scholarly journals Tectonic Setting of the Kenya Rift in the Nakuru Area, Based on Geophysical Prospecting

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 80
Author(s):  
Paolo Conti ◽  
Marco Pistis ◽  
Stefano Bernardinetti ◽  
Alessio Barbagli ◽  
Andrea Zirulia ◽  
...  
Keyword(s):  
Cross Sections ◽  
Fractured Rock ◽  
Tectonic Setting ◽  
Middle Pleistocene ◽  
Hydrogeological Model ◽  
Kenya Rift ◽  
Lithostratigraphic Units ◽  
Single Station ◽  
Geophysical Investigations ◽  
Extension Direction

In this paper, we present results of tectonic and geophysical investigations in the Kenya Rift valley, in the Nakuru area. We compiled a detailed geological map of the area based on published earlier works, well data and satellite imagery. The map was then integrated with original fieldwork and cross sections were constructed. In key areas, we then performed geophysical survey using Electrical Resistivity Tomography (ERT), Hybrid Source Audio MagnetoTelluric (HSAMT), and single station passive seismic measurements (HVSR). In the study area, a volcano-sedimentary succession of the Neogene-Quaternary age characterized by basalts, trachytes, pyroclastic rocks, and tephra with intercalated lacustrine and fluvial deposits crops out. Faulting linked with rift development is evident and occurs throughout the area crosscutting all rock units. We show a rotation of the extension in this portion of the Kenya rift with the NE–SW extension direction of a Neogene-Middle Pleistocene age, followed by the E–W extension direction of an Upper Pleistocene-Present age. Geophysical investigations allowed to outline main lithostratigraphic units and tectonic features at depth and were also useful to infer main cataclasites and fractured rock bodies, the primary paths for water flow in rocks. These investigations are integrated in a larger EU H2020 Programme aimed to produce a geological and hydrogeological model of the area to develop a sustainable water management system.

scholarly journals Unraveling the shallow geology of the western Wadden Sea using high resolution seismics

2012 ◽  
Vol 91 (3) ◽  
pp. 341-355 ◽  
Author(s):  
B.F. Paap ◽  
C.W. Dubelaar ◽  
J.L. Gunnink ◽  
A.P. Oost
Keyword(s):  
High Resolution ◽  
Cross Sections ◽  
Seismic Data ◽  
Wadden Sea ◽  
Seismic Facies ◽  
Middle Pleistocene ◽  
Seismic Profiles ◽  
Hydrogeological Model ◽  
Geological Interpretation ◽  
Shallow Subsurface

AbstractModelling of the shallow subsurface of the Dutch Wadden Sea is merely based on lithological information extracted from a limited amount of core samples. In order to improve the subsurface model and to provide a better basis for engineering purposes, seismic data have recently been acquired, processed and interpreted. This study focuses on the interpretation of seismic data in a pilot area in the southwestern part of the Dutch Wadden Sea near the Afsluitdijk. In order to acquire a maximum detail of subsurface information in a time-efficient way, multiple types of seismic systems were deployed simultaneously in a ‘one-sweep-survey’, providing information over depth ranges up to 60 m subsurface depth. Data from three seismic systems are presented; a chirp system, a boomer and sparker source in combination with hydrophone streamers. Geological interpretation of the seismic data was made by identifying seismic facies units and subsequently correlating them to geological cross-sections, running parallel to the Afsluitdijk. Geological cross-sections were derived from the existing geological and hydrogeological model and from relatively densely spaced borehole information. Six key reflectors were identified on the seismic data along the Dutch Afsluitdijk that make up four seismic facies units. Results of seismic profiles show good recognition of internal structures in especially Holocene sediments. A clay plug and a shallowing of a channel at the eastern side of the pilot area were interpreted as channel infills resulting from the rather sudden dominance by newer tidal channels to the west, probably coinciding with the opening of the Marsdiep channel. The channel wall deposits observed were interpreted as a turning of the drainage channel after closure of the IJsselmeer. Strong reflections of deeper levels (>15 m below Dutch vertical datum, i.e. N.A.P.) were interpreted as clay/sand interfaces in the Middle-Pleistocene Urk Formation and were more continuous than previously thought. It is concluded that high resolution seismics add valuable information yielding improved understanding of the sedimentary structure of the shallow subsurface, which in turn can be useful for near future engineering works along the Afsluitdijk.

