Mechanical properties of Mesozoic rift basin formations

Natalia V. Zakharova, David S. Goldberg

Research output: Contribution to journalArticlepeer-review

Abstract

Abstract: The Newark basin is one of the largest Mesozoic rift basins in Eastern North America, which preserves tectonic and climatic archives and has been considered for geologic CO2 storage. This paper describes geomechanical properties of the Newark basin formation, focusing primarily on mudstone intervals. Compressive strength, elastic moduli and acoustic velocities were evaluated with a series of triaxial tests at confining pressures ranging from 0 to 41 MPa. The predominantly lacustrine mudstones are characterized by XRD clay content from 30 to 70%, and a large range of compressive strength, from 50 to 300 MPa, in excess of most published values for clay-rich rocks. The strength does not exhibit a strong relationship to clay content and can vary significantly for similar lithotypes. Important factors affecting rock strength in these rift basin formations are: (a) albitization by sodium metasomatism, which increases strength; and, (b) thin bedding, which introduces significant strength anisotropy, most pronounced in the Lockatong mudstones. Unlike rock composition, the elastic moduli correlate well with compressive strength. Overall, our results indicate high spatial heterogeneity of mechanical properties in these rift basin formations and a lack of characteristic strength ranges for common lithotypes in the Newark Supergroup and/or specific formations in the Newark basin. However, a strong correlation of acoustic velocity and elastic moduli with compressive strength would allow using those parameters to estimate strength when direct measurements are not available. Article highlights: Compressive strength of the Newark basin mudstones exhibits poor correlation to clay contentThe mudstone strength is greater than most published values for similar lithologiesThe mudstone strength is affected by albitization due to sodium metasomatism.

Original languageEnglish
Article number70
JournalGeomechanics and Geophysics for Geo-Energy and Geo-Resources
Volume7
Issue number3
DOIs
StatePublished - Aug 2021

Keywords

  • Compressive strength
  • Elastic moduli
  • Mesozoic rift basins
  • Mudstones
  • Newark basin
  • Strength anisotropy

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