Rio Grande Delta Research Articles

Modern sand provenance and transport across the western Gulf of Mexico margin

Petrographic and detrital zircon U-Pb analysis of modern beach sands and river sands from major catchments in northeastern Mexico draining to the Gulf of Mexico provides evidence for a minimum of 650 km of littoral sand transport southward from the mouth of the Rio Grande at the Mexico-U.S. border to the central part of the state of Veracruz, Mexico. Principal tracers of Rio Grande sand include: (1) quartzose composition that contrasts with lithic compositions of sand in eastern Mexico rivers and (2) detrital zircon ages with Mesoproterozoic modes at 1.8−1.5 Ga and 1.4 Ga, age groups that are typical of basement and derivative sediment of the SW United States but are uncommon to rare in Mexican river catchments. In contrast, abundant Miocene and younger grains in beach sands of Veracruz indicate primary sediment derivation from active and recently active volcanoes in the Trans-Mexican volcanic belt in central Mexico. A proportional decrease in sand of Rocky Mountain provenance with distance southward along the coast from the mouth of the Rio Grande and absence of Miocene and younger zircon grains in beaches north of rivers draining the Trans-Mexican volcanic belt indicate net littoral sand transport southward along the eastern coast of Mexico, demonstrating that wintertime shoreline-parallel surface currents rather than north-directed summertime currents dominate sediment transfer. Sand samples of Tamaulipas beaches in northeastern Mexico commonly have equal or higher proportions of U.S.-derived Mesoproterozoic zircon grains than are present in river bar sand of the lower Rio Grande and the Rio Grande delta, and thus require that littoral processes rework and incorporate coastal dune and beach sands of northeastern Mexico that are enriched in predam Rio Grande sediment. Implied coastal erosion may be related to Holocene transgression or interruption of sediment supply to the coastal sediment transport system by dams in the Rio Grande drainage basin. Such coastal erosion is impacting long-term shoreline stability and viability of the littoral environment.

Draft Genome Sequences of 13 Vibrio cholerae Strains from the Rio Grande Delta.

ABSTRACTVibrio cholerae is the etiologic agent of cholera, an acute and often fatal diarrheal disease that affects millions globally. We report the draft genome sequences of 13 non-O1/O139 V. cholerae strains isolated from the Rio Grande Delta in Texas. These genomes will aid future analyses of environmental serovars.

Rio Grande an International Boundary River Is Drying up and in Need of Restoration

The headwater source of the Rio Grande is in the Colorado San Juan Mountains as it flows southeast and south. The river crosses deserts and steppes, watering rich irrigated agricultural regions as it drains into the Gulf of Mexico near Brownsville, Texas. The river flow pattern is disrupted by hundreds of dams and irrigation diversions, which has left sections of the Rio Grande River dry. The lower Rio Grande Valley including the Rio Grande Delta is heavily irrigated and has become an important agricultural region. Since the mid-1990s, the flow has been reduced to 20% because of many large diversions, dams and consumption of water by cities and irrigated farmland. Even with a series of 2001 and 2002, Mexico-United States agreements administered by the International Boundary and Water Commission (IBWC) the Rio Grande River had continued to failed to reach the Gulf of Mexico. Mexico and United States share the river. Historically, the Rio Grande has provided limited navigation and border security. There is a need to restore navigation and shipping by creating a lock and dam system from El Paso, Texas and Matamoros, Mexico to the Gulf of Mexico, In addition there is also a need to restore border security for the Lower Rio Grande, an international border river. If the Rio Grande is ever going to recover, it will require a lock and dam system and an increased river flow. The increased flow needs to be achieved by adding additional water from feeder lakes, a water pipeline, and a balanced approach to water management must include efficiency measures and aggressive conservation in urban areas and on irrigated agricultural lands.

