Upland Complex Research Articles

New 26Al/10Be and (U-Th)/He constraints on the age of the Upland Complex, central Mississippi River Valley

The Upland Complex is a widespread terrace of the ancestral Mississippi River. It has played a central role in studies of the Pliocene Mississippi River drainage, as well as uplift and seismicity in the central Mississippi River Valley. Previous efforts to date the Upland Complex have yielded a range of age estimates spanning the Miocene through Pleistocene. We dated gravels and Fe-oxide cements from quarries of the Upland Complex in Arkansas, Kentucky, Mississippi, and Tennessee using 26Al/10Be burial dating and (U-Th)/He geochronology. Our 26Al/10Be burial dates revealed possible Pliocene-to-Pleistocene depositional ages, while (U-Th)/He dating showed that the onset of weathering dates to at least the Pliocene. Taken together, the 26Al/10Be and (U-Th)/He age constraints demonstrate that the Upland Complex is at least Pliocene in age, and likely formed during a prolonged period of base level stability that preceded Pleistocene glaciations.

Age and provenance of upland gravels in Missouri, USA, and their relationship to Early Pleistocene glaciation

The age and origin of the Grover Gravel, which is preserved on stable uplands in St. Louis County, Missouri, USA, and similar gravels along the Mississippi River bluffs farther south, have been controversial for over a century. These gravels have some features consistent with a glacial origin but lack obvious erratics such as igneous rock fragments. New observations, however, show that the earliest tills within the Mississippi basin nearly lack such constituents as well, and that the Grover Gravel is a Pleistocene deposit derived from such a till. A Mississippi River terrace deposit in St. Louis County also includes typical clasts of this till and formed between 2.0–1.8 Ma, based on various dating methods. This deposit may correspond to a pulse of glacial meltwater recorded within sediment near the mouth of the Mississippi River and represent outwash from a previously unrecognized glaciation within the US midcontinent. The Mounds Gravel (or Upland Complex) is present farther south around the perimeter of the Mississippi Embayment and contains the same distinct clasts as the gravels in St. Louis County. Given that the age of the Mounds is <~3 Ma based on cosmogenic‐nuclide ratios, the southern gravel could be the same age as the gravel terrace in St. Louis County. If so, these gravels could mark a geomorphic transition to glacial‐dominated sedimentation farther south in and around the Gulf of Mexico. Regardless, all the upland gravels have insignificant amounts of zircon from provinces west of Hudson Bay. Therefore, detrital zircon provenance does not support a recent hypothesis that the Mounds (Upland Complex) was deposited by a giant Mississippi River with a drainage basin extending across broad areas west of Hudson Bay.

Drone Geologic Mapping of an Active Sand and Gravel Quarry, Desoto County, Mississippi

Aerial drone photography of an active pit within a sand and gravel quarry in DeSoto County, Mississippi, was conducted to better understand the Upland Complex, which is a high-level Pliocene terrace of the Mississippi River. The Upland Complex is of great interest economically, as it is the primary source of sand and gravel for Memphis, Tennessee and the surrounding region. The pit dimensions were approximately 820 ft (250 m) by 655 ft (200 m) and 79-ft (24 m) deep upon completion of the mining. Eight 3-D models of the pit were made at different times to illustrate the mining progression. Oblique and horizontal stereo aerial photography of the highwalls was conducted to produce 3-D models and high-resolution photomosaics of the highwalls for geologic mapping and interpretation. The mapped highwall geology included Pliocene Mississippi River bars consisting of sand, sand and gravel, and gravel ranging in thickness from 2 ft (0.6 m) to 32.8 ft (10 m), with variable cross-bed dip directions suggesting a meandering river environment of deposition. Pleistocene loess overlies the Pliocene sediment. The highwalls also revealed northerly-striking late Pliocene or Pleistocene tectonic folding, faulting, and probable earthquake liquefaction in northwestern Mississippi, where no Pliocene or Quaternary tectonic deformation had previously been reported. This study demonstrated Drone aerial photography as a quick, low cost, and safe means to study poorly accessible open-pit mining and to help understand the geology of the lower Mississippi River Valley.

