Boundary In Texas Research Articles

Global bioevents and the Cretaceous/Paleogene boundary in Texas and Alabama: Stratigraphy, correlation and ocean acidification

Abstract With increasing levels of atmospheric pCO2 the oceans are becoming progressively more acidic, with the impact of a lowered pH beginning to affect the calcification of numerous invertebrate groups, including foraminifers, pteropods, heteropods and calcareous nannoplankton. Research on the ecology of foraminifera in the Mediterranean Sea, Gulf of California, Caribbean Sea and elsewhere has shown how modern assemblages are responding to acidification. Experimental work in mesocosms and laboratory cultures are also adding to our knowledge of the response to pH changes. Near Ischia (Italy), natural CO2 vents amongst sea grass meadows are creating low pH environments in which it is possible to observe the response of benthic foraminifera. At a pH of 7.8 the foraminiferal assemblages are already becoming less diverse and below pH 7.6 there are often no calcite-secreting benthic foraminifera. In the Gulf of California, in a deeper-water setting, natural CO2 (and methane) vents are also lowering sea floor pH. The foraminifera show the impact of this change, although the relatively high carbonate saturation ensures that calcite-secreting foraminifers are able to live and reproduce in these relatively low pH environments, only becoming impacted by dissolution effects once dead. Using data from the Cretaceous–Paleogene boundary in Texas, Alabama and north-west Europe it is clear that the plankton was severely impacted by surface water acidification while the relatively shallow water benthic foraminifera show little change and no visible signs of post-mortem dissolution due to ocean acidification.

Linguliform brachiopods across a Cambrian–Ordovician (Furongian, Early Ordovician) biomere boundary: the Sunwaptan–Skullrockian North American Stage boundary in the Wilberns and Tanyard formations of central Texas

AbstractThe Cambrian-Ordovician Diversity Plateau, between the Cambrian Explosion and the Ordovician Radiation, is punctuated by a series of well-documented Laurentian trilobite extinction events. These events define the bounding surfaces of trilobite ‘biomeres’ that correspond to North American stages, including those of the Sunwaptan and Skullrockian. Trilobites show a consistent pattern of recovery across these boundaries, and commonly each extinction and replacement of taxa is interpreted as a single event as changing environmental conditions spurred shoreward migration of shelf or oceanic faunas that displaced established cratonic faunas. Linguliform brachiopods are also abundant in strata of this interval, and we investigate their stratigraphic distribution across the Sunwaptan–Skullrockian Stage boundary in Texas through high-resolution stratigraphic sampling of subtidal sediments. We document complete genus- and species-level turnover of the linguliform brachiopod fauna coincident with trilobite extinction events, suggesting that these brachiopods were affected by the same factors that affected trilobites. The Skullrockian replacement fauna was cosmopolitan, with ties to Gondwana and Kazakhstan and to the Laurentian shelf environment. The timing of appearances of taxa suggests that the faunal migration onto the Laurentian shelf came from elsewhere during a transgression. The disappearance of the Sunwaptan fauna and the arrival of the Skullrockian fauna are distinct events. We suggest that ‘biomere’ events may be complex, and the cause of the extinction is not necessarily the same event that facilitates the appearance of a replacement fauna. We describe one new species,Schizambon langei.UUID:http://zoobank.org/f6a5c11f-cd3d-4c16-b184-d808d3a5285f

