A geological model of the chalk of East Kent
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Abstract:
This report describes the geological modelling of the Chalk in the North Downs of East Kent,
within the catchment of River Great Stour and eastwards to the coast, including the Isle of
Thanet. This work was funded by the Environment Agency to support investigations of the local
hydrogeology and thereby to enhance catchment management.
The whole area is underlain by the Upper Cretaceous Chalk Group, with the Palaeogene
succession of the Thanet Sand Formation, the Lambeth Group and the Thames Group overlying
it in the northern and central eastern parts.
The project included a desk study revision of the Chalk of the North Downs, using the new
Chalk lithostratigraphy. The revisions to the geology are shown on the 1:50 000 scale geological
map which accompanies this report. Together with evidence from boreholes and from seismic
surveys, the new outcrop patterns have been incorporated into a geological model, using both
computer software (EarthVision) and manual methods.
The introduction describes the background to the project. The second chapter describes the
sources for the data used in the model: published and unpublished geological maps, borehole
records (both lithological and geophysical), seismic surveys, biostratigraphic records, digital
topographic information, and the published literature.
Each Chalk formation present in the area is then briefly described in the third chapter, noting its
relationship to the older lithostratigraphic divisions, and to biostratigraphic zones. The local
Chalk succession extends from the base of the Chalk Group to the Newhaven Chalk Formation,
here represented by the Margate Chalk Member. Evidence for the thickness of each formation is
reviewed.
The early Palaeogene formations (the Thanet Sand, Upnor, Harwich and London Clay
formations) are also briefly described (Chapter 4) and the local superficial deposits mentioned,
with references to detailed descriptions (Chapter 5). Apart from minor adjustments to the outcrop
of the basal Palaeogene surface, no revision of these formations was done for this study.Keywords:
Lithostratigraphy
Outcrop
Geologic map
Geological survey
Geologic record
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A 400 kV electricity transmission line is required to cross the Menai Strait to connect the proposed Wylfa Newydd nuclear power station on Ynys Mon (also known as Anglesey) with the mainland. Through an initial feasibility study, the preferred Menai Strait crossing option has been shown to require the construction of a tunnel. This region has a complex geological history, where the oldest strata, consisting of schist and tuff deposits, are interpreted as Precambrian. There are also Carboniferous bedrocks of interbedded limestones, mudstones and sandstones, and Ordovician siltstones and quartzite sandstones. The superficial deposits and landforms are understood to be almost entirely the signature of the last Devensian glaciation, except for occasional deposits and landforms resulting from fluctuations in sea-level. A 3D geological model has been created using published geological records and project-specific surveys, including field surveys, rock exposure mapping, ground investigations and geophysical surveys. This allows the visualization of the anticipated geology of the area, the identification of geological hazards and efficient design and planning for construction. Thematic collection: This article is part of the Ground models in engineering geology and hydrogeology collection available at: https://www.lyellcollection.org/cc/Ground-models-in-engineering-geology-and-hydrogeology Supplementary material : An overview video is available at https://doi.org/10.6084/m9.figshare.c.5045048
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The Ngalia Basin has been the subject of systematic geological and geophysical investigation by the Bureau of Mineral Resources since 1967 and by Magellan Petroleum Australia Ltd. since 1968. The Ngalia Basin is an intracratonic structural depression, containing a small accumulation of late Precambrian and Palaeozoic sediments in the southern part of the Northern Territory. It covers an area of about 6000 sq.mi. and contains shallow marine, glacial and continental rocks of Adelaidean, Cambrian, Ordovician and Carboniferous age. It is asymmetrical in north-south cross-section with the thickest sediments preserved near the faulted northern margin. These sediments can be correlated with those of the prospective Amadeus Basin, but they are yet to be tested for hydrocarbons by exploratory drilling.Within the basin, where outcrops are sparse, seismic and gravity data provide valuable information pertaining to the depositional and tectonic history. The geological and geophysical studies have upgraded the hydrocarbon potential of the area. Structural traps are thought to exist, particularly in the western part of the basin, associated with folded faults developed over slightly dipping thin thrust plates. Further detailed interpretation of the geophysical results is under way directed towards defining drillable prospects.
