This study aims to determine the late-Quaternary evolution of an ephemeral, transverse river system developed in southeast Spain, with particular reference to sediment provenance variation. The Rio Alias drains two inter-montane east-west orientated Neogene sedimentary basins; the Sorbas and Almeria basins. Pliocene to present transpressional tectonics has led to inversion of the sedimentary basins and incision of the developing fluvial system. Fluvial incision has led to the preservation of a suite of alluvial terraces recording the late-Quaternary development of the Rio Alias. Fluvial system inauguration began in the Plio-Pleistocene epoch. The primary fluvial system developed as a consequent river later becoming superimposed and transverse to structure. The drainage basin of the Rio Alias has been sub-divided into 4 sub-basins; The Lucainena, Polopos, Argamason and El Saltador sub-basins. Each basin is structurally controlled. The impact of climate, tectonics, river-capture and eustatic sea-level variation on the fluvial system evolution varies both spatially and temporally across the sub-basins of the Rio Alias. Across the region alluvial aggradation is thought to relate to global glacial periods and incision to interglacial periods. The Lucainena sub-basin is largely controlled by climatic variation related to glacial interglacial cycles with slight modification due to local small scale river-capture and regional epeirogenic uplift. The Polopos sub-basin is also largely controlled by climatic variation, however a major river-capture event c.70ka beheaded the Rio Alias of c.70% of its drainage area. Following the loss of drainage the beheaded Rio Alias system lost stream power, this is reflected in the decrease in size of bedform geometry and the reduced incisional capacity of the fluvial system of the post-capture terrace sequence. In the Argamason sub-basin the Rio Alias crosses the Carboneras Fault Zone, a left-lateral strike slip fault. Late-Quaternary tectonic activity has significantly modified the climatically generated signal. Large tortuous meanders developed in response to normal tectonic activity and continued tectonically driven base-level lowering led to abandonment of terraces and local incision. The El Saltador sub-basin is located at the seaward end of the system and the climate generated phases of aggradation and incision have been greatly complicated by eustatic sea-level variation related to glacial/interglacial cycles. The lowering of base-level due to sea-level regression initially led to pronounced incision along steep gradients and to the development of meander loops in the seaward end of the Rio Alias, during what regionally was a climate driven phase of aggradation. Analysis of the alluvial sediment using a combination of field based clast analysis and laboratory analysis (petrology, SEM, magnetic analysis) allows a detailed picture of sediment provenance variation to be established throughout the evolution of the Rio Alias. Provenance analysis provides information on the timing and extent of river-capture related loss of drainage area, the relative timing of local tectonic activity and also provides new information regarding sediment source area variation throughout the development of the fluvial system. Detailed analysis of the terrace sediments and the modern channel indicates that as the fluvial system incises, local input of sediment from the steepening valley sides grows increasingly dominant. The coupling between the hillslopes and the channel thus changes through time. Sediment provenance analysis has increased our understanding of the long-term fluvial evolution of the Rio Alias, identifying not only sediment provenance variation due to river-capture and changing geology but to fluvial system development.

Indiana University-Purdue University Indianapolis (IUPUI) / The outwash deposits of the Eel River paleo meltwater channel in DeKalb and Allen Counties, Indiana predominantly originated from the Erie Lobe of the Laurentide Ice Sheet, but do contain some sediment from the Saginaw Lobe. This determination helps clarify the ice dynamics and Last Glacial Maximum sediment depostional history in northeastern Indiana, which is complicated because of the interactions between the Erie and Saginaw Lobes. Outwash deposits were analyzed from IGS core SC0802 in the Eel River paleo meltwater channel, which intersects the previously identified Huntertown Formation. The core includes 29.2 m of deposits underlain by the hard glacial till of the Trafalgar formation. Mean grain size, sediment skewness, lithology, magnetic susceptibility, and quantitative X-ray diffraction were used to evaluate the provenance of the outwash deposits. Representative samples of Erie Lobe and Saginaw Lobe deposits were analyzed to develop end member provenance signatures. A weight of evidence approach was developed and revealed that deposits from 8.0-13.8 m are of mixed origin from the Erie and Saginaw Lobes, whereas the 0-8.0 and 13.8-29.2 m deposits are Erie Lobe in origin. Cluster analysis and discriminant function analysis supported the findings of this approach. These findings suggests that the Eel River paleo meltwater channel was formed as an outwash channel, and that the adjacent Huntertown Formation does not appear to have been directly deposited by the Saginaw Lobe. The sediments of Saginaw origin from ~8-14 m in the Eel River paleo meltwater channel were likely transported from an upgradient source. The sediments from this zone have a larger mean grain size indicating deposition occurred during higher meltwater discharge, such as the release of meltwater from the drainage of proglacial or subglacial lake(s) associated with the disintegration of the Saginaw Lobe, thus resulting in the mixing of Saginaw Lobe deposits with Erie Lobe deposits. However, the majority of the sediment in the Eel River paleo channel near SC0802 is Erie Lobe in origin. Based on the provenance and depositional sequence at SC0802, the Saginaw Lobe disintegrated prior to the Erie Lobe retreat from the Wabash moraine around 16-17 cal ka.

