Late Upper Cretaceous Research Articles

Integrative taxonomy of a new species of Therodamas (Ergasilidae) infecting the Amazonian freshwater fish Leporinus fasciatus (Anostomidae).

Crustaceans of the subclass Copepoda are an important component of the invertebrate aquatic fauna. They occur in all aquatic environments and include some representatives that are free-living organisms and others that have a parasitic lifestyle. The genus Therodamas comprises marine and freshwater copepods whose females are parasites of fish in their adult phase, with only seven species described so far. During a field survey of fish parasites in the Jari River, a large tributary of the Amazon River system, in Brazil, we found a new species of the genus Therodamas infecting Leporinus fasciatus. Therodamas longicollum n. sp. is the second strictly freshwater species known. Phylogenetic analysis showed that the new species is grouped in the family Ergasilidae, and divergence estimates showed that T. longicollum n. sp. diverged from its ancestor at around 66.34Ma, in the late Upper Cretaceous. Therodamas longicollum n. sp. differs from its congeneric in that it does not have lobes and/or expansion of the anterior neck region. Besides describing a new Therodamas species, thereby increasing the diversity of the genus to eight species, this study points out the existence of a lineage of these copepods that has adapted to the freshwater environment of the Amazon. This study also corroborates the genus Therodamas as part of the family Ergasilidae.

Phylogenetic morphometrics, geometric morphometrics and the Mexican fossils to understand evolutionary trends of enchodontid fishes

Enchodontids were a diverse and abundant fish marine clade that during the Upper Cretaceous became common inhabitants of temperate coastal environments around the world. The recent studies on Mexican enchodontid species have contributed to better understand their evolutionary relationships; however, the phylogenetic significance of the morphological variability of some bones in these fishes is unclear. Here, we explore the morphological variation and the phylogenetic implications that the preopercle, and lower jaw have throughout the geological time; these bones were selected because usually are well-preserved in fossils belonging to the group. Our results indicate that temporally, the enchodontid species herein studied can be divided into two main groups, one present in the early-Upper Cretaceous group and the other in the late-Upper Cretaceous. Additionally, our results indicate that body size in Enchodontidae seems to adjust to the phyletic increase of size or Cope's rule. The shapes of the preopercle and lower jaw of enchodontids are highly variable that it is hard to use these as supra-specific distinctive features. Among these fishes, the most differentiated shapes correspond to those that developed an elongated and shallow lower jaw, and those with preopercles that bear a posteroventral well-developed spine, as in Eurypholinae and Unicachichthys. The phylogenetic relationships of enchodontid fishes defined by the configurations of these two skeletal structures provide a glimpse of the biogeographical relationships of the family; however, these patterns should be analyzed considering a most complete and inclusive phylogeny.

Systematics of the enigmatic South American Streblopus Van Lansberge, 1874 dung beetles and their transatlantic origin: a case study on the role of dispersal events in the biogeographical history of the Scarabaeinae (Coleoptera: Scarabaeidae)

Streblopus Van Lansberge, 1874 has been one of the most mysterious dung beetle groups of the Neotropical fauna, having a rather peculiar morphology, very few known specimens in collections and a difficult placement among the scarabaeine lineages. In this work, based on the examination of a recently collected series of specimens and a synthesis of some scattered, but deeply valuable, information available in the literature, we readdress many of the questions posed by past authors. It is shown that Streblopus is a relict genus composed of two currently living species of widely disjunct distribution, namely S. opatroides Van Lansberge, 1874, from patches of Atlantic Forest in the Brazilian states of Bahia and Espírito Santo, and S. punctatus (Balthasar, 1938), known from a few localities across Sub-Andean humid forests in the Peruvian and Ecuadorian Amazon Forest. We redescribe both and present in detail the evidence pointing to their validity as two independent species; a discussion of their remarkable sexual dimorphism is also given. The biogeography of Streblopus in South America is addressed, and we conclude that the present disjunct distribution of the genus is a consequence of the retreat of the tropical forest corridors that once connected the Atlantic Forest to the Amazon Basin through the South American Dry Diagonal during several periods of the Neogene, particularly until the Middle Miocene. Finally, we propose an African origin for the genus based on its close phylogenetic relationship with a group of Old World taxa ‒ particularly Circellium Latreille, 1825 and Scarabaeini. Having diverged from those groups in the late Upper Cretaceous, we argue that the ancestor of Streblopus arrived in South America crossing the Atlantic Ocean by rafting. We present a synthesis of data from a wide variety of biological groups to support our ideas and contend that long-distance dispersal hypotheses should be taken more seriously by scarab beetle specialists.

