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  • Abstract: The Mesozoic Era experienced several instances of abrupt environmental change that are associated with instabilities in the climate, reorganizations of the global carbon cycle, and elevated extinction rates. Often during these perturbations, oxygen-deficient conditions developed in the oceans resulting in the widespread deposition of organic-rich sediments - these events are referred to as Oceanic Anoxic Events or OAEs. Such events have been linked to massive injections of greenhouse gases into the ocean- atmosphere system by transient episodes of voluminous volcanism and the destabilization of methane clathrates within marine environments. Nevertheless, uncertainty surrounds the specific environmental drivers and feedbacks that occurred during the OAEs that caused perturbations in the carbon cycle; this is particularly true of the Early Jurassic Toarcian OAE (ca. 183.1 Ma). Here, we present biostratigraphically constrained carbon isotope data from western North America (Alberta and British Columbia, Canada) to better assess the global extent of the carbon cycle perturbations. We identify the large negative carbon isotope excursion associated with the OAE along with high-frequency oscillations and steps within the onset of this excursion. We propose that these high-frequency carbon isotope excursions reflect changes to the global carbon cycle and also that they are related to the production and release of greenhouse gases from terrestrial environments on astronomical timescales. Furthermore, increased terrestrial methanogenesis should be considered an important climatic feedback during Ocean Anoxic Events and other similar events in Earth history after the proliferation of land plants. Category: geoscientificInformation Source: Supplement to: Them II, Theodore R; Gill, Benjamin C; Gröcke, Darren R; Tulsky, E T; Martindale, Rowan C; Poulton, T P; Smith, P L (2017): High-resolution carbon isotope records of the Toarcian Oceanic Anoxic Event (Early Jurassic) from North America and implications for the global drivers of the Toarcian carbon cycle. Earth and Planetary Science Letters, 459, 118-126, https://doi.org/10.1016/j.epsl.2016.11.021 Supplemental Information: Not Availble Coverage: Not Available
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  • Abstract: Atoll islands are subject to a variety of processes that influence their geomorphological development. Analysis of historical shoreline changes using remotely sensed images has become an efficient approach to both quantify past changes and estimate future island response. However, the detection of long-term changes in beach width is challenging mainly for two reasons: first, data availability is limited for many remote Pacific islands. Second, beach environments are highly dynamic and strongly influenced by seasonal or episodic shoreline oscillations. Consequently, remote-sensing studies on beach morphodynamics of atoll islands deal with dynamic features covered by a low sampling frequency. Here we present a study of beach dynamics for nine islands on Takú Atoll, Papua New Guinea, over a seven-decade period. A considerable chronological gap between aerial photographs and satellite images was addressed by applying a new method that reweighted positions of the beach limit by identifying “outlier” shoreline positions. On top of natural beach variability observed along the reweighted beach sections, we found that one third of the analyzed islands show a statistically significant decrease in reweighted beach width since 1943. The total loss of beach area for all islands corresponds to 44% of the initial beach area. Variable shoreline trajectories suggest that changes in beach width on Takú Atoll are dependent on local control (that is, human activity and longshore sediment transport). Our results show that remote imagery with a low sampling frequency may be sufficient to characterize prominent morphological changes in planform beach configuration of reef islands. Category: geoscientificInformation Source: Supplement to: Mann, Thomas; Westphal, Hildegard (2014): Assessing long-term changes in the beach width of reef islands based on temporally fragmented remote sensing data. Remote Sensing, 6(8), 6961-6987, https://doi.org/10.3390/rs6086961 Supplemental Information: Not Availble Coverage: Not Available
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  • Abstract: Knowledge of past natural flood variability and controlling climate factors is of high value since it can be useful to refine projections of the future flood behavior under climate warming. In this context, we present a seasonally resolved 2000 year long flood frequency and intensity reconstruction from the southern Alpine slope (North Italy) using annually laminated (varved) lake sediments. Floods occurred predominantly during summer and autumn, whereas winter and spring events were rare. The all-season flood frequency and, particularly, the occurrence of summer events increased during solar minima, suggesting solar-induced circulation changes resembling negative conditions of the North Atlantic Oscillation as