Stream Response to Repeated Coseismic Folding, Tiptonville Dome, New Madrid Seismic Zone

Geomorphology 43 (2002) 313–349 www.elsevier.com/locate/geomorph

Stream response to repeated coseismic folding, Tiptonville dome, New Madrid seismic zone

M.J. Guccione a,*, K. Mueller b, J. Champion b, S. Shepherd a, S.D. Carlson a, B. Odhiambo c, A. Tate b

aDepartment of Geosciences, University of Arkansas, Fayetteville, AR 72701, USA bDepartment of Geological Sciences, University of Colorado, Boulder, CO 80309-0399, USA cEnvironmental Dynamics Program, University of Arkansas, Fayetteville, AR 72701, USA

Received 12 January 2001; received in revised form 9 July 2001; accepted 16 August 2001

Abstract

Fluvial response to tectonic deformation is dependent on the amount and style of surface deformation and the relative size of the stream. Active folding in the New Madrid seismic zone (NMSZ) forms the Tiptonville dome, a 15-km long and 5-km wide surface fold with up to 11 m of late Holocene structural relief. The fold is crossed by streams of varying size, from the Mississippi River to small flood-plain streams. Fluvial response of these streams to repeated coseismic folding has only been preserved for the past 2.3 ka, since the Tiptonville meander of the Mississippi River migrated across the area forming the present flood plain. This surface comprises a sandy point-bar deposit locally overlain by clayey overbank and silty sand crevasse-splay deposits, an abandoned chute channel infilled with laminated sandy silt and silty clay, and an abandoned neck cutoff filled with a sandy cutoff bar and silty clay oxbow lake deposits. Dating various stream responses to coseismic folding has more tightly constrained the timing of earthquake events in the central NMSZ and provides a means of partitioning the deformation amount into individual seismic events. Three earthquakes have been dated in the Reelfoot Lake area, ca. A.D. 900, 1470, and 1812. The latter two earthquakes had large local coseismic deformation. Both of these events were responsible for numerous stream responses such as shifting depocenters, modification of Mississippi River channel geometry, and derangement of small streams. Overbank sedimentation ceased on the dome as it was uplifted above the normal flood stage, and sedimentation of crevasse-splay deposits from the Mississippi River, colluvium from the scarp, and lacustrine sediment accumulated in the adjacent Reelfoot basin. The much larger Mississippi River channel responded to uplift by increasing its sinuosity across the uplift relative to both upstream and downstream, increasing its width/depth ratio across and downstream of the uplift, and decreasing the width/depth ratio upstream of the uplift. Despite the size of the Mississippi River, it has not yet attained equilibrium since the latest uplift 190 years ago. Small channels that could not downcut through the uplift were filled, locally reversed flow direction, or formed a lake where they were dammed. Uplift and stream response to folding along the Tiptonville dome is less dramatic between 2.3 and 0.53 ka. During this interval, abandoned channel fill and overbank deposition across the dome suggests that it was not a high-relief feature. One earthquake event occurred during this interval (ca. A.D. 900), but coseismic stream response was probably limited to a slight aggradation of a small flood-plain stream. D 2002 Elsevier Science B.V. All rights reserved.

Keywords: Mississippi River; New Madrid seismic zone; Stream response; Folding

* Corresponding author. E-mail address: [email protected] (M.J. Guccione).

1. Introduction forms a single meander belt along the eastern valley margin in the NMSZ (Saucier, 1994; Guccione et al., Active faults and folds cut by stream valleys pro- 1999). vide an opportunity to examine the response of streams Deformation in the NMSZ during the Holocene and to earthquakes (Yielding et al., 1981; Philip and perhaps late Pleistocene formed a positive topographic Meghraoui, 1983; Philip et al., 1992) and date defor- feature, termed the Tiptonville dome of the Lake mation events. Stream response in seismically active County uplift (e.g., Russ, 1982; Schweig and Van areas is controlled by the amount and style of fault Arsdale, 1995; Mueller et al., 1999; Van Arsdale, surface rupture and folding, the style and scale of the 2000) (Figs. 1 and 2). The dome is the surface expres- drainage networks, and in some cases, other extrinsic sion of a fold formed at a compressive stepover in the factors such as climate change and geology. Intraplate dominantly strike–slip system of the NMSZ. Tipton- tectonic activity may be at a smaller scale than at plate ville dome was interpreted by Mueller et al. (1999) to margins, and therefore, stream response is commonly be a fault-bend fold formed in response to slip on the less dramatic (e.g., Burnett and Schumm, 1983; Mer- blind Reelfoot thrust fault. Alternatively, the dome has ritts and Hesterberg, 1994; Holbrook and Schumm, been interpreted as a fault-propagation fold where 1999; Guccione et al., 2000; Marple and Talwani, deformation in the hanging wall has been accommo- 2000) than along plate margins (e.g., Mulder and dated by shear above the west-dipping Reelfoot re- Burbank, 1993; Olsen and Larsen, 1993; Audemard, verse fault (Purser and Van Arsdale, 1998; Champion 1999; Friend et al., 1999; Snyder et al., 2000). et al., 2001) (Fig. 2). Although there are some large-scale fluvial responses The recurrence interval of great earthquakes in the to intraplate doming such as the incision of the Colo- NMSZ, approximately 300–600 years during the last rado River into the Colorado Plateau to form the Grand 1200 years (Tuttle et al., 1999b), is less than that of Canyon (Patton et al., 1991) and intraplate subsidence channel migration and flood plain renewal within the such as the position of the lower Mississippi River Mississippi River meander belt. Thus, the river has alluvial valley within the Mississippi Embayment responded to multiple seismic events during the late (Fisk, 1944; Autin et al., 1991; Saucier, 1994; Cox Holocene, and these responses are preserved in both and Van Arsdale, 1997), most intraplate tectonic the depositional record and the geomorphology of the deformation occurs at relatively small spatial scales. area. Vertical accretion on uplifted parts of flood plains The New Madrid seismic zone (NMSZ) is unique in is thin or absent and finer grained compared to the that it is an active seismic zone in an intraplate setting accumulation of relatively thicker and coarser grained developed across the alluvial valley of the third largest overbank sediment in downwarped areas (Ouchi, river in the world. The general character of the Mis- 1985). Channel width, depth, and pattern can respond sissippi Alluvial Valley, including its location and to the new gradients created by deformation (Burnett aggradation of deltaic and alluvial sediment through and Schumm, 1983; Jorgensen, 1990; Schumm and the Tertiary and Quaternary, is controlled by a failed Galay, 1994), but the size of the Mississippi River rift [initiated in the early Paleozoic (Hildebrand and precludes drainage derangement given the relatively Hendricks, 1995)] or passage of the Mississippi graben small amount of surface deformation from individual system over a hotspot (Cox and Van Arsdale, 1997). earthquakes in the seismic zone. Small streams also Evidence for recurrent faulting in the NMSZ is defined respond to the individual earthquake events and record by the growth strata across the Reelfoot scarp during their effects with changes in gradient that the stream is episodes in the late Cretaceous, early Tertiary, and late incapable of modifying during the interval between Quaternary (Van Arsdale, 2000). During the late Pleis- earthquakes. As in the case of the larger Mississippi tocene, thick widespread deposits of braided-stream River, longitudinal profiles along small streams may sand were deposited by glacial meltwater across the deviate from the estimated natural profiles for hundreds broad alluvial valley and the channel position moved of years in this setting (Merritts and Hesterberg, 1994). eastward (Van Arsdale et al., 1995b; Blum et al., Unlike the Mississippi River, small channels may fill 2000). In contrast, during the Holocene, the river has where the gradient is reduced, and channel patterns been a single-channel meandering stream. It currently may become deranged (e.g., Matmon et al., 1999). M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 315

Fig. 1. Location map of geomorphic and structural features in the New Madrid seismic zone (NMSZ). Filled circles are the locations of historic earthquakes and dates of occurrence (modified from Rhea and Wheeler, 1995). Square is the outline of study area shown in Fig. 3. MO— Missouri; AR—Arkansas; KY—Kentucky; TN—Tennessee. Modified from Guccione et al. (2000).

