GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 10-6
Presentation Time: 9:20 AM


MOON, Seulgi1, PERRON, J. Taylor2, MARTEL, Stephen J.3, GOODFELLOW, Bradley W.4, MAS IVARS, Diego5, SIMEONOV, Assen6, MUNIER, Raymond6, NÄSLUND, Jens-Ove6, HALL, Adrian7, STROEVEN, Arjen P.8, EBERT, Karin7 and HEYMAN, Jakob9, (1)Department of Earth, Planetary, and Space Science, University of California, Los Angeles, 595 Charles Young Dr. East, Los Angeles, CA 90095, (2)Department of Earth, Atmospheric and Planetary Sciences, Massachusets Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, (3)Geology and Geophysics, University of Hawaii, Honolulu, HI 96822, (4)Geological Survey of Sweden, Lund, Sweden, (5)Swedish Nuclear Fuel and Waste Management Company, Stockholm, Sweden; Department of Soil and Rock Mechanics, KTH Royal Institute of Technology,, Stockholm, Sweden, (6)Swedish Nuclear Fuel and Waste Management Company, Stockholm, Sweden, (7)Geomorphology & Glaciology, Department of Physical Geography, Stockholm University, Stockholm, Sweden, (8)Geomorphology & Glaciology, Department of Physical Geography, Stockholm University, Stockholm, Sweden; Bolin Centre for Climate Research, Department of Physical Geography and Quaternary Geology, Stockholm University, Stockholm, SE-10691, Sweden, (9)Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden

Fracturing of bedrock promotes water-rock interactions and the formation of the life-sustaining layer of soil at Earth’s surface. Theoretical models predict that topography and loads from sediment and water should influence bedrock fracturing in three dimensions by perturbing gravitational and tectonic stress fields. Testing model predictions of the depth and distribution of topographically-affected fractures has proven difficult because comprehensive fracture datasets in three-dimensions for the subsurface are rare. Thus, it is not clear how strongly fractures respond to landscape features or how deep the effects extend. Here, we compare models of three-dimensional stress fields that include effects of topography, sediment weight, ocean loading, and pore water pressure with a dataset of ~50,000 fractures documented from 18 cores reaching depths of 600 m in the Precambrian crystalline rocks at Forsmark, Sweden. Stress proxies for the formation or reactivation of fractures correlate strongly with the fraction of observed fractures that are open (have a visible aperture in cores) at depths down to 500 m, despite the low topographic relief in Forsmark (~ 40 m). This result implies that present-day stress fields, perturbed by landscape features, can induce or reactivate fractures, potentially beginning to form the critical zone as deep as hundreds of meters beneath the land surface.