Quaternary Uplift in the Lower Mississippi River Valley

AbstractDiscontinuous high-level terrace remnants of the ∼3.1 Ma ancestral Mississippi River floodplain, locally called the Upland Complex (UC), are mapped from Louisiana into Illinois. We interpre...

Continuity of the Reelfoot Fault across the Cottonwood Grove and Ridgely Faults of the New Madrid Seismic Zone

Previous investigators have argued that the northwest‐striking Reelfoot fault of northwest Tennessee and southeastern Missouri is segmented. One segment boundary is at the intersection of the northeast‐striking Cottonwood Grove and Ridgely strike‐slip faults with the Reelfoot fault. We use seismic reflection and geologic mapping to locate and determine the history of the Reelfoot South fault across this boundary zone. One reflection profile revealed a southwest‐dipping (81°) Reelfoot South reverse fault that displaces the top of the Paleozoic 65 m, Cretaceous 40 m, Paleocene 31 m, Eocene Wilcox Group 20 m, and Eocene Memphis Sand 16 m. A second reflection profile reveals a north‐dipping (84°) reverse fault 4.3 km south of the Reelfoot South fault, which defines the southwest margin of the Tiptonville dome. A geologic profile of the base of the ∼3.1 Ma Upland complex (Mississippi River terrace alluvium) within the Mississippi River bluffs reveals ∼6 m of displacement across the Reelfoot South fault. Similarly, Quaternary stream terrace distribution suggests ∼6 m of Reelfoot South hanging‐wall (Tiptonville dome) uplift that is probably Holocene. Fault strike trends show the Reelfoot fault and its hanging‐wall Tiptonville dome are not laterally offset across the Cottonwood Grove and Ridgely faults. The Reelfoot South fault northwest and southeast of the Cottonwood Grove and Ridgely faults has very similar vertical displacement on common stratigraphic marker horizons in the upper 900 m. These data indicate the Reelfoot fault/Tiptonville dome has acted as one continuous fault zone across the Cottonwood Grove and Ridgely faults since Late Cretaceous.

Petrology of Pliocene Mississippi River Alluvium: Provenance Implications

Pliocene Mississippi River terrace gravels, the Upland Complex, crop out east and west of the present Mississippi River in the northern Mississippi Embayment. As the only sedimentary unit in the northern Mississippi Embayment deposited between the end of the Eocene and the onset of glaciation, its origin provides ground truth about conditions that existed in the heartland of North America within this 30-m.yr. interval. Recent studies concluded that the Pliocene Mississippi River originated in what is now southern Canada and that the Upland Complex is the remnant of a much larger deposit that once extended from Canada to the Gulf of Mexico. Is there some evidence in the petrology of the Upland Complex that can confirm this conclusion? To determine the provenance of the Upland Complex, we sampled 18 exposures, analyzed ∼50 thin sections, and obtained source terrane age data from its zircons. Upland Complex gravel came from proximal early Paleozoic carbonate rocks containing bedded and nodular chert north and northeast of the Mississippi Embayment with a possible distant contribution from as far away as southcentral Canada. Upland Complex sand came from multiple sources, including the Saint Francois Mountains of Missouri, the Grenville Terrane, and, possibly, southcentral Canada. We conclude that the Pliocene Mississippi River probably drained a much larger area than present Mississippi, an area that extended well north of the US-Canada border into Manitoba and Ontario.

Possible Relict Meanders of the Pliocene Mississippi River and Their Implications

AbstractAlthough the late Quaternary history of the Mississippi River, the largest North American river, has been intensely studied, its Pliocene history is largely unknown. We assert that large relict meander bends (oxbows) of the Pliocene Mississippi River are preserved as arcuate valleys of local streams in the northwest area of the state of Mississippi. These arcuate valleys are within the Pliocene Upland Complex stratigraphic unit that occurs as a high-level alluvial terrace along the lower Mississippi River Valley. Outside these arcuate valleys, the Upland Complex is a braided-river gravel deposit that shows southward (downvalley) paleoflow directions. Interiors of the arcuate valleys are occupied by Upland Complex point bar deposits with large-scale cross-bedding showing a range of paleoflow directions, commonly upvalley flow indicative of a meandering regime. We used measurements of the radii of the putative relict meander bends and of their paleochannel widths to estimate paleodischarge of the Pl...