The purpose of this paper is threefold: first, to Reelfoot Lake area; second, to further constrain the determine the style and amount of response of small- style and timing of surface folding produced by these and large-scale rivers to well-dated earthquakes in the earthquakes; and third, to partition the amount of 316 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 2. Topographic profile (upper) and cross-section (lower) of Tiptonville dome, oriented east–west through CT-2 boring transect shown in Fig. 3. Seismicity from Mueller and Pujol (in press) shown as white circles on cross-section, details of strata folded across Reelfoot monocline shown as insert from Champion et al. (2001). Area of insert (with no vertical exaggeration) is shown as small rectangle at uppermost fault tip, above 800-m depth on cross-section. Fault geometry is from Champion et al. (2001) and Mueller and Pujol (in press). deformation produced by individual events. Data from 2. Methods this study are integrated with that from earlier studies (Fuller, 1912; Russ et al., 1978; Russ, 1979, 1982; Geomorphic, sedimentologic, and chronologic ana- Kelson et al., 1992; Fischer and Schumm, 1993, 1995; lyses of the Reelfoot Lake area were undertaken to Merritts and Hesterberg, 1994; Van Arsdale et al., evaluate the stream response to, and timing of, defor- 1995a, 1998b; Kelson et al., 1996; Rosenbaum et al., mation along the Reelfoot scarp. Geomorphic analysis 1996; Mueller et al., 1999; Carlson, 2000; Champion included interpretation of 1964 (photorevised 1981 et al., 2001). and 1982) 1:24,000 topographic maps; a bathymetric M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 317 map of Reelfoot Lake (Carlson, 2000), 1:20,000 scale; describing and sampling soils (Schoeneberger et al., black and white aerial photos taken March 6, 1963; 1998). Particle size was analyzed on 235 samples and a digital terrain model generated for this study. from 15 cores. Each soil horizon and/or stratigraphic Valley and channel gradients and channel sinuosity unit was sampled and multiple samples were generally (channel length/valley length) were measured on the taken from horizons > 30 cm thick. Dry sieving was 1:24,000 topographic maps. The topographic maps used to separate the gravel (>2 mm) and sand fractions have a 5-ft contour interval, and the bathymetric map (2.0–0.63 mm). Pipette analysis was used to deter- has a 0.5-m contour interval. mine the silt (0.63–0.002 mm) and clay fractions Sites were chosen to field check the geomorphic ( < 0.002 mm) (Day, 1965). Terminology for the map made from aerial photographs (Fig. 3), to deter- textures of gravel-free sediment is from Folk (1968). mine stratigraphic relationships, to measure thickness Dates of various stratigraphic units were deter- and map distribution of deposits that are transected by mined using 14C dating and diagnostic artifacts from the scarp or are a consequence of deformation, and to archeological sites (Mainfort, 1996). In this study, 18 obtain organic material for radiometric dating. We radiocarbon dates were obtained from nine sites. In examined eight backhoe trenches and 87 cores in five addition, 23 previously determined dates from the area transects across the Cronanville and Tiptonville aban- (Russ, 1979; Kelson et al., 1992, 1996) were also doned meanders and the Reelfoot scarp (CT-2, CT-3, used. All dates from this study and prior studies where CT-4, CT-5, T-2); one transect across the Cronanville radiocarbon dates are available in the literature have abandoned meander on the Tiptonville dome (CT-1); been calibrated to calendar years using CALIB 4.1.2 six transects transverse and longitudinal to the Tipton- (Stuiver et al., 1998). ville abandoned meander on the Tiptonville dome (CE- Thirteen of the radiocarbon dates obtained in this 1 to 6, core sites 2–4, 7–14); and several individual study are considered to be reliable based on correct sites in point-bar sand (core sites 5 and 6), natural levee stratigraphic order, concordance with accepted sand (T-4), and abandoned channel fill (core site 1) of regional chronology, and similarity to other dates from the Cronanville abandoned meander (Fig. 3). Seven of the same unit. Five other dates are reported but are not the trenches were 3–4 m deep and approximately 3–4 used in this study because they are interpreted to be m long. One nearly continuous trench (T-2), 3–3.5 m significantly older (reworked) or younger (introduced) deep and 240 m long, extended across a point bar than the enclosing sediment. deformed by the Reelfoot scarp, which is a forelimb on Diagnostic prehistoric artifacts and one radiocar- the fault-propagation fold (i.e., Tiptonville dome) bon date from archeologic sites in the region (Main- uplifted by recent earthquakes. Continuous cores were fort, 1996) provide an age estimate for enclosing obtained with a hydraulically driven 7.6-cm diameter sediment or a minimum age for sediment into which Giddings probe and extended from 3 to 11 m depth. they intrude. Typically, these archeologic sites are Locations for the cores were determined using a Trim- located along oxbow lakes found in abandoned mean- ble Pro XR Global Positioning System (GPS) or by ders (Weinstein, 1981), and the age of the site was surveying nearby features marked on USGS 7.5-min used to infer that the lake was nearby at the time of topographic maps. Altitudes for core transects 2 and 3 occupation. This inference and the radiocarbon dates were obtained from the total station surveys tied into from the lake fill aided in developing the chronology spot altitudes from the USGS 7.5-min maps. Altitudes of oxbow lake fill and constrained dates of uplift for the remaining cores and trenches are estimated from across the abandoned meander. 7.5-min topographic maps. Data were also utilized from the three previously published trenches that cross Reelfoot scarp (T-1 in Russ et al., 1978; T-3 in Kelson 3. Geomorphology et al., 1992; T-2 in Kelson et al., 1996; this study) and six additional borehole descriptions (CE-1 through 6, The study area is within the Holocene meander belt U.S. Army Corps of Engineers, 1978, 1993). of the Mississippi River. Alluvial landforms within this Cores and trenches were described according to the belt are the basis of the initial geomorphic interpreta- U.S. Department of Agriculture Field book for tion. Stratigraphy beneath the landforms presented in 318 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 3. Location map showing former Mississippi River channel positions, cores, and backhoe trench locations. C designates core sites from this study; CE designates unpublished U.S. Army Corps of Engineers (1978, 1993) borehole descriptions; cores from this study were also acquired at CE-5 and CE-6, and CT designates core transects with variable numbers of cores. T designates backhoe trench locations: T-1 is from Russ et al. (1978); T-2 is from this study, Mueller et al. (1999), and Kelson et al. (1996); and T-3 is from Kelson et al. (1992). Backhoe trenches were also present at CT-5 and C-3, C-4, and C-6. Square denotes the location of aerial photo (Fig. 6). M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 319

Fig. 4. Digital terrain model of the Lake County uplift region. Data were compiled from digitized 7.5-min USGS quadrangles with 5V contours, sonar profiles oriented normal to thalweg in the Mississippi River (bathymetric profiles spaced 300–400 m apart) and 1-ft contours from soundings (Reelfoot Lake Bathymetry). Data were provided by MapInfo, U.S. Army Corps of Engineers, and Tennessee Fish and Game Commission. Artifacts along river edges reflect lateral migration of meanders (measured in 1999–2000) into surface topography (measured between 1952 and 1971). 320 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 5. Geomorphic map of the Reelfoot Lake area showing scroll bars associated with the Lake Isom, Cronanville, and Tiptonville abandoned meanders, the modern Mississippi River channel belt with present and former channel positions, Reelfoot scarp, and Reelfoot Lake. Tiptonville dome extends between Reelfoot scarp and the modern Mississippi River channel belt. The mapped area is covered on the digital terrain model (Fig. 4). M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 321 the subsequent section supports and refines these ville meander) that is difficult to map in detail because geomorphic interpretations. Landforms include the it is largely infilled; and a younger, more obvious neck present and abandoned channels of the Mississippi cutoff (Tiptonville meander) (Figs. 4 and 5). Scroll River, scroll bars indicating Mississippi River migra- marks north and east of Tiptonville indicate that a tion, natural levees, and crevasse channels and splays moderately sinuous channel migrated from west to (Figs. 4 and 5). These fluvial landforms are deformed east across the position of Reelfoot scarp, eroding any by active folds that include Tiptonville dome and earlier relief produced by active folding, to the posi- Ridgely ridge (Fig. 1). Erosion by the Mississippi tion of the Cronanville abandoned meander. Based on River along the west portion of the Tiptonville dome aerial photographs and topographic maps, the Cronan- has reduced the surface form of the fold to approx- ville abandoned meander has been mapped as many as imately half of its original west-to-east width. The three small channels NW of Reelfoot Lake by various dome is separated from the adjacent Reelfoot Lake researchers (Fisk, 1944; Saucier, 1994; Kelson et al., basin by the Reelfoot scarp (Russ, 1982), the fold limb 1991), indicating that the Mississippi River may have that defines the eastern edge of the Tiptonville dome split the flow through several channels separated by a (Fig. 2) (Russ, 1982; Purser and Van Arsdale, 1998). sandy towhead (in-channel sand bar or island). These Also present, but not well-defined topographically, are researchers also interpreted the relative age of the the Cottonwood Grove and Ridgely strike–slip fault Cronanville meander arms differently. Based on strat- zones (Fig. 3) (Van Arsdale et al., 1998a). igraphy from land-based cores (CT-1, CT-2, CT-3, and CT-4, discussed in the Stratigraphy), we interpret that 3.1. Meander chronology the Cronanville meander was a full-sized Mississippi River channel with a central sand bar and that the Four generations of Mississippi River channel channel was probably abandoned by a chute cutoff. positions are present along the Reelfoot scarp: the Only a small swale remains at the surface after most Lake Isom abandoned meander, the Cronanville aban- of the cutoff channel was filled. Thus, previous doned meander, Tiptonville abandoned meander, and investigators (Fisk, 1944; Saucier, 1994; Kelson et the present Mississippi River channel belt. The rela- al., 1991) show an abandoned channel that is narrower tive age of the three positions (Isom, Cronanville/ than the present Mississippi River. In addition, the Tiptonville, and present channel belt, Fig. 5) was orientation of the abandoned Cronanville channel and determined by cross-cutting relationships from aerial the associated scroll bars and truncation of this chan- photographs, but the junction of the Cronanville and nel by the Tiptonville abandoned channel beneath Tiptonville abandoned meanders occurs beneath Reel- Reelfoot Lake (Fig. 5) (Carlson, 2000) indicate that foot Lake and was therefore determined with bathy- this Cronanville abandoned channel position was a metric, geophysical, and subsurface data (Carlson, slightly earlier phase of the Tiptonville abandoned 2000; this study). The oldest preserved channel is channel. The Reelfoot scarp crosscuts the Cronanville the Lake Isom abandoned channel at the south margin abandoned channel. of the Reelfoot scarp and Reelfoot Lake (Figs. 4 and Subsequently, the northern meander limb was aban- 5) (Fisk, 1944; Saucier, 1994; Kelson et al., 1991). doned, leaving the Cronanville chute cutoff and a series Arcuate scroll bars south of Tiptonville indicate that of scroll bars NE of Tiptonville (Figs. 5 and 6). Because this channel migrated east >7 km, leaving a well- the southern, downstream meander arm was relatively defined, abandoned, now largely infilled channel. The stationary, the Tiptonville meander became more sin- northern portion of the Lake Isom abandoned meander uous forming a 9–13-km long, 1.2-km wide loop. and associated scroll bars have been truncated by the Ultimately, a neck cutoff west of Tiptonville, TN, Tiptonville meander. The Cottonwood and Ridgely formed the present Mississippi channel position (Figs. fault zones obliquely cross the abandoned Lake Isom 4 and 5) and caused the Tiptonville meander to be meander (Fig. 3). Subsurface information is not avail- abandoned, probably a few years after the cutoff able for this meander. (Gagliano and Howard, 1984). The exact location of The second channel position is marked by two the cutoff is unknown because of subsequent Missis- abandoned channels: an older chute cutoff (Cronan- sippi River migration across a modern 4–6-km wide 322 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 323 path that forms the present channel belt. The Reelfoot The eastern portion of the abandoned meander scarp crosscuts the Tiptonville meander, approximately arms and the oxbow lake/swamp were depressed perpendicular to the meander axis. forming the Reelfoot basin (Figs. 4 and 5). The small The present Mississippi channel belt is the third oxbow lake, located east of the scarp (Carlson, 2000), channel position folded by the Reelfoot scarp (Figs. 4 was enlarged to form the present Reelfoot Lake. and 5). At the northern margin of the study area, the Although the Mississippi River is quite large and channel forms a very long (15 km), sinuous Kentucky capable of significant erosion and deposition in its bend with a 1.3-km wide neck. Along the western alluvial valley, it is still responding to uplift of the margin of the study area, the channel is relatively Tiptonville dome and subsidence of the Reelfoot Lake. straight. This straight section of the channel formed First, the channel has not completely scoured the Lake the Tiptonville cutoff. The northern portion of the County uplift, nearly 190 years since the coseismic Reelfoot scarp crosses the present Mississippi River deformation in 1812. Compared to upstream and channel belt and deforms point-bar sand associated downstream of the uplift, the channel depth is reduced with the present meander (Van Arsdale et al., 1995a). (Fig. 4) and the channel bottom (though not the water Within the channel, the scarp has been eroded by the surface) has a negative gradient across the uplift (Table Mississippi River (Fig. 4) (Fischer and Schumm, 1) (Fischer and Schumm, 1993, 1995). Because the 1995; Johnston and Schweig, 1996). channel has not completed downcutting, the channel width is greater than both upstream and downstream of 3.2. Deformation the Lake County uplift to maintain the channel con- veyance over this shallower section of the river. As a result of deformation, the western portion of Second, the channel has not aggraded or completely the Cronanville and Tiptonville abandoned meander infilled Reelfoot basin upstream of the Lake County fill and small batture channels within the abandoned uplift. Across the Reelfoot basin, the Mississippi River meanders were uplifted to form the Tiptonville dome channel depth is greater and channel width is less than (Figs. 4 and 5). Uplift of the swale that marks the that of the downstream of the uplift (Table 1). This abandoned Cronanville meander causes it to slope increase in depth has been accomplished by the rela- both east and west away from the center of uplift. tive depression of the channel at the time of deforma- Along the Tiptonville meander arms, the gradient was tion as well as subsequent crevasse-splay deposition to also modified, and flow of water and sediment raise the banks (Figs. 4 and 6). Although individual through small batture channels from the Mississippi cross-sections of the channel are within the range of River into the oxbow lake became restricted or the channel cross-section dimensions upstream and nonexistant, probably because the flow was inad- downstream of the basin and associated uplift, the equate to incise the channels. Either prior to or as a consistent trend of the channel dimensions across the result of deformation, the batture channel in the uplift and basin is unique in the northern alluvial valley northern arm has infilled. Although it lacks morpho- (Fischer and Schumm, 1995). logical expression, the fill is preserved in the subsur- Channel gradient and sinuosity are more ambigu- face (CE-1; Fig. 3) and will be discussed in the ous in their response to uplift than the channel Stratigraphy section. In the southern meander arm, dimensions. As expected, the valley gradient is low the batture channel is present, although mostly filled, upstream of the uplift, high across the uplift, and and is also deranged by the uplift (cores 10 and 14; intermediate downstream of the uplift (Table 1) (Bur- Fig. 3). nett and Schumm, 1983). Modifications of sinuosity

