Orientation Uncertainty of Structures Measured in Cored Boreholes: Methodology and Case Study of Swedish Crystalline Rock

The petrographic composition and grain shape variability of beach gravels in the Pogorzelica–Dziwnów coast section (363.0 to 391.4 km of coastline), southern Baltic Sea, Poland were analyzed herein to characterize the lithodynamics and trends of seashore development. Gravels were sampled at 0.25 km intervals, in the midpart of the berm, following an early-autumn wave storm and before beach nourishment. Individual variations in petrographic groups along the shore were investigated. Gravel data were compared and related to coastal morpholithodynamics, seashore infrastructure, and geology of the study area. The contribution of crystalline rock gravels (igneous and metamorphic) was observed to increase along all coast sections, whereas the amount of less resistant components (limestones, sandstones, and shales) usually declined. This effect is explained by the greater wave crushing resistance of igneous and metamorphic components, compared with sedimentary components. Similarly, the gravel grain shape (mainly elongation or flattening) was observed to change, depending on resistance to mechanical destruction, or due to the increased chemical weathering in mainly the limestones, marbles, and sandstones. Observed increase in contribution of discoid and ellipsoid grains is a potential indicator of depositional trends along the coast sections investigated. On the other hand, increased contents of spheroidal and spindle-shaped grains may be related to erosional trends, where intensive redeposition and mechanical reworking of gravels occurs. However, due to the great number of coastal embankments, the petrographic composition and shape parameters of beach gravels do not always clearly indicate the dominant direction of longshore bedload transport. Increased amount of eroded limestone located east of Pogorzelica indicate increased erosion of glacial tills. These sediments are deposited, building the shallow foreshore, with additional redeposition of morainic material towards the shore.

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New weathering indices for evaluating durability and weathering characterization of crystalline rock material: A case study from NE Turkey

Journal of African Earth Sciences ◽

10.1016/j.jafrearsci.2014.12.005 ◽

2015 ◽

Vol 103 ◽

pp. 54-64 ◽

Cited By ~ 15

Author(s):

Sener Ceryan

Keyword(s):

Crystalline Rock ◽

Rock Material ◽

Weathering Indices

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HYDROGEOPHYSICS IN FRACTURED CRYSTALLINE AQUIFERS IN ENGLISH GUYANA

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v37i3.2009 ◽

2019 ◽

Vol 37 (3) ◽

pp. 299

Author(s):

Gerlane Cavalcante Messias ◽

Jose Agnelo Soares ◽

Felipe Kipper ◽

Igor Fernandes Gomes ◽

Vandir Pereira Soares Júnior ◽

...

Keyword(s):

Electrical Resistivity ◽

Crystalline Rock ◽

Electrical Resistivity Imaging ◽

Second Phase ◽

Resistivity Imaging ◽

Rock Formations ◽

Controlled Porosity ◽

Two Phases ◽

Resistivity Meter

ABSTRACT: This work is a case study in Guyana with the goal of finding groundwater in rock layers with fracture-controlled porosity using electrical resistivity imaging. This work was carried out in two phases by the Brazilian Army, in eight communities in the region of Alto Tacutu – Alto Essequibo in southeast Guyana. All work was done in accordance with a technical agreement between Brazil and Guyana. In the first phase, the surveys were completed by the team which collected resistivity data using a SuperSting R8 electrical resistivity meter with dipole-dipole and dipole-gradient arrays. Then the software EarthImager was used to analyze the data and create two-dimensional (2D) pseudo-sections with depths up to 70m. In the second phase, eight wells were drilled in areas of low resistivity. The geology of this region consists of Precambrian granite rock layers with varying levels of fracturing. In this way, the effectiveness of the multielectrode resistivity imaging technique was demonstrated as a way to explore the availability of groundwater in crystalline rock formations with fracture-controlled porosity.Keywords: electrical resistivity imaging, well siting, groundwater.RESUMO: Este trabalho se constitui em um estudo de caso na Guiana Inglesa, com o objetivo de encontrar água subterrânea por meio de levantamentos de resistividade elétrica, nas áreas de porosidade controladas pelas zonas de fraturas. O trabalho foi realizado em duas fases pelo Exército Brasileiro em oito comunidades da região do Alto Tacutu – Alto Essequibo no sudeste da Guiana Inglesa, através de um acordo de cooperação técnica entre o Brasil e a Guiana. Na primeira fase, os levantamentos foram feitos por uma equipe que coletou dados de resistividade usando um eletrorresistivímetro SuperSting R8 com arranjos dos tipos dipolo-dipolo e dipolo gradiente. Em seguida foi utilizado o software EarthImager para analisar os dados e criar pseudoseções de duas dimensões (2D) até 70m de profundidade. Na segunda fase, oito poços foram perfurados em pontos de baixa resistividade. A geologia da região é constituída de rochas graníticas Pré-cambrianas com níveis variados de fraturamento. Desse modo, demonstrou-se a efetividade do método de resistividade elétrica multieletrodo para explorar a disponibilidade de água subterrânea em aquíferos fraturados em terrenos cristalinos.Palavras-chave: imageamento de resistividade elétrica, locação de poços, água subterrânea.

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