Comparative structural analysis of inverted structures in the San Bernardo fold belt (Golfo San Jorge basin, Argentina): Inversion controls and tecto-sedimentary context of the Chubut Group

The Golfo San Jorge Basin is one of the most important hydrocarbon-bearing basins of Argentina. Its position in the distal Patagonian Broken Foreland confers a particular structural architecture. Specifically, the western margin was affected by positive tectonic inversion, with higher degrees of inversion at the San Bernardo Fold Belt (SBFB). This paper synthesizes the comparative structural analysis of outcropped and buried inverted structures in the SBFB. The study areas are regionally distributed, and the geometric characterizations integrate field structural data, topographic trends, cutting records, borehole logs, and 2D-3D seismic data. The geometries of the studied inversion folds are poorly vergent and can be classified as asymmetric anticlines or pop-up growth folds. The architecture of the inverted fault system shows: along-strike variability in reverse displacement, inherited extensional growth-strata, selective inversion, oblique inversion, and heterogeneous deformation. Pre-inversion major controls include: 1) an extensional network linked to the fabric of the pre-rift basement, 2) a non-coaxial extensional phase during the early Upper Cretaceous times, and 3) a basin-scale paleohigh of crystalline rocks located to the east of the SBFB. The kinematic analysis evaluates the timing of the tectonic inversion phase, which is actually under discussion. Our results are consistent with a tecto-sedimentary context dominated by normal fault reactivations during the deposition of the basal units of the Chubut Group (Barremian-Albian), and a reverse-reactivation during the record of the Laguna Palacios Formation (late Upper Cretaceous). The geometric-kinematic characterization of the inverted structures at the SBFB contradicts many of the evidence that supports recently proposed geodynamic models for the Cretaceous evolution of Southern Patagonia.

The evolution of volcano-hosted geothermal systems based on deep wells from Karaha-Telaga Bodas, Indonesia

In late Mesozoic time, the southern Cordilleran foreland basin was bounded on the west by the Sevier thrust belt and on the south by the Mogollon highlands. Paleocurrent indicators in fluvial and fluviodeltaic strata imply sediment delivery into the basin from both tectonic features. Ages of detrital zircons in sandstones of the basin provide insights into the nature of the sediment sources. Upper Jurassic and Lower Cretaceous fluvial strata were deposited as sediment blankets across the width of the basin but Upper Cretaceous marginal-marine facies were restricted to the basin margin, with marine facies in the basin interior. Most Upper Jurassic and Lower Cretaceous fluvial sandstones contain heterogeneous age populations of Precambrian and Paleozoic detrital zircons largely recycled from Jurassic eolianites uplifted within the Sevier thrust belt or antecedent highlands, and exposed as sedimentary cover over the Mogollon highlands, with only minor contributions of Mesozoic zircon grains from the Cordilleran magmatic arc along the continental margin. Sources in Yavapai-Mazatzal Proterozoic basement intruded by anorogenic Mesoproterozoic plutons along the Mogollon highlands were significant for the Westwater Canyon Member of the Upper Jurassic Morrison Formation and for early Upper Cretaceous (Turonian) fluviodeltaic depositional systems, in which arc-derived Cordilleran zircon grains are more abundant than in older and younger units composed dominantly of recycled detritus. Detrital zircons confirm that the Salt Wash and Westwater Canyon Members of the Morrison Formation formed separate foreland megafans of different provenance. Late Upper Cretaceous (Campanian) fluvial sandstones include units containing mostly recycled sand lacking arc-derived grains in the Sevier foredeep adjacent to the Sevier thrust front, and units derived from both Yavapai-Mazatzal basement and the Cordilleran arc farther east, with some mingling of sand from both sources at selected horizons within the Sevier foredeep. Evidence for longitudinal as well as transverse delivery of sediment to the foreland basin shows that paleogeographic and isostatic analyses of thrust-belt erosion, sediment loads, and basin subsidence in foreland systems need to allow for derivation of foreland sediment in significant volumes from sources lying outside adjacent thrust belts.