The geology and significance of the interglacial sediments at little Oakley, Essex

1990 ◽  
Vol 328 (1248) ◽  
pp. 307-339 ◽  
Keyword(s):  
Late Glacial ◽  
Large River ◽  
Sensu Stricto ◽  
Middle Pleistocene ◽  
Terminal Phase ◽  
Northern Margin ◽  
Lithostratigraphic Units ◽  
History Of ◽  
London Clay ◽  
Geomagnetic Polarity

Subdepartment of Quaternary Research, Botany School, University of Cambridge, Downing Cambridge Downing Street, Cambridge CB2 3EA, U.K. At Little Oakley, near Harwich, an interglacial deposit has been identified and mapped over a distance of ca. 1 km by means of boreholes and from temporary sections. The interglacial sediments are chiefly silts and sands, which occupy a large river channel (150-175 m wide) trending W.S.W.-E.N.E. The channel sediments are variously underlain by London Clay, Red Crag and another fluvial deposit, the ‘Oakley Gravel’ (one of 15 newly defined lithostratigraphic units), against which they also abut on their northern margin. The channel occurs at an elevation of between 18 and 24 m o.D. and is thought, on the basis of clastlithology, to have been occupied by the pre-diversion Thames at a point immediately upstream of its confluence with the Medway. The interglacial deposits are rich in fossils, which indicate accumulation during the pre- and early temperate substages of an early Middle Pleistocene interglacial stage. Pollen spectra from the base of one borehole may possibly relate to the terminal phase of the preceding late-glacial period. The balance of the palaeontological evidence suggests correlation of the main sequence with the Cromerian sensu stricto. The essential facts leading to this conclusion are given here, but detailed discussions of the palaeobotany, vertebrates, molluscs and ostracods are given in a series of separate papers. This correlation gains some support from amino acid epimerization data from the shells of certain aquatic molluscs. Palaeomagnetic measurements, indicating normal geomagnetic polarity, are also consistent with this correlation. The relation of the Little Oakley sequence to the regional geology is discussed, and the palaeogeographic history of the Thames—Medway river systems in this area is briefly reviewed.

scholarly journals Application of Radar Imagery to Tectonic, Structural and Geological Studies in Afikpo Basin, Southeastern Benue Trough, Nigeria

2019 ◽  
pp. 1-9
Author(s):  
Minapuye Isaac Odigi ◽  
Prince Suka Momta
Keyword(s):  
Tectonic Setting ◽  
Field Work ◽  
Structural Features ◽  
Drainage Pattern ◽  
Ground Field ◽  
Transform Faults ◽  
Benue Trough ◽  
Lithostratigraphic Units ◽  
Geological Information ◽  
Radar Imagery

Radar imagery was used to identify geological features and the production of geological maps of the Afikpo basin. The essence of this study was to delineate significant geological and geomorphological features that have not been imaged by the traditional ground field mapping. The application of Radar imagery technique will be relevant to the discovery of subsurface structures that will aid the accumulation or concentration of certain economic minerals or natural resources. It will enhance the identification of significant geological information such as lineaments, geologic structures, drainages, etc, that will serve as a guide to the actual ground field work investigation. Results from radar imageries revealed drainage pattern, major geomorphological units, mega lithostratigraphic units, lineaments and structures. The geology of Afikpo basin consist of Cretaceous, Tertiary and Quaternary rocks are recognizable; the highly deformed Cretaceous rocks are characterized by regional lineaments. Some of the rivers are aligned along the regional lineaments. The NW-SE and NE-SW lineaments truncate one another, suggesting different ages for the lineament groups. A few sinistral tensional movements occur in the eastern sector of the basin.  The major folds in the Afikpo basin have NE-SW and NW-SE trends, and occur as anticlines and synclines. The basement structuring and basin framework suggest a tectonic setting in the southeastern Benue Trough resulting from the Early Cretaceous opening of the South Atlantic Ocean and interpolate movement in Africa. From the evidence currently available we may conclude that the post Santonian Afikpo basin falls within the transtenstional basin categories associated with transform faults. The regional tectonics interpreted from the radar imageries are likely hydrocarbon related structural features.

