Detrital zircon age spectra of middle and upper Eocene outcrop belts,U.S. Gulf Coast region

Recently reported detrital zircon (DZ) data help to associate the Paleogene strata of the Gulf of Mexico region to various provenance areas. By far, recent work has emphasised upper Paleocene‐lower Eocene and upper Oligocene strata that were deposited during the two episodes of the highest sediment supply in the Paleogene. The data reveal a dynamic drainage history, including (1) initial routing of western Cordilleran drainages towards the Gulf of Mexico in the Paleocene, (2) an eastward shift of the western continental divide, from the Jura‐Cretaceous cordilleran arc to the eastern edge of the Laramide province after the Paleocene and (3) a southward shift, along the eastern Laramide province, of the headwaters of river systems draining to the Mississippi and Houston embayments at some time between the early Eocene and Oligocene. However, DZ characterisation of most (~20 Myr) of the middle Eocene‐lower Oligocene section remains limited. We present 60 DZ age spectra, most of which are from the middle or upper Eocene outcrop belts, with 50–200‐km spacing. We define six to eight distinct groups of DZ age spectra for middle and upper Eocene strata. Data from this and other studies resolve at least six substantial temporal changes in age spectra at various positions along the continental margin. The evolving age spectra constrain the middle and upper Eocene drainage patterns of large parts of interior North America. The most well‐resolved aspects of these drainage patterns include (1) persistent rivers that flowed from erosional landscapes across the Paleozoic Appalachian orogen either into the low‐lying Mississippi embayment or directly into the eastern Gulf; (2) at least during marine regressions, a trunk channel that likely flowed southward along the axial part of Mississippi Embayment and integrated tributaries from the east and west; and (3) rivers that flowed to the Houston embayment in the middle Eocene that likely originated in the Laramide province in central Colorado and southern Wyoming, as Precambrian basement highs in those source areas were being unroofed.     

Encounters with an unearthly mudstone: Understanding the first mudstone found on Mars

The Sheepbed mudstone forms the base of the strata examined by the Curiosity rover in Gale Crater on Mars, and is the first bona fide mudstone known on another planet. From images and associated data, this contribution proposes a holistic interpretation of depositional regime, diagenesis and burial history. A lake basin probably received sediment pulses from alluvial fans. Bed cross‐sections show millimetre to centimetre‐scale layering due to distal pulses of fluvial sediment injections (fine‐grained hyperpycnites), fall‐out from river plumes, and some aeolian supply. Diagenetic features include mineralized synaeresis cracks and millimetre‐scale nodules, as well as stratiform cementation. Clay minerals were initially considered due to in situ alteration, but bulk rock chemistry and mineralogy suggests that sediments were derived from variably weathered source rocks that probably contained pre‐existing clay minerals. X‐ray diffraction analyses show contrasting clay mineralogy in closely spaced samples, consistent with at least partial detrital supply of clay minerals. A significant (ca 30 wt%) amorphous component is consistent with little post‐depositional alteration. Theoretical modelling of diagenetic reactions, as well as kinetic considerations, suggest that the bulk of diagenetic clay mineral formation occurred comparatively late in diagenesis. Diagenetic features (synaeresis cracks and nodules) were previously thought to reflect early diagenetic gas formation, but an alternative scenario of synaeresis crack formation via fabric collapse of flocculated clays appears more likely. The observed diagenetic features, such as solid nodules, hollow nodules, matrix cement and ‘raised ridges’ (synaeresis cracks) can be explained with progressive alteration of olivine/glass in conjunction with centrifugal and counter diffusion of reactive species. Anhydrite‐filled fractures in the Sheepbed mudstone occurred late in diagenesis when fluid pressures built up to exceed lithostatic pressure. Generating fluid overpressure by burial to facilitate hydraulic fracturing suggests a burial depth of at least 1000 m for the underlying strata that supplied these fluids.     

