Joints, tensile strength and preferred fracture orientation in sandstones. New Brunswick and Prince Edward Island, Canada

Authors

  • E.Z. Lajtai Department of Geological Engineering University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
  • P. Stringer Department of Geology, University of New Brunswick P.O. Box 4400, Fredericton, New Brunswick, Canada E3B SA3

DOI:

https://doi.org/10.4138/1377

Abstract

The orientations of tensile fractures in Upper Devonian, Carboniferous and Lower Permian sandstones of southern New Brunswick and Prince Edward Island show correlation at the submicroscopic scale of microcrack alignments, the macroscopic scale of joints, and the megascopic scale of airphoto lineaments. Planes of minimum tensile strength and planes of preferred fracture, induced in visibly unfractured sandstone test-samples by line-loading and point-loading tests, are identified as microcrack alignments. The joints and airphoto lineaments have microcrack alignments parallel to them, but not all microcrack alignments are represented at the macroscopic and megascopic scales. Deformed Carboniferous sandstones east of Saint John have two prominent orthogonal Joint systems with microcrack alignments parallel to the four joint sets. The airphoto lineaments are parallel to only three joint sets. Southeast and northeast striking joints in one orthogonal system are tentatively interpreted as planes of extension and release respectively, related to the direction of compression during the Variscan-Appalachian orogeny. The other orthogonal system, with joint sets striking close to 010° and 100°, is interpreted as post-Triassic in age, possibly related to the presently acting crustal stresses in eastern North America. RÉSUMÉ Il y a correspondance dans les grès du Dévonien supérieur, du Carbonifère et du Permien inférieur du aud du Nouveau-Brunswick et de l'ile du Prince-Edouard entre l'orientation des fractures de tension à diverses échelles: microscopique — alignement des microfissures; macroscopique — dis-clases; et megascopique — linéaments observes à partir de photographies aériennes. On reconnait comrae alignements de microfissures les plans de force de traction minimale et les plans de fracture préférentlelle occasionnés par des essais de charges linéaires et ponctuelles sur des échantillons types de grès préalablement exempts de fractures apparentes. Bien que parallèlement aux diaclases et aux linéaments on retrouve des alignements de microfissures, ce ne sont pas tous les alignements de microfissures qui s'expriment aux échelles macroscopique et megascopique. À l'est de Saint-Jean, les grès déformes du Carbonifère possèdent deux systèmes distincts de diaclases orthogonales accompagnes d'alignements de microfissures parallèles aux quatre ensembles de diaclases. Les linéaments observes sur photographié aérienne ne sont parallèles qu'a trois ensembles de diaclases. On interprète provisoirement les diaclases de direction sud-est et nord-est dans l'un des systèmes orthogonaux comme, respectlvement, des plans d'extension et de relâchement reliés à la direction de compression durant l'orogenèse varisque-appalachienne. Des orientations se rapprochant de 010" et 100° caractérisent l'autre système orthogonal qui serait d'Sge post-triasique et peut être relié aux forces de tension contemporaines agissant sur l’écorce terrestre dans l'est de l'Amèrique du Nord. [Traduit par le journal]

Downloads

Published

1981-05-05

How to Cite

Lajtai, E., & Stringer, P. (1981). Joints, tensile strength and preferred fracture orientation in sandstones. New Brunswick and Prince Edward Island, Canada. Atlantic Geoscience, 17(2). https://doi.org/10.4138/1377

Issue

Vol. 17 No. 2 (1981)

Section

Articles

License

All material contained in Atlantic Geology is copyrighted by the journal. Permission to photocopy for internal or personal use or for the internal or personal use of specific clients is granted by Atlantic Geology to libraries and other users registered with the Copyright Clearance Center (CCC), provided that the stated fee per copy is paid directly to the CCC, 21 Congress Street, Salem, Massachusetts 01970 USA. Other requests should be addressed to one of the journal editors, or sent to Atlantic Geology, Box 116, Acadia University, Wolfville, NS, Canada B4P 2R6. Permission to use a single graphic for which Atlantic Geology owns copyright is considered “fair dealing” under the Canadian Copyright Act and “fair use” by the journal, and no other permission need be granted, subject to the image being appropriately cited in all reproductions. The same fair dealing/fair use policy applies to sections of text up to 100 words in length.