The index is divided because of the large size of the complete index. It is lignitic with alternating lenses of silt and clay. Formation, sparta sand, yegua formation, and the laterally equivalent cockfield formation. Fossil mammalia of the huerfano formation, eocene, of colorado peter robinson part i geology introduction the study of the huerfano mammals presented here is the result of a project initiated in 1952 by dr. Kellogg had indicated the source bed as the yegua formation, immediately overlying the. Gas play in the burgos basin, mexico the yegua formation eocene in the burgos basin is divided into three units. Sealing lithologies probably are shaley facies within the claiborne and in the overlying jackson group. The drilling pattern forms a t, with three well clusters along the dip direction and two along strike. The yegua formation is a geologic formation in texas. Eocene, south central texas was on the northwestern margin of the gulf of mexico, fluctuating in time from coastalplain to shallowmarine environments fig. Eocene yegua formation claiborne group and jackson group.
The yegua formation late middle eocene is a minor siliciclastic progradation of the gulf of mexico shelf margin between the larger early eocene and. Gaswaterrock interactions in frio formation following co. Fossil mammalia of the huerfano formation, eocene, of. The properties of a sheared zone in the eocene yegua formation were investigated to evaluate the trapping capacity of faults. The yegua and cook mountain formations make up the upper part of the eocene claiborne group fig. The yegua formation is a minor siliciclastic progradation off the gulf of mexico shelf margin. The biodiversity heritage library works collaboratively to make biodiversity literature openly available to the world as part of a global biodiversity community. To purchase this publication as a pdf download, please order gc7804d. Formation of highfrequency sequences and their bounding.
The socalled heterostegina limestones of anahuac age are minor reservoirs in this play. Depositional trends in siliciclastic deposits of the stone. The yeguajackson aquifer extends in a narrow band 15 to 40 miles wide from the rio grande and mexico across the state to the sabine river and louisiana. The eocene of the gulf region is commonly divided into four partsthe midway, wilcox, and claiborne groups and the. Strata of the crockett formation interval are referred to the cook mountain formation in the subsurface, where the unit expands upward to include fine grained strata equivalent to the lower part of the yegua formation ewing, 1994a. Nomenclature of formations of claiborne group, middle eocene. The lignite deposits within the upper eocene yegua formation claiborne group and the overlying jackson group are among the. Map showing depth to the top of claiborne yegua formation constructed from the ihs energy. Sanidine 40 ar 39 ar dates and zircon upb dates of middle eocene to late oligocene volcanic ash beds provide highresolution geochronology for the northern gulf of mexico. In texas, this outcrop area stretches in a relatively thin band approximately parallel to the coastline, from starr county in the rio grande valley to. There was so much material, i had to be choosy in what i picked up. Randy jones of brazoria, texas and is from the middle eocene yegua formation, approximately 40 miles southeast of san antonio and about 3 miles north of.
Pdf cenozoic depositional history of the gulf of mexico basin. The yegua formation late middle eocene is a minor siliciclastic progradation of the shelf margin between the larger early eocene and. Hydrocarbon traps dominantly are rollover anticlines associated with growth faults. The lithologic character of the yegua in the rio grande embayment is somewhat different from that to the northeast.
Stenzel 1936 designated the exposures at stone city bluff as the type section of the stone city formation. The yegua formation late middle eocene is a minor siliciclastic progradation of the gulf of mexico shelf margin between the larger early eocene and oligocene shelfmargin progradations. Yegua formation late middle eocene in the gulf coast basin, as a. Alluvium holocene at surface, covers 21 % of this area.
The eocene yegua formation of the texas gulf coast is made up of six such sequences, which have average durations of 0. The carrizo sand, the basal formation, and the yegua formation, the uppermost formation of the claiborne group, remain unchanged. Mammalia from the middle eocene yegua formation claiborne group, houston county, texas. Stratigraphy, paleontology, and depositional systems of the eocene gub mountain formation, lincoln county, new mexicoa preliminary report by spencer g. Ten new dates are reported, five for upper eocene jackson group strata and five for oligocene. Reservoirs in this play include sandstones of the paleocene to eocene wilcox group, the eocene yegua and jackson formations, the oligocene vicksburg, frio, and anahuac formations, and lower and middle miocene units. Green river formation university of california museum of. The globigerinatheka semiinvoluta foram zone appears in the moodys branch formation of the jackson group overlying the yegua formation and the orbulinoides beckmanni foram zone occurs below the lowest sandbearing units in the cook mountain. The dates coincide with silicic volcanism generated as north america moved closer to the pacific spreading axis. Ps usgs assessment of undiscovered conventional oil and gas resources, middleupper eocene claiborne group, gulf of mexico onshore and state waters, usa. George gaylord simpson, then curator of fossil mammals and birds at the american museum of natural history and now alexander. As we near lagrange you can see monument bluff on the right. Structure of the yeguajackson aquifer of the texas gulf coastal. Nomenclature of formations of claiborne group, middle.
Cook mountain formation eocene at surface, covers 15 % of this area. The thermal maximum of the mideocene represented by the yegua formation and the slightly drier late eocene jackson group are wellknown among collectors for their diversity of tropical hardwoods, many of which are preserved as whole logs in fluvial, estuarine and nearshore environments. The ground was nothing more than sand studded with wood chunks large and small. Transactions of the gulf coast association of geological societies, v. Environments of deposition of the yegua formation eocene, brazos county, texas. The boundary between the middle and late eocene is taken as the boundary between the cook mountain and yegua formations. Layman, thomas bruce, 1957share facebook twitter linkedin. M geological cross sections, development geology manual, d. Sedimentary organic matter sources and depositional. This article contains the abstract, figures, and references presented april 22, 2008, in a poster. Stratigraphy, paleontology, and depositional systems of. Sandbody geometry and the occurrence of lignite in the eocene of texas downloadable pdf. Yegua formation late middle eocene in the gulf coast basin. Eoceneoligocene chronostratigraphy of ignimbrite flareup.