controlling atmospheric mechanism. Furthermore, the most extreme autumn events occurred during a period of warm Mediterranean sea surface temperature. Interpreting these results in regard to present climate change, our data set proposes for a warming scenario, a decrease in summer floods, but an increase in the intensity of autumn floods at the South-Alpine slope. Category: geoscientificInformation Source: Supplement to: Wirth, Stefanie B; Gilli, Adrian; Simonneau, Anaëlle; Ariztegui, Daniel; Vannière, Boris; Glur, Lukas; Chapron, Emmanuel; Magny, Michel; Anselmetti, Flavio S (2013): A 2000 year long seasonal record of floods in the southern European Alps. Geophysical Research Letters, 40(15), 4025-4029, https://doi.org/10.1002/grl.50741 Supplemental Information: Not Availble Coverage: EVENT LABEL: (S3) * LATITUDE: 45.876700 * LONGITUDE: 10.750600 * ELEVATION: 655.0 m * LOCATION: Central Alps * METHOD|DEVICE: Piston corer
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  • Abstract: A geochemical study of sediments from Ocean Drilling Program Site 983 was conducted to examine low-frequency variations in carbonate content as expressed by blue-band reflectance (450-500 nm) over the last 1.2 Ma. Sedimentary percent organic carbon, percent carbonate, and excess barium (Ba[ex]) were used as the primary tools to evaluate the factors responsible for these long-term changes. We observe positive correlation between the mass-accumulation rate of various biogenic components and the mass-accumulation rate of Ba(ex), especially in sediments younger than ~600 ka. Deeper in the section (~600-1200 ka), the correlation between Ba(ex) and the other biogenic tracers is weak. The lack of correlation between Ba(ex) and biogenic carbonate likely results either from a higher supply of terrigenous material at that time (which confounds Ba[ex] estimation), or remobilization of Ba resulting from low pore-water sulfate ion concentrations, or both. Nonbiogenic sediments at Site 983, represented by Th, K2O, and the molar Ti/Al ratio, exhibit cyclic variations that represent mixing between continental and oceanic (i.e., basaltic) terrigenous sources. The timing of these cycles matches that of the major glacial-interglacial cycles, which suggests that they result from the supply of continental material as ice-rafted debris during glacial periods and fine-grained basaltic material by bottom currents during interglacial periods. Given these observations, the most likely causes for the low-frequency carbonate variations observed in the Site 983 sediments are shifts in surface productivity and, to a lesser extent, dilution by the input of terrigenous material. Category: geoscientificInformation Source: Supplement to: Hyun, Sangmin; Ortiz, Joseph D; Raymo, Maureen E; Taira, Asahiko (1999): Low-frequency oscillations in Site 983 sediments: relationships between carbonate and productivity proxies. In: Raymo, ME; Jansen, E; Blum, P; Herbert, TD (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 162, 1-11, https://doi.org/10.2973/odp.proc.sr.162.019.1999 Supplemental Information: Not Availble Coverage: EVENT LABEL: * LATITUDE: 60.403500 * LONGITUDE: -23.640667 * DATE/TIME START: 1995-07-21T00:00:00 * DATE/TIME END: 1995-07-24T00:00:00 * ELEVATION: -1983.7 m * Penetration: 766.5 m * Recovery: 798 m * LOCATION: North Atlantic Ocean * CAMPAIGN: Leg162 * BASIS: Joides Resolution * METHOD|DEVICE: Composite Core
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  • Abstract: Late Neogene planktonic foraminifera have been examined at Site 310 in the Central North Pacific and their stratigraphic ranges and frequencies are presented here. Blow's (1969) zonation developed for tropical regions has been applied where applicable. Where tropical index taxa are rare or absent in this temperate region, Globorotalia crassaformis, and the evolutionary bioseries G. conoidea - G. conomiozea and G. puncticulata - G. inflata have been found useful for zonal subdivisions. A correlation between stratigraphic ranges and frequency distributions of these species at Site 310 in the Central North Pacific, and Site 284 in the Southwest Pacific indicates that these species are relatively consistent biostratigraphic markers in temperate regions of both the North and South Pacific Oceans. An informal zonation for temperate latitudes of the Southwest Pacific has been established by Kennett (1973) and a similar zonal subdivision can be made at Site 310. Paleoclimatic/paleoceanographic interpretations based on coiling ratios, percent abundance, and phenotypic variations of Neogloboquadrina pachyderma indicate four major cold events during early, middle, and late Pliocene, and early Pleistocene. Faunal correlations of these events with similar events elsewhere in the Northeast and Southwest Pacific which have been paleomagnetically dated indicate the following approximate ages for these cold events: 4.7 Ma, 3.0 Ma, 2.6-1.8 Ma, and 1.2 Ma. Faunal assemblages have been divided into three groups representing cool, intermediate, and warmer water assemblages. Cool water assemblages are dominated by ~60% N. pachyderma; intermediate temperature faunas are dominated by