A cystoid with two left facets: the significance of Tetracystis in the evolution and classification of the Callocystitidae (Echinodermata,Glyptocystitoida)

Revision of some North American Silurian callocystitid cystoids shows that Tetracystis Schuchert has the first two brachioles to the left in ambulacra B and D (B D different pattern), whereas Troosticystis Paul and Lovenicystis Regéll have only the first brachiole to the left in all four ambulacra (B–E the same pattern). ‘Apiocystites’ elegans Hall is transferred to Tetracystis because it has the B D different pattern. Lovenicystis kopfi sp. nov. is characterized by four short ambulacra. Salirocystis gen. nov. has the B D different pattern and two hydropores. All callocystitids that lack ambulacrum A are assigned to a new subfamily, the Tetracystinae; those with five ambulacra are referred to informally as ‘lepadocystines’. The previously recognized subfamily Callocystitinae is reduced in rank to a tribe within the ‘lepadocystines’. Preliminary character analysis suggests that the loss of ambulacrum A was the most significant evolutionary event within the family Callocystitidae, but has been overlooked in taxonomy. Character analysis also shows that all ‘lepadocystines’ had the B D different pattern of primary brachioles, which is retained in four tetracystine genera, Lepocrinites Conrad, Sphaerocystites Hall, Tetracystis and Salirocystis. Since Salirocystis has the plesiomorphic B D different pattern plus the apomorphic double hydropore, one cannot define a monophyletic taxon characterized by the B–E the same pattern plus one characterized by a double hydropore. Both alternatives are equally parsimonious. Here a new monophyletic tribe Lipsanocystini is defined characterized by a double hydropore. The B–E the same pattern evolved independently twice. Among current characters the loss of ambulacrum A, development of the B–E the same pattern and development of two hydropores are the most significant evolutionary events. Number of periproct border plates, length and structure of ambulacra are less significant. Copyright © 2014 John Wiley & Sons, Ltd.     

Facies architecture of asymmetrical branching distributary channels: Cretaceous Ferron Sandstone,Utah, USA

Distributary channel systems are an important component of deltaic systems, but details of their branching pattern, stream‐order, internal variability and relation with adjacent levée, bay and bayhead delta are rather poorly documented in ancient examples. Photomosaic and measured sections collected along a gooseneck‐shaped canyon in southern Utah allow direct mapping of the branching pattern of an ancient distributary system. The main channel belt is ca 250 m wide and narrows to ca 200 m downstream of the branching point. A subordinate channel belt, ca 80 m wide, branches off of the main channel, forming a distinctly asymmetrical branching pattern. Water discharge in the main channel is estimated to be 85 to 170 m³ sec^?1. Comparison with palaeodischarge estimates of trunk rivers mapped in previous studies suggests that the branching documented in this study probably is a fourth‐order split. The distributary channels are characterized by a U‐shaped geometry filled with medium‐grained, cross‐bedded sandstone, and are dominated by lateral accretion, suggesting limited lateral migration and moderate sinuosity. Tidally influenced facies and limited trace fossils indicate direct marine influence. The distributary channels erode into adjacent levée and underlying heterolithic bay‐fill deposits, and the marine influence suggests that they were deposited on a lower delta plain, rather than on a non‐marine floodplain. The subordinate channel fed a bayhead delta, suggesting that it was formed by a partial avulsion, rather than bifurcation around a mouth bar, as is more characteristic of terminal distributary channels. Channel‐floor drapes, bar‐accretion drapes and abandoned channel fills within the sandstone channel belts represent the most important heterogeneity from the perspective of reservoir characterization.     

The identity of the British Ordovician cystoid ‘Hemicosmites rugatus Forbes‘

New articulated specimens of the British Ordovician cystoid first mentioned under the name ‘Hemicosmites rugatus Forbes’ in 1848 allow its morphology and systematic affinities to be established for the first time. Despite being based on isolated plates, ‘H. rugatus Forbes’ has been reported from England and Wales, Belgium, France, Spain and Thailand, and has been attributed to four genera. It is characterized by a heteromorphic, circular stem, a theca with four basal, six infra‐lateral and eight lateral plates, all with sharp‐crested ridges running to plate angles, multiple arms in each ambulacrum and an extensive tegmen. These characters indicate it belongs in the family Caryocrinitidae and genus Caryocrinites. Caryocrinites rugatus had arms with lateral brachioles that folded in against the main arm axis, as in the type species C. ornatus Say. It is the first Ordovician species known to possess this character. Isolated plates show sorting and a few may represent other species of Caryocrinites s.l. Copyright © 2013 John Wiley & Sons, Ltd.     