Galaxy destruction and diffuse light in clusters

Deep images of the Centaurus and Coma clusters reveal two spectacular arcs of diffuse light that stretch for over 100 kpc, yet are just a few kiloparsecs wide. At a surface brightness of m _b ∼27–28 mag arcsec⁻² , the Centaurus arc is the most striking example known of structure in the diffuse light component of a rich galaxy cluster. We use numerical simulations to show that the Centaurus feature can be reproduced by the tidal debris of a spiral galaxy that has been tidally disrupted by the gravitational potential of NGC 4709. The surface brightness and narrow dimensions of the diffuse light suggest that the disc was corotating with its orbital path past pericentre. Features this prominent in clusters will be relatively rare, although at fainter surface brightness levels the diffuse light will reveal a wealth of structure. Deeper imaging surveys may be able to trace this feature for several times its presently observed extent, and somewhere along the tidal debris, a fraction of the original stellar component of the disc will remain bound, but transformed into a faint spheroidal galaxy. It should be possible to confirm the galactic origin of the Centaurus arc by observing planetary nebulae along its length with redshifts close to that of NGC 4709.     

Research progress and prospect on development geography

In this paper,we review the research progress in development geography since the 20th century,focusing on its connotation and theory,fields,methods,and development trends.Specifically,we systematically review the research and applications of development geography,comprising fields such as the convergence of underdeveloped countries and re-gions,and the convergence of the process of improving the quality of life in developed coun-tries and regions.Then,based on an analysis of research progress in development geogra-phy in foreign countries,we examine the development conditions and disciplinary advantages of development geography in China.Further,we highlight that future development geography research in China should focus on the latest international academic research and China's national macro-strategic needs.Future research in development geography should be guided by the theory of sustainable development,the core of which is to improve sustainable liveli-hood capacity and regional green development levels in underdeveloped regions.This core includes the construction of industrial policy and development geography theory,as well as an interdisciplinary integrated research system.The focus must be placed on researching the spatial patterns,diffusion characteristics,and the convergence mechanism of regional de-velopment.Such a focus will facilitate exploration of the regulatory policies and scientific paths that serve regional economic construction and industrial development.     

Effects of petroleum hydrocarbons on the hepatic cytochrome P450 1A1 system in rainbow trout

Effects on the hepatic cytochrome P450 1A1 system were investigated in juvenile rainbow trout i.p. injected with three different aromatic containing fractions: kerosene, light gas oil or heavy gas oil, originated from distilled North Sea crude oil. Kerosene treatment resulted in no effect on the P450 1A1 system, light gas oil injection caused a weak induction of EROD activities and heavy gas oil treatment resulted in a prominent induction of EROD activities as well as accumulation of CYP1A1 mRNA and P450 1A1 protein levels. The effects of heavy gas oil were compared with effects of β-napthoflavone (β-NF) on the P450 1A1 system. It was obvious that important discrepancies seemed to exist between EROD activities and corresponding CYP1A1 mRNA and P450 1A1 levels in rainbow trout treated with either heavy gas oil or β-NF i.e. heavy gas oil treatment resulted in higher specific EROD activities (EROD/P450 1A1) compared to β-NF. GC-MS analyses revealed that liver and bile from heavy gas oil treated rainbow trout in addition to naphthalene also contained polycyclic aromatic hydrocarbons such as phenanthrenes, anthracene, pyrenes, fluoranthene benz(a)anthracene and chrysene, while none of these compounds were detected in control trout.     

Quantification of cytochrome P4501A1 and catalytic activities in liver microsomes of isosafrol- and β-Naphthoflavone-treated rainbow trout (Oncorhynchus mykiss)

The effects of isosafrol (ISF) or β-naphthoflavone (βNF) treatments on cytochrome P450 (P450) levels in rainbow trout liver were investigated using immunochemical and catalytic techniques. The discrepancies in catalytic activities and ELISA quantification of rainbow trout P4501A1 protein levels between ISF- and βNF-treated fish indicate that important differences exist between the responses induced by βNF and ISF treatments in the rainbow trout liver.     