Late Pliocene and Quaternary deformation of the Reelfoot rift

The Reelfoot rift is a N45°E-trending Cambrian rift that has controlled late Pliocene and Quaternary deformation and current seismicity beneath the central Mississippi River Valley. Analysis of 557 well logs between 35°N and 37°N latitude reveals that the Pliocene Upland Complex of western Kentucky and Tennessee and the Upland Complex in Crowley’s Ridge of eastern Arkansas have been displaced by east-striking normal faults that extend across the Eastern Lowlands of the Mississippi River Valley. The normal faults extend east and west of the margins of the Reelfoot rift, thus indicating that the region between the Commerce fault and the Big Creek–Ellendale fault has been subjected to right-lateral simple shear since the Pliocene.

Geology, Geotechnical Engineering, and Natural Hazards of Memphis, Tennessee, USA

The generally flat landscape of the Memphis, TN, area hides a fascinating geologic history. Cambrian rifting resulted in the concealed faults of the Reelfoot rift, currently the active component of the New Madrid Seismic Zone, lying immediately northwest of the city. Memphis also sits within the Mississippi Embayment. Subsidence of the embayment brought about deposition of the thick Late Cretaceous and Cenozoic sedimentary sequence underlying the city. This sequence provides one of the finest groundwater aquifers in the world, the Memphis Sand. Pliocene ancestral Ohio River alluvium (Upland Complex) is an excellent source of sand and gravel for the region. Plio-Pleistocene fluvial degradation by the Mississippi River and its tributaries, in addition to deposition of Pleistocene loess sheets, have produced the subtle topography of Memphis and Shelby County. Memphis geology makes geotechnical engineering design challenging because loess is highly sensitive to disturbance. Exploratory sampling techniques tend to cause disturbance to loess during sampling and sample extraction. Thus, conventional sampling techniques yield variable engineering property test results (e.g., strength and compressibility). The city of Memphis and Shelby County have together become a major commodities distribution center for the United States, North America, and the global economy. The principal natural hazards are the frequent severe weather and the prospect of a repeat of the >7M 1811–1812 New Madrid earthquakes. These unavoidable exposures to severe weather, urban and riverine flooding, and earthquakes combined with social conditions tend to amplify the consequences of hazard events.