Land Cover Trends in South Texas (1987–2050): Potential Implications for Wild Felids

The Rio Grande Delta and surrounding rangelands in Texas has become one of the fastest urbanizing regions in the United States over the last 35 years. We assessed how land cover trends contributed to the large-scale processes that have driven land cover change since 1987. We classified LANDSAT imagery from 1987 to 2016 to quantify different rates of land cover change and used housing density scenarios to project changes in the amount and spatial distribution of woody cover until 2050 and its potential impact on wild felid habitat. Since 1987, woody cover increased from 3.9% along with patch and edge density, whereas mean patch area and Euclidean nearest neighbor decreased. Closer inspection revealed that woody encroachment of small patches (<1 ha) was the leading cause of woody cover increase by a magnitude of 4, with an observed significant skewness and kurtosis in the frequency distribution of patch size across years. By 2050, urbanization will be the dominant landscape type and at least 200 km2 of woody cover may be lost, thereby affecting felid populations in South Texas. These results provide important information for predicting future woody cover fragmentation and its potential impact on the connectivity of wild felid populations.

Evaluating the Impacts of Dam Construction and Longshore Transport upon Modern Sedimentation within the Rio Grande Delta (Texas, U.S.A.)

Moore, S.; Heise, E.A.; Grove, M.; Reisinger, A., and Benavides, J.A., 2021. Evaluating the impacts of dam construction and longshore transport upon modern sedimentation within the Rio Grande Delta (Texas, U.S.A.). Journal of Coastal Research, 37(1), 26–40. Coconut Creek (Florida), ISSN 0749-0208.The modern Rio Grande delta system has experienced a century of dam construction, water removal for irrigation and municipal use, and land use modifications that have dramatically reduced its sediment load. This study examines whether damming has sufficiently limited delivery of upstream sediment to permit locally eroded sources and/or littoral transport along the coast to influence the provenance signal of the Rio Grande delta. Changes in sediment provenance within the Rio Grande's delta can be detected and quantified by measurement of detrital zircon Uranium–lead dating age distributions. Previous provenance studies indicate that modern Rio Grande river sand upstream of Falcon Dam is enriched in zircon derived from Oligocene volcanic fields within the southern Rocky Mountains and the Sierra Madre Occidental. Results from this study indicate that the abundance of Oligocene zircon is depleted in the modern Rio Grande delta relative to river sand sampled upstream of Falcon Dam. Mixing calculations performed with age distributions representative of Eocene–Miocene fluvial sedimentary deposits that crop out downstream of the dam indicate that erosional reworking of these materials has significantly altered sedimentary provenance within the delta. The importance of north-directed longshore transport along the Mexican (Tamaulipas-Veracruz) Gulf Coast was also evaluated. The absence of distinctive zircon from the Trans Mexican volcanic belt and the basement of southern Mexico within the barrier islands of the Rio Grande delta support previous conclusions that sediment transport along the Tamaulipas-Veracruz shelf is highly compartmentalized and restricted in lateral movement due to seasonal variation in littoral current polarity, topographic barriers along the shelf, and other phenomena. Nevertheless, the results of this study demonstrate that construction of dams across rivers such as the Rio Grande is capable of sufficiently limiting upstream sediment transport to permit otherwise unimportant local sources to dominate sand provenance within their delta systems.

Making it and breaking it in the Midwest: Continental assembly and rifting from modeling of EarthScope magnetotelluric data

A three-dimensional lithospheric-scale resistivity model of the North American mid-continent has been estimated based upon EarthScope magnetotelluric data. Details of the resistivity model are discussed in relation to lithospheric sutures, defined primarily from aeromagnetic and geochronologic data, which record the southward growth of the Laurentian margin in the Proterozoic. The resistivity signature of the 1.1Ga Mid-continent Rift System is examined in detail, in particular as relates to rift geometry, extent, and segmentation. An unrecognized expanse of (concealed) Proterozoic deltaic deposits in Kansas is identified and speculated to result from axial drainage along the southwest rift arm akin to the Rio Grande delta which drains multiple rift basins. A prominent conductor traces out Cambrian rifting in Arkansas, Missouri, Tennessee, and Kentucky; this linear conductor has not been imaged before and suggests that the Cambrian rift system may have been more extensive than previously thought. The highest conductivity within the mid-continent is imaged in Minnesota, Michigan, and Wisconsin where it is coincident with Paleoproterozoic metasedimentary rocks. The high conductivity is attributed to metallic sulfides, and in some cases, graphite. The former is a potential source of sulfur for multiple mineral deposits types, occurrences of which are found throughout the region. Finally, the imprint left within the mantle following the 1.1Ga rifting event is examined. Variations in lithospheric mantle conductivity are observed and are interpreted to reflect variations in water content (depleted versus metasomatized mantle) imprinted upon the mantle by the Keweenawan mantle plume.

