Compound specific isotope analysis of lake sediments is a powerful tool in deciphering evidence of changing climatic and paleoenvironmental conditions through time. Isotopic analysis of Lake El’gygytgyn pilot sediment cores, PG1351 and LZ1029, have contributed increased insight into paleoenvironmental interpretations regarding conditions of permanent ice cover and water column anoxia at the lake over the past 250 kyr. Bulk sediment δ15N was measured as a proxy for denitrification and a possible indicator for water column anoxia intensity. However, it appears that insufficient quantities of water column nitrate to fuel denitrification make its correlation with anoxia intensity ineffective. In pilot core LZ1029, compound-specific δ13C of alkanes, fatty acids, and alcohols were analyzed to determine the changing sources of organic matter as well as the source of a strong negative isotopic shift in the bulk sediment δ13C (-26‰ to -33‰) over the past 50 kyr. Results indicate that the majority of alkanes, fatty acids, and alcohols are long chain compounds consistent with a terrestrial plant origin, with increased aquatic contribution during the local last glacial maximum (LLGM). Among the compound classes examined, only the mid chain fatty acids display a strong LLGM depletion (δ13C = -43‰). Short chain fatty acids exhibit an LLGM depletion (δ13C = -35‰) similar to bulk sediment δ13C, while the δ13C trend of long chain alkanes, fatty acids, and alcohols differ from the bulk sediment δ13C trend, suggesting an autochthonous source of bulk isotope depletion. Evidence of methane cycling exists only in the presence and isotopic value of diplopterol (LLGM δ13C = -93.4‰), a biomarker for aerobic oxidation of methane. Two compounds indicative of archaeal lipids were present at considerable concentrations during the LLGM (394 and 668 µg/g TOC), but without the extreme negative δ13C associated with methanogenesis and methanotrophy. These results suggest insufficient generation of methane in the lake to have derived from such a large anaerobic archaeal methanogen community suggesting that archaea are not acting entirely as methanogens. Furthermore, it appears unlikely that a significant anoxic layer existed in the water column of Lake El’gygytgyn during the past ~50kyr. The results of this work will be applied to ongoing investigations on the newest cores from Lake El’gygytgyn, which represent the past 3.5 Myr.

The objective of this study was to use soil chemical properties, particularly carbon isotopes to describe the agricultural landscape in the Blue Creek region on the Rio Bravo Escarpment in northwestern Belize. The primary question associated with this study focused on the comparative agricultural potential of the soils between the upland karst environment and the lowland coastal plains using the distribution and frequency of ancient Maya maize production. Soil physical features, such as clay concentrations throughout profiles in conjunction with soil chemical properties were used to aid in determining the level of ancient maize production. Isotopic evidence suggests that anciently, lowland soils were used for maize production more so than upland soils. In addition, profiles at Crocodile Lake indicate the potential for transport of soil δ13C signatures as a result of mass movement events.

