Previously Interpreted Research Articles

Tracking updates in clinical databases increases efficiency for variant reanalysis

PurposeVariant interpretation, guided by American College of Medical Genetics and Genomics guidelines, can inform clinical decision-making. However, interpretations may change over time for a variety of reasons. Periodic reanalysis of previous variant interpretations is important to ensure that reported genetic findings remain accurate according to current knowledge. MethodsWe performed automated filtering by comparing ClinVar variants available in August 2020 with those from August 2021 to screen for potential reanalysis candidates from 3 projects. These variants were subsequently interpreted based on the American College of Medical Genetics and Genomics/Association for Molecular Pathology variant interpretation guideline or ClinGen revised gene-specific guidelines if applicable. ResultsOur method annotated 241 unique variants requiring reanalysis, from 3 projects containing 3,832,210 previously interpreted variants, including those filtered automatically. Among these 241 variants, 43 variants changed interpretation, including 55.81% (N = 24) with upgraded and 44.19% (N = 19) with downgraded classifications. An efficiency study showed that our strategy increased the reanalysis efficiency and saved reviewing time. ConclusionWe demonstrated an effective high-throughput method, initiating from external data updates, to achieve variant reanalysis in a clinical laboratory. This filtering method reduced the number of variants that need to be reanalyzed, screened potential variants, and saved time and cost for clinical laboratories.

Light fractions can also be heavy hitters: Comparison of detrital zircon U–Pb and detrital K‐feldspar Pb–Pb as provenance indicators—A case study from Cretaceous strata of southern Utah, USA

AbstractComparison of detrital zircon U–Pb geochronology and detrital K‐feldspar Pb–Pb isotopic data from Upper Cretaceous sandstones of southern Utah reveals important provenance information that is unrecorded by more chemically and physically durable detrital minerals like zircons. To better understand these signals, we also present an updated database of Pb‐isotopic ratios in ores, whole rocks and feldspars, for potential sediment source terranes in North America. Detrital K‐feldspar Pb‐isotopes indicate sediment provenance of the Western Cordillera/Mojave, Yavapai‐Mazatzal and Wyoming terranes, with limited input from recycled Sevier fold‐thrust belt strata. The K‐feldspar data broadly support previous interpretations, largely based on detrital zircon datasets, of a Cretaceous palaeo‐river system transporting sediment from the southwest. However, the light‐fraction data also provide important, complementary and otherwise unrecognized perspectives as compared to detrital zircon datasets. For example, K‐feldspars indicate a stronger apparent influence of Western Cordillera/Mojave and Wyoming terrane sources than previously interpreted. We interpret the K‐feldspar Wyoming terrane signal as the result of south‐directed longshore drift, with preferential loss of zircons due to hydraulic sorting processes. As relatively new detrital K‐feldspar detrital methods continue to be developed, this multi‐proxy approach to provenance could be informative in other sedimentary basins where suitable source terranes can be identified.

Forensic Geology Applied to Decipher the Landslide Dam Collapse and Outburst Flood of the Santa Cruz River (12 November 2005), San Juan, Argentina

A well-known landslide dam that collapsed and generated a large outburst flood is used to show the importance of forensic geology analysis, which is the on-site multidisciplinary study of geohazards carries out as soon as possible after their occurrence; this study is focused on understanding the complete spectrum of all mechanisms that caused the disaster. Diagnostic elements of all natural processes fade with time, allowing for progressively divergent interpretations that may impact the appropriateness of potential mitigation actions, as we demonstrate. The multidisciplinary field control of the abrupt rupture of a natural dam on the Santa Cruz River on 12 November 2005, that released c. 37 million m3 of water and sediment, can radically change the interpretation of how this dam collapsed. In situ sedimentological, geomorphological and topographical analyses of the remains of the collapsed natural dam suggest it was built in two mass-wasting episodes instead of one, as previously interpreted, involving different slide materials. The first episode matches previous interpretations; a landslide that evolved into a rock avalanche, generating an initial dam of high stability due to its density, and observed angles of repose. This dam was not removed completely during the rupture, but rather suffered minor erosion at its top by the flood drag effect. The second episode is interpreted as a snow-dominated mixed avalanche, reaching much greater heights on the opposite side of the valley. This avalanche is estimated to be 85% snow, 8% debris and 7% ice-cemented permafrost fragments, and is evidenced by a thin residual deposit draping the valley sides, as most of this deposit melted out before any field control was undertaken. The growth of the lake level, along with the dam weight loss due to ablation, generated the hydrostatic instability that caused the floating of the central sector of this second dam and the violent evacuation of the water, similar to a jökulhlaup. This analysis explains the partial dam collapse, sudden water release and the preserved field evidence. This different interpretation suggests that the mitigation actions already taken can be improved and that monitoring systems are urgently needed. A rapid and professional assessment of any large-scale geohazard site would be the way to avoid interpretation discrepancies, and to guarantee that mitigation actions taken are adequate. Learning from this event may help decision makers to take better mitigation measures and potentially save lives.