Rapid Mud Accumulation On the Central Texas Shelf Linked To Climate Change and Sea-Level Rise

Abstract The Holocene Texas Mud Blanket (TMB) is a large (~ 300 km3 containing ~ 5 × 1011 t of sediment) depocenter on the central Texas shelf and represents a stratigraphic anomaly in that it is the only significant transgressive-highstand depocenter in the northern Gulf of Mexico other than the Mississippi River Delta. Given its size and remoteness from large rivers, the origin of the TMB has remained problematic. Our results demonstrate that the TMB accumulated mainly in the late Holocene as a result of increased sediment supply from rivers and an increase in delivery of Mississippi River sediments to the region by marine currents. Approximately 3000 km of high-resolution 2D seismic data was used to construct detailed isopach maps of the TMB. A robust radiocarbon age model derived from long sediment cores is used to measure its accumulation through time. Mineralogical (XRD) results provide information about temporal variability in the source of sediments to the TMB and indicate that sediments came mainly from the Colorado, Brazos, and Mississippi rivers, with the Rio Grande and smaller rivers of Texas having been minor contributors. The second largest source is from transgressive erosion of the shelf. The TMB accumulated in a shelf depression that exists between the falling-stage Colorado and Brazos deltas to the north and the Rio Grande Delta to the south. Initial inundation of the outer shelf occurred ~ 17 ka when terrestrial and lagoonal sediments filled the deepest parts of the depocenter. Between ~ 17 and ~ 9 ka was a time of rapid eustatic rise and low sedimentation (VAR, volumetric accumulation rate, = 0.4 km3/ka; MAR, mass accumulation rate, = 0.7 × 106 t/y). At ~ 9 ka, sediment accumulation dramatically increased to 41 km3/ka (69 × 106 t/y). This sediment was mainly generated by ravinement of shelf strata, including the ancestral Brazos and Colorado deltas. Between ~ 7.5 and ~ 4 ka, Texas was experiencing maximum temperature and minimum precipitation for the Holocene (the Climatic Optimum). This was a time of minimum sedimentation in the TMB. This was followed by a period of remarkable growth during the late Holocene (~ 3.5 ka to Present) when the TMB accumulated 172 km3, total volume, or 2.86 × 1011 t of sediment, accounting for 57% of its volume. Mineralogical results, plus the sheer volume of sediment deposited during this time, calls for a corresponding increase in sediment delivery to shelf from the Brazos and Colorado rivers and an increase in the delivery of sediment from the Mississippi River. By the late Holocene the Brazos and Colorado rivers had filled their lower valleys with sediment, thus eliminating onshore accommodation and increasing sediment delivery to the Gulf. The dramatic increase in sediment delivery from the Mississippi River to the TMB during the late Holocene is best explained by an increase in southeasterly winds, which drive westward-flowing marine currents in the northwestern Gulf.

Freshwater fishes and water status in México: A country-wide appraisal.