Fig. 6. Aerial photograph (March 3, 1963) of well-developed crevasse-splay deposits into the Reelfoot basin east of Reelfoot scarp, contrasted with less extensive crevasse-splay deposits on the Tiptonville dome west of Reelfoot scarp. The overbank deposit on the dome becomes thinner with increasing distance from the Mississippi River and the abandoned Cronanville meander. Point-bar morphology becomes more obvious to the southwest where the overbank deposit is thinner. The abandoned meander is cut by the Reelfoot scarp (arrows at north and south edges of the scarp). Location of cores, core transects, and trenches identified in Fig. 3 are shown. 324 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Table 1 Geomorphic response of the Mississippi River to the Lake County uplift (margins of Lake County uplift in river miles from Russ, 1982, Fig. 4A) Response Upstream of Lake County uplift Lake County uplift Downstream of Lake County uplift (river miles 902–920) (river miles 858–902) (river miles 790–858) Deptha deep with high variability shallow with low variability intermediate with high variability (8.8–16.5 m depth) (7.9–13.4 m depth) (6.6–15.2 m depth) Widtha low with low variability high with high variability intermediate and high variability (0.8–1.9 km wide) (1.0–3.1 km) (0.8–2.7 km) Width/depth ratioa low with low variability high with high variability intermediate with high variability (50–190) (85–380) (60–365) Valley gradientb low (0.852 Â 10 À 4) high (2.15 Â 10 À 4) intermediate (1.55 Â 10 À 4) Channel gradient low (0.546 Â 10 À 4)c high (0.804 Â 10 À 4) high (0.876 Â 10 À 4) (water surface)b Channel gradient neutral to slightly negative negative ( À 1.4 to 0.3 ft/mile) negative to positive (thalweg)a ( À 0.5 to 0 ft/mile) ( À 0.7 to 2.0 ft/mile) Sinuosityb less sinuous (1.55) more sinuous (2.91) less sinuous (1.66) a Low and high values determined from graph plotting 1880, 1903, and 1994 data (Fischer and Schumm, 1993, Figs. 12–14 and 16). b This study, using 1982–1983 photorevised topographic maps. c Includes river miles 909–892, which extend upstream of the uplift and across part of the uplift because this river segment has a gradient very similar to that upstream of the Lake County uplift.

in response to surface deformation of the valley cent point bar as an overbank deposit. The overbank gradient have changed the channel gradient. As with sediment generally thins with increasing distance the valley gradient, the channel gradient is low from the abandoned Cronanville meander and is upstream of the uplift. Here, the valley slope is so generally absent across the Tiptonville meander. Prior low that it would require a nearly straight channel to to artificial levee construction, sand and silt crevasse- attain a channel gradient similar to that upstream and splay deposits from the present Mississippi River downstream of the uplift and basin. In contrast to the accumulated in the Reelfoot basin, and a more high valley gradient across the uplift, the increase in limited splay deposit accumulated on the Tiptonville sinuosity along this segment reduces the channel dome. gradient to that downstream of the uplift. Although the variations in sinuosity across the uplift are as 4.1. Point-bar sand expected, they are not unique to the uplift and are within the sinuosity range of the lower Mississippi As the Mississippi River channel migrates across River (Fischer and Schumm, 1993). an area, it deposits sand along its channel margin as a series of point bars leaving a scroll-bar topography (Figs. 5 and 6) (e.g., Saucier, 1994). Within the 4. Stratigraphy meander belt, this sand may be associated with a variety of meanders (Figs. 4 and 5) (Russ, 1979; Stratigraphic units present in the area are Holo- Kelson et al., 1992; 1996). At a depth of 1.2 to 5.7 cene deposits of the Mississippi River within its m, the lower point-bar sediment of all the meanders is meander belt. Much of the Tiptonville dome is un- a brown to olive brown (10YR-2.5Y 4/3), medium- to derlain by point-bar sand. Sand and silt have infilled fine-grained bedded sand. In the upper point bar, the most of the abandoned Cronanville meander. Silt and silt abundance increases to a silty sand and the sand clay have infilled the abandoned Tiptonville channel size decreases to fine and very fine sand. Bedding is and are presently accumulating in Reelfoot Lake. A 0.1–0.3 m thick in the upper point bar, generally clayey silt fills the margins of the Cronanville aban- thinner than that in the lower point bar. The upper doned meander channel and extends across the adja- surface of the point bar is undulatory with a relief of M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 325 ca. 0.5–1.0 m. Although bioturbation is present, stream along the CT-3 (Fig. 9), up to 6 m of aban- buried soils were not observed in the upper point bar. doned channel fill is also present, but more clay is deposited at the base of the fill relative to CT-1. 4.2. Abandoned channel fill Most important for this study is the distribution of the channel fill with respect to the scarp. Along CT-1, The Tiptonville meander has had two cutoff events. the channel fill is present at the crest of the uplift; The first event, a 1-km wide channel chute cutoff along CT-2, the channel fill is at the base of the (Cronanville abandoned meander, Figs. 5 and 6) is Reelfoot scarp; and along CT-3, the fill is present located along the northern section of the meander. This across the scarp. Deep acoustic penetration in sonar chute cutoff is filled with more than 7 m of fine- reflection surveys (Carlson, 2000) suggests that the grained sediment (Fig. 7). The initial fill is 5.2+ m, same silt/clay abandoned channel fill is also present dark bluish gray (5PB 3-4/1) to olive brown (2.5Y 5/2- beneath Reelfoot Lake. Folding of abandoned channel 3), laminated and cross-bedded silt along the deeper fill that grades to overbank silty clay and the uniform part of the channel. A bedded fine sand forms a bar in thickness of stratigraphic units across the scarp and the center of the channel and grades to the upper point into the basin demonstrate that the channel fill accu- bar along the channel margins. Subsequent flow mulated prior to deformation. through the channel was more episodic and includes The second cutoff of the Tiptonville meander was a two additional periods of filling. The second fill neck cutoff (Figs. 4 and 5). Sediment that filled the episode is clay, which includes thin lenses of silt. 1.2-km wide abandoned meander accumulated in The clay is 2–3 m thick along both the cutbank and three subenvironments: the cutoff bar, the batture the point-bar channel margins, and thins to 0.3 m in the channel, and the oxbow lake (based on the model of channel axis. The third fill episode is more sandy along Gagliano and Howard, 1984). The cutoff bar probably the ca. 450-m wide channel axis (less than half the formed rapidly after the meander neck was breached, width of the original channel). This sandy fill is similar to historic Mississippi River cutoff bars that bedded dark grayish brown to brown (10YR 4/2-3) form within a few decades (Gagliano and Howard, sand and silt that includes some brown to dark grayish 1984) and consistent with the radiocarbon ages of the brown (10YR 4-5/2-3) clay lenses V 0.3 m thick. bar and point-bar deposits of the Tiptonville meander Laterally, the fill becomes clayey so that along the (discussed in the Chronology). Based on the width of channel margins, the upper clay overlies the earlier the cutoff Mississippi channel less the width of the clay fill. At many locations, a weakly developed batture channel, the wedge-shaped cutoff bar is at buried soil separates the two clay units. The upper least 1.0 km long (Fig. 10A). Based on the depth of clay extends beyond the channel as an overbank the batture channel, the bar is at least 12 m thick (Fig. deposit that is approximately 2.5 m thick along the 10A) (Shepherd, 2001). Perpendicular to the aban- southern point-bar channel margin and < 1 m thick doned Mississippi channel, the bar surface slopes along the northern cutbank channel margin (CT-1 and from the land surface to 4.4 m below the ground -2, T-2; Figs. 7 and 8). After eliminating the structural surface adjacent to the batture channel (Fig. 10A). deformation, there is < 1.5 m of relief remaining Parallel to the abandoned Mississippi channel, the bar across the paleochannel and this decreases to 0 m surface slopes toward the apex of the meander. The downstream. bar is shorter and the slope is steeper, however, in the Similar to the fill in the northern part of the upstream meander arm (Fig. 10B) than in the down- meander, the upper channel fill is also present further stream arm (Fig. 10C). The cutoff bar is composed of downstream. Along CT-2 (Fig. 8), a 2.5-m thick brown (10YR 5/4) fine-grained sand grading up to massive overbank silty clay grades laterally into interbedded brown fine sand and silty sand (U.S. bedded sandy silt, silty sand, and clayey silt that fills Army Corps of Engineers, 1993). This upper bar the abandoned channel axis. Compared to CT-1, more becomes thicker (3 m thick) and finer grained, includ- clay is present within the upper abandoned channel fill ing beds of clay, adjacent to the batture channel (U.S. of CT-2; and the clay thickness does not increase Army Corps of Engineers, 1993). More than 2 km along the channel margin of CT-2. Further down- from the cutoff, the upper bar is gray (2.5Y 5/1) silty 326 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 7. Cross-section of core transect 1 projected to a north–south line across the Cronanville abandoned meander. Transect is along the crest of the Tiptonville dome. Present topography is due to deformation and does not reflect the depositional topography. Intersection of extended core transect 2 (east–west) is shown. Trench excavated by Russ et al. (1978) is projected onto this cross-section based on its location within the abandoned channel and trench log (Fig. 3). Bedded silt and massive clay fill most of the abandoned channel. Overbank clayey silt overlies upper point bar or lower channel fill of the Cronanville meander. Interpretation shows lateral gradation of the overbank clayey silt into the upper sandy silt channel fill of the Cronanville abandoned meander. In an alternative interpretation, the upper channel fill is crevasse-splay sediment and is younger than, rather than equivalent to, the upper portion of the overbank clayey silt. A sandy crevasse-splay deposit derived from the present Mississippi River channel is present along the northern margin of the transect. Numbers above vertical lines designate cores in this transect. ..Gcin ta./Goopooy4 20)313–349 (2002) 43 Geomorphology / al. et Guccione M.J.