Detrital U-Pb zircon and 40Ar/39Ar muscovite geochronology from Middle Pennsylvanian strata in the Anadarko Basin, Texas Panhandle, USA

The Late Mississippian-Permian Anadarko Basin formed in Texas and Oklahoma, USA as the result of inversion of Neoproterozic and Cambrian rift structures. Subsidence was driven by flexural loading of the Amarillo-Wichita Uplift, and this uplift may represent the easternmost element of the Ancestral Rocky Mountains system. The northwestern part of this basin has generally been interpreted to have been filled by sediment derived from the Ancestral Front Range Uplift, ~475 km to the northwest during the early stages of basin filling. We test this model using U-Pb detrital zircon and 40Ar/39Ar detrital muscovite results from three subsurface samples of the Morrow B sandstone in the northwestern part of the Anadarko Basin. We provide a new maximum depositional age of 310.9 ± 4.9 Ma that indicates the age of the Morrow B to be no older than late Atokan to early Desmoinesian Age (Moscovian), ~10 Myr younger than previously interpreted. In contrast to some previous interpretations, we propose that the most likely source for the sediment in the Morrow B is the Amarillo Uplift to the south. Detrital zircon and detrital muscovite data have age peaks at 900–1300 Ma, 1370 Ma and 1600–1800 Ma corresponding to derivation from Grenville, Granite-Rhyolite and Yavapai-Mazatzal basement provinces, respectively. A dominant detrital zircon peak at 1370 Ma suggests that Mesoproterozoic granites in the Amarillo Uplift were exposed by Middle Pennsylvanian time, and detritus eroded from the Amarillo Uplift dominated the lowstand sediment budget of the Texas Panhandle during this time; small volumes of sediment were likely sourced from the Ancestral Front Range. This study presents the first detrital geochronology data from the subsurface Anadarko Basin and the first detrital muscovite data from late Paleozoic southwestern Laurentia. The results presented here highlight the interpretive power of combined detrital zircon and muscovite datasets.

Obsidian pyroclasts in the Yellowstone-Snake River Plain ignimbrites are dominantly juvenile in origin

Dense, glassy pyroclasts found in products of explosive eruptions are commonly employed to investigate volcanic conduit processes through measurement of their volatile inventories. This approach rests upon the tacit assumption that the obsidian clasts are juvenile, that is, genetically related to the erupting magma. Pyroclastic deposits within the Yellowstone-Snake River Plain province almost without exception contain dense, glassy clasts, previously interpreted as hyaloclastite, while other lithologies, including crystallised rhyolite, are extremely rare. We investigate the origin of these dense, glassy clasts from a coupled geochemical and textural perspective combining literature data and case studies from Cougar Point Tuff XIII, Wolverine Creek Tuff, and Mesa Falls Tuff spanning 10 My of silicic volcanism. These results indicate that the trace elemental compositions of the dense glasses mostly overlap with the vesiculated component of each deposit, while being distinct from nearby units, thus indicating that dense glasses are juvenile. Textural complexity of the dense clasts varies across our examples. Cougar Point Tuff XIII contains a remarkable diversity of clast appearances with the same glass composition including obsidian-within-obsidian clasts. Mesa Falls Tuff contains clasts with the same glass compositions but with stark variations in phenocryst content (0 to 45%). Cumulatively, our results support a model where most dense, glassy clasts reflect conduit material that passed through multiple cycles of fracturing and sintering with concurrent mixing of glass and various crystal components. This is in contrast to previous interpretations of these clasts as entrained hyaloclastite and relaxes the requirement for water-magma interaction within the eruptive centres of the Yellowstone-Snake River Plain province.

