Academic literature on the topic 'Plio-Pleistocene geomorphology'

AbstractWe describe the glacial geomorphology and initial geochronology of two ice-free valley systems within the Neptune Range of the Pensacola Mountains, Antarctica. These valleys are characterized by landforms associated with formerly more expanded ice sheet(s) that were at least 200 m thicker than at present. The most conspicuous features are areas of supraglacial debris, discrete debris accumulations separated from modern-day ice and curvilinear ridges and mounds. The landsystem bears similarities to debris-rich cold-based glacial landsystems described elsewhere in Antarctica and the Arctic where buried ice is prevalent. Geochronological data demonstrate multiple phases of ice expansion. The oldest, occurring > 3 Ma, overtopped much of the landscape. Subsequent, less expansive advances into the valleys occurred > 2 Ma and > ~1 Ma. An expansion of some local glaciers occurred < 250 ka. This sequence of glacial stages is similar to that described from the northernmost massif of the Pensacola Mountains (Dufek Massif), suggesting that it represents a regional signal of ice-sheet evolution over the Plio-Pleistocene. The geomorphological record and its evolution over millions of years makes the Neptune Range valleys an area worthy of future research and we highlight potential avenues for this.

The Plio-Pleistocene Whalers Bluff Formation (WBF) of the offshore Otway Basin is composed of mixed siliciclastic-carbonate sediments. In seismic cross sections, this formation includes an interval that consists of higher amplitude seismic reflections that display alternating depressional ponds and raised ridges. This interval is shallowly buried and lies between 40 and 150 ms two-way traveltime below the present-day seafloor. In this study, we have used 2D and 3D seismic data sets in combination with the available shallow subsurface well logs to characterize the geomorphology and investigate the origin of these enigmatic features. The ponds are expressed as densely packed, circular to polygonal, and in some cases, hexagonal-shaped features in time-slice maps, and they closely resemble previously documented honeycomb structures. In our study area, the honeycomb-like structures (HS) are comprised of large (200–800 m diameter range) depressed ponds that are separated by narrow (approximately 20 m at the top) reticulate ridges. In total, these HS cover an area of 760 km2. Geospatial analysis shows that the ponds of HS, especially those in the northeast of the study area, are aligned along the northwest–southeast trend lines. There are several possible origins for the HS. The most probable mechanism is that the HS resulted from the bulk contraction of soft sediment, associated with shallow-burial diagenesis processes such as subaqueous dewatering of the fine-grained successions within the WBF. Interestingly, irregular furrows of various lengths on the seafloor correspond to the ridges of the HS, and we hypothesize that these furrows may have formed due to differential compaction of the underlying alternating ponds and ridges. Our results demonstrate the benefits of using seismic reflection data sets in combination with geospatial analysis to investigate the buried paleogeomorphologic features and their impact on the present-day seafloor physiography. Geological feature: Honeycomb-like, soft sediment deformation associated with shallow-burial diagenesis, Otway Basin, southeastern Australia Cross-section appearance: Alternating depressional ponds and raised ridges Map view appearance: Densely packed, oval to polygonal-shaped features Features with a similar appearance: Acquisition footprints, carbonate mounds/dissolution features, polygonal faults, pockmarks, opal-A to opal-CT transition Formation: Whalers Bluff Formation, offshore Otway Basin Age: Pliocene to recent Location: Continental shelf of the Otway Basin, southeastern Australia Data sets: 2D and 3D seismic reflection data, borehole data, from Geological Survey of Victoria, Australia Analysis tools: Interpretation and visualization (Petrel 2019 and DUG Insight, v.4.7, 2020), Geospatial analysis (ESRI‘s ArcMap 10.5)

AbstractBondoró Volcanic Complex (shortly Bondoró) is one of the most complex eruption centre of Bakony-Balaton Highland Volcanic Field, which made up from basaltic pyroclastics sequences, a capping confined lava field (~4 km2) and an additional scoria cone. Here we document and describe the main evolutional phases of the Bondoró on the basis of facies analysis, drill core descriptions and geomorphic studies and provide a general model for this complex monogenetic volcano. Based on the distinguished 13 individual volcanic facies, we infer that the eruption history of Bondoró contained several stages including initial phreatomagmatic eruptions, Strombolian-type scoria cones forming as well as effusive phases. The existing and newly obtained K-Ar radiometric data have confirmed that the entire formation of the Bondoró volcano finished at about 2.3 Ma ago, and the time of its onset cannot be older than 3.8 Ma. Still K-Ar ages on neighbouring formations (e.g. Kab-hegy, Agár-teto) do not exclude a long-lasting eruptive period with multiple eruptions and potential rejuvenation of volcanic activity in the same place indicating stable melt production beneath this location. The prolonged volcanic activity and the complex volcanic facies architecture of Bondoró suggest that this volcano is a polycyclic volcano, composed of at least two monogenetic volcanoes formed more or less in the same place, each erupted through distinct, but short lived eruption episodes. The total estimated eruption volume, the volcanic facies characteristics and geomorphology also suggests that Bondoró is rather a small-volume polycyclic basaltic volcano than a polygenetic one and can be interpreted as a nested monogenetic volcanic complex with multiple eruption episodes. It seems that Bondoró is rather a “rule” than an “exception” in regard of its polycyclic nature not only among the volcanoes of the Bakony-Balaton Highland Volcanic Field but also in the Neogene basaltic volcanoes of the Pannonian Basin.