Notatudiadema and Aegyptiaris: Two new regular echinoids genera with two new species from the Cenomanian of north Sinai,Egypt

Revision of the Cenomanian echinoids deposited in the Cairo Geological Museum resulted in the erection of two new genera with two new species of regular echinoids. The first, Notatudiadema rekeibensis gen. and sp. nov. is established for specimens from the Cenomanian of Gabal El-Rekeib, southeast the Maghara massif, north Sinai to accommodate diadematoid echinoids having hemi-crenulate ambital and sub-ambital interambulacral tubercles with the adapical part of platform non-crenulate and the adoral one of same tubercle coarsely crenulate. The second is Aegyptiaris halalensis gen. and sp. nov., erected for material from the lower Cenomanian of Gabal El-Halal, northeast Sinai as an emiratiid echinoid with throughout polyporus ambulacra and extremely reduced adapical ambulacral tubercles. The functional morphology and paleobiology of these taxa are also discussed. A new family is established: family Monodiadematidae fam. nov.     

Llandovery Crinoidea of the British Isles,including description of a new species from the Kilbride Formation (Telychian) of western Ireland

A new species of cladid(?) crinoid, Segmentocolumnus (col.) clarksoni, based on distinctive, disarticulated stem material, is described from the Upper Llandovery Kilbride Formation. Hitherto, this unit has yielded two taxa based on single, nearly complete crinoids. In contrast, S. (col.) clarksoni is known from numerous specimens, including common long pentagonal, pentameric, heteromorphic pluricolumnals with symplectial articulations, broad pentagonal lumina and narrow claustra. A related morphospecies is known from the Ashgill (Upper Ordovician) of Ireland. The fossil echinoderms of the Llandovery (Lower Silurian) are poorly known globally. Where present in this interval, echinoderms are more commonly preserved as disarticulated ossicles and rarely as complete specimens. Complete crinoids have now been identified from nine horizons in the Llandovery of the British Isles, making this one of the better known pelmatozoan faunas from this time interval. However, only two of these occurrences have yielded as many as five or more identifiable taxa. Seven of the nine occurrences are Upper Llandovery (Telychian). Genera are typical of the Silurian or (Upper Ordovician + Silurian); the only remnant Ashgill taxon that did not survive the Llandovery was the morphogenus Segmentocolumnus (col.) Donovan, an ‘extinction’ that probably owes more to taxonomic method than any evolutionary pattern. Copyright © 2003 John Wiley & Sons, Ltd.     

Neogene echinoids from the Cayman Islands,West Indies: regional implications

The first fossil echinoids are recorded from the Cayman Islands. A regular echinoid, Arbacia? sp., the spatangoids Brissus sp. cf. B. oblongus Wright and Schizaster sp. cf. S. americanus (Clark), and the clypeasteroid Clypeaster sp. are from the Middle Miocene Cayman Formation. Test fragments of the mellitid clypeasteroid, Leodia sexiesperforata (Leske), are from the Late Pleistocene Ironshore Formation. Miocene echinoids are preserved as (mainly internal) moulds; hence, all species are left in open nomenclature because of uncertainties regarding test architecture. All Miocene taxa are recorded from single specimens apart from the 27 assigned to Brissus. Schizaster sp. cf. S. americanus (Clark) is compared to a species from the Oligocene of the south‐east USA. Brissus sp. cf. B. oblongus is close in gross morphology to a taxon from the Miocene of Malta. Leodia sexiesperforata is identified from fragments with confidence, being the only extant Antillean sand dollar with elongate ambulacral petals that is limited to carbonate substrates. The Miocene echinoids of Grand Cayman, although of limited diversity, are mainly comprised of genera common in comparable mid‐Cenozoic carbonate environments. Copyright © 2015 John Wiley & Sons, Ltd.     