The ancient inhabitants of the Maya Lowlands enjoyed a long and fruitful period of growth which climaxed at around AD 800. At that time, millions of people successfully subsisted in a challenging environment that today only supports a population a fraction of that size. These facts, and the subsequent "Maya Collapse", are the impetus of many recent studies that utilize environmental data, in addition to conventional archaeology, to investigate this Maya mystery. Pedological studies and stable carbon isotope analysis of soil organic matter, combined with Geographic Information Systems (GIS) are three tools that can be used to answer crucial questions as to how the Maya managed their soil resources. GIS maps that indicated areas of best agricultural potential based on slope and soil type were used as a guide to opportunistically sample soils in an area south of Piedras Negras Guatemala – an area that was densely vegetated and unexplored. Soils that represented the different soil resources of the area were sampled with a bucket auger at 15 cm intervals. The samples were then tested in a laboratory for physical and chemical characteristics and δ-13C values were determined for soil organic matter. Soil taxonomical descriptions indicated that overall the soil resources of the area were very good as almost all the soils were classified as Mollisols - the most fertile of all the soil orders. The suite of great groups found was Haprendolls, Argiudolls, Argiaquolls and Udorthents. The characteristics which distinguish these great groups were used to further investigate relative agricultural productivity from an ancient soil resources point of view. Haprendolls were better drained and probably made for good agricultural soils given soil depth and rainfall were adequate. The Argiudolls and especially the Argiaquolls were probably less favored because of very high clay contents that made them more difficult to work with and poor drainage. Stable carbon isotope analyses revealed strong evidence for maize agriculture in some environments of the study area. δ-13C values as high as -16.6‰ (76% C4—Carbon) were observed in areas of significant soil accumulation in well drained and moderately drained soils. Minimal evidence of maize agriculture was found in more marginal environments such as those with little soil accumulation or poorly drained areas. Also, the pattern of the graph of δ-13C values versus depth indicated that ancient agriculture occurred continuously in some areas, but in other areas as distinguishable events. Finally, when the strength of the C4 signal was represented graphically and overlaid with a modified GIS agricultural potential map, a visual representation of the extent and degree of ancient agriculture was achieved. Our findings suggest that upland agriculture was favored by the ancient Maya of Piedras Negras and that the region between Piedras Negras and Yaxchilan was an agriculturally important breadbasket. The methods and results of this study provide foundational information for the investigation of ancient Maya agriculture. In future studies, it may be possible to more systematically map ancient agricultural fields and estimate the carrying capacity of a region based on its soil resources.

The objective of this study was to use pedological evidence in conjunction with Geographic Information Systems, and soil physical and chemical analyses as means to better understand the agricultural landscape surrounding the ancient Maya city of Uci. Specifically, the query of this thesis is to determine whether there is an association between settlement density and soil resources, and what relationship if any there is between the ancient sacbe of Uci and its surrounding agricultural potential. Stable carbon isotope analysis of the humin fraction of the soil organic matter was conducted on several profiles from karst depressions known as rejolladas near the site center, and from a select number of sufficiently deep profiles along and surrounding the ancient sacbe, and from beneath ancient structures. A strong C isotopic signature of ancient C4 crops was found in a limited number of profiles while a majority of the profiles showed no evidence, or little to inconclusive evidence due to a mixture of C3 and C4 plants in the natural landscape. A majority of the soils surrounding Uci are shallow to extremely shallow and many profiles sampled and studied did not allow for C isotopic analysis. Isotopic evidence along with other soil chemical and physical characteristics suggests that settlement density was linked to soil resources, specifically in the case of the rejolladas proximity to the Uci site center. However, it does not appear that the construction and location of the sacbe was linked to its surrounding soil resources or agricultural potential even though ancient maize crops may have been cultivated sporadically close to the sacbe and nearby structures. The soil resources of Uci are not conducive to the production of large maize crops and the ancient Maya of this area likely utilized maize along with alternative crops, arboriculture, wild game and trade to sustain its population.

In 2001, 3269 unidentified individuals were found in a mass grave on the Northern part of Vilnius, Lithuania. Artifactual context indicates that these individuals were likely soldiers that were a part of Napoleon’s Grand Army. Stable oxygen isotope analysis was performed on bone apatite from 9 femoral bone samples to determine whether or not these individuals were Lithuanian locals and to test ratio variation. If individuals were foreigners, then geographical origins were approximated utilizing percentages of C4 plants from Holder (2013) and δ18O values that were extracted from bone apatite. The carbonate oxygen isotope compositions (δ18Ocarbonate) of bone apatite from the femoral samples (-4.4‰ to -6.2‰) indicate that these individuals were from central and western Europe (-4.0‰ to -6.9‰). It is significant that none of the individuals have values consistent with the area around Lithuania (-10.0‰ to -11.9‰), because it means that they all were non-local. It is also indicative that the Lithuanians were not burying their citizens in the grave and therefore strongly support that these individuals were Napoleonic soldiers. Additionally, although C4 percentages in the diet ranged from 17.8% to 31.7%, which overlaps with eastern European consumption patterns (approximately 15% to 25% of C4 plants) (Reitsema et al., 2010), the slight shift towards a higher C4 percentage is more representative of a central and western European diet. These results are significant because they provide stable isotopic evidence that these individuals were Napoleon’s soldiers whom participated in the Russian campaign of 1812.