The oleananes: Origin, maturation and limits of occurence in Southern Nigeria sedimentary basins

Oleananes occur within well-defined age and paleogeographic boundaries in the sedimentary province of Southern Nigeria thus signifying that the biomarkers may be analogous to index Fossils. In Anambra Syncline/Lower Benue Trough the biomarkers are found in rocks which are as old as late Upper Cretaceous. In Tertiary Niger Delta the concentration, composition and distribution of the oleananes in rocks and oils are determined mainly by palaeodepositional environment and thermal history and are independent of age and geographical location of specific samples. Oleanane content varies with increasing burial-depth with peak concentration coinciding within R m% range, 0.4–0.6 implying early generation of hydrocarbons from the basin's typically resin-rich kerogens. It is evident that the oleanane content parameter is superior to the hopane and sterane isomerisation indices for monitoring thermal maturation in the delta and for differentiating paralic from paralic-marine source-facies as well as early from late generated oils.

Large allochthonous sediment masses and their role in the construction of the continental slope and rise off southwestern Africa

Large Neogene slumps have affected over 260,000 km 2 of the outer continental margin and adjacent Cape Basin off southwestern Africa. Individual structures cover areas up to 68,700 km 2 and proximally are commonly composed of huge rotated sediment blocks up to 450 m thick and several kilometers across. Seismic shocks, possibly in conjunction with lower-slope undercutting by bottom-current erosion, are suggested as possible trigger mechanisms for these features which are all thought to be post-Pliocene (possibly Pleistocene) in age. Older slumps are also recognized along the margin and four cycles of sedimentation/slumping are identified: early Upper Cretaceous (I); late Upper Cretaceous (II); Palaeogene (III); and Neogene (IV). In the main part of the Orange Basin depocentre (west of Childs Bank) the Cretaceous slump styles are thought to represent Mississippi delta-type down-slope sediment cascades (with reverse faulting and mud diapirism) over 1 km thick which resulted from very rapid dumping of terrigenous material from the Orange River. Cainozoic slumps show a different tectonic style and locus and this is thought to reflect a change in sedimentation patterns which resulted from lower terrigenous input onto the margin, higher biogenic/authigenic sedimentation, and slowed crustal subsidence. A connection possibly exists between low sea level stands and the Cainozoic episodes of slumping.

Late Upper Cretaceous in Northwest Anatolia and Thrace (Contribution to the Geology of Anatolia No. 18)

Late Upper Cretaceous in Northwest Anatolia and Thrace (Contribution to the Geology of Anatolia No. 18)