Heterochronic evolution in the Late Cretaceous echinoid Gauthieria (Echinoidea,Phymosomatidae)

Based on representatives of the Late Cretaceous genus Gauthieria (Gauthieria radiata – Gauthieria spatulifera – Gauthieria princeps), ontogenetic trajectories within the family Phymosomatidae are described for the first time. Due to shared similarities in their ontogenetic development, an intimate evolutionary relationship must be assumed. This interpretation is most supported by analyses of the development in the ambulacral plating pattern (alternation of simple plates and compound plates), which is not commonly found among the Phymosomatoidae. This pattern, however, is present among all three species during development. The developmental trajectories of 8 further characters were included in this study (arrangement of the adapical pore pairs, number of pore pairs, pore pair numbers in ambital ambulacral plates, number of interambulacral plates, peristomal opening, apical opening diameter, test height, radial ornament of the areoles). The evolution in this lineage is characterised by several different heterochronic processes, which suggest a dissociated heterochronic evolution, indicating a developmental modularity. Additionally, the systematic treatment of G. princeps is discussed on account of the presented results.     

Site selectivity of the boring Rogerella isp. infesting Cardiaster granulosus (Goldfuss) (Echinoidea) in the type Maastrichtian (Upper Cretaceous,Belgium)

A burrowing spatangoid echinoid (heart urchin), Cardiaster granulosus (Goldfuss), from the type area of the Maastrichtian Stage (Upper Cretaceous) in Belgium, was infested only in the plates of the ambulacral petals by acrothoracian barnacle borings, Rogerella isp. This infestation was after the death and exhumation of the echinoid. The distribution of Rogerella may indicate the azimuth of current flow at the time of exhumation prior to final burial. Copyright © 2015 John Wiley & Sons, Ltd.     

Parameters of Coseismic Reverse‐ and Oblique‐Slip Surface Ruptures of the 2008 Wenchuan Earthquake,Eastern Tibetan Plateau

Abstract: On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan plateau. Field investigations constrain the surface rupture pattern, length and offsets related to the Wenchuan earthquake. The Beichuan fault has a NE-trending right-lateral reverse rupture with a total length of 240 km. Reassessment yields a maximum vertical offset of 6.5±0.5 m and a maximum right-lateral offset of 4.9±0.5 m for its northern segment, which are the largest offsets found; the maximum vertical offset is 6.2±0.5 m for its southern segment. The Pengguan fault has a NE-trending pure reverse rupture about 72 km long with a maximum vertical offset of about 3.5 m. The Xiaoyudong fault has a NW-striking left-lateral reverse rupture about 7 km long between the Beichuan and Pengguan faults, with a maximum vertical offset of 3.4 m and left-lateral offset of 3.5 m. This pattern of multiple co-seismic surface ruptures is among the most complicated of recent great earthquakes and presents a much larger danger than if they ruptured individually. The rupture length is the longest for reverse faulting events ever reported.     

Micritization of crinoids by diagenetic dissolution

Bands within the Chalk of Kansas made up of masses of Uintacrinus socialis show an unusual preservation of crinoid ossicles: in contrast to their normal preservation in full relief as single large calcite crystals the ossicles are compressed and transformed to micrite. The micrite originated by a process different from the well-known micritization by algal and fungal borings and subsequent cementation of the borings: it is the outcome of partial dissolution. Dissolution proceeded inside the sediment and preferentially attacked the echinoderms as the most soluble calcareous component of the chalk sediment. Later, the remains of the Uintacrinus crystals preferentially attracted syntaxial cement so that the layer changed to a hard band of limestone within the soft chalk. In addition to a second process of micritization the preservation of Uintacrinus demonstrates (1) that the magnesium content of magnesian calcites survives the earliest stages of diagenesis within chalk, and (2) that a diagenetic comminution of large crystals (in an optical sense) to smaller ones is possible. Provided the ossicles of echinoderms are true single crystals (the knowledge in this field is summarized), this is an example of the often discussed ‘crystal diminution’.     