Protecting a Pict?

A detailed discussion of the inscription on the silver chape (NMS FC 282) discovered in 1958 as part of a large hoard of silver from the major early medieval ecclesiastical site on St Ninian’s Isle, Shetland (NGR: HU 3685 2090). Previous interpretations and a range of parallels are explored. A new interpretation of the inscription is proposed: that it contains a Pictish male personal name, Resad. This has implications for previous arguments in favour of an Anglo-Saxon origin for the metalwork. Features of the lettering previously interpreted as errors are instead argued to indicate familiarity with the type of cursive writing used on wax-tablets, rather than bookhand. It is argued that the inscription was designed and manufactured by a single literate artisan, possibly in an ecclesiastical workshop.
 
 Canmore ID 587

Teleseismic P-Wave Coda Autocorrelation Imaging of Crustal and Basin Structure, Bighorn Mountains Region, Wyoming, U.S.A.

ABSTRACT We demonstrate successful crustal imaging via teleseismic P-wave coda autocorrelation, using data recorded on a 261 station array of vertical-component high-frequency geophones in the area of the Bighorn Mountains, Wyoming, U.S.A. We autocorrelate the P-wave coda of 30 teleseismic events and use phase-weighted stacking to yield seismic profiles comparable to low-passed versions of those produced via controlled-source vertical seismic reflection. Our process recovers reflections from the bottoms of the Bighorn and Powder River basins that flank the Bighorn Mountains. We also identify a mid-crustal reflector that aligns with a region of increased reflectivity, previously interpreted as a Precambrian province boundary. Our results demonstrate the utility of crustal imaging with teleseismic P-wave coda energy using modern large-array seismic data, and they corroborate previous interpretations of crustal structures in the study area.

Base level changes based on Basin Filling Modelling: a case study from the Paleocene Lishui Sag, East China Sea Basin

Estimation of base level changes in geological records is an important topic for petroleum geologists. Taking the Paleocene Upper Lingfeng Member of Lishui Sag as an example, this paper conducted a base level reconstruction based on Basin Filling Modelling (BFM). The reconstruction was processed on the ground of a previously interpreted seismic stratigraphic framework with several assumptions and simplification. The BFM is implemented with a nonlinear diffusion equation solver written in R coding that excels in shallow marine stratigraphic simulation. The modeled results fit the original stratigraphy very well. The BFM is a powerful tool for reconstructing the base level, and is an effective way to check the reasonableness of previous interpretations. Although simulation solutions may not be unique, the BFM still provides us a chance to gain some insights into the mechanism and dynamic details of the stratigraphy of sedimentary basins.

Reinvestigation of Ostreopsis mascarenensis Quod (Dinophyceae, Gonyaulacales) from Réunion Island (SW Indian Ocean): molecular phylogeny and emended description

ABSTRACTOstreopsis mascarenensis is a toxic dinoflagellate described from the Indian Ocean based only on morphology, without molecular data. Morphological features of Ostreopsis have poor taxonomic value, and the addition of genetic data would ensure correct species identification. The present study reinvestigated field samples from Réunion Island and the western Indian Ocean to validate morphological and genetic data of O. mascarenensis from the type locality. A detailed morphological study used light, epifluorescence and scanning electron microscopy, and phylogeny was inferred from sequences of the LSU rDNA (D1–D3 and D8–D10 domains) and ITS–5.8S region obtained from isolated single cells. Morphology mostly agreed with the original description, but we highlight some features that were probably in error in the original description. SEM showed that the epitheca was conspicuously flattened while the hypotheca was convex, which had been previously interpreted as the opposite. Moreover, in contrast with the previous interpretation, the second apical plate was long and narrow, 1.6 to 2 times longer than the apical pore. Phylogenetic analyses showed that O. mascarenensis forms a new lineage among Ostreopsis species, confirming that it is well separated from all other species. Based on these analyses, O. mascarenensis appeared to be related to Ostreopsis fattorussoi and the undescribed species Ostreopsis sp. 3 and sp. 4, but the topologies were not well supported and these relationships remain unclear.