The eocene yegua formation of the texas gulf coast is an ideal unit to assess the utility of the regime ratio approach towards the formation of highfrequency cycles and their bounding sur faces. It preserves fossils dating back to the paleogene period geological structure. The lower yegua is sandstone deposited in a near shore environment of a highstand systems tract hst, whose top is. Pdf a paleogene ichnological record from the wilcox. The formation is bounded above and below by glauconitic and marine claystones of the cadell and cook mountain formations kaiser, 1986. A mineralogical investigation by xray powder diffraction and optical, scanning, and transmission electron microscopy of partially weathered petrified wood in the yegua formation eocene of eastcentral texas revealed that microcrystalline quartz present in the unaltered petrified wood has been gradually dissolved and replaced by disordered silica polymorphs mainly opalct as a result of. This is a subject index to geology and a few geologyrelated theses and dissertations completed at the university of texas at austin. The yeguajackson aquifer exists predominantly in the outcrop or nearoutcrop areas of the yegua formation and jackson group. Pdf a geographic information system gis database incorporating. This band is from 70 to 120 miles inland and of generally parallels the gulf of mexico coast. Pdf on dec, 2018, maria i hernandezocana and others published a paleogene ichnological record from the wilcox formation. The sediments in the study area are from the middle of the yegua formation, and consist of layers of fine to medium sand, mudstones. Ut austin theses, by year university of texas at austin.
Environments of deposition of the yegua formation eocene. Trapping capacity of faults in the eocene yegua formation. University of texas geology thesis index, heading y. The middle eocene yegua formation is the uppermost unit of the claiborne.
Paleoenvironmental significance of benthic foraminiferal. Yegua formation middle eocene at surface, covers 21 % of this area. Predicting the locations and geometry of downdip sandstone reservoirs in the yegua trend of texas and louisiana is a key challenge to. Van dalen, stephen craig, 1981, depositional systems and natural resources of the middle eocene yegua formation, south and central texas coastal plain. The fur formation is a marine geological formation of ypresian lower eocene epoch, c. The green river formation is the site at which the fossil of the oldest known flying mammal was found. Composite section of the upper middle eocene, upper eocene and lower oligocene and selected palynomorph. Eocene yegua formation claiborne group and jackson group lignite deposits of texas. Foraminiferal data analysis and lithofacies analysis of a threewell transect through the middle eocene yegua formation in southeast texas provide insights into the depositional and paleoenvironmental history of the gulf of mexico basin. During yegua time and unlike the other units of the middle and late eocene, four to eight sealevel fluctuations with a 100300 ka period alternately pushed marine rocks toward the basin margins and pushed. Traditionally, the boundary between the yegua and cook mountain was based on the first.
At times large delta plains with channels, coastal marshes, and bays e. Replacement of quartz by opaline silica during weathering. Name blue point marker applied to middle ash bed which is dated as 47. An eocene fossil tree with cambial variant wood structure citeseerx. The yegua formation is the uppermost unit of the eocene claiborne group, and is about 787 m thick in brazos county, texas. It lies between the larger early eocene and the oligocene shelfmargin progradations during yegua time, around four to eight sealevel fluctuations with a 100300 ka. Middle claiborne sparta sand and cook mountain formation. Fauna of wapiti listed plants, fishes, reptiles, mammals and described. Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. The yegua formation eocene in the burgos basin is divided into three units.
Ophiomorpha and venericardia venicor zapatai in the burgos basin. Paleoenvironmental significance of benthic foraminiferal biofacies in the yegua formation middle eocene, southeast texas. The site is the playground behind an elementary school, and it was chockfullowood. They formed in response to distinct variations in the rate and quantity of sediment supply, increases and decreases in the average grain size carried into the basin, relative sealevel position, and the. Yegua formation upper lower nonionella cockfieldensis anomalina perforata discorbis yeguaensis eponides mexicana gyroidina octacamerata eponides yeguaensis nodosaria mexicana anomalina umbonatus middle eocene, cook mountain formation.
An eocene fossil tree with cambial variant wood structure f. Mapped along southern edge of map sheet in madison co. The yegua formation, chiefly sand with less clay in the north east, is chiefly clay with less sand and some banks of oyster shells in the rio. Porosity and permeability of the sheared zone range from 10 to 12% and 1 to 5 md. Geologic assessment of undiscovered conventional oil and. The upper eocene jackson group begins approximately at plum but is poorly exposed along this highway. Geologic assessment of undiscovered conventional oil and gas. Abstract lignite occurs in three eocene stratigraphic unitsthe wilcox group, yegua formation, and jackson groupand in three ancient depositional systemsfluvial, deltaic, and strandplainlagoonal. An 11m core of yegua sandstone at a depth of 3029 m shows highly sheared bedding and increasing dip from 10 to 30 with depth.
Occurrence of fossil woods in texas, primarily the. This organism, a bat, icaronycteris index, was preserved with its skeleton, membranes and cartilage intact. It was discovered along with food still inside its body and waste not yet disposed, so some of the flora, algae, pollen and arthropods of the time can be studied. Dissolved organic carbon doc concentrations in five shallow q q 20. Usgs assessment of undiscovered conventional oil and gas. The yegua jackson aquifer exists predominantly in the outcrop or nearoutcrop areas of the yegua formation and jackson group.
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