Numerical age calibration of the Albian/Cenomanian boundary

New biostratigraphic and sequence stratigraphic correlations of the U.S. Western Interior Albian/Cenomanian sections with North Texas and European sections calibrate the Albian/Cenomanian boundary at 97.2 Ma, which supports previous correlations in the Western Interior. This age, however, is 2.4 myr younger than the recent calibration at 99.6 Ma derived from radiometric ages of volcanic beds with diagnostic marine fossils in northern Japan. This discrepancy suggests that additional analyses are required to test the age calibration of the geologic time scale. New data of cosmopolitan dinoflagellates enable direct correlation with the European reference sections of the Albian and Cenomanian. Previous correlations in the Western Interior were based on endemic or Boreal ammonites. The first and last occurrences of dinoflagellate species bracket the Albian/Cenomanian boundary in Europe and many of these species also bracket the Clay Spur Bentonite bed previously dated 97.17±0.69 Ma. The high number of radiometrically dated bentonites in the Western Interior provides a numeric age control for the ranges of many dinoflagellates. Sequence stratigraphic correlation of the North Texas section with the U.S. Western Interior sections also demonstrates that the Clay Spur Bentonite bed correlates with the Ablian/Cenomanian boundary in Texas defined by the ammonite succession. The flooding contact SB WA6 in Texas at the Albian/Cenomanian zonal boundary of Stoliczkaia dispar and Mantelliceras mantelli correlates into the Western Interior with an erosional sequence boundary SB4 at the base of the Romeroville Sandstone in New Mexico and the Dakota Sandstone in Colorado. This contact correlates with the base of the Belle Fourche Shale that overlies the Clay Spur and the Mowry Shale in Montana. The revised correlation of the Western Interior poses two questions. 1) What is the accurate age of the boundary? Both cannot be correct. 2) What were the durations of the Albian and Cenomanian stages? Cyclostratigraphic analyses estimate that the Albian was 11.9 to 11.6 myr in duration but the Western Interior data project the duration at about 15 myr.

CONTINUED RANGE EXPANSION BY BRONZED COWBIRDS IN THE SOUTHWESTERN UNITED STATES

Abstract The brood-parasitic bronzed cowbird (Molothrus aeneus,) continues to expand its range in New Mexico and Texas. The current breeding range is 280 km outside of the historic breeding range. In Texas, spread rate increased from 6.22 km per year prior to 1956 to 13.75 km per year after 1956. Spread rate in New Mexico was constant at 12.72 km per year. Flight-range estimates based on fat indices of spring migrant cowbirds trapped at their northern range boundary in Texas suggest the potential for migration 341 km further north. We discuss factors that might limit or promote further range expansion.

Stratigraphic placement of the Santonian-Campanian boundary (Upper Cretaceous) in the North American Gulf Coastal Plain and Western Interior, with implications to global geochronology

Recent micro- and macropaleontological research in the northern Aquitaine Basin of France, the stratotypic area for the Upper Cretaceous Santonian and Campanian Stages, was used to resolve a long-standing discrepancy in the stratigraphic position of the Santonian-Campanian boundary in east-central Texas as based upon zonations of planktonic foraminifers versus ammonites. On the basis of the presence in Texas of species of ammonites restricted to the lower reaches of the basal Campanian Placenticeras bidorsatum Zone of the Aquitaine Basin, the Santonian-Campanian boundary in Texas is significantly lower than has generally been considered by micropaleontologists. Specifically, it is within the foraminifer-based Globotruncana (= Marginotruncana ) concavata Zone ( sensu lato ). Such placement involves middle reaches of the type Austin Chalk, perhaps within the Dessau Chalk Member. An assumption that underlies the following conclusions is that the boundaries of the G. concavata Zone as recognized in European Tethys, the Atlantic and Caribbean basins, and North American Gulf Coast represent approximately synchronous stratigraphic levels. The following represent additional conclusions of pertinence to global chronology of the Cretaceous. (1) Rather than being younger than the Globotruncana concavata Zone, the Placenticeras bidorsatum Zone should be thought of as being contemporary with at least the younger half of the G. concavata (species total range) Zone. (2) Most of the Merchantville and Magothy Formations on the Atlantic seaboard of New Jersey and Delaware were deposited during early Campanian time, rather than principally during the Santonian. (3) The traditional placement of the Santonian-Campanian boundary in the Western Interior of North America slightly below the zone of Scaphites hippocrepis I is essentially correct. (4) The chronology of the Niobrara Formation of the North American Western Interior as based upon planktonic foraminifers is shown to be in serious error; specifically, it has been considered much too young. (5) Paleomagnetically sampled parts of the Niobrara Formation probably correlate with upper reaches of the “Cretaceous Long Normal Interval”, below magnetochron 33R. (6) Although the Santonian Stage surely represents a surprisingly brief interval of earth history, the Coniacian-Santonian boundary probably should be placed below the G. concavata Zone. (7) The Santonian-Campanian boundary slightly post-dates initiation of the last general Cretaceous regression of the North American Western Interior Seaway. (8) The beginning of the North American Aquilan Land Mammal “Age” represents earliest Campanian time. (9) Rather than representing an earliest Campanian geomagnetic event, the temporal span of global magnetochron 33R equates with approximately the second quarter of the total duration of the Campanian.