Quaternary Faulting beneath Memphis, Tennessee

Other| September 01, 2005 Quaternary Faulting beneath Memphis, Tennessee Maria Velasco; Maria Velasco Department of Earth Sciences University of Memphis Memphis, Tennessee 38152 +1-901-678-2177 Fax +1-901-678-2178 rvanrsdl@memphis.edu 1Department of Earth Sciences, University of Memphis Search for other works by this author on: GSW Google Scholar Roy Van Arsdale; Roy Van Arsdale * Department of Earth Sciences University of Memphis Memphis, Tennessee 38152 +1-901-678-2177 Fax +1-901-678-2178 rvanrsdl@memphis.edu 1Department of Earth Sciences, University of Memphis * Corresponding author Search for other works by this author on: GSW Google Scholar Brian Waldron; Brian Waldron Department of Earth Sciences University of Memphis Memphis, Tennessee 38152 +1-901-678-2177 Fax +1-901-678-2178 rvanrsdl@memphis.edu 2Ground Water Institute, University of Memphis Search for other works by this author on: GSW Google Scholar James Harris; James Harris Department of Earth Sciences University of Memphis Memphis, Tennessee 38152 +1-901-678-2177 Fax +1-901-678-2178 rvanrsdl@memphis.edu 3Geology Department, Millsaps College Search for other works by this author on: GSW Google Scholar Randel Cox Randel Cox Department of Earth Sciences University of Memphis Memphis, Tennessee 38152 +1-901-678-2177 Fax +1-901-678-2178 rvanrsdl@memphis.edu 1Department of Earth Sciences, University of Memphis Search for other works by this author on: GSW Google Scholar Seismological Research Letters (2005) 76 (5): 598–614. https://doi.org/10.1785/gssrl.76.5.598 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Maria Velasco, Roy Van Arsdale, Brian Waldron, James Harris, Randel Cox; Quaternary Faulting beneath Memphis, Tennessee. Seismological Research Letters 2005;; 76 (5): 598–614. doi: https://doi.org/10.1785/gssrl.76.5.598 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search Abstract A geologic investigation of the city of Memphis and southern Shelby County, Tennessee reveals Quaternary faulting. Structure contour maps and cross-sections of the top of the Pliocene-Pleistocene Upland Complex (Lafayette gravel), Eocene Upper Claiborne Group, and Eocene Lower Claiborne Group reveal two 20-m down-to-the-northwest faults that strike approximately N30°E The western fault is herein called the Memphis Fault and the eastern, the Ellendale Fault.The Ellendale Fault is projected to pass beneath the Wolf River flood plain in east Memphis. At this location, a cut bank exposes flood-plain sands that are folded into an anticline with a wavelength of ∼ 100 m, an amplitude of ∼4 m, and a hinge oriented 10°N7°W. The folded sands are truncated by overlying, flat-lying, clayey silt overbank sediments. A 1-m-wide earthquake liquefaction sand dike was found above the crest of the anticline, in the overbank sediments. 14C dates reveal that the folding occurred between A.D. 390 and 450, and the liquefaction occurred post A.D. 450. Seismic-reflection lines indicate that the fold extends to more than 60 m depth into the Lower Claiborne Group, has a length of more than 1 km, and is thus tectonic in origin. The reflection lines also reveal a N25°E down-to-the-west fault with 5 m of displacement in the Upper Claiborne Group that we believe is within the Ellendale Fault zone. We believe the anticline formed during ∼5 m of Quaternary right-lateral strike-slip movement on the N25°E-trending fault. Based on these observations, we also believe that the Ellendale Fault, and perhaps the Memphis Fault, may pose seismic threats to the city of Memphis and Shelby County, Tennessee. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Sensitivity of tropical forests to climate change in the humid tropics of north Queensland

AbstractAn analysis using an artificial neural network model suggests that the tropical forests of north Queensland are highly sensitive to climate change within the range that is likely to occur in the next 50–100 years. The distribution and extent of environments suitable for 15 structural forest types were estimated, using the model, in 10 climate scenarios that include warming up to 1°C and altered precipitation from –10% to +20%. Large changes in the distribution of forest environments are predicted with even minor climate change. Increased precipitation favours some rainforest types, whereas decreased rainfall increases the area suitable for forests dominated by sclerophyllous genera such as Eucalyptus and Allocasuarina. Rainforest environments respond differentially to increased temperature. The area of lowland mesophyll vine forest environments increases with warming, whereas upland complex notophyll vine forest environments respond either positively or negatively to temperature, depending on precipitation. Highland rainforest environments (simple notophyll and simple microphyll vine fern forests and thickets), the habitat for many of the region’s endemic vertebrates, decrease by 50% with only a 1°C warming. Estimates of the stress to present forests resulting from spatial shifts of forest environments (assuming no change in the present forest distributions) indicate that several forest types would be highly stressed by a 1°C warming and most are sensitive to any change in rainfall. Most forests will experience climates in the near future that are more appropriate to some other structural forest type. Thus, the propensity for ecological change in the region is high and, in the long term, significant shifts in the extent and spatial distribution of forests are likely. A detailed spatial analysis of the sensitivity to climate change indicates that the strongest effects of climate change will be experienced at boundaries between forest classes and in ecotonal communities between rainforest and open woodland.