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Northern Alaska remains one of the most prospective exploration frontiers in onshore North America. In 2006, The Alaska Division of Geological & Geophysical Surveys conducted a field program in the Kavik area of the east-central North Slope, providing new constraints on the evolution of the petroleum system. This region includes two undeveloped gas discoveries (Kemik and Kavik fields) and is one of few areas that permit examination of all three depositional megasequences (Ellesmerian, Beaufortian, and Brookian) in close association. The focus of this project was to: 1) better constrain the timing and nature of regional burial and Tertiary exhumation events affecting the hydrocarbon maturation and migration history, and 2) further define the depositional environments and sequence stratigraphy of selected Brookian and Beaufortian source and reservoir units. Detailed stratigraphic and structural data, in conjunction with some of the first 1:63,360-scale geologic mapping in the area, provide insight on the complex deformation history in the region. The southern, well exposed portion of map area is dominated by detachment folding. Key structures in the Cretaceous and Tertiary strata to the north (including the trapping structure at the Kavik field) are poorly exposed, although newly acquired 2-D seismic and existing well data will allow for a more robust structural analysis. New observations of Beaufortian stratigraphy (associated with the rift-related opening of the Arctic Ocean Basin) indicate a potentially more complex paleogeography than previously assumed. Within the Cretaceous Brookian foreland succession, facies considerations suggest possible structural telescoping emplacing the informally named Juniper Creek sandstone along a detachment within the Jurassic Kingak Shale.
Isopach map
Sequence Stratigraphy
Geologic map
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INTRODUCTION This is Number 9 of a series of correlation charts prepared by the Committee on Stratigraphy of the National Research Council, which will cover the post-Proterozoic sedimentary formations of North America. For general information about the project the reader is referred to the general introduction preceding this paper. The senior author, Lloyd W. Stephenson, is responsible for that part of the chart treating of the Upper Cretaceous series in the Atlantic and Gulf Coastal Plain (exceptions noted below) and the Lower Cretaceous series of the North Atlantic Coastal Plain; with respect to the Upper Cretaceous his presentation is based largely on his personal knowledge of the paleontology and stratigraphy of the area, gained from field and laboratory studies ranging from reconnaissance to detailed; all published information has been considered, and much of it utilized, but it is not practicable to include a complete bibliography. References are given to papers . . .
Outcrop
Coastal plain
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The eight papers in this issue of Petroleum Geoscience form a thematic set that describes the recent advances in understanding of the structural development, stratigraphic evolution and sedimentary history of the North Falkland Basin, and the combined impact that they have had on its petroleum geology with a focus on the Sea Lion Field. The set of papers evolved from integrated geoscience carried out by Rockhopper Exploration plc and their contractors following the discovery of the Sea Lion Field and its subsequent appraisal.
The geology of the Falkland Islands and surrounding basins has been of interest to geoscientists for a considerable time for both academic and commercial reasons. Fieldwork carried out in the early 1920s (Baker 1924) was subsequently updated by a photo-geological survey supported by the British Antarctic Survey (Greenway 1972). However, it was not until 1996 that the British Geological Survey resurveyed the islands and produced the first modern geological map (Aldiss & Edwards 1999). Despite the complex and interesting onshore geology and fascinating geomorphological features, the islands themselves have no documented onshore hydrocarbon potential.