A new tectono sedimentary framework of the Jurassic succession in the Merjan oil field, Central Iraq

In the Merjan oil field (Central Iraq), the previous 2D seismic interpretation of subsurface geometry had been revealed mound facies which was interpreted as large carbonate buildup within carbonate Najmah formation of Jurassic age. The exploration well (Me-1) had been drilled depending on these results, but carbonate buildup did not exist. The current research provides new sight to interpretation of this feature in the Jurassic succession. High accurate 3D seismic reflection data have been used. Two scenarios have been presented to interpretation. Scenario (A) includes tectono stratigraphic study which finds out that mound shape is due to fault system and tectonic activity during the sedimentation which led to the formation of a graben structure and after sedimentation led to tectonic inversion. These events cause the camouflage stratigraphic feature. Scenario (B) relies on conversion of seismic section from time into depth domain using appropriate velocity model. The resultant seismic depth section helps to present another seismic analysis of feature. The proposed structural model according to the depth section interpretation is anticlinal fault-bend fold. Quantitative geometric relationships between fault and fold shapes were established. Both scenarios explain the causes of the formation of the mound seismic facies which was previously interpreted as carbonate buildup. In conclusion, the stratigraphy interpretation based on 2D data might be very risky and 3D seismic is a must for exploration of stratigraphy traps.

Integrated Ichnological and Sedimentological Analysis of the Cambrian Kunzam La (Parahio) Formation, Shian Section, Pin Valley, Spiti, Northwest Himalaya

The Kunzam La (Parahio) Formation along the Shian section of the Pin Valley was previously interpreted as containing Ediacaran–Cambrian boundary trace fossils, but re-examination of the Shian section shows that the oldest part of the section belongs to the late part of Cambrian Series 2, Stage 4, which contradicts the previous interpretation. The trace fossil assemblage comprises ?Arborichnus isp., Archaeonassa isp., Diplichnites isp., Hormosiroidea isp., Monomorphichnus lineatus, Bergaueria aff. langi, Palaeophycus tubularis, Rusophycus isp., and Treptichnus-like fossils that occur stratigraphically below the Oryctocephalus indicus biozone (Series 3, Stage 5) along the section and belong to the late part of Series 2, Stage 4. Sedimentary structures recorded along the section include hummocky cross-stratification (HCS) with deeply bioturbated tops, trough- and low-angle cross stratification, ball and pillow structures and climbing-ripple cross stratification. Integrated ichnofabric and sedimentological data suggest a storm-dominated, lower to upper shoreface shallow-marine environment of deposition.

Antecedent aeolian dune topographic control on carbonate and evaporite facies: Middle Jurassic Todilto Member, Wanakah Formation, Ghost Ranch, New Mexico, USA

AbstractThe Middle Jurassic Todilto Member of the Wanakah Formation is a carbonate and gypsum unit inset into the underlying aeolian Entrada Sandstone in the San Juan Basin. Field and thin section study of the uppermost Entrada and Todilto at Ghost Ranch, New Mexico, identified Todilto facies and their relationship to remnant Entrada dune topography. Results support the previous interpretation that the Entrada dunes, housed in a basin below sea level, were rapidly flooded by marine waters. Mass wasting of the dunes gave rise to sediment‐gravity flows that largely buried remnant dune topography, leaving ca 12 m of relief that defined the antecedent condition for Todilto deposition. Previously interpreted as seasonal varves deposited in a stratified water body, the Todilto is reinterpreted as a microbial biolaminite. Most diagnostic are organic‐rich laminae with structures characteristic of filamentous microbes and containing trapped aeolian silt, and clotted‐texture laminae with a fabric associated with calcification of extracellular polymeric substances. The spatial arrangement of Todilto facies is controlled by the dune palaeotopography. A continuous basal laminated mudstone thickens over the dune crest, reflecting the optimum conditions for microbial mat development, and is interpreted to have been deposited when marine waters submerged the topography. Subsequent drying caused emergence of the crestal area, and formation of tepee structures and a dissolution breccia. Gypsiferous mudflats and periodic ponds occupied the dune flanks and interdune area, with gypsum concentrated within the interdune area. Entrada sands remained unstable during Todilto deposition with common injection structures into the Todilto, and a remnant slope caused the downslope movement and folding of Todilto strata on the upper lee face. Although some expansion of the gypsum occurred in the subsurface, facies architecture fostered development of a dissolution front adjacent to the interdune gypsum body with section collapse of gypsiferous limestone on the dune flanks.

