Plate-scale stress fi elds driving the tectonic evolution of the central Ouachita salient, Oklahoma and Arkansas Amy E. Whitaker† Terry Engelder‡ Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA ABSTRACT not rectilinear contemporary tectonic stress fi eld also display joints that record a well-organized (Zoback, 1992). Most of these intraplate stress regional stress fi eld (Fig. 1). There, joints Two stages of regional cross-fold jointing fi elds arise from plate-boundary conditions, propagate in a fan-like pattern approximately refl ect the rearrangement of a lithospheric- including shape of the boundary and conver- perpendicular (dip system) and parallel (strike plate-scale stress fi eld during the Ouachita gence direction (e.g., Nakamura et al., 1977). system) to overthrust faults of the Ouachita (i.e., Alleghanian) orogeny. These joints over- Because joints open parallel to the least principal foreland (Melton, 1929). This fan-like pattern print northward-verging thrust-related folds stress more or less instantaneously, a well-orga- of NNW-striking joints in the distal foreland in the Ouachita foreland. Stage-one jointing nized regional set may record the orientation of belies the dominant northward vergence of during the Ouachita orogeny is associated with a lithospheric-scale maximum horizontal stress, predominately E-W–striking imbricate thrust a stress fi eld recorded by an Atokan and ear- SH, as is the case for a neotectonic joint set in faults along more than 250 km of the Oua- lier regional joint set, which has a NNE strike. northwestern Europe (Hancock and Engelder, chita salient crossing the Oklahoma-Arkansas Stage-one jointing is separated into two phases 1989). Joint sets present in a suffi ciently large border (Fig. 2). Although not consistent with in the central Ouachita salient, where a second- region of the upper crust refl ect past plate-bound- the north-directed kinematics of the central order recess is marked by a prominent bend in ary stress fi elds in several forelands, including Ouachita salient, the fan-like pattern argu- the Windingstair fault below the forelandmost the Canadian foothills (Babcock, 1973), the ably refl ects the plate-scale stress fi eld during sheet of the central thrust belt. The Big Cedar Appalachian plateau (Nickelsen and Hough, assembly of Pangea in the Pennsylvanian. recess developed when the Windingstair sheet 1967; Engelder and Geiser, 1980), the Variscan An objective of this paper is to sort out jointing overrode the frontal imbricate zone, thereby (Dunne and North, 1990), the Sevier (Laubach controlled by a well-organized if not rectilinear causing the Big Cedar pinch zone, a structure and Lorenz, 1992), the Pyrenees (Turner and salient-wide stress fi eld in the Ouachita foreland refl ecting fold-parallel shortening proximal to Hancock, 1990; Arlegui and Simon, 2001), and from jointing that propagated in response to localized dextral transpression in the Choctaw others. In some instances, the rearrangement of local structural and stratigraphic boundary con- thrust sheet. A later regional joint set, repre- plate-scale stress fi elds is recorded by crosscut- ditions. To achieve this end, we couple an out- senting the second stage of jointing during the ting or abutting regional joint sets (e.g., Younes crop-by-outcrop sampling of joint patterns with Ouachita orogeny, affects rocks in the Arkoma and Engelder, 1999; Engelder, 2004). detailed geological mapping working outward foreland as well as in the fold belt. Stage-two These types of regional joint patterns are into the foreland of Arkansas and Oklahoma jointing records a stress fi eld associated with found largely in lightly deformed forelands. from the Big Cedar recess in eastern Oklahoma NNW-directed closure during the fi nal stage Moving toward the hinterland of mountain (Fig. 3). Data were collected on the orientation, of plate convergence; this stage persisted into belts, joint patterns become increasingly com- crosscutting relationships, and the shear reacti- the Desmoinesian. plex, with joint sets forming in response to local vation of joints at outcrops covering 10,000 km2 stresses associated with fault-related folding in a more proximal portion of the Ouachita Keywords: joints, Ouachita fold-and-thrust and other processes in the brittle crust (e.g., foreland relative to Melton’s (1929) mapping belt, stress fi elds, fracture, Arkoma Basin, Delaney et al., 1986; Dyer, 1988; Dunne and (Fig. 3). Foreland deformation in the Ouachita pinch zone. North, 1990; Rawnsley et al., 1992; Lemiszki fold belt consists of three distinct styles pointing et al., 1994; Cooke et al., 2000; Engelder and to a disparate history of stress-fi eld development INTRODUCTION Peacock, 2001; Rogers et al., 2004; Fischer across the structural provinces (Arbenz, 1989). and Christensen, 2004). As local structures and This begs the question whether or not there is The