Mid-Ediacaran incised valleys in the Johnnie Formation of eastern California (the Johnnie valleys) and the Wonoka Formation of South Australia (the Wonoka canyons) are of interest for their unusually large scale and broad time concordance with the largest negative carbon-isotope anomaly in Earth history (the Shuram excursion) and the emergence of multicellular life (the Ediacara fauna). The Johnnie valleys and Wonoka canyons have been widely accepted as originating in a submarine setting at a continental margin. My new data suggest an alternative scenario: that both features were cut subaerially concomitant with sea-level lowering in excess of 200 m, and were subsequently drowned and filled by marine sediments. Critical evidence includes 1) the presence in the basal fill of both valley systems of polymictic conglomerate/breccia with a quartz sand matrix that is locally associated with stratified quartz sandstone, suggesting both local and far-traveled fill components; 2) multiple upward-fining, polymictic conglomerate-based cycles in the basal Wonoka canyon fill; 3) beds and blocks of giant ooid packstone-grainstone indicative of shallow marine sedimentation during the early stages of Johnnie valley filling; 4) the observed transition in the direction of paleoflow in the Wonoka from stratified boulder conglomerate to sandstone and siltstone event beds; and 5) regional restoration of the northern Flinders Ranges indicating that several deep canyons in the Wonoka are > 20 km inboard of the paleoshelf edge. Modern submarine canyons rarely incise that far into continental shelves. My new carbon isotopic data demonstrate negative carbon-13 (δ13C) values in the basal Johnnie valley fill, indicating that like the Wonoka canyons, the Johnnie valleys are bracketed by the Shuram excursion. Additionally, in South Australia, regional allochthonous salt breakout is observed at the same stratigraphic level as the canyon-cutting unconformity, with no evidence for triggering by regional crustal shortening or deep marine non-deposition. Clasts from diapiric breccia and the basal Wonoka canyon fill share sedimentologic, petrographic, and geochemical characteristics indicating the presence of diapiric contributions to the canyon fill, and that allochthonous salt and the canyons interacted dynamically at the Earth’s surface during the Ediacaran. Each of these observations is more consistent with the expectations of a subaerial rather than submarine setting. I hypothesize that the Johnnie valleys and Wonoka canyons were cut by a combination of fluvial incision and subaerial mass wasting, before being drowned. Sea-level lowering is thought to have been triggered by the ~580 Ma Gaskiers glaciation. My interpretation is based on high-resolution physical stratigraphic mapping supported by sub-meter scale 3-D drone imagery, geochemical analysis (δ13C, δ18O, δ26Mg, Mg/Ca), structural restoration, as well as sedimentologic and petrographic analysis. The overall interpretation has several implications for connections between mid-Ediacaran phenomena globally. Given that the Johnnie valleys and Wonoka canyons are stratigraphically bracketed by negative δ13C values putatively correlated with the Shuram excursion, my data suggest that the Shuram excursion may encompass rather than postdate the Gaskiers glaciation in eastern California and South Australia, and that the onset of the excursion may be diachronous at a global scale. My interpretation presents the first outcrop evidence for subaerial erosion and non-deposition as a mechanism capable of triggering appreciable salt breakout. The suggested occurrence of regional isolation and rapid environmental change closely precedes the emergence of the Ediacara fauna, and presents new context for the organisms and the sediments in which they are recorded.