O objetivo do trabalho é apresentar um novo mapa dos sedimentos cenozóicos da região litorânea do Estado do Paraná. A área foi mapeada na escala 1:50.000. Foram identificadas unidades compostas por sedimentos continentais e costeiros com idades do Mioceno Inferior até o Holoceno. O litoral paranaense é composto por três unidades geomorfológicas principais: Serra do Mar, Primeiro Planalto e Planície costeira. A Serra do Mar é composta por bordas dissecadas de planalto e por núcleos serranos formados por erosão diferencial denominados altas serras. Os setores de Primeiro Planalto paranaense incluídos na área de estudo correspondem a áreas que antigamente pertenciam à bacia do Rio Iguaçu e que, atualmente, como conseqüência de sucessivas capturas, drenam para as bacias das baías de Paranaguá e Guaratuba. A planície costeira se estende ao longo de toda a costa paranaense e tem largura de até 55 km. A planície formou-se durante os dois últimos ciclos transgressivo/regressivos do Quaternário, relacionados aos ciclos glaciais. Na planície costeira foram mapeadas: planícies com cordões litorâneos e planícies paleoestuarinas do Pleistoceno Superior e Holoceno, dunas frontais do Holoceno e planície de maré, fundos rasos, deltas de maré, depressões intercordões e praias atuais. Também foram mapeadas unidades compostas por sedimentos continentais tais como, Fm. Alexandra do Mioceno Inferior, leques e cones aluviais do Plio-Quaternário e tálus, colúvios e sedimentos fluviais do Quaternário. CENOZOIC MAP OF THE STATE OF PARANÁ COASTAL ZONE Abstract This work aims at presenting a new map of the Cenozoic sediments of the coastal zone of the State of Paraná, Brazil. The study area was mapped on 1:50.000 scale. There were mapping units of continental and coastal sediments ranging from Lower Miocene to Holocene. The Paraná coastal zone is made up of three main geomorphologic units: mountains (Serra do Mar), plateau (Primeiro Planalto) and coastal plain. The mountains were formed by two main different processes: the dissection of the plateau border and differential erosion. The mountains formed by differential erosion are the higherst ones and reach more than 1,500 m in height. The plateau sectors includes in the study area drained in the past to the Iguaçu River, that flows westward to Paraná River. After several captures, the rivers of these areas flow eastward to the Guaratuba and Paranaguá estuaries on the State of Paraná coastal zone. The coastal plain occurs along the whole Paraná coast and reaches 55 km in wide. The coastal plain was formed during the last two transgressive regressive cycles in the Quaternary, related to the two late glacial-interglacial cycles. On the coastal are the following features were mapped: Pleistocene and Holocene strand plains and paleoestuarine plains, Holocene foredunes, present tidal flats, shoals, tidal deltas, interdune depressions and beaches. Also continental sediments were mapped: Lower Miocene Alexandra Formation, Pliocene-Quaternary alluvial fans and alluvial cones, Quaternary talus, colluviums and fluvial sediments.

Thesis (Ph. D.)--University of Kentucky, 2004.
Title from document title page (October 12, 2004). Document formatted into pages; contains xi, 216 p. : ill., maps. Includes abstract and vita. Includes bibliographical references (p. 202-212).

The primary goal of this project is to develop a relative chronology of events in the geologic history of the Kentucky River, and to consider the geologic controls on those events. This study utilized published geologic and topographic data, as well as field observations and extensive compilation and comparison of digital data, to examine the fluvial record preserved in the Kentucky River valley in central Kentucky. Numerous fluvial features including abandoned paleovalleys, fluvial terraces and deposits, bedrock benches, and relict spillways between adjacent river valleys were identified during the course of the study. The morphology of the modern valley coincides with bedrock lithology and can be used to describe the distribution and preservation of modern and ancient fluvial deposits and features in the study area. Bedrock lithology is the dominant control on valley morphology and on the distribution and preservation of fluvial deposits and features in the study area. Some stream trends are inherited from the late Paleozoic drainage of the Alleghanian orogeny. More recent inheritance of valley morphology has resulted from the erosion of the river from one lithology down into another lithology with differing erosional susceptibility, thus superposing the meander patterns of the overlying valley style onto the underlying lithology. One major drainage reorganization related to a pre-Illinoisan glacial advance disrupted the northward flow of the Old Kentucky River toward the Teays River system and led to organization of the early Ohio River. This greatly reduced the distance to baselevel, and led to abrupt incision and a change in erosional style for the Kentucky River. The successful projection of valley morphologies on the basis of bedrock stratigraphy, the history of erosion suggested by fission track data and the results of this study, as well as soil thickness and development, all argue against the existence of a midto late-Tertiary, low-relief, regional erosional surface. This study instead hypothesizes that the apparent accordance of ridge-top elevations in the study area is a reflection of a fluvially downwasted late Paleozoic depositional surface.