Notes on Mississippian echinoderms from Hurdlow,Derbyshire, central England

The fossil echinoderms of the Lower Carboniferous (Mississippian) of Derbyshire remain understudied, principally due to the nature of the preservation rather than any lack of biodiversity. Echinoids and crinoids are described in float blocks of limestone from near Hurdlow, Derbyshire, which have been etched naturally after many years of being washed by weakly acidic rain. Surface detail is variable, commonly poor, but rare specimens retain enough features for tentative identification. Two species of echinoids are identified from rare disarticulated plates, namely Melonechinus? sp. (ambulacral plates) and archaeocidarid sp. (interambulacral plate); more and superior material will be necessary to confirm this division. Crinoids include a cladid brachial ossicle sp. with a distinctive sculpture; a columnal of a monobathrid camerate platycrinitid sp.; Annulocolumnus (col.) sp. cf. A. annulus Donovan, a columnal morphotaxon with an unusually broad axial canal; and Cyclocyclicus (col.) spp. This is the tenth echinoid site to be recognized from the Mississippian of the White Peak. Examination of etched float blocks provides a further method of investigation of the echinoderm fauna of this and other limestone areas.     

Climatic influence on peatland formation and lateral expansion in sub‐arctic Fennoscandia

Weckström, J., Seppä, H. & Korhola, A. 2010: Climatic influence on peatland formation and lateral expansion in sub‐arctic Fennoscandia. Boreas, Vol. 39, pp. 761–769. 10.1111/j.1502‐3885.2010.00168.x. ISSN 0300‐9843. The initiation and lateral expansion patterns of five small sub‐arctic peatlands in the Fennoscandian tree‐line region were studied by 21 accelerator mass spectrometry (AMS) ¹⁴C‐dated basal‐peat samples representing three to six dates per site. The radiocarbon dates were converted to calendar years and are based on the median probability. When combined with earlier basal‐peat dates from the region, four distinctive periods can be observed in the cumulative record of the dates. The early Holocene, from c. 10 000 to 8000 cal. yr BP, was characterized by the fast initiation and rapid expansion of peatlands, whereas at 8000–4000 cal. yr BP lateral expansion was modest. The most intensive period of peatland expansion occurred at the beginning of the late Holocene at c. 4000 to 3000 cal. yr BP, after which it slowed down towards the present. All these periods are in rough agreement with the main Holocene climatic periods in the area, namely the relatively warm and moist early Holocene, the warm and dry Holocene thermal maximum (HTM) at 8000–4000 cal. yr BP, and the start of the cooler and moister trend (neoglacial cooling) from c. 4000 cal. yr BP to the present, indicating a broad‐scale climatic control on the lateral growth of sub‐arctic peatlands in Fennoscandia. In order to study the lateral expansion of peatlands and to evaluate their Holocene succession patterns, more studies based on multiple dates from the same peatland are needed.     

Bed‐scale spatial patterns in dolomite abundance: Part II. Effect of varied fluid chemistry,flow rate,precursor mineralogy,temperature, textural heterogeneity,nucleation density and bed geometry

Reaction‐transport modelling shows that a lateral, metre‐scale pattern in dolomite abundance can form during replacive dolomitization of calcite and aragonite precursors by Mississippian, Triassic and modern seawaters advecting at >20 cm year^?1 in low temperature (≤60°C) hydrogeological systems. The modelled pattern develops best in beds >1 m thick with a relatively uniform nucleate density and a low variance in reactive surface area (for example, grainstones). These conditions suggest that a lateral pattern in dolomite abundance should be expected in dolomites formed by any shallow hydrodynamic system that advects dolomitizing fluid horizontally, including the down‐gradient portion of a reflux system, the oceanward reaches of geothermal (Kohout) convection systems, and the seaward reaches of a seawater entrainment zone below a freshwater aquifer. However, even in those systems, a pattern will not form in all dolomites. Pattern will be muted in thinner (≤ ca 50 cm thick) beds and non‐emergent where the precursor had a high variance in reactive surface area (for example, a skeletal wackestone) and/or large variation in nucleate density. Pattern also did not form at temperatures above ca 60°C, which implies that pattern should not be expected in dolomites formed at intermediate to deep burial depths. As the patterns are horizontal, they also should not be expected where dolomitizing fluids moved vertically (for example, reflux immediately below a brine source). Pattern metrics (short‐range correlation length, and wavelength and amplitude of the longer cyclic component) vary with flow rate, fluid chemistry, bed thickness, porosity, grain size, temperature and the flow complexity (one‐dimensional, two‐dimensional or three‐dimensional) within the bed. However, no modelled pattern produced metrics larger than those documented on dolomite outcrops. The results thus constrain the length scales of porosity and permeability variance to include in petrophysical models of dolomite reservoirs, as well as the geological scenarios in which to consider metre‐scale lateral petrophysical variability.     

