A Study of Rock Densities in the English Midlands

Parasnis, Dattatraya Shripad; Cook, A. H.

doi:10.1111/j.1365-246x.1952.tb03013.x

Cited by 75 publications

(31 citation statements)

References 7 publications

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“…Density can be measured on samples from a study area, but the results often are not helpful, because (1) densities within individual geologic units often vary widely over outcrop areas and a large number of samples are needed to characterize that variability, (2) it is frequently difficult to obtain samples that aren't weathered, and (3) possible effects of compaction and water content may be unknown and/or not fully resolved (Nettleton, 1942;Parasnis, 1952). Density is also the physical property that all types of gravity surveys aim to map and ultimately interpret.…”

Section: Nettleton-style Profiling For Density Determinationmentioning

confidence: 99%

Expression of terrain and surface geology in high-resolution helicopter-borne gravity gradient (AGG) data: Examples from Great Sand Dunes National Park, Rio Grande Rift, Colorado

Drenth

2013

The Leading Edge

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Airborne gravity gradient (AGG) data are rapidly becoming standard components of geophysical mapping programs because of their advantages in cost, access, and resolution over measurements of the gravity field on the ground. Unlike conventional techniques that measure the gravity field, AGG methods measure derivatives of the gravity field. This means that effects of terrain and near-surface geology are amplified in AGG data, and that proper terrain corrections are critically important for AGG data processing. However, terrain corrections require reasonable estimates of density for the rocks and sediments that make up the terrain. A recommended philosophical approach is to use the terrain and surface geology, with their strong expression in AGG data, to the interpreter's advantage. An example of such an approach is presented here for an area with difficult ground access and little ground gravity data. Nettleton-style profiling is used with AGG data to estimate the densities of the sand dunefield and adjacent Precambrian rocks from the area of Great Sand Dunes National Park in southern Colorado. Processing of the AGG data using the density estimate for the dunefield allows buried structures, including a hypothesized buried basement bench, to be mapped beneath the sand dunes.

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Section: Nettleton-style Profiling For Density Determinationmentioning

confidence: 99%

Expression of terrain and surface geology in high-resolution helicopter-borne gravity gradient (AGG) data: Examples from Great Sand Dunes National Park, Rio Grande Rift, Colorado

Drenth

2013

The Leading Edge

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“…The method as described by Nettleton involves the personal judgment of the computer and the final choice of the correct density value is not always easy. The most satisfactory computational form seems to be that published by Parasnis (1952) and it is his method that has been used in all the cases to be described. It assumes a straight line relationship between gravity anomaly and height.…”

Section: Drymentioning

confidence: 99%

“…The different methods have, where convenient, been made to overlap and a correlation between them is thus possible and yields interesting results. Work on such correlations has been published by Hammer (1950) and Parasnis (1952) but their results differ to some extent. This further contribution to the solution of the problems should be of some interest.…”

mentioning

confidence: 99%

Correlation of Rock Density Determinations for Gravity Survey Interpretation*

Whetton

Myers

Smith

1957

Geophysical Prospecting

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The results of field and laboratory methods of density determination on a series of Coal Measure, Permian and Triassic rooks are presented and the different methods compared. It is concluded that the most satisfactory method is that of measuring the vertical change of gravity in a mine shaft. Nettleton's method is unsatisfactory to us, due to weathering of the rocks (particularly Magnesian Limestone) and possible effects from drift. Laboratory measurements are of variable value depending on the lithology and source of the samples.A method adopted to solve the problem of finding the true densities for use in a local gravity survey in N.E. England is given.

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“…Historically, lateral density variations have been measured directly on rock samples or estimated by correlating measured gravity data with synthetic data from known terrain (Nettleton ; Parasnis ; Vajk ; Rao and Murty ; Mankhemthong, Doser, and Baker ) and by high pass filtering and 3D inversion (Granser, Meurers and Steinhauser ). More recent examples for producing maps of terrain‐corrected AGG data were given by Tschirhart et al .…”

Section: Introductionmentioning

confidence: 99%

A priori models and inversion of gravity gradient data in hilly terrain

Pedersen

Kamm

Bastani

2019

Geophysical Prospecting

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A B S T R A C TThe increased popularity of airborne measurements of the gravity gradient tensor for resource studies and geological mapping has resulted in a new awareness of the importance of terrain effects. In these measurements, the terrain effect often overwhelms that of the underlying crust and it becomes important to formulate a strategy for taking it into account when presenting the data and when inverting the data into density models. Using newly acquired data from Northern Sweden, we first attempted to estimate a variable terrain density model by inverting the data using a terrain model with a laterally varying density. Using data weights related to the topography variations, we find the best estimate of the lateral variation of the terrain density. We translate this model into a full three-dimensional model such that all columns have the same vertical centre of mass as estimated from inspecting the radially averaged power spectrum of the area. This then defines a reference model for subsequent three-dimensional inversion of the gravity gradient tensor dataset. We tested this approach first on synthetic data calculated from the measured topography including two density anomalies before we applied it to the measured data. The result is a model in which the surface density variations are propagated downwards in a systematic manner now in better agreement with measured densities of rock samples in the area.

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A Study of Rock Densities in the English Midlands

Cited by 75 publications

References 7 publications

Expression of terrain and surface geology in high-resolution helicopter-borne gravity gradient (AGG) data: Examples from Great Sand Dunes National Park, Rio Grande Rift, Colorado

Expression of terrain and surface geology in high-resolution helicopter-borne gravity gradient (AGG) data: Examples from Great Sand Dunes National Park, Rio Grande Rift, Colorado

Correlation of Rock Density Determinations for Gravity Survey Interpretation*

A priori models and inversion of gravity gradient data in hilly terrain

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