México is the southernmost country in North America, and extends into Central America, south of the Isthmus of Tehuantepec. The northern half of México is located on the Temperate belt and is arid in character (Nearctic), while the rest is within the Tropical belt (Neotropical). Climate varies from extremely temperate desert in the north, to tropical humid in the south. México has more than 500 freshwater fish species, about 271 of them country endemics, and approximately 48 endemics from binational basins. There are still some 30–40 fish species not yet described. There are 563 fish species colonizing coastal flood plain species. In addition to the numbers of colonizing fishes, the burden of introduced exotics has also been growing. In 1904, only 4 species were recognized as exotics; by 1997 the number had increased to 94, and by 2008 to 115. The main fish collections in Mexico are at IPN, UNAM, and UANL and are the most representative, being national in scope, although concentrated in the tropics, central region, and general in coverage, respectively. The decline of the native fish fauna has been in focus in recent years, usually as trend-in-time comparisons, where the loss of native forms and increase of exotics and/or colonizer species is evident in many basins, mainly in Río Balsas, Río Grande, and Río Lerma-Santiago. As a result, the numbers of species reported at some degree of risk have been increasing also, from 17 in 1963 to 192 in 2005. The trends in colonizers, exotics, and species at risk among Mexican fishes are parallel. The Index of Biological Integrity (IBI), in either its geographical, or historical form (IBIh), has been applied to the Rio Grande/Río Bravo basin, USA and México. IBIh values go between 0–91 (average 31). Alien species are regarded as detrimental. Overall, the IBI trends have been similar in all regions, starting from 70–95% in upper reaches, decreasing to less than 0–35% in the lower reaches of West central basins, and then down to 15% or less near the Lower Rio Grande delta. Several alien species of plecos have been recognized in the rivers Balsas, Grijalva-Río Usumacinta complex, and, also, one in the Rio Grande. Mexican rivers are notoriously dewatered in the northern half of the country. Until 1962, the Rio Grande had an average runoff of 12,000+ millions of cubic meters/year; however by 2002 it was less than 2% of that value. The river went nearly dry along the Big Bend region and was dry for months in the delta region, both in 2002 and 2004. The Rio Grande is mostly dry north of the Río Conchos junction, its main Mexican tributary, and other tributaries provide now between 1% (Río San Juan) and 20% (Río Conchos) of pre-1960 runoff. A modified Index of Biological Integrity for Rio Grande resulted in grades from 70 to 95% of the baseline in upper reaches, less than 35% in lower reaches, to less than 15% near the coast. The Texan version of the IBI was not representative as it suppresses data on euryhaline fishes. The reports of total toxics were masked, since the sum should have included both organics and heavy metals exceeding USA regulations to the total count, but only one of the two was included.

Petrologic database to define the human-reworked, sediment-deficient plain of the Rio Grande delta, Texas

Petrologic investigation of surficial samples collected on the Rio Grande delta plain in Texas in 1999 provides the record of a sediment cover resulting from interaction of natural transport processes and rapidly increased human activity. Numerous sediment samples collected in 10 different depositional environments identified on the plain are used to generate a database that includes information on grain size, total organic matter and composition of sand-size particles. Petrologic data record a less altered sediment cover than might have been expected, with little overall blurring of areal boundaries of depositional environments and obvious modification of original depositional facies. This apparent lack of sediment change has occurred in spite of markedly diminished discharge of water and sediment to the Rio Grande delta, and continued in situ anthropogenic reworking of the pre-dam (1916 and older) surficial cover. The most important influence on delta plain evolution since the latter half of the 1800s has been artificial subdivision of the former plain into hundreds of small, sediment-starved sections that are topographically and hydrographically isolated from each other by a dense network of irrigation canals, levees and roads. Human activity has artificially transformed the original Holocene Rio Grande delta to a destructional phase coastal plain that is no longer progradational, but rather undergoing substantial coastal erosion.

Abstract: Surface Geology of the Rio Grande Delta, United States-Mexico, a GIS Layer

Abstract: Surface Geology of the Rio Grande Delta, United States-Mexico, a GIS Layer

Plants of the Rio Grande Delta

Plants of the Rio Grande Delta

Sequence Stratigraphic Model of the Rio Grande Delta, South West Texas: Potential Analog for the Niger Delta: ABSTRACT

A sequence stratigraphic model developed from the ancient Rio Grande Delta in South West Texas is suggested as an analog for the Niger Delta. The two delta systems are characterized by high sand bedloads, shale diapirism with associated listric normal faulting, and large amounts of tidal and wave influence forming lower coastal plains characterized by swamps and estuaries. The sequence stratigraphic model of the ancient Rio Grande delta is based on approximately 1200 kilometers of single channel, 15 cubic inch water gun data, lithologic descriptions from approximately 25 long cores (28-30 m) located in 17-94 meters water depth, three gamma ray logs, paleontologic data from two cores, and oxygen isotopic data from one core (152 meters in length and located in 94 meters water depth). The combined data indicate that considerable quantities of sand are sequestered on the continental shelf and point sourcing the slope. The Rio Grande sequence stratigraphic model provides an improved understanding of sand deposits on the shelf, of the role of sediment bypass during lowstands, and of the base of slope deposits formed by headward eroding canyons ( ) or channels ( ) located at the shelf break. This information regarding the distribution of sand inmore » the Rio Grande system can provide valuable insight into the reservoir distribution in the Niger system, improving existing reservoir predictions.« less

