Computerized density contouring and statistical evaluation of orientation data using counting circles and continuous weighting functions

Robin, Pierre-Yves F.; Jowett, E. Craig

doi:10.1016/0040-1951(86)90044-2

Cited by 73 publications

(42 citation statements)

References 13 publications

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“…Results were processed with Anisoft 3 software using Jelinek statistics (Jelinek, 1978), and performing structural correction. SpheriStat software was used for applying Gaussian counting point density distribution statistics (E = 3 * Sigma; Robin and Jowett, 1986) and to facilitate plotting all the AMS data in high quality stereodiagrams: the susceptibility axes and their means, point density distribution curves, bedding and magnetic foliation planes (Fig. 5).…”

Section: Sampling and Laboratory Proceduresmentioning

confidence: 99%

“…Short and long name of sites is described as well as bedding plane and facies (I = proximal, II = intermediate and III = distal). In each site 2 statistics (Stat column) are shown, J : Jelinek's statistic (Jelinek, 1978); D: Gaussian counting (E = 3 * Sigma) point density distribution (Robin and Jowett, 1986). k 1 is maximum AMS axis and k 3 is the minimum.…”

Section: Susceptibility and Ams Parametersmentioning

confidence: 99%

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Anisotropy of magnetic susceptibility analysis of the Cantera Ignimbrite, San Luis Potosi, México: flow source recognition

2009

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Anisotropy of magnetic susceptibility (AMS) was selected as the key technique to find the source of the widespread Cantera Ignimbrite and to seek its possible relationship with the San Luis Potosí Caldera. Eighteen sites (372 specimens from 155 cores) from the Oligocene Cantera Ignimbrite were sampled. AMS was measured on a KLY2 Kappabridge. AMS data were processed with Anisoft 3 software using Jelinek statistics as well as 'SpheriStat' principal components and density distribution. Mean susceptibilities range from 290 to 5026 × 10 −6 SI (average = 2526 × 10 −6 SI). The anisotropy degree (P j ) ranges from 1.005 to 1.055, with only one site displaying a value of 1.134 (P j average = 1.031). AMS ellipsoid shapes are mostly oblate, with the T -factor ranging from 0.843 to 0.144 (T average = 0.529), although one site is mainly prolate (T = −0.005), and three additional sites have an important proportion of prolate specimens. Magnetic fabrics of most sites shows k 3 axes around nearly circular distributions and k 1 -k 2 axes around elongated-girdle distributions defining sub-horizontal foliation planes; exceptions to this are related to sites with a significant percentage of prolate specimens. Flow directions inferred from AMS analysis indicate several ignimbrite sources located along selected NW-SE linear features (faults and fractures such as El Potosino Fault) as well as along the rim of the caldera structure. The geometry of volcanic outcrops, the NW-SE faulting-fracture system, as well as the AMS results suggest that this is a caldera structure resembling the trapdoor-type (Lipman, 1997).

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Section: Sampling and Laboratory Proceduresmentioning

confidence: 99%

Section: Susceptibility and Ams Parametersmentioning

confidence: 99%

Anisotropy of magnetic susceptibility analysis of the Cantera Ignimbrite, San Luis Potosi, México: flow source recognition

2009

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“…No clear cross-cutting relationships, giving the relative ages of the joints, are discernible. The principal joint trend, determined statistically using a circular counting routine (Robin and Jowett, 1986), is 091°. The secondary trends are 027° and 152°, corresponding to the orientations of topographic lineaments (Table I 1 Fig.…”

Section: Jointsmentioning

confidence: 99%

Pop-Up Structures and the Fracture Pattern in the Balsam Lake Area, Southern Ontario