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The Nilpena Hills are a small group of low hills extending south from the Ediacara Hills. They are detached from the main Flinders Ranges by an expansive of floodplain about twenty kilometres wide. They consist of uplifted and tilted Precambrian sediments of the Wilpena Group, in particular Pound Subgroup rocks that largely consist of quartzites and sandstones. Surfaces have been interpreted as remnant land surfaces that have been rotated due to the tilting of the Nilpena Hills. These surfaces consist of silcrete skinned cobbles and ironstone stained cobbles, as well as more recent calcrete and gypsum layers. Also in the area are lacustrine sediments. The lacustrine sediments consist of a basal limestone layer, the Nilpena Limestone, and subsequent gypsiferous clays. The age of these lacustrine sediments has been interpreted as Pleistocene and their extents has been mapped. X-ray diffraction analysis was performed on the clays to determine their composition and it was found that some of them contain glauconite. The surfaces also give an important indication of climate in the area and how it has varied from a predominantly warm and wet climate during the formation of the silcretes to a much drier climate during the formation of the ironstone stained cobbled surfaces. Faulting has also played an important part in what is a predominantly extensional area. Reactivation of ancient faults in the late Tertiary or early Quaternary has possibly served as a mechanism for the lake formation. The formation of numerous horsts and grabens in the southern region of the area has also promoted the formation of more armoured surfaces. Faulting in northern area allowed for the generation of a laterite which was subsequently overlain by sand dunes.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2000

abstract: The tectonic significance of the physiographic transition from the low-relief Tibetan plateau to the high peaks, rugged topography and deep gorges of the Himalaya is the source of much controversy. Some workers have suggested the transition may be structurally controlled (e.g. Hodges et al., 2001), and indeed, the sharp change in geomorphic character across the transition strongly suggests differential uplift between the Himalayan realm and the southernmost Tibetan Plateau. Most Himalayan researchers credit the South Tibetan fault system (STFS), a family of predominantly east-west trending, low-angle normal faults with a known trace of over 2,000 km along the Himalayan crest (e.g. Burchfiel et al., 1992), with defining the southern margin of the Tibetan Plateau in the Early Miocene. Inasmuch as most mapped strands of the STFS have not been active since the Middle Miocene (e.g., Searle & Godin, 2003), modern-day control of the physiographic transition by this fault system seems unlikely. However, several workers have documented Quaternary slip on east-west striking, N-directed extensional faults, of a similar structural nature but typically at a different tectonostratigraphic level than the principal STFS strand, in several locations across the range (Nakata, 1989; Wu et al., 1998; Hurtado et al., 2001). In order to explore the nature of the physiographic transition and determine its relationship to potential Quaternary faulting, I examined three field sites: the Kali Gandaki valley in central Nepal (~28˚39'54"N; 83˚35'06"E), the Nyalam region of south-central Tibet (28°03'23.3"N, 86°03'54.08"E), and the Ama Drime Range in southernmost Tibet (87º15'-87º50'E; 27º45'-28º30'N). Research in each of these areas yielded evidence of young faulting on structures with normal-sense displacement in various forms: the structural truncation of lithostratigraphic units, distinctive fault scarps, or abrupt changes in bedrock cooling age patterns. These structures are accompanied by geomorphic changes implying structural control, particularly sharp knickpoints in rivers that drain from the Tibetan Plateau, across the range crest, and down through the southern flank of the Himalaya. Collectively, my structural, geomorphic, and thermochronometric studies confirm the existence of extensional structures near the physiographic transition that have been active more recently than 1.5 Ma in central Nepal, and over the last 3.5 Ma in south-central Tibet. The structural history of the Ama Drime Range is complex and new thermochronologic data suggest multiple phases of E-W extension from the Middle Miocene to the Holocene. Mapping in the accessible portions of the range did not yield evidence for young N-S extension, although my observations do not preclude such deformation on structures south of the study area. In contrast, the two other study areas yielded direct evidence that Quaternary faulting may be controlling the position and nature of the physiographic transition across the central Tibetan Plateau-Himalaya orogenic system.
Dissertation/Thesis
Ph.D. Geological Sciences 2012