Fig. 8. Cross-section of core transect 2 across the Cronanville abandoned meander. Transect extends from the Tiptonville dome across the Reelfoot scarp into the Reelfoot basin. Present topography is due to deformation and does not reflect depositional topography (Figs. 4 and 5). A massive clayey silt overbank deposit overlies point bar or lower channel-fill silty sand of the Cronanville meander. Laterally, the overbank deposit grades into the upper bedded sandy silt and clayey silt channel fill of the Cronanville abandoned meander. A crevasse-splay deposit probably onlaps the overbank deposit at the base of Reelfoot scarp, but it is difficult to distinguish the crevasse-splay deposit from the channel-fill deposit in cores. Bedding in the crevasse-splay/channel-fill sediment is probably more complex than the one shown in the cross-section. Numbers above vertical lines designate cores in this transect. 327 328 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 9. Cross-section of core transect 3 across part of the Cronanville abandoned meander. Transect extends from the Tiptonville dome across the Reelfoot scarp into the Reelfoot basin. Present topography is due to deformation and does not represent depositional topography (Figs. 4 and 5). Channel fill of the Cronanville abandoned meander is bedded silt and clayey silt that laterally grades to upper point-bar silty sand at the channel margin. An overbank clayey silt overlies the Cronanville meander point-bar sand and the abandoned channel fill. Clay has probably been locally eroded along the scarp (core 2). Numbers above vertical lines designate cores in this transect. M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 329

Fig. 10. Cross-sections of abandoned Tiptonville channel. (A) Cross-section of CE-1 to CE-4 (Fig. 3) of neck cutoff with cutoff bar on central and north portion of transect and batture channel along the south margin of transect. Boring descriptions were from the U.S. Army Corps of Engineers (1993). Depth of channel is unknown but estimated based on the present Mississippi River depth (Memphis District Engineer, U.S. Army Corps of Engineers, 1990). Location of point-bar sand on both channel margins was based on the interpretation of surface morphology using topographic maps and aerial photographs. (B) Longitudinal cross-section of neck cutoff along the upstream meander arm. (C) Longitudinal cross-section of neck cutoff along the downstream meander arm. (D) Longitudinal cross-section of batture channel in downstream meander arm. Dashed line separates bedded channel-fill silt below from massive channel-fill silt above. Only dates interpreted to be reasonable are plotted. Present topography is due to deformation and does not represent depositional topography. Numbers above vertical lines designate boring or cores along these transects (Fig. 3). sand with interbedded organic matter that has been 4/1) clay, silty clay, and clayey silt fills the oxbow dated (cores 4 and 13; Fig. 10B and C). lake and buries the cutoff bar (Fig. 10). The deposit is As a cutoff sand bar aggrades to the river surface, thin (0–4.4 m thick) adjacent to the cutoff and flow into the meander bend becomes restricted, and becomes thicker toward the meander apex. The lower the abandoned river channel evolves to a lacustrine fill is bedded and the upper portion of the deposit is environment (Gagliano and Howard, 1984). Within massive with common root pores, implying that plant the abandoned Tiptonville meander, dark gray (2.5Y growth was initiated as the lake became shallower. 330 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 10 (continued).

In the upstream meander arm, a sandy silt facies of based on relatively low penetration of low-frequency the channel fill overlies the clayey facies (Fig. 10B). (28 kHz) acoustic pulses into sublacustrine sediment This silt thickens and includes slightly more abundant compared to that of the central and downstream and coarser sand toward the meander apex. The unit meander arm channel fill (Carlson, 2000). This has been interpreted to extend into Reelfoot Lake increase in grain size in the upper fill of the northern M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 331

Fig. 10 (continued). meander arm and its absence in the southern meander Historic data supports the location of the lake. Doh- arm may be due to progradation of a lacustrine delta erty land grants of 1785 extend into the present where the batture channel terminates at the edge of the Reelfoot Lake but not into the inferred preexisting cutoff bar, consistent with the 1984 model of Gagliano oxbow lake (Stahle et al., 1992). A core from the and Howard. Alternatively, the upward increase in drowned oxbow lake penetrated 4–5 m of massive silt sand may be caused by a change in the source below the interpreted 1811–1812 ground surface direction from the west through the batture channel (Rosenbaum et al., 1996). Rosenbaum et al. inter- to a source outside of and NE of the abandoned preted the magnetic properties (preservation of mag- channel. An NE source could be from the flooding netite in water >3 m deep and destruction of magnetite of the Mississippi River into Reelfoot basin. If the in water < 2 m deep) of this pre-1812 silt to indicate later interpretation is correct, it suggests that this an intermediate water depth that was less than that of portion of the lacustrine fill accumulated after the the present lake. uplift of the Tiptonville dome and depression of The third environment in the abandoned meander, Reelfoot basin. a batture channel, is a conduit for water and sediment Apparently, the apex of the abandoned meander from the river into the oxbow lake (Gagliano and has not completely filled. The oxbow lake is drowned Howard, 1984). As the lake fills with sediment, the within the larger Reelfoot Lake but can be recon- channel becomes less active and also infills. The structed using lake bathymetry and distribution of batture channel is no longer a topographic feature in submerged tree stumps (Fig. 5) (Carlson, 2000). the upstream cutoff channel of the Tiptonville mean- 332 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 10 (continued).

