A COMINED ISOTOPE (C, O, H and Sr) AND CHEMICAL STUDY OF CRUDE
OILS AND FORMATION WATERS FROM THE UPPER CRETACEOUS WOODBINE AND LOW
CRETACEOUS TRAVIS PEAK FORMATIONS, EAST TEXAS BASIN.
Vladimir V. Liakhovitch
The project is designed to characterize the regional variations in the isotopic and chemical composition of the crude oils and formation waters from the Upper Cretaceous Woodbine and Low Cretaceous Travis Peak formations, East Texas basin. The overall goals of the study are: 1) to reconstruct the diagenetic history of the waters, 2) to discuss a possible bearing of local geological structures (salt domes, fault zones, etc.) on the compositional variations, 3) to detect any correlation between the composition of coexisting crude oil and formation water, and 4) to determine if the oil and aqueous phase migrated together from their source (source formation) to the trap (producing formation). The Upper Cretaceous Woodbine and Low Cretaceous Travis Peak formations are the main oil-producing formations of the East Texas basin separated by the regionally defined aquitard, the Ferry Lake Massive Anhydrite. Our data confirm that the Upper Cretaceous and Low Cretaceous waters differ in their chemical, radiogenic (Sr) and stable isotope (O, H and C) composition and follow different evolutionary paths representing two major hydrologic subsystems in the basin. The East Texas crude oils are of Upper Cretaceous, Low Cretaceous and Jurassic origin. A combined geochemical and isotope study of the crude oils and formation waters from the two formations not only allows one to reconstruct the evolution and circulation of the aqueous and oil phases in one of the world's largest continental basins but also provides a unique opportunity to address a most intriguing problem of petroluem geology: "Do formation waters reflect reservoired oil?"
A PRIMITIVE HADROSAUR (DINOSAURIA: ORNITHISCHIA) FROM
THE CENOMANIAN OF TEXAS AND ITS IMPLICATIONS FOR
HADROSAURIAN PHYLOGENETIC AND BIOGEOGRAPHIC HISTORIES
Jason J. Head
The nearly complete skull of a hadrosaur from the Cenomanian Woodbine Formation
(95 Ma) of northeast Texas is a mixture of derived hadrosaurian and generalized
iguanodontid characters. The premaxillae form an expanded rostral bill, a
wide diastema occurs between the predentary and dentary tooth battery, and
the maxillary teeth are small. The jugal-ectopterygoid articulation and surangular
foramen are retained, and the quadrate is massive with poorly differentiated
mandibular condyles. The most striking features of the specimen are the massive,
expanded dentary and ventrally deflected
Phylogenetic analysis places the specimen at the basal position within Hadrosauridae. The age and location of the Texas hadrosaur along the eastern coast of the Western Interior Seaway makes it the oldest definitive hadrosaur from eastern North America, and indicates that the suggested Turonian radiation of hadrosaurs from western Asia may have occurred earlier elsewhere.
ARRAY MEASUREMENTS OF TELESEISMIC P AND PcP SLOWNESS AND
AZIMUTH RESIDUALS WITH IMPLICATIONS FOR LATERAL
HETEROGENEITY IN THE LOWER MANTLE
Ileana M. Tibuleac
Anomalous slowness residuals as large as 2-3 s/deg, for P waves turning in the lower-most mantle as well as for PcP waves, were observed for all the seismic arrays in North America. Actual data recorded at TXAR (Lajitas, Texas) present definite patterns with abrupt changes of sign between different regions. Seismic reflections from the Earth's core (PcP) show angles of incidence up to 75 percent greater than predicted by the standard Earth model currently used in seismology. The variations are reflected also by the azimuth residuals but not by the travel time residuals.
These observations indicate that the velocity gradient in the lower 1500 km of the mantle in the vicinity of the reflection points is not radial as assumed in the standard model, but is significantly inclined. A non-radial gradient is to be expected in the transition zone between high velocity and low velocity regions in the lower mantle.
The method uses short period (about 1 second) P and PcP waves, therefore has a resolution of several tens of kilmoeters, unattained by other previously used methods and should prove to be a powerful tool for the investigation of mantle velocity structure when used in conjunction with travel time tomography.