Sediments of Biśnik Cave (Poland): Lithology and stratigraphy of the Middle Palaeolithic site

Biśnik Cave is an important Palaeolithic site located in the Kraków-Częstochowa Upland. The cave fill is a complex well-stratified sequence composed of 35 layers/sublayers interrupted by number of hiatuses and ranging from Pliocene till modern times. Fifteen Middle Palaeolithic horizons, some of them among the oldest in Poland, represent the most important part of the sequence from an archaeological point of view. The sedimentary sequences in particular parts of the cave have been studied for more than 20 years to investigate the chronostratigraphy and palaeoenvironment. The recent multi-proxy study is based on the application of new methods for the site: analysis of sedimentary and post-sedimentary structures, and weathering stage of limestone rubble and fossil bones, pollen analysis, molecular biomarkers, palaeomagnetic analysis and radiometric dating. Results indicated a more intensive role of re-working and re-deposition in the cave. Older sediments were transported into some stratigraphic horizons from sources within the cave itself as well as from outside, including palaeontological and archaeological materials. Some the detected layers therefore represent a mix derived from different sources. A record of two interglacials (Eemian Interglacial, MIS 5e and Penultimate Interglacial, MIS 7) was established in layers Nos. 15–14–13a–13 and 19a–19, respectively. Middle–Upper Pleistocene sedimentary units were identified with MIS 3–MIS 7/8, instead of previous interpretation to MIS 4–MIS 9. The age of the basal vario-colored complex, previously interpreted mostly as pre-Pleistocene, was newly correlated with MIS 7/8 and Early Pleistocene/Pliocene.

Morphology and function in the Cambrian Burgess Shale megacheiran arthropod Leanchoilia superlata and the application of a descriptive matrix.

BackgroundLeanchoilia superlata is one of the best known arthropods from the middle Cambrian Burgess Shale of British Columbia. Here we re-describe the morphology of L. superlata and discuss its possible autecology. The re-description follows a standardized scheme, the descriptive matrix approach, designed to provide a template for descriptions of other megacheiran species.ResultsOur findings differ in several respects from previous interpretations. Examples include a more slender body; a possible hypostome; a small specialised second appendage, bringing the number of pairs of head appendages to four; a further sub-division of the great appendage, making it more similar to that of other megacheirans; and a complex joint of the exopod reflecting the arthropod’s swimming capabilities.ConclusionsDifferent aspects of the morphology, for example, the morphology of the great appendage and the presence of a basipod with strong median armature on the biramous appendages indicate that L. superlata was an active and agile necto-benthic predator (not a scavenger or deposit feeder as previously interpreted).

Mechanisms of collapse of the cretaceous helvetiafjellet formation at Kvalvågen, eastern Spitsbergen

Coastal cliffs at Kvalvågen, eastern Spitsbergen, expose palaeolandslide blocks and related slope failure features that record local collapse of an otherwise undisturbed succession of paralic sediments. The collapse occurred along a shallow sloping shelf at the edge of an epicontinental sea in the Early Cretaceous. The event was coincident with a rise in relative sea level along a coast that had just previously experienced a major paralic regression across a muddy marine environment. The low relief environment in which the slope failure structures formed, as well as the timing of the collapse raise questions regarding the cause of the topographic instability and the possible influence of sea level changes or tectonic activity. These outcrops have been previously interpreted as the collapse of a deltaic system triggered by local seismic activity or collapse of a shelf break in the headwall regions of submarine canyons. This paper presents new structural and stratigraphic data that refine and adjust the previous interpretations through the evaluation of a variety of possible mechanisms for collapse based on the new data. Our data suggest that active delta deposition was not occurring at Kvalvågen at the time of collapse and that the collapse was likely due to allogenic forcing. Despite the possible influence of pore fluids and rheological controls on the collapse, we find that the geometry and kinematics of landslide slip planes, synsedimentary folds, and other slope failure related features require over-steepened topography and that these are most consistent with westward-directed collapse off of a north striking escarpment with elevated topography on the east side. Fault exposures, a large contrast in palaeo-elevation, and liquifaction features support previous interpretations of a tectonic cause for the collapse and suggest that this topographic feature may have been a fault or fold scarp. This study demonstrates the importance of combining stratigraphic and sedimentological data with structural data and kinematic analysis in the interpretation of sedimentary processes.