der, but can be identified with subsurface information In summary, evidence from each of the subenviron- (core 1; Fig. 10A). Along the downstream abandoned ments indicates that the Tiptonville meander neck channel arm of the Tiptonville meander, the batture cutoff occurred prior to uplift but that the filling of channel persists as a topographic swale, but flow has the abandoned channel was not complete at the time become deranged due to tectonic uplift (Fig. 3). Based of initial deformation in A.D. 900. Oxbow lake fill on topographic expression and subsurface informa- and batture channels are present along the dome and tion, the batture channels in both the upstream and in the basin (Carlson, 2000) and must predate sig- downstream Tiptonville meander arms are a maxi- nificant formation of the Tiptonville dome. A remnant mum 0.1–0.2 km wide and 10–12 m deep. These of the oxbow lake within Reelfoot Lake, disruption channels have filled with thin bedded very fine sand and rapid infilling of batture channels, and coarsening and laminated dark gray (5Y 4/1) clay and silty clay of oxbow lake fill within the basin all indicate or that includes thin beds of fine organic debris. Similar suggest that filling was not complete prior to defor- to the lacustrine fill, the upper meter of the unit is mation and that deformation has impacted deposition massive because of bioturbation by plant roots. of the channel fill. In addition, lacustrine sediment M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 333 deposition within Reelfoot Lake now occurs both graphic feature between ca. 400 B.C. and A.D. 1470 within and beyond the abandoned channel. (see the Chronology section). During this period, the area could be flooded and overbank sediment accu- 4.3. Overbank mulated. Significant deformation of the Tiptonville dome postdates deposition of the overbank sediment, Three overbank deposits that overlie silty sand in agreement with the conclusions by Kelson et al. point-bar sediment are present in the study area. The (1992, 1996). most extensive overbank unit is associated with the A second overbank deposit, probably derived from Cronanville meander fill in the northern portion of the the Tiptonville meander when it was an active chan- study area, and a much more limited deposit is nel, is present in the southern portion of the study associated with the Tiptonville meander bend in the area. The small batture channels and the lake that southern portion of the study area. Finally, crevasse- occupied the abandoned Tiptonville meander appear splay deposits are present along the present cutbank of to have been large enough to contain most of the flood the Mississippi River in the northern study area. water during the past 2.3 ka so that little deposition of The more extensive overbank deposit laterally overbank sediment occurred on the adjacent flood grades into fill of the Cronanville abandoned channel plain. Only local lenses of mud with fine sand up to (Figs. 7 and 8). It is a massive, grayish brown to gray 1 m thick overlie the point-bar deposit of the Tipton- (10YR 3/2 to 5Y 5/1) clayey silt to silty clay. Adjacent ville abandoned channel (Fig. 11). The relatively to the inside bend of the Cronanville abandoned coarse texture of this overbank deposit suggests that channel and 1.3 km from the present Mississippi the source was nearby. Assuming that the lenses of River, the overbank deposit is 2.5 m thick. In contrast, mud are equivalent, the presence of this overbank unit the overbank deposit is thinner ( < 1 m) along the across the upper scarp suggests that the scarp was not cutbank of the abandoned channel that is only 0.2 km a substantial feature when the unit was deposited. from the Mississippi River, and the deposit is absent The third overbank deposit present within the study within the Tiptonville meander loop, 7.2 km from the area is crevasse-splay sediment associated with the Mississippi River (Fig. 11). This distribution of the current Mississippi River channel. Geomorphic fea- overbank deposit is similar to the geomorphic obser- tures typical of crevasse splays, such as bifurcating vations of less obvious scroll bars near the Mississippi swales oriented perpendicular to the present Missis- River and along the Cronanville abandoned meander sippi River, are present within 1 km of the Mississippi (Fig. 6), where they have been buried by the overbank River (Figs. 4 and 6). They are present across both the silt (Figs. 7–9) as opposed to more obvious swale Tiptonville dome and Reelfoot basin, but on aerial bars at a greater distance from these locations. Thus, photographs, they appear to be more laterally exten- we interpret the source of the overbank clay in the sive in the basin. On the dome, this splay landform is northern study area to be flooding from the Missis- underlain by up to 1.1 m of an interbedded, grayish sippi River through the swale of the abandoned brown to brown (10Y 4-5/2-3), medium sand to sandy Cronanville meander, with the flood water probably silt (north end of CT-1; Fig. 7), and may also fill the entering the abandoned channel where it intersects the remaining swale of the Cronanville abandoned mean- present path of the Mississippi River. The axis of the der. In the basin, Kelson et al. (1996) reported fluvial abandoned channel was deep enough that bedded silty sand and overlying silty clay overbank deposits sandy silt and silty sand accumulated, but adjacent that pinch out at the edge of the scarp in T-2, 2.5 km to the channel massive silty clay accumulated on from the present Mississippi River channel. They relatively higher topographic areas. identified these beds as a channel deposit, but they Perpendicular to the Reelfoot scarp, the thickness may be a crevasse-splay deposit. The upper portion of of overbank and laterally equivalent channel-fill the deposit at the base of the scarp along CT-2 (1.8 km deposits is nearly uniform, except where the unit(s) from the Mississippi River channel), which is identi- has been removed by erosion across the scarp (Figs. 8 fied as channel fill, may also be a crevasse-splay and 9) (Kelson et al., 1992, 1996). This suggests that, deposit (Fig. 8). This distribution of crevasse land- if the scarp was present, it was only a minor topo- forms and deposits suggests that initial crevasse 334 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 11. Cross-section of core transect 5 across the point bar of the Tiptonville abandoned meander (Fig. 3). Transect extends from the Tiptonville dome across the upper part of the Reelfoot scarp. Present topography is due to deformation and does not represent depositional topography (Figs. 4 and 5). Reelfoot Lake covers the lower part of the Reelfoot scarp east of the transect. A thin mud overbank deposit locally overlies point-bar sand of the Tiptonville abandoned meander. Numbers above vertical lines designate cores in this transect.

deposition may predate significant uplift of the dome origin, the detritus may not be substantially older than and, at least, the upper portion of the deposit postdates the deposit because the delicate nature of the material formation of the basin by uplift of Reelfoot scarp. precludes long-distance or long-term transport. How- ever, sampling of thin lenses may include small grains of lignite included in the surrounding sediment and 5. Chronology therefore produce erroneously old ages. In contrast, minimum ages of wood are commonly interpreted as 5.1. Depositional events intrusive roots. All available dates from the study area and data available in the literature concerning the date Radiocarbon dating fluvial deposits is difficult are presented so that the reader can assess the reli- unless an in situ organic material such as a peat is ability of the dates and interpretations (Table 2). Dates available. Maximum ages may result from dating that are in inverted stratigraphic order or that are detrital organic matter older than the enclosing sedi- interpreted to be unreasonable based on well-known ment. In the Mississippi River valley, radiocarbon regional geology have been noted as such. Limitations dating has been particularly difficult because this of reasonable dates, such as maximum or minimum contamination includes both Quaternary wood and ages, are also noted (Table 2). Only those dates charcoal and Tertiary lignite. Although lenses of fine deemed to be reasonable by the authors have been organic debris such as leaves may also be detrital in used for the interpretations presented in the paper. M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 335

The oldest dated landform/deposit examined in of the remaining swale as water flowed through the this study, based on cross-cutting relationships, is channel at the same time overbank clay accumulated the Cronanville abandoned meander (Fig. 12A). A along and beyond the swale margins in the northern radiocarbon date of 475–200 B.C. on charcoal from a portion of the study area. If this is the case, the point-bar sand at the Proctor City trench (T-2; Fig. 3; sediment was probably deposited prior to the sub- Table 2) (Kelson et al., 1996 ) is statistically the same stantial uplift of the Tiptonville dome. Alternatively, age as two dates of 406–204 B.C. on lenses of fine these silty sands may be crevasse-splay deposits organic debris in the Tiptonville meander cutoff bar derived from the Mississippi River only 1 km to the (cores 4 and 13; Fig. 10B and C; Table 2). These north. If the latter is the case, the sandy channel-fill three maximum radiocarbon dates on two different deposit is correlative to the crevasse-splay adjacent to types of material, collected by two different research- the Mississippi River, and the deposit may have ers, and analyzed at two different labs are statistically accumulated after some uplift of the Tiptonville the same and argue that the dates are probably dome. reasonable. They also suggest rapid migration of the In contrast, filling of the abandoned Tiptonville alluvial river, not unreasonable for large alluvial meander occurred more slowly than that of the Cro- rivers (Fisk, 1944; Brice, 1984; Hudson and Kesel, nanville abandoned meander and is still occurring 2000). (Fig. 12B–F). Within the Tiptonville meander, the Utilizing core transect data, the Cronanville aban- southern arm filled faster than the northern arm with doned channel is interpreted as a full-sized Missis- the batture channel beginning to aggrade in the west sippi channel, rather than the smaller channel (based by A.D. 891–1024 (maximum age) (core 10; Fig. on aerial photography) mapped by Fisk (1944), Russ 10D; Table 2). Toward the east, batture channel filling et al. (1978), Saucier (1994) and Kelson et al. (1991). proceeded later with rapid aggradation ca. A.D. 1470 Based on cross-cutting relationships, we interpret that (core 14; Fig. 10D; Table 2). Based on the fill the Cronanville channel had been cutoff prior to the chronology of the batture channel, the oxbow lake Tiptonville meander abandonment (ca. 300 B.C.) and probably was also filling and the shoreline may have was mostly filled by A.D. 1300 (maximum age) (Fig. receded 3 km from the downstream arm cutoff ca. 12B–D). Lower fill of bedded sand and laminated silt 1400 years after the cutoff (A.D. 1026–1248) (core was accumulating in the channel and on the adjacent 10; Figs. 10D and 12C; Table 2) and an additional 2– upper point bar by A.D. 1001–1218 (maximum age) 3 km to the west ca. 1800 years after the cutoff (ca. (Fig. 8; Table 2). By A.D. 1222–1298, flow through 1460–1470) (core 14; Figs. 10D and 12E; Table 2). the channel had ceased and clay was accumulating Fill in the northern arm of the Tiptonville aban- (Figs. 7 and 12D; Table 2). We correlate this clay with doned meander was slower than the southern arm, the clay in Russ’ trench (T-1), suggesting that the probably because the cutoff bar was shorter and the radiocarbon date of the shell by Russ (761 B.C. to lake was deeper than in the southern arm. Within the A.D. 596, Table 2) is probably too old due to a northern arm, only 1.6 m of clay had accumulated 2 reservoir effect. The upper portion of the sandy km from the cutoff ca. 1400 to 1700 years after the channel fill and the lower part of the overlying clayey cutoff (A.D. 1159–1278) (core 4; Figs. 10B and 12C) channel fill correlate with at least part of the silty clay (Table 2). This suggests that the shoreline recession in overbank sediment adjacent to the abandoned chan- the northern arm was at least 1 km less than that of the nel. Fourteen dates (Kelson et al., 1996), of which 10 southern arm during approximately the same length of were judged to be the most reasonable maximum time. Thus, a 4.8- to 6.4-m deep oxbow lake (core 4; dates, suggest that the overbank clay accumulated Fig. 3) was adjacent to the Lindamood archeological between A.D. 777 and 1443 (CT-1 and T-2; Fig. 7; site (core 6; Fig. 3) at the time it was occupied in A.D. Table 2). 780–980 (Table 2). This section of the lake did not Although there are no age dates from the upper become completely filled until at least two centuries sandy channel fill of the Cronanville abandoned after the archeological site was abandoned. meander, we propose two possible interpretations. The final phase of oxbow lake fill is not complete. The sandy fill might have accumulated in the axis Prior to A.D. 1812 and the formation of the present 336