K0 estimation in level granular soil from anisotropic wave velocities on the basis of micromechanics

This study aims to explore the possibility for estimating K₀ in a level ground of granular soil by seismic methods on the basis of micromechanics theory. The idea was to simulate in situ cross‐hole seismic method for the measurement of wave velocities along various directions of wave‐propagation. This work made use of a field simulator to control a K₀ condition (zero lateral strain condition) in specimens. A series of vertical loading containing subsequent loading and unloading were applied to the specimen prepared by pluviation. In general, the K₀ values determined experimentally in this work agreed with the exiting empirical relations. K₀ value was also calibrated from measured anisotropic wave velocities using an optimization procedure. From the comparison of the back‐calculated and measured results of K₀, it revealed the feasibility for the determination of the in situ lateral stress in granular soil by seismic methods and on the basis of micromechanics theory as long as enough wave‐velocity measurements along various directions of wave‐propagation were available. The potential for the usage of the presented methodology for the determination of the in situ lateral stress in level‐ground of granular soil by seismic methods seems encouraging. Copyright © 2004 John Wiley & Sons, Ltd.     

New Macroscopic Problematic Fossil from the Early Cambrian Yanjiahe Biota,Yichang, Hubei,China

Yanjiahella gen. nov., a distinctive fossil taxon from the Early Cambrian Yanjiahe Biota in Yichang, Hubei Province, is characterized by: 1) an overall body plan composed of a stalk and a calyx (also arms in some species); 2) a stalk with closely spaced, transverse wrinkles and a medial, longitudinal ridge; and 3) a calyx preserved with three-dimensional radiating striations, as well as a probable madreporite in some specimens. Three species that can be assigned to this genus, which are Y. ancarpa sp. nov., Y. monocarpa sp. nov., and Y. biscarpa sp. nov. Yanjiahella is comparable to certain echinoderm taxa in terms of morphology and some biological structures, which might indicate the early evolution and diversification of ancestral echinoderm lineages from the early Early Cambrian Yangtze Platform. The discovery of putative echinoderms in the Yanjiahe Biota provides significant clues about the origination and evolution of the deuterostome phylum Echinodermata.     

Microboudin structures of piemontite along the Sambagawa metamorphic belt, Japan: implications for lateral variation of differential stress during regional metamorphism

Evidence is presented of a lateral variation in differential stress during metamorphism along a regional metamorphic belt on the basis of the proportion of microboudinaged piemontite grains (p) in a quartz matrix in metacherts. It is proposed that p is a practical indicator of relative differential stress. Analysis of 123 metacherts from the 800 km long Sambagawa metamorphic belt, Japan, reveals that p‐values range from < 0.01 to 0.7 in this region. Most samples from Wakayama in the mid‐belt area have p‐values of 0.4–0.6, whereas those from western Shikoku have p‐values of < 0.1. This difference cannot be explained by variations in metamorphic temperature, and is instead attributed to a regional, lateral variation in differential stress during metamorphism.     

What can strike‐slip fault spacing tell us about the plate boundary of western North America?