world stress map demonstrates that the cogenetic joint sets increase in complexity, it evidence for a plate-scale stress fi eld preserved upper continental crust within several litho- becomes more diffi cult to sort out those joints in evolving structures of all three foreland prov- spheric plates is subject to a well-organized if controlled by a foreland-wide stress fi eld arising inces of the Ouachita fold-and-thrust belt. from tractions at the plate boundary (e.g., Gray and Mitra, 1993; Fischer and Jackson, 1999; Sil- TECTONIC SETTING †Present address: Chevron Energy Technology liphant et al., 2002). Company, 1500 Louisiana Street, Houston, Texas 77002, USA. Outcrops in the distal portion of the Oua- The Ouachita fold-and-thrust belt is part of a ‡Corresponding author e-mail: engelder@geosc. chita foreland, including the Central Plains and system of Pennsylvanian-Permian thrust belts psu.edu. (mostly outer) Arkoma Basin in Oklahoma, formed along the southeastern margin of North GSA Bulletin; May/June 2006; v. 118; no. 5/6; p. 710–723; doi: 10.1130/B25780.1; 13 fi gures; 1 table. 710 For permission to copy, contact [email protected] © 2006 Geological Society of America TECTONIC EVOLUTION OF THE CENTRAL OUACHITA SALIENT o 96 W o 36 N CP Figure 1. Melton’s (1929) map of joint patterns in the Central Plains (CP), Arkoma Basin (AB), and AB Ouachita fold-and-thrust belt (OFB). OFB Figure 2. Tectonic map of the Ouachita salient showing zones of strike-slip dis- Arkansas placement during the Ouachita orog- Oklahoma Figure 3 Alabama eny. Background map is after Viele AU AB recess and Thomas (1989). Foreland basins are shaded; Broken Bow and Benton BU AMB JM uplifts are stippled. Abbreviations: belt st ru AB—Arkoma Basin; BWB—Black h BWB t BBU d o MSB Warrior Basin; BU—Benton uplift; n 94 W 250 kilometers a o 33 N OAJ d BBU—Broken Bow uplift; FWB—Fort 0 100 200 fol Worth Basin; AMB—Ardmore/Mari- WB F Ouachita etta Basin (sinistral slip from Granath, Texas Salient 1989; Pindell, 1985, indicates the slip Texas Mississippi is dextral); AU—Arbuckle uplift; recess JM—Jackfork Mountain (dextral slip DRU Louisiana from Miser et al., 1954; Arbenz, 1989); Marathon MSB—Mississippi slate belt (dextral salient slip from Pindell, 1985); OAJ—Oua- chita-Appalachian juncture (dextral PTF slip from Hale-Erlich and Coleman, 1993); DRU—Devil’s River uplift (dextral slip from Pindell, 1985); PTF—Pedregosa Trough fault system (dextral slip from Pindell, 1985). Geological Society of America Bulletin, May/June 2006 711 WHITAKER and ENGELDER 94 45' W 94 00' W Greenwood Arka Arkoma nsas Basin Oklahoma Poteau 35 00' N N35 00' zone axis pinch Choctaw F ault Frontal Strike-slip Imbricate discontinuities Figures 7 & 9 Win Zone dings ta Big Cedar pinch zone i r fa u lt SM 34 40' N Big RM N34 40' C eda r r ecess LMS Mena Octavia fault BU 25 kilometers Central North Thrust Belt Ms Bok kola f W94 45' Pj Pjv Pa Phm Psb tu au lt Figure 3. Simplifi ed geological map of the central Ouachita fold-and-thrust belt and Arkoma Basin with mean joint azimuth of the most- frequent joint set plotted for selected outcrops. Major thrust faults (Boktukola, Octavia, Windingstair, Choctaw) are traced with bold lines. Imbrications in the frontal imbricate zone are traced with lighter lines. Formation symbols are: Ms—Mississippian Stanley Group; Pj—Pennsylvanian (Morrowan) Jackfork Group; Pjv—Pennsylvanian (Morrowan) Johns Valley Formation; Pa—Pennsylvanian (Atokan) Atoka Formation; Phm—Pennsylvanian (Desmoinesian) Hartshorne and McAlester Formations; Psb—Pennsylvanian (Desmoinesian) Savanna and Boggy Formations. See Figure 2 for the location of the study area. LMS—Lynn Mountain syncline; SM—Simmons Mountain syncline; RM—Rich Mountain syncline; BU—Benton uplift. America as Pangea amassed (e.g., Viele and was occupied by one or more exotic landmasses (Fig. 4), largely turbidites, accumulated in the Thomas, 1989). The Ouachita salient is a fi rst- that encroached from the southeast in the Mis- Ouachita trough and had an exotic source to order tectonic feature, the present-day geometry sissippian and Pennsylvanian periods (Pindell, the southeast (Johnson et al., 1988). By the of which was determined fi rst by the embayment 1985; Mickus and Keller, 1992). early Pennsylvanian deposition of the Jackfork developed along the margin of Laurentia during Paleozoic Ouachita strata consist of deep- Group, the Ouachita trough had narrowed with the rifting in the late Proterozoic (e.g., Thomas, water pre-orogenic rocks overlain by a synoro- continued closing of the ocean basin (Johnson et 1977) and then by the collision between the genic sequence that was deposited at extremely al., 1988). The Atoka Formation represents the southern margin of Laurentia and Gondwanan high rates (up to 2 km/m.y.) (Viele and Thomas, most rapid sedimentation in the Ouachita belt, terranes in the Carboniferous (Fig. 2). Plate 1989; Morris, 1989).