Table 2 313–349 (2002) 43 Geomorphology / al. et Guccione M.J. Radiocarbon dates from abandoned meanders, Tiptonville, Tennessee Lab number Material Trench/core Depth Environment Conventional Calibrated age Interpretation (cm) radiocarbon 2r (B.C./A.D.) of date age (BP) Tiptonville meander point bar NSRL-10167a organic detritus core 9 within 280–316 point bar 56900 F 2100 not applicable Maximum within sediment CT-5 age lignite contamination CAMS-13553b charcoal T-2 150 sandy fluvial 2290 F 60 475–200 B.C.c Maximum to (point bar) reasonable Beta-48553d charcoal T-3 30 upper levee not available A.D. 430–890 Minimum age (point bar) in literature of occupation, associated artifacts suggest A.D. 800–900 NSRL-10330a charcoal Lindamood 31 midden on 1150 F 30 A.D. 780–980c Minimum age, archeological site point bar date of 40LK5e core 6 occupation

Cronanville abandoned meander channel fill W-3950f gastropod shell T-1 not clay channel fill 2000 F 250 761 B.C.–A.D. 596c Probably available contaminated with old carbonate NRSL-11782a charcoal core 3 within 338 clay channel fill 740 F 35 A.D. 1222–1298c Maximum to CURL-5174 CT-1 reasonable NSRL-10115a charcoal core 4 within 432–434 point bar 935 F 50 A.D. 1001–1218c Maximum to CT-2 reasonable

Tiptonville abandoned meander channel fill NRSL-10315a macroflora core 13 246 channel fill 0 F 0 modern Modern root Beta-119881a macroflora core 13 250–270 channel fill 0 F 0 modern Modern plant material NSRL-10162a fine organic core 4 483 channel fill 830 F 35 A.D. 1159–1278c Maximum to detritus reasonable NSRL-10166a fine organic core 13 458–459 cutoff bar 2240 F 20 387–204 B.C.c Maximum to detritus reasonable NSRL-10164a fine organic core 4 722–728 cutoff bar 2310 F 40 406–233 B.C.c Maximum to detritus reasonable NSRL-10317a macroflora core 4 585 cutoff bar 3050 F 110 1522–996 B.C.c Maximum age to slight lignite contamination NSRL-10651a fine organic core 13 449–451 cutoff bar 6700 F 55 5720–5513 B.C.c Maximum age detritus some lignite contamination 313–349 (2002) 43 Geomorphology / al. et Guccione M.J.

Tiptonville meander batture channel fill NSRL-11040a wood core 14 636–664 batture 320 F 40 A.D. 1464–1656c Maximum to channel fill reasonable NSRL-11039a wood core 14 475–495 batture 350 F 40 A.D. 1444–1645c Maximum to channel fill reasonable NSRL-11038a wood core 14 421–428 batture 385 F 40 A.D. 1436–1636c Maximum to channel fill reasonable NSRL-11037a wood in core 14 384–390 batture 475 F 40 A.D. 1403–1477c Maximum to sediment channel fill reasonable NSRL-11034a wood core 10 321–336 batture 890 F 40 A.D. 1026–1248c Maximum to detritus in channel fill reasonable sediment NSRL-11036a wood core 10 414–425 batture 970 F 55 A.D. 981–1210c Maximum to CURL-5173 channel fill reasonable NSRL-11035a wood core 10 604 batture 1070 F 40 A.D. 891–1024c Maximum to channel fill reasonable

Tiptonville meander natural levee NSRL-10120a organic detritus T-4 279–290 natural levee 11,800 F 50 13,238–11,535 B.C.c Maximum within sediment over point bar age lignite contamination (continued on next page) 337 338 ..Gcin ta./Goopooy4 20)313–349 (2002) 43 Geomorphology / al. et Guccione M.J.

Table 2 (continued) Lab number Material Trench/core Depth Environment Conventional Calibrated age Interpretation (cm) radiocarbon 2r (B.C./A.D.) of date age (BP) Mississippi river overbank CAMS-13555b charcoal T-2 80 overbank 1320 F 50 A.D. 642–780c Maximum to replicate of reasonable Beta-72689 CAMS-13534b not available T-2 70 upper 1420 F 60 A.D. 537–690c Maximum to in literature overbank reasonable CAMS-13535b not available T-2 80 upper 1290 F 60 A.D. 644–888c Maximum to in literature in graben overbank reasonable CAMS-13541b charcoal T-2 90 overbank 1240 F 50 A.D. 664–938c Maximum to reasonable CAMS-13537b not available T-2 150 levee 1110 F 60 A.D. 777–1023c Maximum to in literature reasonable CAMS-13558b charcoal T-2 170 overbank 1070 F 70 A.D. 780–1155c Maximum to reasonable CAMS-13538b not available T-2 180 levee (overbank) 990 F 60 A.D. 901–1206c Maximum to in literature in graben reasonable CAMS-13540b not available T-2 160 levee (overbank) 960 F 60 A.D. 981–1217c Maximum to in literature in graben reasonable CAMS-13557b charcoal T-2 30 cm overbank 940 F 60 A.D. 989–1222c Maximum to reasonable CAMS-13536b charcoal T-2 120 overbank 910 F 70 A.D. 996–1275c Maximum to in graben reasonable CAMS-14039b charcoal T-2 90 overbank 690 F 80 A.D. 1211–1413c Maximum to reasonable CAMS-13559b charcoal T-2 20 overbank 660 F 60 A.D. 1262–1410c Maximum to reasonable Beta-72689g charcoal T-2 80 cm overbank 620 F 90 A.D. 1245–1443c Maximum to replicate of reasonable CAMS-13555 Beta-49609d charcoal T-3 100 overbank not available A.D. 1220–1390 Maximum to in literature reasonable

Mississippi River crevasse splay/colluvium Beta-49608d charcoal T-3 30 colluvium not available A.D. 1430–1650 Maximum to in literature reasonable Beta-57026g not available T-2 not crevasse 310 F 60 A.D. 1444–1945c Maximum to in literature available splay reasonable CAMS-13554b not available T-2 50 crevasse 160 F 60 A.D. 1642–1953c Maximum to replicate of in literature splay reasonable Beta-72692 313–349 (2002) 43 Geomorphology / al. et Guccione M.J. Beta-57023g not available T-2 not crevasse 110 F 60 A.D. 1659–1955c Maximum to in literature available splay reasonable Beta-72692g not available T-2 50 crevasse 90 F 50 A.D. 1670–1955c Maximum to replicate of in literature splay reasonable CAMS-13554 CAMS-13635b charcoal T-2 not available crevasse 40 F 70 A.D. 1673–1955c Maximum to splay reasonable Dates in bold are considered reasonable and can be used for the interpretations in this study. a This study. b Kelson et al. (1996), AMS date from Center for Accelerator Mass Spectrometry (CAMS) (Livermore). c Determined using CALIB (rev. 4.1.2) (Stuiver et al., 1998) and may not be the same as calibration date in the literature for previously published dates. d Kelson et al. (1992), date is from Beta Analytic, Miami, FL, unknown whether conventional or AMS. e Tennessee state archeological designation number. f Russ (1979), date is from Meyer Rubin, 1978, personal communication. g Kelson et al. (1996), conventional date from Beta Analytic. 339 340 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 12. Paleogeographic maps of the Reelfoot area showing the formation, migration, cutoff, and filling of various meanders and development of the Reelfoot scarp. M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 341

Reelfoot Lake, a small (estimated to have been < 0.5 imately equal thicknesses after this event (Figs. 8 and km2), permanently inundated oxbow lake probably 9). Second, sand blows probably would be more likely existed and a larger area (estimated to have been when the oxbow lake was present and the water table approximately 3.5 km2) of the abandoned meander was close to the ground surface, two conditions most may have been periodically inundated (Figs. 5 and likely to occur when the Tiptonville dome did not 12F) (Carlson, 2000). Lacustrine sediment is continu- exist or was a very modest topographic feature. ing to fill the last remnant of the abandoned meander. Although no clear evidence exists for substantial surface deformation associated with this earthquake 5.2. Seismic events and surface deformation (Fig. 12C), enough deformation may have occurred to modify the gradient and cause some aggradation in Several authors have reported evidence of seismic the batture channel. Based on aggradation of 2.8 m events in the region that we have not observed in this within the batture channel between A.D. 891 and study. Saucier (1991) described a liquefaction feature 1248 (core 10; Fig. 10D; Table 2), we speculate that 30 km north of the study area that formed prior to A.D. 780–890 may be the more likely interval for A.D. 690. Tuttle et al. (1999b) reported three earth- seismic event X (Fig. 13). quakes large enough to induce liquefaction between A second earthquake event (event Y) has been 4040 B.C. and A.D. 780. Holbrook and Autin (2000) interpreted to have occurred between A.D. 1260 and inferred three earthquakes prior to 2700 YBP based 1650 (Kelson et al., 1996) at Reelfoot Lake. Within on avulsion and channel straightening events. Rose- the region, Schweig and Tuttle (2000) have dated nbaum et al. (1996) suggested possible earthquakes what is likely to be the same event A.D. 1450 F 150. ca. A.D. 1150 and 1350 based on resuspension and Finally, Russ (1979) reported two periods of faulting redeposition of oxidized sediment from shallower with minor displacements exposed in T-1. We spec- water into deeper water of Reelfoot Lake. ulate that the older of these faults could be associated The oldest earthquake event (event X) for which with seismic event Y because it crosscuts silty sand there is definitive evidence in the Reelfoot area that overlies a clay dated A.D. 1222–1298 (core 3 in (Kelson et al., 1996) occurred between A.D. 780 CT-1; Fig. 7; Table 2). Younger silty sand crosscuts and 980 (Kelson et al., 1996; this study). Kelson et this older fault and is in turn crosscut by younger al. have dated the event between A.D. 780 and 1000 faults, which may be related to the 1812 seismic based on dates of liquefied sand and the sediment event. which it crosscuts. This date is consistent with reports We have recognized seismic event Y based on by Saucier (1991) of a possible earthquake between multiple responses to significant uplift of the Tipton- A.D. 260 and 1240 north of Reelfoot Lake, and by ville dome and depression of Reelfoot basin (Fig. Tuttle et al. (1998, 1999b) of a seismic event in the 12E). The first probable response to uplift is rapid region A.D. 900 F 100 years. Our research confirms aggradation, 2.5 m of fill accumulated between ca. this date for seismic event X and can constrain it to a A.D. 1470 and 1480 (core 14; Fig. 10D; Table 2;) in slightly narrower range than Kelson et al.’s. This the batture channel that crosses the Tiptonville dome. seismic event was large enough to liquefy sand and This aggradation is interpreted to have shortly post- occurred sometime prior to the occupation of the dated drainage disruption when the gradient of the Lindamood archeological site on what is now the batture channel was significantly reduced or reversed Tiptonville dome (A.D. 820–980; Fig. 5, dated 900; due to deformation and is the best estimate for event Table 2) because prehistoric humans disturbed the Y. The extension of this batture channel into Reelfoot sand blow. Thus, the seismic event must be older than Lake had also filled prior to 1812 (Carlson, 2000). A A.D. 980, and reduces the interval slightly from A.D. second response to uplift was the ceassation of over- 780 to 980 (Fig. 13). Our data suggest that little bank deposition across the uplifted Tiptonville dome, surface deformation occurred prior to and associated except perhaps along a narrow area adjacent to the with this A.D. 780–980 seismic event. First, over- present Mississippi River (Fig. 7). The youngest date bank sediment and channel-fill sediment accumulated of this overbank deposit is A.D. 1262–1410 (Table 2), on what are now the dome and the basin in approx- a maximum age for seismic event Y. 342 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Fig. 13. Dated depositional and seismic events in the Reelfoot area. Horizontal bars are the duration of the event in 2r calibrated radiocarbon years. Location and type of event are listed. Boxes with fill are the possible ranges of the prehistoric earthquake events. The vertical solid line is the historic 1812 seismic event.

