Reelfoot rift and its impact on Quaternary deformation in the central Mississippi River valley

Abstract

Geophysical and drill-hole data within the Reelfoot rift of Arkansas, Tennessee, Missouri, and Kentucky, USA, were integrated to create a structure contour map and threedimensional computer model of the top of the Precambrian crystalline basement. The basement map and model clearly defi ne the northeast-trending Cambrian Reelfoot rift, which is crosscut by southeast-trending basement faults. The Reelfoot rift consists of two major basins, separated by an intrarift uplift, that are further subdivided into eight subbasins bound by northeast-and southeast-striking rift faults. The rift is bound to the south by the White River fault zone and to the north by the Reelfoot normal fault. The modern Reelfoot thrust fault, responsible for most of the New Madrid seismic zone earthquakes, is interpreted as an inverted basement normal fault. Geologic interpretation of 5077 shallow borings in the central Mississippi River valley enabled the construction of a structure contour map of the Pliocene-Pleistocene unconformity (top of the Eocene-base of Mississippi River alluvium) that overlies most of the Reelfoot rift. This map reveals both river erosion and tectonic deformation.Deformation of the Pliocene-Pleistocene unconformity appears to be controlled by the northeast-and southeast-trending basement faults. The northeast-trending rift faults have undergone and continue to undergo Quaternary dextral transpression. This has resulted in displacement of two major rift blocks and formation of the Lake County uplift, Joiner ridge, and the southern half of Crowley's Ridge as compressional stepover zones that appear to have originated above basement fault intersections. The Lake County uplift has been tectonically active over the past ~2400 yr and corresponds with a major segment of the New Madrid seismic zone. The aseismic Joiner ridge and the southern portion of Crowley's Ridge may refl ect earlier uplift, thus indicating Quaternary strain migration within the Reelfoot rift.

New Madrid seismic zone fault geometry

“…2) is interpreted to be a Cambrian intracratonic rift associated with the opening of the Paleozoic Iapetus Ocean (Ervin and McGinnis, 1975;Thomas, 1989Thomas, , 2006. normal faults (Howe and Thompson, 1984;Nelson and Zhang, 1991) that are segmented by northwest-striking vertical faults (Stark, 1997;Csontos et al, 2008). During rifting, the Reelfoot rift accumulated up to 8 km of Cambrian sediment, while outside the rift 1.5 km of Cambrian sediment accumulated (Howe and Thompson, 1984).…”

“…Tectonic landforms within the central Mississippi River valley are directly linked to the underlying Reelfoot rift faults (Fig. 3) (Mihills and Van Arsdale, 1999;Csontos et al, 2008). Quaternary displacement has been documented along the Eastern Rift Margin (Cox et al, 2001(Cox et al, , 2006, Western Rift Margin (Van Arsdale et al, 1995b;Baldwin et al, 2005), Axial (Van Arsdale, 1998; Guccione et al, 2000), and Reelfoot fault (Russ, 1982;Kelson et al, 1996;Mueller et al, 1999;Van Arsdale et al, 1999;Champion et al, 2001).…”

“…1), southern half of Crowley's Ridge, the Big Lake and Lake Saint Francis Sunklands area, and Joiner Ridge are interpreted to be tectonic or tectonically infl uenced landforms ( Fig. 4) (Csontos et al, 2008). New Madrid seismic zone faults have also modifi ed Mississippi River gradients and infl uenced sedimentary processes during the Quaternary (Spitz and Schumm, 1997;Guccione et al, 2002;Guccione, 2005;Holbrook et al, 2006).…”

“…2) have large normal displacements within the crystalline basement and Cambrian section (Howe 1985;Parrish and Van Arsdale, 2004;Csontos et al, 2008). The Western Rift Margin fault is a steeply eastward-dipping normal fault, displacing the Precambrian surface up to 3 km (Howe, 1985;Nelson and Zhang, 1991).…”

“…The Reelfoot rift (Mississippi Valley Graben) is a major basement structure mapped from gravity, magnetic, seismic refraction, seismic refl ection, and a few deep petroleum exploration wells (Fig. 2) (Hildenbrand, 1982;Hildenbrand et al, 1982;Hamilton and Zoback, 1982;Howe and Thompson, 1984;Howe, 1985;Hildenbrand and Hendricks, 1995;Dart and Swolfs, 1998;Parrish and Van Arsdale, 2004;Csontos et al, 2008) that is covered by up to 6 km of Phanerozoic sediments. New Madrid seismic zone seismicity is occurring along these rift faults primarily between depths of 4 and 14 km within the Cambrian and Precambrian section (Chiu et al, 1992;Pujol et al, 1997;Van Arsdale and TenBrink, 2000).…”