Pleistocene stratigraphy in the southern Lower Mississippi Valley

Scientific inquiry into Pleistocene stratigraphy of the Lower Mississippi Valley (LMV) dates to early writings of European naturalists in the late 19th century. By the early 20th century, landscape evolution concepts, stratigraphic models, and regional syntheses had developed for most areas. The 1944 monograph of H.N. Fisk marks the advent of a predictive stratigraphic and landscape evolution model that links form and process to a predominantly glacioeustatic mechanism. The Fiskian model gained widespread acceptance, and decades passed before significant alternate models began to emerge. Revised stratigraphic and geomorphic concepts are presently developing from newly acquired environmental and engineering data. Present scenarios classify Pleistocene outcrop areas into erosional and constructional landscapes, and veneers of eolian, colluvial, fluvial, coastal, and marine origin can drape both types of surfaces. The southern LMV and adjacent Gulf Coastal Plain (GCP) experienced significant landscape change during the Pleistocene. Late Tertiary (Pliocene?) to Early Pleistocene deposition of the Upland Complex was by streams with a high sand and gravel load relative to its mud load. The regional drainage network and fluvial system behavior was probably significantly different from the modern. Braided stream alluvial fan complexes received sediment from highland source areas adjacent to the LMV and the glaciated mid-continent. It is plausible that part of Upland Complex deposition predates initial glacial advances. From Early to Middle Pleistocene, an erosional landscape formed during a dissection period that chiefly postdates soil formation on stable landscape positions of the Upland Complex. Slope evolution truncated a regionally extensive geosol in multiple phases, and parts of the erosion surface complex are graded to the oldest preserved constructional alluvial plains in present valleys. Toe and foot slope positions of the erosion surface complex and its correlative alluvial plains are presently delineated as the Intermediate Complex. Constructional landscapes formed at this time are sparsely preserved; Fisk's Montgomery Terrace in the Lower Red River Valley (LRRV) is the best preserved example. Influences on the development of erosion surfaces in the LMV are not well understood; however interactions of relative sea level fall, climate change, and epirogenic crustal movement are plausible factors. From the latter part of Middle Pleistocene to the Holocene, there was widespread evolution of modern constructional landscapes. Constructional alluviation preserved lithofacies of mixed load, laterally accreting, meandering streams that developed over large areas of the southern LMV to form parts of the Prairie Complex. Lateral planation in valleys and stable rates of upland sediment generation were dominant processes during Prairie Complex deposition. Pleistocene stratigraphic examples considered important by Fisk are still considered relevant to modern stratigraphic investigators. Presently, Pleistocene units of the southern LMV, the adjacent LRRV, and central GCP can be correlated only by relative stratigraphic relationships. Refined chronostratigraphic and paleoenvironmental models for these areas would help improve the understanding of the geomorphic influences on Quaternary landscape evolution in the region.

Vascular Vegetation of Buldir Island, Aleutian Islands, Alaska, Compared to Another Aleutian Island

The vegetation of Buldir Island, Alaska, was studied from 1974 to 1976. On this treeless volcanic island, two distinct vegetation complexes were conspicuous, one with relatively tall dominant plants which generally occurred below 300 m elevation (called the Lowland Tall-plant complex), and the other composed of much shorter plants about 300 m elevation (called the Upland Short-plant complex). The lowland complex contained eight plant communities, but over 90% of the complex consisted of three; Elymus-umbel, Elymus-umbel-fern, and Carex-fescue meadow. The upland complex was less diverse, containing only four communities of which the moss-willow tundra was the most widespread. At Buldir 119 species of vascular plants were identified, considerably fewer than at a nearby larger island, Amchitka.Key words: vascular plants, volcano, Aleutian Islands, plant ecology

Species Diversities in Drosophila (Diptera): A Dependence Upon Rain Forest Type of the Queensland (Australian) Humid Tropics

The Drosophila species compositions within the rain forests of north Queensland, Australia, are closely correlated with rain forest type. The floristically complex rain forests (complex mesophyll vine forests) growing on rich basaltic soils harbour much greater species diversities than do less diverse forests (mesophyll and microphyll vine forests) of granitic soils. This is true for the three major collection methods used, namely fermented fruit baiting, mushroom baiting and sweeping, so implying general higher niche diversity in the floristically complex forests. Rare endemic Australian species of subgenera Hirtodrosophila and Scaptodrosophila appear to be almost entirely restricted to these complex forests, which are the most promising habitats for future biogeographic studies on the Australian Drosophila fauna of the humid tropics. These rare species include certain lek species of subgenus Hirtodrosophila found mainly in upland complex forests. Cosmopolitan Drosophila species are almost entirely excluded from the forests presumably because of severe competition for niches.