Reinterpretation of the Miocene Sea-Snake Egg Moniopterus Japonicus as a Boring of Rock-Boring Bivalve Lithophaga (Mytilidae: Mollusca)

The enigmatic fossil Moniopterus japonicus Hatai et al., 1974 from the early Middle Miocene Moniwa Formation of northern Japan has been described as the only known example of fossil sea-snake eggs and also as fossilized pupal chambers of a coleopteran insect. A reexamination of the holotype provides no evidence in support of these previous interpretations. Scanning electronic microscopy and computed tomography observations on the holotype reveal that the calcareous lining, previously interpreted as eggshell, is instead composed of irregular spherulitic prisms, thin in the middle and becoming thicker toward both ends. In addition to the elongate oval shape and the presence of an opening at the more pointed end, these observations strongly suggest that M. japonicus is a boring of the mytilid boring bivalve Lithophaga isolated from the host rock. This reinterpretation is further supported by the occurrence of similar isolated and in situ borings with Lithophaga shells within the type and a nearby locality. Regarding this fossil as an ichnofossil makes the generic name Moniopterus a junior synonym of Gastrochaenolites Leymerie, 1842 and the species name japonicus is a senior synonym of Gastrochaenolites torpedo Kelly and Bromley, 1984. G. torpedo should thus be replaced with Gastrochaenolites japonicus (Hatai et al., 1974).

Cross-borehole slug test analysis in a fractured limestone aquifer

Summary This work proposes new semi-analytical solutions for the interpretation of cross-borehole slug tests in fractured media. Our model is an extension of a previous work by Barker [Barker, J.A., 1988. A generalized radial flow model for hydraulic tests in fractured rock. Water Resources Research 24 (10), 1796–1804; Butler Jr., J.J., Zhan X., 2004. Hydraulic tests in highly permeable aquifers. Water Resources Research 40, W12402. doi:10.1029/2003/WR002998]. It includes inertial effects at both test and observation wells and a fractional flow dimension in the aquifer. The model has five fitting parameters: flow dimension n, hydraulic conductivity K, specific storage coefficient Ss, and effective lengths of test well Le and of observation well Leo. The results of a sensitivity analysis show that the most sensitive parameter is the flow dimension n. The model sensitivity to other parameters may be ranked as follows: K > Le ∼ Leo > Ss. The sensitivity to aquifer storage remains one or two orders of magnitude lower than that to other parameters. The model has been coupled to an automatic inversion algorithm for facilitating the interpretation of real field data. This inversion algorithm is based on a Gauss–Newton optimization procedure conditioned by re-scaled sensitivities. It has been used to interpret successfully cross-borehole slug test data from the Hydrogeological Experimental Site (HES) of Poitiers, France, consisting of fractured and karstic limestones. HES data provide flow dimension values ranging between 1.6 and 2.5, and hydraulic conductivity values ranging between 4.4 × 10−5 and 7.7 × 10−4 m s−1. These values are consistent with previous interpretations of single-well slug tests. The results of the sensitivity analysis are confirmed by calculations of relative errors on parameter estimates, which show that accuracy on n and K is below 20% and that on Ss is about one order of magnitude. The K-values interpreted from cross-borehole slug tests are one order of magnitude higher than those previously interpreted from interference pumping tests. These findings suggest that cross-borehole slug tests focus on preferential flowpath networks made by fractures and karstic channels, i.e. the head perturbation induced by a slug test propagates only through those flowpaths with the lowest hydraulic resistance. As a result, cross-borehole slug tests are expected to identify the hydrodynamic properties of karstic-channels and fracture flowpaths, and may be considered as complementary to pumping tests which more likely provide bulk properties of the whole fracture/karstic-channel/matrix system.

Radiative transfer modeling of lunar highlands spectral classes and relationship to lunar samples