scholarly journals Stratigraphic Investigations into the Late Miocene-Early Pliocene of the Northern Aorangi Range, Wairarapa

2021 ◽  
Author(s):  
◽  
Tamsin Lesley Beatrice Bertaud-Gandar
Keyword(s):  
Cross Sections ◽  
Late Miocene ◽  
High Energy ◽  
Depositional Environments ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Geological History ◽  
Early Pliocene ◽  
Lithostratigraphic Units ◽  
Uplift And Erosion

<p>The late Miocene-early Pliocene geology of the Makara and Ruakokoputuna Valleys in the northern Aorangi Range, south-east Wairarapa, is described in detail. In this area, a succession of Neogene sedimentary units laps onto basement rocks of Cretaceous age, and late Miocene-early Pliocene stratigraphy varies markedly, from bathyal mudstone to high energy coastal environments, over distances of only a few kilometres. Sections were measured at four key locations, which provided reference sites for stratigraphic changes across the study area. Additional detailed field mapping was carried out around Te Ahitaitai Ridge. Depositional environments were interpreted using grain size analysis, macrofossil and foraminiferal assemblages, and palynology. Foraminiferal biostratigraphy was used to constrain the ages of samples. Data obtained by these methods were combined with previous authors’ work to produce a synthesis map, unit correlations, and geological cross-sections of the Makara and Ruakokoputuna Valleys. Late Miocene-early Pliocene geological history is interpreted, and a depositional model is proposed to explain the presence of giant cross-beds in the Clay Creek Limestone.  Despite major differences in lithology, the Clay Creek Limestone and Bells Creek Mudstone are shown to be partially laterally equivalent, while the overlying Makara Greensand is shown to be a diachronous unit which ranges from late Miocene (Kapitean) to early Pliocene (Opoitian) in age. This revised stratigraphy raises questions about the current classification of the Palliser and Onoke Groups, and provides new insights into regional geological history. The late Miocene-early Pliocene stratigraphy records a history of regional subsidence, punctuated by episodes of deformation which caused localised uplift and erosion. Previous seismic imaging studies identified one such episode of accelerated crustal shortening and deformation in the Wairarapa region near the Miocene-Pliocene boundary. The Clay Creek Limestone has proven to be a useful marker horizon for constraining the timing and style of deformation, which is interpreted to have occurred prior to 7.2 Ma. Major differences in stratigraphy between the upthrown and downthrown sides of the Mangaopari Fault indicate that the fault was active during this deformational episode. Lithostratigraphic units from the study area have been correlated with units in other parts of the Wairarapa, and these correlations suggest that late Miocene deformation in the region may have propagated from south to north.</p>

scholarly journals Palynologic and Lithostratigraphic Research of Lacustrine, Marsh and Fluvial Quaternary Deposits in Rašica Dolina and Mišja Dolina, and on Radensko Polje

Hacquetia ◽  
2007 ◽  
Vol 6 (1) ◽  
pp. 91-101
Author(s):  
Metka Culiberg ◽  
Stevo Dozet
Keyword(s):  
Pollen Analysis ◽  
Carbonate Rocks ◽  
Middle Pleistocene ◽  
Quaternary Sediments ◽  
Quaternary Deposits ◽  
Lithostratigraphic Units ◽  
Lacustrine Clay ◽  
Bottom To Top

Palynologic and Lithostratigraphic Research of Lacustrine, Marsh and Fluvial Quaternary Deposits in Rašica Dolina and Mišja Dolina, and on Radensko Polje The article deals with the results of palynological and stratigraphical research of lacustrine, marsh and fluvial Quaternary deposits in the Rašica dolina and Mišja dolina, and on Radensko polje. Correlation with equivalent Quaternary deposits and their palynoflora from the Grosuplje polje area was also performed. In the study area, Mesozoic, predominantly carbonate rocks are transgressively covered by Quaternary deposits which are in general composed of five lithostratigraphic units (from bottom to top): 1. gravel, 2. grey lacustrine clay, 3. reddish brown loam, 4. light grey marly clay and 5. alluvial marsh deposits. On the basis of pollen analysis the Quaternary sediments of the study area are chronostratigraphically classified to the Late or Middle Pleistocene and Holocene.