Rutty¹,

Cruden²

2007

gpq

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An examination of topographic lineaments detectable in Landsat TM images and measurement of joints in outcrop in the Balsam Lake area reveals a systematic bedrock fracture pattern with three principal sets oriented 091°, 027°, and 152°. The 027° trend is parallel to a major aeromagnetic anomaly, the Niagara-Pickering Linear Zone (NPLZ), which underlies the Balsam Lake area and is thought to mark the sub-Paleozoic continuation of the Proterozoic Central Metasedimentary Belt Boundary Zone (CMBBZ). Possible origins of the main joint sets due to Acadian (091° set), Alleghanian (152° set) and St. Lawrence rift system tectonics (091° and 027° sets) are discussed. En-echelon pop-up structures have a mean principal trend of 118°. They displace Lake Algonquin paleobeaches, suggesting formation less than 12,500 years ago. The orientation of the pop-up structures is subnormal to the current in situ maximum horizontal stress direction, SHmax (020°), and is parallel to members of the 091° joint set, indicating possible nuclea-tion on favourably-oriented pre-existing joints. These pop-ups are the only features in the Balsam Lake area with strong evidence for a neotectonic age.L'examen des linéaments topographiques repérables sur les images Landsat (TM) et la mesure des diaclases dans un affleurement de la région de Balsam Lake révèle la présence d'un réseau de fractures dont l'orientation des trois principaux ensembles est 091°, 027° et 152°. La direction 027° est parallèle à une anomalie aéromagnétique majeure, la zone linéaire Niagara-Pickering, présente sous la région de Balsam Lake; on croit qu'elle identifie le prolongement sub-paléozoïque de l'aire limite de la zone méta-sédimentaire centrale protérozoïque. On traite des origines possibles des principaux ensembles de fractures attribuables aux systèmes acadien (091°), alléghanien (152°) et du rift du Saint-Laurent (091 °et 027°). La direction des structures de soulèvement en échelon est de 118°. Elles ont déplacé des paléo-plages du Lac Algonquin, indiquant ainsi une formation postérieure à 12 500 ans. L'orientation des structures de soulèvement est subnormale à la direction de la contrainte horizontale maximale actuelle, SHmax(020°), et est parallèle à des éléments de l'ensemble des fractures de direction 091°, montrant ainsi leur formation possible dans des fractures existantes bien orientées. Ces structures de soulèvement sont les seuls éléments de la région démontrant un âge néotectonique.Eine Untersuchung der topographischen Lineamente die in Landsat TM-Bildern nachweisbar sind und Messungen der Fugen in den Aufschlùssen des Balsam Lake-Gebiets lassen ein systematisches Bruchmuster des anstehenden Gesteins erkennen mit drei nach 091°, 027° und 152° ausgerichteten Haupteinheiten. Die Ausrichtung nach 027° ist parallel zu einer wichtigen aeromagnetischen Anomalie, der linearen Zone von Niagara-Pickering, die unter dem Balsam Lake-Gebiet liegt; man halt sie fur eine subpalàozoische Fortfùhrung des Grenz-bereichs der proterozoischen zentralen metasedimentàren Gùrtel-zon...

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“…The plots show a) all data collected, b) data from Unit 4, c) data from Unit 3T, and d) data from Unit 3. Lower hemisphere equal area stereonets are contoured using the Gaussian counting method of Robin and Jowett (1986). Contour intervals are equal to E + 2σ, E + 4σ, etc., where E is the number of points expected to be found in the counting circle if points were extracted randomly from a uniform population and σ is the standard deviation.…”

Section: Fractures and Minor Faults At Materialsmentioning

confidence: 99%

“…Using the computer program Spheristat (© Pangaea Scientific), we determined preferred orientations using a Gaussian counting routine (Robin and Jowett 1986) that allows determination of the principal directions of the strain ellipse with 2σ uncertainties (Fig. 11).…”

Section: Appendix a Whole Rock Geochemistrymentioning

confidence: 99%

Geology of the Western Part of Los Alamos National Laboratory (TA-3 to TA-16), Rio Grande Rift, New Mexico

Lewis¹,

Lavine²,

Reneau³

et al. 2002

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Computerized density contouring and statistical evaluation of orientation data using counting circles and continuous weighting functions

Cited by 73 publications

References 13 publications

Anisotropy of magnetic susceptibility analysis of the Cantera Ignimbrite, San Luis Potosi, México: flow source recognition

Anisotropy of magnetic susceptibility analysis of the Cantera Ignimbrite, San Luis Potosi, México: flow source recognition

Pop-Up Structures and the Fracture Pattern in the Balsam Lake Area, Southern Ontario

Geology of the Western Part of Los Alamos National Laboratory (TA-3 to TA-16), Rio Grande Rift, New Mexico

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