Tompkins and Pieters (1999) identified eleven spectral classes present on the surface of the Moon. Here we model these spectral classes to determine the compositions that define them. We do this by mathematically matching spectral classes to radiative transfer computed spectra using spectral shape, contrast, and excursion parameters as defining characteristics. Model spectra are based upon known mineralogies, mafic‐mineral Mg′s (molar (Mg/(Mg + Fe)) · 100), and maturities. We compare these compositional results to a compilation of ∼100 Apollo samples to determine plausible representative samples for these spectra. Results indicate that unique mineralogic solutions for several spectral classes can be determined unambiguously; however, classes previously interpreted to be pyroxene‐rich are compositionally ambiguous. Results suggest these ambiguous mineral assemblages are not random, but correlate with variations in absolute reflectance. These data further suggest absolute reflectance is a compositionally diagnostic spectral parameter that should be used in conjunction with relative reflectance analysis to constrain mineralogy. Although absolute reflectance for the eleven spectral classes is not available to constrain their composition, we detail mineral, chemical (i.e., Mg′), and absolute reflectance variations of matching model relative reflectance spectra to narrow the possibilities. This information is used in a pilot study of Bullialdus crater, for which Clementine absolute reflectance is known. Results indicate Bullialdus's central peak consists of Tompkins and Pieters' spectral classes AN, AGN, and N. Bullialdus's spectra that match class N are roughly consistent with previous compositional interpretations; however, matches to classes AN and AGN indicate more mafic assemblages typical of Mg‐suite norite/gabbronorite rocks.

Restudy of the worm-like carbonaceous compression fossils Protoarenicola, Pararenicola, and Sinosabellidites from early Neoproterozoic successions in North China

The carbonaceous compression fossils Protoarenicola baiguashanensis Wang, 1982, Pararenicola huaiyuanensis Wang, 1982, and Sinosabellidites huainanensis Zheng, 1980, from the early Neoproterozoic Liulaobei and Jiuliqiao formations in northern Anhui, North China, were previously interpreted as worm-like metazoans, largely on the basis of transverse annulations and purported proboscis structures. If correct, these would be some of the earliest known bilaterian animals and would provide a key paleontological calibration to molecular clock analyses. In this study, we examine a large population of these carbonaceous fossils, clarify their taxonomy, and provide new insights into their morphological, paleoecological, and phylogenetic interpretations. Although all three species are characterized by annulated tubes, P. baiguashanensis bears a bulbous terminal structure at one end of its tube. P. huaiyuanensis is characterized by a constricted opening at one end and a closed termination at the other. The two ends of S. huainanensis tubes are both closed and round. The bulbous terminal structure in P. baiguashanensis was previously interpreted as an animal proboscis, but new observations suggest that it was more likely a holdfast structure analogous to discoidal holdfast structures of the Mesoproterozoic Tawuia-like fossil Radhakrishnania Kumar, 2001, and the frondose Ediacara fossil Charniodiscus Ford, 1958. Furthermore, it is possible that at least P. baiguashanensis and P. huaiyuanensis may represent reproductive or taphonomic fragments of the same organism. This reinterpretation weakens the previous interpretation that P. baiguashanensis and P. huaiyuanensis were worm-like bilaterian animals. Instead, they can be alternatively interpreted as erect epibenthic organisms, possibly coenocytic algae reaching a tiering height of 30 mm. The predominance of discoidal holdfasts, as opposed to rhizoidal holdfasts, in pre-Ediacaran epibenthic organisms was probably related to more stable substrates in the presence of microbial mats and in the absence of bioturbating animals.

Architecture and depositional pattern of the Rhône Neofan and recent gravity activity in the Gulf of Lions (western Mediterranean)

The Rhône Deep Sea Fan is the largest sedimentary body in the western Mediterranean Sea. We present here the results of a detailed geophysical and sedimentological analysis of the most recent gravity deposits situated on the western flank of this large sedimentary body. These results are based on the interpretation of seismic profiles as well as acoustic and coring data acquired during the MARION cruise conducted in 2000 onboard R/V Le Suroît and Images V cruise on board of the R/V Marion Dufresne (1999). We found that (1) a new channel-levee unit developed during the last stage of the Rhône Neofan evolution and (2) the last phase of up-building of this channel/levee system dates back to 15.1 ka BP ( 14C). This implies that the last lobe of the Rhône deep-sea fan was built during the last low sea-level and the ensuing sea-level rise. We also identified (3) 10 recent sandy deposits, previously interpreted as related to the Neofan activity. In fact, their origin is probably linked to the Sète canyon that collect sandy shelf-edge deposits remobilised at the head of the Pyreneo-Languedocian canyons. We also characterised (4) the morphology and discuss the origin of the scours previously identified in the study area. These results contrast with previous interpretation which assigned a much younger age to the Neofan ( Méar and Gensous, 1993; Torres et al., 1997).