, com base na assembleia de foraminíferos planctônicos, isótopos de oxigênio e na razão Mg/Ca. Adicionalmente, foram avaliadas as variações na ocorrência e na geoquímica dos dois morfotipos de G. ruber (branca), principal espécie utilizada em estudos paleoceanográficos de regiões tropicais e subtropicais. Os resultados mostraram que as diferenças geoquímicas e de abundância relativa dos morfotipos de G. ruber branca evidenciam dois grupos de espécimes ecologicamente distintos, confirmando que o morfotipo sensu stricto calcifica em menores profundidades com relação ao morfotipo sensu lato e que reconstituições paleoceanográficas baseadas no uso não-seletivo dos morfotipos poderiam ser tendenciosas. A Análise Fatorial realizada nos dados de abundância relativa dos foraminíferos planctônicos identificou 4 fatores principais: o Fator 1, representado pelas espécies G. tenella, G. calida, e G. rubescens e relacionado com a temperatura subsuperficial; o Fator 2, representado pelas espécies N. incompta, N. dutertrei e G. truncatulinoides, relacionado com a profundidade da termoclina; o Fator 3, representado pela espécie G. bulloides, associado com o processo de ressurgência e o Fator 4, representado pelas espécies G. ruber e G. glutinata, associado com a intensidade da Corrente do Brasil. As variações mais expressivas de paleotemperatura e paleosalinidade da superfície do mar e da fauna de foraminíferos planctônicos estão relacionadas com os eventos climáticos abruptos do Hemisfério Norte ocorridos durante a deglaciação, tendo sido moduladas pelas variações de arranjo e intensidade da AMOC. Durante os eventos frios Heinrich 1 e Younger Dryas, relacionados a um enfraquecimento da AMOC, foi observado um aumento das paleotemperatura e paleosalinidade e da intensidade da Corrente do Brasil (Fator 4). Contrariamente, durante o evento quente Bolling-Allerod, a paleotemperatura e a paleosalinidade diminuíram expressivamente, como resposta à retomada da AMOC, e houve aumento da produtividade e presença de uma termoclina mais rasa (Fatores 2 e 3). Sugere-se ainda, que entre 26 e 15 ka houve um deslocamento para norte da Confluência Brasil-Malvinas, possivelmente alcançando a latitude da área de estudo (&#8764;23&#176;S), inferido pela presença da espécie G. inflata. Durante o Holoceno, também foi registrada variação significativa na intensidade da Corrente do Brasil, indicada pelos valores máximos do Fator 4 em torno de 7 ka. O reaparecimento das espécies do plexo G. menardii se deu em 8 ka, assim como o aumento das espécies de foraminíferos planctônicos subsuperficiais, indicado pelo Fator 1. Essas mudanças no Holoceno foram atribuídas à entrada efetiva das águas quentes e salinas do Oceano Índico via vazamento das Agulhas, as quais foram essenciais para o restabelecimento da AMOC moderna. / The objective of the present study was to investigate the response of the planktonic foraminiferaassemblage to the superficial paleoceanographic variations in the western South Atlantic, which plays a key role in the AMOC. For this purpose, a continuous marine sedimentary record was analyzed from the Late Glacial Maximum to the present, based on the planktonic foraminifera assemblage, oxygen isotopes and the Mg/Ca ratio. In addition, variations in the occurrence and geochemistry of the two morphotypes of G. ruber (white) were evaluated. This is the main species used in paleoceanographic studies of tropical and subtropical regions. The results showed that the geochemical and relative abundance differences between the G. ruber morphotypes show two ecologically distinct groups of specimens, confirming that the morphotype sensu stricto calcifies at lower depths with respect to the morphotype and sensu lato, and paleoceanographic and paleoceanographic reconstructions using non-selective mixture of morphotypescould potentially be biased. The Factorial Analysis identified four factors: Factor 1, represented by G. tenella, G. calida, and G. rubescens, is related to the subsurface temperature; Factor 2, represented by N. incompta, N. dutertrei and G. truncatulinoides is related to the depth of the thermocline; Factor 3, represented by G. bulloides, is related toupwelling; and Factor 4, represented by G. ruber and G. glutinata, is related to the intensity of the Brazil Current. The results showed that the most significant variations of paleotemperature and paleosalinity and the planktonic foraminifera assemblage are related to the abrupt climatic events of the Northern Hemisphere occurred during deglaciation and were modulated by variations in AMOC arrangement and intensity. During the cold events Heinrich 1 and Younger Dryas, related to a weakening of the AMOC, an increase of paleotemperature and paleosalinity and intensity of the Brazil Current (Factor 4) in the western portion of the South Atlantic was observed. Conversely, during the hot event Bolli-Allerod, paleotemperature and paleosalinity decreased expressively, as a response to AMOC resumption, with increased productivity and presence of a shallower thermocline (Factors 2 and 3). It is also suggested that between 26 and 15 ka there was a displacement to the north of the Brazil-Malvinas Confluence, possibly reaching the latitude of the study area (&#8764;23&#176;S), inferred by the presence of the G. inflata. Along the Holocene, there was also a significant variation in the intensity of the Brazil Current, indicated by the maximum values of Factor 4 around 7ka. The reappearance of G. menardii plexus occurred in 8ka, as well as the increase of the species of subsurface planktonic foraminifera, indicated by Factor 1. These changes in the Holocene were attributed to the effective entrance of the hot and saline waters from the Indian Ocean via the Agulhas Leakage, which were essential for the reestablishment of the modern AMOC.