In 1977–78, several thousand kilometres of speculative seismic data were acquired in the shallow waters surrounding the Falkland Islands. These data allowed the identification of several sedimentary basins; a passive margin to the east (the Falkland Plateau or East Falkland Basin), a thrust belt to foreland basin setting to the south (the South Falkland Basin), the Malvinas Basin to the west and, to the north of the islands, an extensive rift basin known as the North Falkland Basin. Several Deep Sea Drilling Project (DSDP) boreholes drilled on the Maurice Ewing Bank proved the presence of a Late Jurassic–Early Cretaceous source rock (Barker et al . 1976), and exploration of the Malvinas Basin by Esso in …
Palaeogeography
Geobiology
Environmental geology
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The paper gives a general discussion of the surface formations and surface geology of the post-Fleming belt lying between the coast and the outcrop of the Fleming in southeast Texas and south Louisiana. Data and discussion are presented under four main heads, Physiography, Stratigraphy, Origin and History, and Structure. Under Physiography it is shown that the present physiography indicates the general features of the geology of the area, that is, the subdivision of the post-Fleming group into four formations, Recent, Beaumont, Lissie, and Willis, and the general structure and interrelations of these formations. Under Stratigraphy the present subdivision is correlated with earlier classifications. The formations are described. The Willis, which is a new formation roughly equivalent to the old Lafayette and Reynosa of this area, is named, subdivided into three members, and described in detail. Its relation to the Goliad formation of south Texas is discussed. Under Origin and History the deposition of these formations is credited to the ancestors of the present major streams of the coast. The peculiar stratigraphic and structural interrelations of the post-Fleming formations are attributed to cycles of deposition separated by tilting movements which affected this part of the coastal plain at intervals. Under Structure the regional structure of the formations, local irregularities, methods of mapping, and the relation of surface to subsurface structure are discussed.
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Upper Cretaceous rocks, primarily Chalk, cover a vast area of England forming the Downs and Wolds as well as the spectacular chalk cliffs from Flamborough Head to south-east Devon. In south-east Devon and the Inner Hebrides of north-west Scotland, white chalk rests on greensands, calcareous sands and commercially important quartz sandstones. Scientific knowledge of these rocks is an essential part of planning construction projects, developing and protecting groundwater resources and utilising the materials such as flint, chalk and sands for industrial processes. Historically, the fossils from the Chalk, such as the echinoid Micraster, have made major contributions to evolutionary studies. Fossils, combined with detailed analyses of the structure and sedimentology of the Chalk and associated rocks, continue to be a focus for developing new ideas in stratigraphy, modelling past climates and investigating biodiversity and mass extinctions. Thirty-seven GCR sites across the British Isles are described and linked to numerous other sites to provide a comprehensive explanation of the geology and the geological significance of each GCR site. Individual sites vary from coastal cliffs, many kilometres long, to individual small chalk pits. Where possible, sites have been extensively re-investigated to provide the most up-to-date reviews.
Historical geology
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Gravity and seismic surveys conducted over a number of years in the South Australian portion of the Murray Basin are discussed in chronological sequence and related to the geology. Little is known of the pre-Tertiary geology of the area from outcrop or drilling but the geophysical work suggests a development of 7,000 feet of pre-Tertiary sediments in the deepest part, north-west of Renmark. The presence of Permian in this section, interpreted from seismic refraction results has been confirmed by the drilling of A.O.G. North Renmark No. 1. Permian deposition may extend as far north-west as Canegrass Station. Gravity anomalies bear a close relationship to thickness of sedimentary section as interpreted from refraction results.
Outcrop
Seismic refraction
Section (typography)
Sequence (biology)
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North sea
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The West Greenland continental margin has been the subject of petroleum exploration by companies and research projects since the 1970s and many data have been acquired since. Licensing rounds issued by the Greenland authorities in 2002 and 2004 offshore southern West Greenland resulted in company licenses which led to data acquisition and three exploration wells. The extensive new data form a basis for updated mapping by means of data, new analyses of the subsurface geology and improved understanding of the stratigraphy and the geological development. The Geological Survey of Denmark and Greenland (GEUS) has recently completed a comprehensive mapping project of the subsurface in an area covering 116 000 km2 offshore southern West Greenland (Fig. 1). The results include maps displaying large structural highs and faults, Cretaceous sedimentary basins and volcanic areas, illustrated by cross-sections through the area. A new seismic stratigraphy with eight mega-units from the seabed to the basement was also defined. In addition, studies from wells of biostratigraphy and petrology were carried out that provide important new information. The new data include extensive 2D seismic data and eight wells including the three exploration wells AT2-1, AT7-1 and LF7-1 drilled in 2011 by Cairn Energy (Fig. 1). Key results of the work are summarised below.
Basement
Geologic map
Prospectivity mapping
Geological survey
Marine geology
Continental Margin
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