Processes of faulting in jointed rocks of Canyonlands National Park, Utah

Abstract

Detailed studies of 11 segmented normal faults from five grabens in the Needles District of Canyonlands National Park, Utah, demonstrate key processes in the growth, linkage, and evolution of grabens. Field observations and stereophotogrammetry reveal a ubiquitous asymmetry in cross-sectional geometry, based on distinct map patterns of graben-bounding faults, rollover anticlines with attendant joint dilation, footwall uplift with joint closure, and spoon-shaped graben floors. Master and antithetic faults across Devils Lane and several other grabens are defined quantitatively by the displacement distributions along the faults. Two-dimensional shape parameters that characterize the displacement profiles indicate that inelastic processes such as changes in fault frictional strength influence strain accumulation along the faults. The degree of graben asymmetry increases systematically with distance from the Colorado River; greater symmetry is associated with locally greater age and/or strain of grabens nearer the river. Scatter in plots of maximum displacement vs. fault length was attributed previously to linkage of fault segments alone but is here shown to correlate additionally with distance from the Colorado River and, therefore, to spatial strain gradients within the graben array. Extensional strain across the fault array, accumulating at rates of perhaps 1.5 to 2 cm/yr or 10-14 to 10-13 s-1 , is accommodated at depth by salt flow and formation of reactive salt diapirs beneath the grabens and was probably initiated when the Colorado River had cut sufficiently deep into the section for active salt diapirism to commence.

Dilatant normal faulting in jointed cohesive rocks: a physical model study

“…The grabens of CLNP developed as an extensional fault array on top of a deforming layer of evaporites. Faults dip at 60-80 • below the jointed layer McGill and Stromquist, 1979;Moore and Schultz, 1999), comparable to our model setup. Angles between this joint-set and fault strikes inferred from local trends range between 0 • and ∼ 25 • , which is the range covered in our experiments.…”

“…The inherent complexity of naturally fractured rocks, however, makes it difficult to transfer all observations made in the lab to one particular outcrop. The best natural example that we also chose as base for the scaling of our experiments is the grabens area of the Canyonlands National Park, Utah, USA, which is an archetype for dilatant faults in jointed rocks (e.g., McGill and Stromquist, 1979;Moore and Schultz, 1999;Rotevatn et al, 2009). The northern part of the grabens is characterized by prominent vertical joint sets, which are older than the formation of the dilatant faults (McGill and Stromquist, 1979;Schultz-Ela and Walsh, 2002).…”

“…Most prominent large-scale examples can be found not only at mid-ocean ridges (Angelier et al, 1997;Friese, 2008;Sonnette et al, 2010;Wright, 1998), intra-plate volcanoes (Holland et al, 2006), continental rifts (Acocella et al, 2003) but also in cemented carbonates and clastics (Ferrill and Morris, 2003;Moore and Schultz, 1999). They form major pathways for fluid flow, such as water, hydrocarbons or magma, and consequently are of great interest for water and energy supply, geohazard assessment and geodynamics (e.g., Belayneh et al, 2006;Caine et al, 1996;Crone and Haller, 1991;Ehrenberg and Nadeau, 2005;Gudmundsson et al, 2001;Lonergan et al, 2007).…”

Lobate scarps and the Martian crustal dichotomy

“…The ratio of displacement to fault length (y) ranges between 10° and 10-3 for terrestrial faults [Cowie and Scholz, 1992]. Some of the scatter in the D and L data probably reflects the growth of faults by segment linkage where the scaling characteristics change at different stages of fault evo lution [Cartwright et al, 1995[Cartwright et al, , 1996Dawers and Anders, 1995;Wojtal, 1996;Moore and Schultz, 1999].…”

Interpretation and analysis of planetary structures

“…One bounding or border fault (in this case, the northwestern one) is much more pronounced than the other one, and the graben floor is clearly tilted, although the regional topography does not display any tilting. This geometry is typical for terrestrial grabens such as the Canyonlands graben system (e.g., Trudgill and Cartwright, 1994;Moore and Schultz, 1999;Schultz et al, 2007).…”