The spacing of parallel continental strike‐slip faults can constrain the mechanical properties of the faults and fault‐bounded crust. In the western US, evenly spaced strike‐slip fault domains are observed in the San Andreas (SA) and Walker Lane (WL) fault systems. Comparison of fault spacing (S) vs. seismogenic zone thickness (L) relationships of the SA and WL systems indicates that the SA has a higher S/L ratio (~8 vs. 1, respectively). If a stress‐shadow mechanism guides parallel fault formation, the S/L ratio should be controlled by fault strength, crustal strength, and/or regional stress. This suggests that the SA‐related strike‐slip faults are relatively weaker, with lower fault friction: 0.13–0.19 for the SA vs. 0.20 for WL. The observed mechanical differences between the San Andreas and Walker Lane fault systems may be attributed to variations in the local geology of the fault‐hosting crust and/or the regional boundary conditions (e.g. geothermal gradient or strain rate).     

Synthesis of Pb-Feldspar by Ion Exchange Reaction and Its Implications

Feldspar and Pb（NO3）2 were mixed and reacted at T=380℃ to synthesize Pb-feldspar. In the XRD （X-ray diffraction） pattern of the product, the d values （crystal lattice spacing） of the five peaks are 0.654, 0.342, 0.332, 0.327 and 0.257 nm. The XPS analysis results show that the binding energy of Pb 4f（7/2） in the feldspar was between 137.81-138.03 eV. Pb^2＋ can replace alkali and alkali earth cations in the feldspar structure through ion exchange reaction to form Pb-feldspar.     

Chloritoid–glaucophane schist in the north Qilian orogen, NW China: phase equilibria and P–T path from garnet zonation

Chloritoid–glaucophane‐bearing rocks are widespread in the high‐pressure belt of the north Qilian orogen, NW China. They are interbedded and cofacial with felsic schists originated from greywackes, mafic garnet blueschists and low‐T eclogites. Two representative chloritoid–glaucophane‐bearing assemblages are chloritoid + glaucophane + garnet + talc + quartz (sample Q5‐49) and chloritoid + glaucophane + garnet + phengite + epidote + quartz (sample Q5‐12). Garnet in sample Q5‐49 is coarse‐, medium‐ and fine‐grained and shows two types of zonation patterns. In pattern I, X_grs is constant as X_py rises, and in pattern II X_grs decreases as X_py rises. Phase equilibrium modelling in the NC(K)MnFMASH system with Thermocalc 3.25 indicates that pattern I can be formed during progressive metamorphism in lawsonite‐stable assemblages, while pattern II zonation can be formed with further heating after lawsonite has been consumed. Garnet growth in Q5‐49 is consistent with a continuous progressive metamorphic process from ～14.5 kbar at 470 °C to ～22.5 kbar at 560 °C. Garnet in sample Q5‐12 develops with pattern I zonation, which is consistent with a progressive metamorphic process from ～21 kbar at 540 °C to ～23.5 kbar at 580 °C with lawsonite present in the whole garnet growth. The latter sample shows the highest P–T conditions of the reported chloritoid–glaucophane‐bearing assemblages. Phase equilibrium calculation in the NCKFMASH system with a recent mixing model of amphibole indicates that chloritoid + glaucophane paragenesis does not have a low‐pressure limit of 18–19 kbar as previously suggested, but has a much larger pressure range from 7–8 to 27–30 kbar, with the low‐pressure part being within the stability field of albite.     

Rhizocarpon calibration curve for the Aoraki/Mount Cook area of New Zealand

Development of Rhizocarpon growth curve from the Aoraki/Mount Cook area of New Zealand provides a means to assess Little Ice Age glacier behaviour and suggests approaches that have wider application. Employing a sampling strategy based on large populations affords the opportunity to assess which of various metrics (e.g. single largest, average of five largest, mean of an entire population) best characterise Rhizocarpon growth patterns. The 98% quantile from each population fitted with a quadric curve forms a reliable representation of the growth pattern. Since this metric does not depend on the original sample size, comparisons are valid where sample strategy must be adapted to local situations or where the original sample size differs. For the Aoraki/Mount Cook area a surface 100 years old will have a 98% quantile lichen diameter of 34.3 mm, whereas a 200‐year‐old surface will have a lichen diameter of 73.7 mm. In the Southern Alps, constraints from the age range of calibration points, the flattening of the quadric calibration curve and ecological factors limit the useful age range to approximately 250 years. Copyright © 2005 John Wiley & Sons, Ltd.