Wasatch Plateau Gas Fields, Utah

Another geologic province in Utah, the rugged, mountainous Wasatch Plateau, has recently been proved to have gas fields of importance at Clear Creek and Flat Canyon. Important carbon dioxide gas reserves were previously discovered at Gordon Creek. The producing areas of the plateau are located on a regional uplift, herein named the Monument Peak, which consists of two major, northeast-southeast zones of folding. These are considered marginal bands of folding to the adjacent San Rafael swell, an ancient positive element. These flexures represent the culmination of at least three periods of movement: middle Upper Cretaceous, late Upper Cretaceous, and post-middle Eocene. Extensive north-south graben faulting subsequent to the folding has cut across the flexures, thus segmenting them into many fault blocks. Although situated on the crests of two different anticlines, the Clear Creek and Flat Canyon fields are both contained in the same closed fault block which lies west of, and is closed against, the Pleasant Valley graben. Strata ranging from middle Upper Cretaceous to middle Eocene occur on the surface. A deep well at Gordon Creek has penetrated strata as old as early Permian. A major part of the area appears to be underlain by Jurassic salt-bearing beds, the Arapien formation, whose instability has probably contributed to the extensive faulting in the surface strata. The Upper Cretaceous Ferron sandstone is the principal producing formation although the Dakota sandstone is also productive at Flat Canyon.

Mineralogy of Late Upper Cretaceous, Paleocene, and Eocene Sandstones of Los Banos District, West Border of San Joaquin Valley, California

The mineral composition of 192 outcrop and core samples from sandstones of late Upper Cretaceous, Paleocene, and Eocene age in the Los Banos district are tabulated. The mineral composition appears to afford few data for differentiating and correlating late Upper Cretaceous and Paleocene sandstones of the Los Banos district. The Eocene Domengine formation in the southern part of the area shows a marked increase in glaucophane as compared with the Paleocene and late Upper Cretaceous sandstones. The mineral suites are interpreted as indicating derivation from eastern and western sources, glaucophane being the most reliable indicator of a western source. Kaolinite, possibly of the anauxite type, occurs in white sands of Ione type in the Martinez (?) formation of possible Pale cene age, in outcrop sections and in a subsurface sand.

Geology of the Cretaceous of the Uinta Basin, Utah

The Cretaceous rocks of the Uinta Basin, Utah, are exposed along the south flank of the Uinta Mountain anticline and are overlain unconformably by Tertiary sediments throughout this area. The Dakota (?) sandstone of this paper disconformably overlies the Jurassic Morrison and is overlain conformably by the Mancos shale. It probably represents rocks of both Upper and Lower Cretaceous age. The Mancos shale, as mapped and studied, comprises only a lithologic unit since in the Vernal vicinity it is equivalent in age and stratigraphic position to the Mesaverde group sandstones of the Tabby Mountain region to the west. The Mancos is divided into the following members, all easily identified throughout the Basin: lower shale member, Aspen shale, middle shale member, Frontier sandstone, and upper shale member. The Mesaverde group refers only to a lithologic facies since at the west end of the area it is predominantly Niobrara in age, whereas at the east it is completely post-Niobrara. In the Vernal region it is divided into three members: the Asphalt Ridge sandstone, the Rim Rock sandstone, and the Williams Fork formation (contains more than type Williams Fork). The lower members of the Mesaverde group intertongue with the upper portion of the Mancos shale and wedge out toward the east. The name Currant Creek is proposed for a sequence of conglomerate beds unconformably overlying the Mesaverde group in the Tabby Mountain region. This new formation is tentatively referred to the Upper Cretaceous but it probably represents the transitional strata deposited from late Upper Cretaceous to Eocene during the early phases of the Laramide folding. The Uinta Basin is an asymmetrical syncline with its steep side along the flank of the Uinta Mountain anticline to the north from which numerous small noses and supplementary folds plunge southward. The Basin's structural history involves the following movements: local uplift in the west end in early Montana time; folding, progressively from west to east, during late Cretaceous to early Eocene; first uplift during post-Green River (Eocene)—pre-Uinta (Eocene); second uplift during post-Uinta (Eocene)—pre-Duchesne River (Oligocene); regional tilting in post-Duchesne River (Oligocene)—pre-Bishop (Miocene?); subsidence in post Bishop (Miocene?)—pre-Quaternary; continental uplift in late Tertiary or early Quaternary.