In contrast to the limited deposition over most of and it most likely occurred about A.D. 1470, at the the dome, deposition increased within the adjacent time the batture channel rapidly aggraded (Fig. 13). Reelfoot basin after deformation. The Mississippi Deformation at the southern margin of the scarp River began crevassing across the lowered riverbank apparently was not adequate to dam Reelfoot Creek east of the scarp into the depressed basin (Figs. 4 and during seismic event Y because there is no evidence 6). Splay deposits in the basin onlap older deformed that a lake larger than the relatively small oxbow lake overbank and channel-fill sediment along the scarp was present in Reelfoot basin prior to 1812 (Figs. 5 (CT-2 and T-2; Fig. 8) (Kelson et al., 1996; Mueller et and 12F) (Smith et al., 1795; Usher, 1837; Lyell, al., 1999). The oldest splay deposit is dated A.D. 1849; McGee, 1892; Fuller, 1912; Stahle et al., 1992; 1440–1945 (Table 2) (Kelson et al., 1996). With Carlson, 2000). This oxbow lake had intermediate increasing distance from the Mississippi River, the water depths (2–3 m) prior to drowning in 1812 splay deposit thins and only colluvium accumulates at (Rosenbaum et al., 1996). the base of the scarp (T-3; Fig. 3) (Kelson et al., In addition to this study, and that of Russ (1979) 1992). This unit which has been dated A.D. 1430– and Kelson et al. (1996), Merritts and Hesterberg 1650 (Table 2) also provides a minimum age for the (1994) also reported surface deformation prior to seismic event Y (Kelson et al., 1996), consistent with 1812. Longitudinal profiles of low-order streams the aggradation of the batture channel. We suggest draining the Tiptonville dome and Ridgeley ridge that event Y occurred between A.D. 1260 and 1480, support several meters of uplift during the late Hol- M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 343 ocene, and Merritts and Hesterberg speculated that 200 B.C. Although difficult to prove, this high sinu- this amount of deformation probably occurred during osity may have been a response to an earlier uplift more than one earthquake cycle. Although Carlson (Holbrook and Autin, 2000), similar to the sinuosity (2000) concluded that the minimal amount of late of the present Kentucky bend, which is considered to Holocene structural deformation is 7–11 m, consid- be a response to the present uplift. erably greater than that recognized by Merritts and Following cutoff of the Tiptonville meander, little Hesterberg, we would agree that this deformation evidence of sedimentation is found across what is now occurred during at least two events, X (ca. 1260– the Tiptonville dome prior to ca. A.D. 780, nearly 1.1 1480) and Z (1812). ka after cutoff of the Tiptonville meander: channel fill The third earthquake event (event Z) occurred in is minimal in the Tiptonville abandoned meander and 1812 (Fig. 13). Russ (1979) suggested that the defor- overbank sedimentation is not found. A 4–5-m deep mation at the north margin of the scarp was not oxbow lake apparently persisted less than 2 km from substantial because little colluvium accumulated at the cutoff of the northern meander arm more than the base of the slope. Additional support for less 1300 years after the meander cutoff (core 4; Fig. 10B; deformation along the northern portion of the scarp Table 2). This low deposition rate across the present is the relatively low-relief scarp (at least 2.2 m high) Tiptonville dome may have resulted from the presence that deforms a point-bar deposit within the Kentucky of a more distal Mississippi River channel along the bend north of the study area (Van Arsdale et al., western and northern margins of the present channel 1995a). Although this scarp has not been dated, it belt, reduced frequency or depth of flooding com- deforms point bars within a modern meander bend of pared to post-A.D. 780, and/or uplift of the Tipton- the Mississippi River and is probably young. In ville dome enough that inundation of the flood plain contrast, deformation of the southern scarp seems to was infrequent and little sediment accumulated. We have been greater than that to the north and was prefer the more distant channel position hypothesis sufficient to dam Reelfoot Creek, inundating Reelfoot because subsequent sedimentation has occurred across basin and enlarging the oxbow lake to form the what is now the dome, the oxbow lake still existed at present Reelfoot Lake (Fig. 12F). Usher (1837) map- that time, and all three seismic events clearly identi- ped a swamp circled by cypress trees with a new fied in the study area occurred subsequent to this growth of cottonwood trees in the uplifted center, interval (Kelson et al., 1996; this study). A more distal suggesting that the uplift prior to 1812 was not channel position infers low sinuosity of the channel adequate to drain the swamp. A crude sketch map along the west and north margins of the present shows the swamp approximately in the northern channel belt in the study area. Sinuosity of the channel Cronanville abandoned meander, but it is possible belt to the west has remained low since the Tiptonville that the map (made several years after the visit) may neck cutoff. In the north of the study area, the not be accurate. Based on the stratigraphic and geo- paleosinuosity is not preserved, but minimal overbank morphic evidence, the swamp was more likely to have sediment immediately south of the channel belt (Fig. been located in the northern arm of the Tiptonville 7) suggests that the channel was along the northern abandoned meander. margin of its channel belt until recently (Fig. 12). If the channel was in the northern portion of the channel belt, the channel could not have been highly sinuous 6. Discussion or it would have also extended into the southern channel belt. Low sinuosity also indirectly supports Evidence for intrinsic fluvial processes and minimal topographic expression of the dome at this response of the river to extrinsic tectonic processes time. Uplift and modification of the Mississippi River include landforms, the presence/absence of deposits, gradient would presumably have induced increased and their temporal proximity to earthquake events. In channel sinuosity as it has today. the Reelfoot Lake area, the Mississippi River rapidly Widespread sedimentation occurred on what is migrated south approximately at 400 B.C. to become now the Tiptonville dome between ca. A.D. 780 and a sinuous meander bend that was cutoff no later than 1450 (Fig. 12C and D). The final stage of filling the 344 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349