species of Globigerina and Globigerinita and contain between 20% and 30% N. pachyderma. Warmer water assemblages are dominated by species of Globorotalia and contain <10% N. pachyderma. Frequency oscillations within these groups, in addition to paleotemperature parameters evident in N. pachyderma, afford refined paleoclimatic/paleoceanographic interpretations. Category: geoscientificInformation Source: Supplement to: Keller, Gerta (1978): Late Neogene biostratigraphy and paleoceanography of DSDP Site 310 Central North Pacific and correlation with the Southwest Pacific. Marine Micropaleontology, 3(2), 97-119, https://doi.org/10.1016/0377-8398(78)90001-4 Supplemental Information: Not Availble Coverage: EVENT LABEL: * LATITUDE: 36.868500 * LONGITUDE: 176.901500 * DATE/TIME: 1973-09-19T00:00:00 * ELEVATION: -3516.0 m * Penetration: 193.5 m * Recovery: 145.2 m * LOCATION: North Pacific/CONT RISE * CAMPAIGN: Leg32 * BASIS: Glomar Challenger * METHOD/DEVICE: Drilling/drill rig
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  • frequency... oscillations
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  • Abstract: Shallow- to deep-water environments are represented by the sediments and rocks recovered from the Walvis Ridge- Angola Basin transect. These calcareous oozes, chalks, limestones, and volcaniclastic sedimentary rocks are used to define and correlate four lithostratigraphic units. The sediments were deposited in cycles which represent recurring tectonic or Oceanographic events and may be related to climatic fluctuations and orbital perturbations. Turbidites are the most common and easily identified sedimentary cycle. They are Late Cretaceous to Paleocene in age and are repeated in intervals ranging from thousands to tens of thousands of years. They are also found interbedded between basalt layers. Turbidites are easily distinguished from the other cycles present by their sedimentary structures, mineral composition, alteration products, and physical properties (GRAPE) data. Large-scale turbidites, debris, or slump breccias are found at or just above the Cretaceous/Tertiary boundary and indicate an event of considerable energy possibly related to intense tectonic activity. Diagenetic cycles, interpreted as small-scale dissolution cycles or sequences produced by biogenic activity, occur in early Paleocene chalks. The recurrence intervals average -20,000 y. but have a wide range of values. Variations in CaCO3 content, color, gradational boundaries, and trace fossil content characterize these sediments. These cycles reflect bottom-water conditions. Ooze-chalk cycles occur in upper Oligocene to upper Paleocene sediments and represent conditions that once existed at the sediment/water interface where they obtained their diagenetic potential. These oscillations are repeated over tens of thousands of years and may have no modern analogs. Color variations in sediments at the Cretaceous/Tertiary boundary indicate local fluctuations in oxygen content within the sediments or the water column. This situation lasted for several hundred thousand years and is not repeated elsewhere in the sequence. Large dissolution cycles are recorded in the sediments at Site 527 that are of middle Miocene and early Oligocene to middle Eocene age. During this time the seafloor at this site appears to have been located at or subsided to a depth occupied by a fluctuating CCD and lysocline. Category: geoscientificInformation Source: Supplement to: Borella, Peter E (1984): Sedimentology, petrology, and cyclic sedimentation patterns, Walvis Ridge Transect, Leg 74, Deep Sea Drilling Project. In: Moore, TC Jr; Rabinowitz, PD; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 74, 645-662, https://doi.org/10.2973/dsdp.proc.74.118.1984 Supplemental Information: Not Availble Coverage: EVENT LABEL: * LATITUDE: -28.041500 * LONGITUDE: 1.763300 * DATE/TIME: 1980-06-28T00:00:00 * ELEVATION: -4428.0 m * Penetration: 3.845 m * Recovery: 2.434 m * LOCATION: South Atlantic * CAMPAIGN: Leg74 * BASIS: Glomar Challenger * DEVICE: Composite Core EVENT LABEL: * LATITUDE: -28.522050 * LONGITUDE: 2.320100 * DATE/TIME: 1980-07-04T00:00:00 * ELEVATION: -3807.5 m * Penetration: 6.855 m * Recovery: 3.838 m * LOCATION: South Atlantic/RIDGE * CAMPAIGN: Leg74 * BASIS: Glomar Challenger * DEVICE: Composite Core EVENT LABEL: * LATITUDE: -28.930500 * LONGITUDE: 2.768000 * DATE/TIME: 1980-07-18T00:00:00 * ELEVATION: -3043.0 m * Penetration: 4.17 m * Recovery: 3.094 m * LOCATION: South Atlantic/SLOPE * CAMPAIGN: Leg74 * BASIS: Glomar Challenger * DEVICE: Composite Core
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  • oscillations
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  • low-frequency... Oscillation... frequencies,
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  • (1) High frequency of Eryngium and low proportions of Araucaria and Atlantic rain forest.... Oscillating air temperature... Oscillating salinity... (1) High frequency of Myrsine, Arecaceae, Weinmannia, Hedyosmum, Sloanea and Clusia; after the marine regression of the Mid-Holocene, open areas became forested.
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