The use of polyclonal antibodies raised against rat and trout cytochrome P450 CYP1A1 orthologues to monitor environmental induction in the channel catfish (Ictalurus punctatus)

Induction of hepatic cytochrome P450-dependent microsomal mono-oxygenase by xenobiotics is a well-established phenomenon in teleost fish. As in laboratory mammals, fish possess multiple forms of cytochrome P450 that display overlapping substrate specificity. One such isoform, CYP1A1, which has been cloned and sequenced from rainbow trout, has been shown to be orthologous to rat CYP1A1 and, as in mammals, is inducible up to several hundred-fold by planar aromatic hydrocarbons, PCBs and dioxins. It has been suggested that induction of CYP1A1 orthologues might provide a sensitive biomonitor for environmental pollution by mixtures of such compounds. In the current study, polyclonal antibodies directed against CYP1A1 purified from rat and trout liver were used to monitor induction of the CYP1A1 orthologue in hepatic microsomes from the fresh water species, the channel catfish (Ictalurus punctatus). Catfish from a local fish farm were induced in the laboratory by three daily injections of 50 mg/kg of the PCB mixture Aroclor 1254 and compared with fish taken from a site in central Arkansas—the Bayou Meto, known to be polluted with dioxin. Hepatic microsomal activities towards ethoxyresorufin (EROD) and pentoxyresorufin (PROD) were measured and Western blot analysis carried out with the two antibodies. EROD was elevated in both the Aroclor-treated fish and in the Bayou Meto fish compared with untreated fish farm controls; smaller but significant increases were observed in PROD. Spearman's rank correlations of 0·74 and 0·89 were observed between EROD and immunoquantified cross-reactivity towards the rat CYP1A1 and trout CYP1A1 antibodies.     

Ultraviolet dust aerosol properties as observed by MARCI

Observations by the Mars Color Imager (MARCI) on board the Mars Reconnaissance Orbiter (MRO) in two ultraviolet (UV, Bands 6 and 7; 258 nm, and 320 nm, respectively) and one visible (Band 1, 436 nm) channels of the 2007 planet encircling dust storm are combined with those made by the two Mars Exploration Rovers (MERs) to better characterize the single scattering albedo (ω₀) of martian dust aerosols. Exploiting the low contrast of the surface in the UV (and blue) as well as the reduced importance of surface reflectance under very dusty conditions, we utilize the sampling of photometric angles by the MARCI cross-track geometry to synthesize an analog of the classical Emergence Phase Function (EPF). This so-called “pseudo-EPF”, used in conjunction with the “ground-truth” measurements provided by the MERs, is able to effectively isolate the effects of the dust ω₀. The motivation for this approach is the elimination of a significant portion of the type of uncertainty involved in many previous radiative transfer analyses. Furthermore, we produce a self-consistent set of complex refractive indices (m=n+ik) through our use of an explicit microphysical representation of the aerosol scattering properties. Because of uncertainty in the exact size of the dust particles during the epoch of the observations, we consider two effective particle radii (r_eff) to cover the range anticipated from the literature: 1.6 and 1.8 μm. The resulting set of model-data comparisons, ω₀, and m are presented along with an assessment of potential sources of error and uncertainty. Analysis of the Band 1 results is limited to ω₀ as a “proof-of-concept” for our approach through a comparison to contemporaneous CRISM EPF results at 440 nm. The derived ω₀ are: assuming , and 0.765, for Bands 6, 7, and 1, respectively; for , for the same band order. For either r_eff case, the total estimated error is 0.022, 0.019, and 0.010, again for Bands 6, 7, and 1. We briefly discuss our retrievals, including the asymmetry parameter (g) associated with our model phase functions, within the context of previous efforts, with an emphasis on the improved precision of our results compared to those in the literature. We also suggest several applications of our results, including an extension of the dust climatological record using MARCI Band 7 pseudo-EPFs outside of 2007 global dust event. Initial work on this particular application using a sample of 135 pseudo-EPFs near the MERs suggests that optical depth retrievals with a precision in the range 0.2-0.4 may be possible under moderate loading conditions (i.e., τ < 1.5).     

Lunar red spots: Possible pre-mare materials

Some anomalous red features observed on the moon by Whitaker are examined in detail. Crater counts and regional stratigraphy suggest that ages for these features are comparable to that of lunar highland material. Initial gamma-ray spectrometry indicates higher than average native radioactivity is associated with certain red areas. A possible explanation for these observations is that the red objects are the surface manifestation of highly radioactive pre-mare basalts (Apollo 14/KREEP/norite material). Conclusive proof of the nature of these objects will depend on the study of returned samples, making them ideal candidates for future space missions, especially for unmanned vehicles such as the Soviet Union's Luna 20.