Cronanville abandoned chute channel and overbank of the dome, crevasse-splay sediment accumulated on deposit derived from flooding along the Cronanville the dome, although the distribution of the deposit is abandoned channel is present across the northern more limited in aerial extent than the crevasse deposit portion of the study area. In the southern study area, in the basin. Creation of the Reelfoot basin allowed the oxbow lake filled with fine-grained sediment to accumulation of crevasse deposits that onlap the scarp. become a swamp with rooted vegetation, except at the Beyond the limit of crevasse sedimentation, colluvium apex of the meander where the lake/swamp persisted. accumulated at the foot of the scarp. Both of these observations suggest that the Missis- In the southern part of the Tiptonville dome, the sippi River migrated to the east, more proximal to the gradient of the batture channel across the dome was study area, and flood water flowed through a swale significantly modified and it filled rapidly. Uplift of (Cronanville abandoned meander) and batture chan- the dome formed a divide causing the channel to slope nels (Tiptonville abandoned meander) depositing both east and west. To the west of the divide, the more sediments than previously had been deposited channel had already partially filled (Fig. 10D). To the across what is now the dome and filling much of the east of the divide, the channel filled rapidly and oxbow lake. These observations also support the sediment probably also accumulated in the extension hypothesis that little uplift occurred between 440 of batture channel along the SW margin of Reelfoot B.C. and at least A.D. 1260 (maximum age for Lake (Fuller, 1912), because the channel was already seismic event Y), including during the earthquake largely infilled at the time Reelfoot Lake formed in event X, A.D. 780–980. Any uplift that occurred 1812 (Carlson, 2000). was not adequate to prevent frequent flooding. In 1812, deformation was again substantial, espe- Unfortunately, the flood stage is unknown and no cially along the southern part of the scarp. Uplift minimum uplift is estimated. across the batture channel formed Reelfoot Lake and Although coseismic uplift may not have been was responsible for the complete drainage derange- significant in the A.D. 780–980 event, some defor- ment of the channel and associated crevasse channels. mation may have occurred. Part of the batture channel In the northern map area, the uplift was apparently that connected the oxbow lake and the Mississippi greatest, 0.5 km west of Reelfoot scarp because local River began to fill between A.D. 891 and 1024 (core drainage flows east and west of this point. In the 10; Fig. 10D), about the same time earthquake event southern study area, the uplift is apparently greatest, X occurred. This may have been a response to a subtle 2.2–2.8 km west of the scarp, the present divide gradient change. between two segments of the batture channel that Most of the deformation that formed the structural were formerly connected (Figs. 3 and 12E–F). relief of 8–11 m (Carlson, 2000) across Tiptonville Small streams, such as batture and distributary dome and Reelfoot basin occurred during two events, channels, become deranged when deformation with one ca. A.D. 1470 and the other in 1812 (Fig. 12E and up to 11 m of structural relief occurred. Most of this F). Although both events probably affected the entire deformation occurred during the later two seismic scarp, the first event was likely to have caused rela- events in the area, ca. A.D. 1470 and 1812. An alluvial tively more deformation along the northern portion of river, the size of the Mississippi River, would be much the scarp (Russ, 1979), and the 1812 event caused less likely to have become deranged by this amount of more deformation along the southern scarp margin. structural relief. However, the Mississippi River would Uplift of the dome ca. A.D. 1470 was high enough to certainly respond to this scale of deformation, partic- prevent continued overbank sedimentation across most ularly if most of the deformation occurred during two of the dome, except immediately adjacent to the events within 350–550 years as we are suggesting. Mississippi River channel. Assuming that sinuosity This study has shown that not only has the Mississippi of the river increased across the uplift in response to River responded, but that it had not reached equili- the uplift (Burnett and Schumm, 1983), the sinuosity brium in nearly 190 years since 1812. of the Mississippi River downstream of the uplift Total structural relief along the Reelfoot scarp should have increased, at least after A.D. 1470. As decreases from a maximum of 11 m in the northern the channel migrated and eroded into the northern part portion of the study area along the Mississippi River M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 345 to a minimum of 7 m in the southern portion of the the Reelfoot thrust fault, and therefore, deformation of study area at the southern edge of Reelfoot Lake the Tiptonville dome/Reelfoot basin may not have (Carlson, 2000). We have presented evidence that been recognizable using sedimentation patterns. most of these reliefs results from two episodes of coseismic deformation. If this conclusion is correct, we further speculate that the amount of deformation is 7. Conclusions approximately equally divided between these two events or is slightly less during the second event in Holocene tectonic history in the Reelfoot area 1812. Similarly, Mueller and Pujol (in press) esti- began to be recorded about 2.3 ka as fault-related mated overlapping moment magnitudes for the A.D. folding along the Reelfoot thrust fault. This folding is 1450 and 1812 seismic events, with the magnitude of consistent with heterogeneous trishear fault-propaga- the former event perhaps slightly greater than the tion folding, where shear on the Reelfoot thrust is 1812 event. Unlike this study, Mueller and Pujol used expressed at the surface generally as a monoclinal fold smaller uplift in the A.D. 1450 and 1812 earthquakes limb (Champion et al., 2001; Mueller and Pujol, in than we are proposing to calculate moment magnitude press). The fold limb is variably expressed along because they assumed some uplift in the A.D. 900 strike as stepped kink bands (Mueller et al., 1999), event. However, Johnston and Schweig (1996) single monoclines (Van Arsdale et al., 1995a), and a reported 1 to 3 m of uplift near the town of New concave-upward fold (Kelson et al., 1992). Older Madrid and permanent subsidence of 3 m in the surficial sediment recording previous tectonic history Reelfoot basin based on historic reports, combining has been removed by the channel migration of the for approximately the amount of deformation (ca. Tiptonville meander across the area, and uplift can 3.5–5.5 m) proposed in our study. Four meters of only be constrained using subjacent Pleistocene and structural relief was reported by Van Arsdale et al. older units below the zone of scour of the Holocene (1995a,b) within the channel belt of the Mississippi channel (Mihills and Van Arsdale, 1999). River north of the study area. If this young land This Mississippi River migration across the present surface was created between approximately A.D. Tiptonville dome area that removed older sediment 1470 (preferred date for seismic event Y) and 1812, evolved from a low sinuousity channel identified by a it would only preserve a single coseismic deformation chute cutoff (Cronanville abandoned meander) to a of about 4.5 m during 1812, representing 40–60% of highly sinuous channel identified by a neck cutoff the maximum deformation further south. The point- (Tiptonville abandoned meander). Because the style bar sand beneath this land surface is clearly younger of the two channel cutoffs is dissimilar, the channel than the sediment south of the present Mississippi fill of the two abandoned channels is also dissimilar. River channel belt based on cross-cutting relation- Laminated sandy silt and silty sand and a lesser ships, but the age of the Mississippi channel belt at amount of massive silty clay fills the abandoned this location is unknown. Although it is possible that Cronanville meander. Cutoff bar sand and laminated the deformed sediment predates ca. A.D. 1470 (rep- siltgradinguptomassivesiltandclayfillthe resenting both deformation events) and that the abandoned Tiptonville meander. Between these two amount of deformation decreases significantly to the abandoned channels is sandy point-bar sediment that north, we consider this interpretation to be less likely forms scroll bars as the Mississippi River migrated but not impossible. across the area. The lack of evidence for substantial coseismic After the neck cutoff of the Tiptonville meander, deformation in ca. A.D. 900 (seismic event X) is little sedimentation or evidence for appreciable sur- curious. Tuttle et al. (1999b) reported the widespread face deformation occurred for the next 1.1 ka, sug- liquefaction of that age from Marked Tree in the south gesting that the Mississippi River was at the western to NE of New Madrid, and they have concluded that and northern edges of its present channel belt and/or the very large earthquake was centered in the NMSZ. flooding was not common. Although the seismic event may have occurred in the Beginning at about 1.2 ka, the river probably NMSZ, the A.D. 900 rupture may not have been on migrated to the east margin of the channel belt and 346 M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 began to flood over the study area. The remaining deformation occurred during two seismic events, ca. swale of the Cronanville abandoned meander was A.D. 1470 and 1812, during relatively large-magni- filled with sandy silt and an overbank silt and clay tude (Mw 7.5 F 0.1) earthquakes. was deposited adjacent to the channel. One earthquake event occurred between A.D. 780 and 980 during Acknowledgements deposition of this unit, but any deformation associated with this event was not adequate to uplift the area We would like to thank Jason Combs, Linda Fye, above flood stage and may have caused minor sedi- Clay Morton, Curtis Nunn, Angela Polly, Eddie mentary response of channel fill in small channels. Valek, and Greg Vogel of the University of Arkansas, Significant deformation occurred during the two and Bill Lawrence of the Tennessee Deparment of most recent seismic events. Folding during the penul- Environment and Conservation, Division of Archeol- timate event, ca. A.D. 1470, uplifted the Tiptonville ogy for the assistance in the field. Bill Lawrence dome above flood stage, and deposition of channel fill provided information on the archeology of the and the adjacent overbank deposit ceased. In contrast, Reelfoot area and logistical support. We would like depression of Reelfoot basin caused significant flood- to thank landowners including Mr. Terry Hopper and ing and deposition of an extensive crevasse-splay Mr. Bill Lindamood for the access to their property, deposit, accumulation of colluvium at the base of and Jerry Ellis for logistical support. Helpful reviews the scarp, and rapid fill of a small batture channel. were provided by John Holbrook, Eugene Schweig The Mississippi River is deep and narrow upstream of III, Pablo G. Silva, Torbjorn Tornqvist, and Roy Van the uplift, and wide and shallow across the uplift and Arsdale. This research was supported by the U.S. probably responded to the changing gradient by Geological Survey (USGS), Department of the increasing its sinuosity. Interior, Award Number 1434-HQ-97-GR-03137 and Folding occurred again during the most recent Award Number 1434-HQ-97-GR-03131 to M. Guc- large seismic event in 1812 causing the blockage of cione and K. Mueller. The views and conclusions the batture channel and creeks draining the nearby contained in this document are those of the authors uplands to form Reelfoot Lake; deposition of lacus- and should not be interpreted as necessarily represent- trine sediment within the basin; flow reversal of the ing the official policies, either expressed or implied, of batture channel in the Tiptonville abandoned meander the U.S. government. and an unnamed swale along the Cronanville abandoned meander that crosses the fold axis; and continued high sinuosity, anomalous channel shape, and References gradient modifications of the Mississippi River. Nei- ther the channel dimensions nor the channel gradient Audemard, F.A., 1999. Morpho-structural expression of active has equilibrated, and thus, channel response of the thrust fault systems in the humid tropical foothills of Columbia Mississippi River to the deformation 190 years ago is and Venezuela. Zeitschrift fuer Geomorphologie 118, 227–244. Autin, W.J., Burns, S.F., Miller, B.J., Saucier, R.T., Snead, J.I., not yet complete. 1991. Quaternary geology of the Lower Mississippi Valley. In: We have attributed most, if not all, of the structural Morrison, R.B. (Ed.), Quaternary Nonglacial Geology: Conter- relief to two coseismic events. A minor amount of the minous U.S. The Geology of North America, vol. K-2. Geo- relief associated with other seismic events and/or with logical Society of America, Boulder, Colorado, pp. 547–582. slow aseismic deformation may have been possible or Blum, M.D., Guccione, M.J., Wysocki, D.A., Robnett, P.C., Rut- ledge, E.M., 2000. Late Pleistocene evolution of the lower Mis- even probable, but this relief was not enough to affect sissippi River valley, southern Missouri to Arkansas. Geological observable sedimentation patterns. However, we con- Society of America Bulletin 112, 221–235. sider that the abrupt modification of sedimentation Brice, J.C., 1984. Planform properties of meandering rivers. In: patterns that is coincident with dated seismic events Elliott, C.M. (Ed.), River Meandering. Proceedings of the Con- recognized in the Reelfoot Lake area (Russ, 1979; ference Rivers ’83. American Society of Civil Engineers, NY, pp. 1–15. Kelson et al., 1992, 1996; this study) and other areas Burnett, A.W., Schumm, S.A., 1983. Alluvial-river response to neo- of the NMSZ (Tuttle et al., 1998, 1999a,b; Schweig tectonic deformation in Louisiana and Mississippi. Science 222, and Tuttle, 2000) is indicative that considerable 49–50. M.J. Guccione et al. / Geomorphology 43 (2002) 313–349 347

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