Oversize Oxbows: Tentative Dates, Effects and Risks

ABSTRACT An oversize oxbow is a river-channel remnant having a channel width greater than the modern one. Many such lakes, two to six times as wide as the modern stream, represent runoff up to 125 inches/year (317 cm/yr). These oxbows are not due to stream piracy or glacial meltwater. Sea level history is known at 50-year intervals from work in Denmark. The best times for oversize oxbows were 6,500-5,600 B. P. (mid-Holocene high) and 1,800 B. P., and the best times for undersize channels, 5,000-4,000 B. P. and 800-200 B. P. (Little Ice Age). Data from the Rio Grande delta system suggest that many oversize channels formed at various times in the last 3,000 years, and represent common, rather than rare, conditions. A modest northward shift of the boundary between dominant dry westerly winds over the southern states and dominant, wet easterly winds over the Gulf of Mexico should increase east-west air flow from the Atlantic Ocean across those states and increase rainfall. Reversal of the Dog Island (Florida) sand transport system, some 250 years ago, suggests this shift.

Indians of the Rio Grande Delta: Their Role in the History of Southern Texas and Northeastern Mexico

Indians of the Rio Grande Delta: Their Role in the History of Southern Texas and Northeastern Mexico

Review: Indians of the Rio Grande Delta: Their Role in the History of Southern Texas and Northeastern Mexico, by Martín Salinas

Review: <i>Indians of the Rio Grande Delta: Their Role in the History of Southern Texas and Northeastern Mexico</i>, by Martín Salinas

Indians of the Rio Grande delta: their role in the history of southern Texas and northeastern Mexico

Foreword by Thomas R. Hester Acknowledgments 1. Introduction 2. The Environmental Setting 3. Historical Background 4. The Rio Grande Delta 5. Coastal Areas North and South of the Rio Grande Delta 6. Northeastern Nuevo Leon 7. Culture 8. Historical Demography 9. Languages 10. Spanish Missions Nearest to the Rio Grande Delta 11. Summary and Conclusions References Index

Classification of Offshore Gulf of Mexico Oils and Gas Condensates (1)

Five groups of petroleums can be recognized in the offshore Gulf of Mexico on the basis of carbon isotope and sulfur isotope ratios, sulfur content, and relative abundances of nickel and vanadium. Of 355 oils analyzed, 341 (96.1%) are evidently closely related, and cannot be subdivided on the basis of carbon or sulfur isotopes. We suggest that these oils represent a single broad superfamily. However, two subgroups within this set are distinguishable on the basis of sulfur content and relative abundances of nickel and vanadium: group 1A, (sigma){13}C = -26.5 +/- 0.4 parts per mil, (sigma){34}S = -5.6 +/- 2.4 parts per mil, %S = 0.25 +/- 0.15%, V/(Ni + V) = 0.27 +/- 0.10; and group 1B, (sigma){13}C = -26.5 +/- 0.3 parts per mil, (sigma){34}S = -5.9 +/- 1.2 parts per mil, %S = 0.73 +/- 0.43, V/(Ni + V) = 0.67 +/- 0.07. Group 1A oils are broadly distributed across the Louisiana and adjacent Texas continental shelf, whereas group 1B oils are found along the Louisiana shelf edge and continental slope. Group 1B oils have substantial genetic affinities to those from the Campeche Shelf, offshore Mexico, of Mesozoic origin. The remaining 14 analyzed petroleums include supermature condensates from offshore Texas, and oils from offshore southern Florida believed to be cogenetic with those from the Jurassic Smackover Formation. A three-dimensional appraisal of geohistory suggests that petroleum generation began in the Eocene in the region of the Rio Grande delta, progressed coastwise to the Mississippi delta area by the Miocene, and then occurred in regions of progres ively deeper water during the Pliocene-Pleistocene.