Los sedimentos de edad Cenozoico en el sur de Peru, son respuestas de una compleja interaccion de geodinamica activa y sedimentacion, de los cuales es conspicuo de la tectonica de los Andes Centrales. Mediante la combinacion de analisis multi-metodos en minerales pesados detriticos, es posible restringir la historia de levantamiento y exhumacion de los bordes de cuencas sedimentarias en el sur de Peru. Los resultados revelan que los sedimentos cenozoicos en el sur de Peru son deltas de grano grueso depositados desde hace 30 Ma, y son consecuencia de levantamientos simultaneos de la Cordillera de la Costa y la Cordillera Occidental.

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京都大学 / 新制・課程博士 / 博士(理学) / 甲第24175号 / 理博第4866号 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 成瀬 元, 准教授 河上 哲生, 教授 田上 高広 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

To explore whether the dispersion of sediments in the North Atlantic can be related to modern and past Atlantic Meridional Overturning Circulation (AMOC) flow speed, particle size distributions (weight%, Sortable Silt mean grain size) and grain-size separated (0–4, 4–10, 10–20, 20–30, 30–40 and 40–63 μm) Sm-Nd isotopes and trace element concentrations are measured on 12 cores along the flow-path of Western Boundary Undercurrent and in the central North Atlantic since the Last glacial Maximum (LGM). North Atlantic is a useful place to explore how size-specific sediment provenance is related to sedimentary inputs and deep-current advection because mantle-derived materials in Iceland is a unique sedimentary source compared to crustal-derived terranes in Europe, Greenland and North America. The four main processes transporting sediments from continents to the North Atlantic (bottom currents, turbidity currents, ice-rafting events, airborne inputs) can be well distinguished through the size-specific physical and geochemical records. When primarily advected by the bottom currents, Holocene sediments show that the finer-sized fractions (0–4, 4–10, 10–20 μm) were transported further, and the coarser size fraction (40–63 μm) matched local inputs. In the deep coretops (> 2700 m) proximal to southern Greenland, fine-slit size fraction (10–20 μm) instead of clay size fraction (0–4 μm) observed more Icelandic-material contribution. In the past, the 20–30, 30–40 and 40–63 μm particles in the shallower Iceland-proximal core (1249 m) reflect Icelandic composition variation due to the abrupt volcanic eruption around 13–9 ka; while in the deeper Iceland-proximal core (2303 m) they were sensitive to the changing bottom flow speed. Downstream in cores proximal to southern Greenland (> 2272 m) and eastern North America (3555 m), composition of the 20–63 μm sediments could be used as an indicator for the retreating of the Greenland and Laurentide Ice Sheets which affect the sediment accessibility of the covered geological terranes; while the 0–4, 4–10 and 10–20 μm particles were more sensitive towards the changing direction (northern-sourced or southern-sourced) and velocity of the bottom current. In the open North Atlantic, the composition of the 0–10 μm particles were less variable between the cold and warm climate intervals compared to the 10–63 μm particles, and the 30–40 and 40–63 μm size fractions were sensitive towards both ice-rafting events and bottom flow direction. During LGM, shallower and vigorous northern-sourced water (NSW) was observed overlaying the deeper southern-sourced water (SSW), with the boundary between 2133 to 2303 m in southern Iceland, and ~ 2272 m in southern Greenland. Reduced NSW occurred during Heinrich Stadial 1, until AMOC above ~ 3500 m recovered to vigorous modern-like version no later than ~ 13.5 ka. Sluggish overflow was observed in North Atlantic between 12.2–11.7 ka above ~ 3500 m. Reduction of Iceland-Scotland Overflow Water occurred around 9.7 ka, and started recovering to its modern vigorous no later than ~ 8.6 ka. These relative past AMOC strength variations (vigorous/sluggish) are firstly converted to actual bottom-current speed (in cm/s) using laminar advection model in this work: vertical settling velocity of particle having the most Icelandic contribution is calculated by Stokes’ Law, and the lateral deep-sea current speed is calculated when the vertical settling depth and the lateral advection distance of the particle traveled before settling are constrained. Primary modelling errors originating from temperature/salinity variations in past deep seawater, winnowing process in fine particles, basaltic-signature dilution by crustal input, and lateral advection pathways of Icelandic-material are further discussed, indicating relatively low modelling error (< ~ 10–20 %). The modelling results agree well with modern deep-sea current speed measurements and backtrack-trajectory eddy resolving model (Ocean model for the Earth Simulator, OFES18), indicating reasonable quantifications of past AMOC flow speeds.

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