Late Mississippian, Mauch Chunk Group strata constitute a westward-thinning clastic wedge of strata up to 1000m thick that developed in the Central Appalachian Basin over a ~ 7 million year time interval. Included within the Mauch Chunk Group are multiple incised-valley fills and a distinctive prodeltaic succession of laminated sandstones and mudstones. Calculated estimates of drainage basin areas for incised-valley fills in the Mauch Chunk Group range from > 1,000,000 km2 for the Stony Gap Sandstone to < 100,000 km2 for the Princeton Formation. Drainage area estimates are consistent with detrital zircon geochronology and petrographic data and suggest that the Stony Gap and Ravencliff incised-valley fills were derived from distal, northern and northwestern cratonic sources that dispersed sediment into NE-SW-oriented, longitudinal incised-valley drainages and that the Princeton Formation was derived from proximal tectonic highland sources along the eastern margin of the Appalachian Basin which dispersed sediment into a transverse incised-valley. The Pride Shale overlies the Princeton incised valley fill and records a hierarchy of tidal periodicities is preserved in the Pride Shale. Microlaminated, semi-diurnal sandstone-siltstone/shale couplets record the dominant ebb tide of the day. Up to 17 semi-diurnal couplets are stacked into neap-spring (fortnightly) tidal cycles. Neap-spring cycles are arranged in thickening and thinning that record seasonal cycles driven by the annual monsoon. Total organic carbon (TOC) values are a proxy for annual climatic cycles. TOC contents are higher within intermonsoonal and lower within monsoonal components of annual cycles reflecting, respectively, lesser and greater dilution by terrestrial flux. / Master of Science

The waters of the Indian Ocean southeast of Africa are a crucial junction for surface and deep ocean processes that serve as vital controls on Earth’s climate system. At the surface, the Agulhas Current, its retroflection, and Agulhas Leakage transfer water from the Indian and South Atlantic. The addition of this heat and salt to the Atlantic Basin helps drive the Meridional Overturning Circulation and the formation of deep water in the North Atlantic Ocean. On the timescales of centuries, the Meridional Overturning Circulation ultimately returns this water back to the Indian Ocean in the form of North Atlantic Deep Water. Proxy reconstructions show that the vigor of ocean overturning is immensely important to the global climate system, driving changes in atmospheric CO₂ concentrations and temperature and precipitation patterns across the planet. I use x-ray fluorescence core scanning, sediment provenance techniques, and core images from International Ocean Discovery Program Site U1474, located in the Natal Valley of the southwest Indian Ocean, to investigate past changes in the Agulhas Current and North Atlantic Deep Water. 40K/40Ar provenance ages measured on the clay fraction of sediment from Site U1474 indicate that, despite its great distance from the core site, the Zambezi is the most important factor influencing the deposition of terrigenous sediment in the Natal Valley. We present these results in a quantitative way, reinforcing the conclusions of previous studies. However, a comparison to newly available proxy records influenced by current speed and hydroclimate suggests that the strength of the Agulhas does not have a major influence on terrigenous sediment sources, at least at the headwaters of the Agulhas Current. Instead, I suggest that low-latitude hydrologic processes driven by zonal and meridional temperature gradients in conjunction with sea level are responsible for sediment source variability. In core photos, I found evidence for deep water variability in the Natal Valley in the form of millimeter-to-centimeter scale layers of olive-green sediment. To an overwhelming extent, these layers are formed during glacial periods, especially at their termination. I complement observations at Site U1474 with published proxy data for oxygen concentrations and measurements of total organic carbon percent in the Natal Valley and by extending our search for these green layers to core sites around the world. With these data, it is possible to confidently connect these layers to organic carbon concentrations in the sediment, reduction-oxidation processes in sediments following burial, and the local concentration of dissolved oxygen in the deep water. There are comparable fluctuations in the abundances of green layers in core sites in the path of North Atlantic Deep Water during glacial cycles, where more frequent and more intense green layer formation is driven by higher bottom water oxygen concentrations. Peaks in the abundance of green layers approximately 250 ka and 900 thousand years ago coincide with global scale excursions toward isotopically light benthic carbon isotopes. Connecting the green layers to the release of isotopically light organic carbon from sediments leads me to propose that long-observed fluctuations in the carbon cycle may be attributable to deep ocean oxygenation.

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