Loess of the Upper Mississippi Valley Driftless Area

1994 ◽  
Vol 42 (1) ◽  
pp. 30-40 ◽  
Author(s):  
David S. Leigh ◽  
James C. Knox
Keyword(s):  
United States ◽  
Late Quaternary ◽  
Ice Sheets ◽  
Climatic Conditions ◽  
Laurentide Ice Sheet ◽  
Middle Pleistocene ◽  
Mississippi Valley ◽  
Driftless Area ◽  
Lithostratigraphic Units ◽  
Continental Ice Sheets

AbstractLoess of the Driftless Area includes four distinct late Quaternary lithostratigraphic units: the Wyalusing (new), Loveland, Roxana, and Peoria formations. Erosion has removed parts or all of the pre-late Wisconsian loess at many sites. These formations consist largely of loess and retransported loess that typically occurs on uplands, terraces, and valley margins in the region. The oldest widespread formation (probably > 125,000 yr B.P.) is here formally named the Wyalusing Formation. The three younger formations correlate with the Loveland (probably > 125,000 yr B.P.), Roxana (55,000-25,000 yr B.P.), and Peoria (25,000-12,000 yr B.P.) loesses recognized elsewhere in the midcontinental United States. The soil/stratigraphic morphology of the Wyalusing-Loveland and Roxana-Peoria couplets appears to represent two distinct loess sedimentation sequences related to major expansion and contraction of the Laurentide Ice Sheet during oxygen isotope stages 6 and 3-2, respectively. The occurrence-frequency of loess units is inversely related to age, illustrating the erosional nature of the Driftless area landscape. The occurrence of four loess units at some sites in Driftless Area stratigraphic sections corroborates loess stratigraphy along the length of the Mississippi Valley, where typically not more than four or five loess units are found and they represent only the late and middle Pleistocene (<790,000 yr B.P.). Past climatic conditions, which favored erosion of loess, as well as a temporally erratic spatial extent of former continental ice sheets in North America, which provided the dust supply, probably account for the low number of loess units along the Mississippi Valley.

Shale and carbonate geochemistry of the Proterozoic greater McArthur Basin, Australia.

2020 ◽  
Author(s):  
Darwinaji Subarkah ◽  
Morgan Blades ◽  
Alan Collins ◽  
Juraj Farkas ◽  
Bo Yang ◽  
...  
Keyword(s):  
Water Chemistry ◽  
Water Column ◽  
Large Scale ◽  
Tectonic Setting ◽  
Critical Time ◽  
Organic Carbon Content ◽  
Earth System ◽  
Isotopic Tracers ◽  
Lithostratigraphic Units ◽  
Basin System