Distribution and Significance of Coarse Biogenic and Clastic Deposits on Texas Inner Shelf: ABSTRACT

Sediments of the Texas inner shelf are fine grained; coarse clasts (> 0.5 mm) are uncommon (< 1%) over much of the area. Higher concentrations of coarse material, however, occur in discrete areas which apparently represent positions of former deltas. Coarsest constituents are predominantly whole shells and shell fragments with subordinate amounts of lithic clasts. The calcareous skeletal debris represents a mixture of extant shelf fauna and relict brackish-water mollusks including Ragina sp. and Crassostrea virginica. Rounded sandstone and mudstone clasts up to 7 cm long and caliche nodules are common in some areas. Maps showing (1) coarse-fraction percent, (2) distribution of brackish-water mollusks, and (3) rock fragments show similar trends outlining ancestral Ri Grande, Brazos-Colorado, and Trinity deltas. A patchy, arcuate trend between Pass Cavallo and Aransas Pass is enigmatic. Criteria used to determine relative ages of shell debris for each of the four trends are degree of abrasion, fragmentation, etching, boring, and discoloration. Possible explanations for concentration of coarse material include high productivity, low rates of terrigenous clastic sedimentation, selective deposition by modern shelf processes, and reworking of locally shelly relict deposits exposed on the seafloor during the Holocene transgression. However, no single explanation adequately accounts for areal variations in coarse material. Reworking of delta-plain and estuarine deposits during and following sea-level rise is common to all areas which at present are also sites of insignificant coarse-sediment influx. Sabine-Bolivar trends are interpreted as transgressive lags derived from erosion of a late Pleistocene Trinity delta previously dissected by the Sabine River during Wisconsin glaciation. In contrast, Brazos-Colorado and Rio Grande tre ds are interpreted as possibly compound strandline features associated with subsidence, erosion, and retreat of Holocene deltas. Upwelling of nutrient-rich shelf waters and freshwater inflow also may have increased productivity of shelf benthos near the Rio Grande delta. End_of_Article - Last_Page 1608------------

Characteristics of Shallow Subsurface Faults on Texas Inner Shelf: ABSTRACT

Faults mapped on the Texas inner shelf from high-resolution sparker profiles show diverse densities, continuities, orientations, displacements, and degrees of recent activity. Potentially active faults either intersect or are near the seafloor at the upper limit of detection on geophysical records, whereas inactive faults are usually overlain by continuous seismic reflectors. Fault characteristics are broadly defined by geologic age, depositional history, and degree of tectonic subsidence. Faults of greatest density and lateral continuity (< 27 km) are peripheral to the Rio Grande delta, an area of active Holocene deposition. Faults are equally dense and less continuous (< 16 km) near the Brazos-Colorado delta, whereas presently active faults are rare between the de tas except near Corpus Christi. Faults are least continuous (< 5 km) and dense along the upper coast which has remained relatively stable during the late Quaternary. Displacements at depths of 150 m range from 3 to 30 m; most displacements, however, are between 3 and 10 m when rollovers are discounted. These en echelon growth End_Page 498------------------------------ faults coincide with the regional onshore (Willimar) trend oriented subparallel with the coast. Most are down-to-basin faults, but up-to-basin faults also occur. Some topographic highs on the seafloor apparently formed by differential erosion of zones preferentially cemented by fluids migrating along fault planes. Seafloor expression of diapiric structures with radial faults is negligible; however, surface sediments near these structures exhibit subtle changes, which suggests minor differences in slope. Quaternary sediments, specially fluvial sediments, were also locally controlled by faulting. End_of_Article - Last_Page 499------------

A sediment-dispersal model for the South Texas continental shelf, northwest Gulf of Mexico

Textural-distribution patterns of sea-floor sediments on the South Texas continental shelf between Matagorda Bay and the U.S.—Mexico international boundary were evaluated as part of a regional environmental-studies program. Sediment textural gradients support a conceptual model for the regional sediment-dispersal system, which is characterized by both net offshore transport and net south-trending coastwise transport components on a wind-dominated shelf. Coastwise transport results in the net southward migration of both palimpsest sandy mud composing the ancestral Brazos—Colorado delta flank in the northern sector, and modern mud composing the central sector; these migrating sediments are encroaching southward onto immobile relict muddy sands composing the ancestral Rio Grande delta in the southern sector. In the proposed model, the suspension transport of modern silt-enriched mud derived mainly from coastal sources is the dominant dispersal mechanism. Net offshore transport is attributed both to diffusion, and to the advective ebb-tide discharge of turbid lagoonal-estuarine waters from coastal inlets. Net southward transport is attributed mainly to advection by seasonally residual coastwise drift currents reflecting a winter-dominated hydraulic regime. Frequent winter storms characterized by relatively high-speed northerly winds that accompany the passage of cold fronts appear to be dominant regional dispersal agents.