A Tsunami Deposit at the Cretaceous-Tertiary Boundary in Texas

At sites near the Brazos River, Texas, an iridium anomaly and the paleontologic Cretaceous-Tertiary boundary directly overlie a sandstone bed in which coarse-grained sandstone with large clasts of mudstone and reworked carbonate nodules grades upward to wave ripple-laminated, very fine grained sandstone. This bed is the only sandstone bed in a sequence of uppermost Cretaceous to lowermost Paleocene mudstone that records about 1 million years of quiet water deposition in midshelf to outer shelf depths. Conditions for depositing such a sandstone layer at these depths are most consistent with the occurrence of a tsunami about 50 to 100 meters high. The most likely source for such a tsunami at the Cretaceous-Tertiary boundary is a bolidewater impact.

Biostratigraphy of Albian-Cenomanian Boundary in Texas and Implications for Middle Cretaceous Stratigraphy Elsewhere in North America: ABSTRACT

On the basis of comparison of ammonite zonations in Texas and western Europe, the Albian-Cenomanian boundary in Texas is placed in the lower part of the Grayson Formation of the Washita Group. This position contrasts with the Comanchean-Gulfian Series boundary, normally placed at the top of the Washita Group. Comparison of polynomorphs from the Grayson and associated strata with those of other North American middle Cretaceous units reveals inconsistencies in the designations of Albian ages in other areas. Spore-pollen assemblages from the subsurface Dantzler Formation in Mississippi and Louisiana (previously considered Albian) include age-diagnostic taxa characteristic of the Maness and lower Woodbine formations (Cenomanian) in Texas. The Albian-Cenomanian boundary therefore occurs at a major unconformity between the Dantzler and underlying Fredericksburg Group, rather than at the unconformable top of the Dantzler, below Tuscaloosa Group sandstones. Palynology also indicates correlation of the type Dakota Formation of Nebraska and Iowa to the Cenomanian Maness-Woodbine in Texas, overlying the major middle Cretaceous unconformity. In northern Arizona, the Dakota Sandstone contains a Cenomanian assemblage similar to that of the type Dakota, but in Wyoming and Colorado, units traditionally referred to the Dakota Group (e.g., Muddy formation) are clearly Albian in age, and lie belowmore » the middle Cretaceous unconformity. These correlations shed new light on the sedimentary and stratigraphic relationships of unconformities and lithologic units in the middle Cretaceous of central and western North America.« less

The Albian-Cenomanian (Lower Cretaceous-Upper Cretaceous) boundary in Texas and northern Mexico

As first designated by Böse, the Albian-Cenomanian (Lower Cretaceous-Upper Cretaceous) boundary in northern Mexico and Texas is selected at the base of the ammonite zone ofPlesioturrilites brazoensis(Römer). This boundary seems to best agree with boundaries selected for North Africa and Europe, but in North America it may not be the optimum boundary for paleontologists working with foraminiferans.

Iridium anomaly at the Cretaceous-Tertiary boundary in Texas

A fifty-fold increase in the iridium content precisely at the Cretaceous-Tertiary boundary over background values has been found in the Brazos River section in Texas.

Notes on Amphibians and Reptiles from the Central United States

From March through October, 1942, herpetological collections were made along the 100th parallel and west to the 103rd, from the International Boundary in Texas, through Oklahoma and Kansas, into Nebraska. A few specimens were taken in New Mexico, Colorado, and South Dakota. In addition to the 499 specimens collected by the writer, John W. Anderson collected 21; John Davis, 6; Earl S. Herald, 267; Stanley G. Jewett Jr., 32; and Charles G. Sibley, 27; making a total of 852 specimens. Thanks are due all of these for the permission to include their material in this report, as well as for the privilege of examining their field notes. All specimens have been catalogued and complete data may be found in the Natural History Museum, Stanford University.