&lt;p&gt;The greater McArthur Basin is a regionally extensive Palaeo-to-Mesoproterozic, intra-cratonic, super basin system overlying the North Australian craton. Deposition initiated after the Pine Creek Orogeny whereby the basin extends from Western Australia to northwestern Queensland. Lithostratigraphic units are divided into five coherent packages of similar age, stratigraphic position and facies association. Successions of the basin system are dominated by an assemblage of sedimentary siliciclastics, evaporitic carbonates and organic-rich mudstones with minor intersections of volcanic rocks and records nearly a billion years of Earth&amp;#8217;s history from ca. 1.82 Ga to the Tonian. This period has generally been considered a time of stability within the Earth system and is therefore unfortunately titled &amp;#8216;the boring billion&amp;#8217;. However, compilation of new and existing water chemistry proxies shown in this study reflected the contrary. Notably, shales and carbonates from the greater McArthur Basin chronicled a critical time in Earth&amp;#8217;s history; where the oxygenation of the ocean and atmosphere began and multi-cellular eukaryotes started to thrive within the ecosystem, demonstrating that this interval in the geological record is anything but boring.&lt;/p&gt;&lt;p&gt;This study applied a multi-proxy approach based on observations of isotopic tracers and elemental variations from an extensive archive of carbonate-rich units throughout the greater McArthur Basin to reconstruct its palaeoenvironment, determine the tectonic setting and establish regional or global correlations. Elucidating the evolution of the basin is essential for understanding the controls of its petroleum and mineral resources as well as how Earth system processes developed during the Proterozoic. Radiogenic and stable isotopes are used to infer palaeo-depositional constraints such as biological productivity, weathering fluxes and provenance sources. Redox-sensitive elemental concentrations can also be used to reflect the changes in water-column chemistry between oxic, anoxic and euxinic conditions.&lt;/p&gt;&lt;p&gt;Consequently, results from this study illustrate the relationship between the precipitation of metal compounds, production of organic matter and preservation of both systems with large-scale biogeochemical processes. Furthermore, this study also highlights the spatial and temporal variations of water chemistry within the basin. Enrichment in Mo concentrations in the Wollogorang Formation within the Tawallah Group indicated spells of widespread euxinia. Base metal concentrations within the unit showed lithogeochemical, halo-like distribution that is strongly correlated with changes in water column redox conditions. A shift to more radiogenic &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr values up to &amp;#8764;0.722 in the Fraynes Formation of the Limbunya Group reflected an increase in relative contribution of strontium from old continental crust in contrast to hydrothermal input which is consistent with a transient basin restriction from the open ocean. Rare earth and yttrium (REY) plots of the Dook Creek Formation inferred parts of the basin may have been lacustrine at ca. 1.5 Ga. Further up stratigraphy, the Middle Velkerri showed a shift towards more positive &amp;#949;&lt;sub&gt;Nd(t)&lt;/sub&gt; values, representing a change to more juvenile source regions. These mafic provenances are richer in essential nutrients for biological activity such as phosphorus. More juvenile &amp;#949;&lt;sub&gt;Nd(t) &lt;/sub&gt;data within the Velkerri Formation coincide with an increase in P concentrations and total organic carbon content (&gt;8 wt. %).&lt;/p&gt;

Neotectonics and extension direction of the Southern Kenya Rift, Lake Magadi area

2003 ◽  
Vol 364 (1-2) ◽  
pp. 71-83 ◽  
Author(s):  
Nassima Atmaoui ◽  
Dirk Hollnack
Keyword(s):  
Kenya Rift ◽  
Lake Magadi ◽  
Extension Direction ◽  
Rift Lake

Report on Excavations at Jaywick Sands, Essex (1934), with some observations on the Clactonian Industry, and on the Fauna and Geological significance of the Clacton Channel

1937 ◽  
Vol 3 (1-2) ◽  
pp. 217-260 ◽  
Author(s):  
Kenneth P. Oakley ◽  
Mary Leakey
Keyword(s):  
Cross Sections ◽  
River Channel ◽  
Middle Pleistocene ◽  
Cultural Tradition ◽  
The South ◽  
Geological Significance ◽  
South West ◽  
Exact Position ◽  
Asiatic Origin ◽  
Lower Palaeolithic

The foreshore exposures of Pleistocene deposits at Clacton and at Lion Point, two miles to the south-west, mark cross-sections of an ancient river channel which now extends inland in a broad curve between these two localities. The deposits have become famous through the investigations of Mr S. Hazzledine Warren, who has for many years kept a careful watch on the exposures, and who has published a number of important papers on his discoveries (Warren, 1922, 1923, 1924, 1933, 1934).The gravels in the Clacton channel have yielded a contemporary palaeolithic flake-industry which was recognised by the Abbé Breuil as identical in style with an industry represented in the Middle Pleistocene gravels of Mesvin, Belgium (Warren, 1922). Breuil (1929, p. 6) has since proposed the name of Clactonian for this industry in view of the fact that in the Mesvin deposits the implements in question are in a derived condition, and associated with other industries, whereas at Clacton there is no doubt as to their contemporaneity with the containing gravel. Industries of Clacton style have since been recognised in numerous localities, not only in this country, but also on the Continent (Breuil, 1932). They appear to represent a widespread cultural tradition, possibly of Asiatic origin, and very probably ancestral to the later Mousterian industries.The industry of the type station—the Clacton-on-Sea district of Essex—represents neither the earliest nor the latest stage of evolution of the Clactonian culture, and importance attaches to establishing its exact position in the Lower Palaeolithic sequence.

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