Distinguishing between environmental and species-specific physiological signals, recorded in coral skeletons, is one of the fundamental challenges in their reliable use as (paleo)climate proxies. To ...date, characteristic biological bias in skeleton-recorded environmental signatures (vital effect) was shown in shifts in geochemical signatures. Herein, for the first time, we have assessed crystallographic parameters of bio-aragonite to study the response of the reef-building coral Stylophora pistillata to experimental seawater acidification (pH 8.2, 7.6 and 7.3). Skeletons formed under high pCO
conditions show systematic crystallographic changes such as better constrained crystal orientation and anisotropic distortions of bio-aragonite lattice parameters due to increased amount of intracrystalline organic matrix and water content. These variations in crystallographic features that seem to reflect physiological adjustments of biomineralizing organisms to environmental change, are herein called crystallographic vital effect (CVE). CVE may register those changes in the biomineralization process that may not yet be perceived at the macromorphological skeletal level.
Otoliths are calcium carbonate components of the stato-acoustical organ responsible for hearing and maintenance of the body balance in teleost fish. During their formation, control over, e.g., ...morphology and carbonate polymorph is influenced by complex insoluble collagen-like protein and soluble non-collagenous protein assemblages; many of these proteins are incorporated into their aragonite crystal structure. However, in the fossil record these proteins are considered lost through diagenetic processes, hampering studies of past biomineralization mechanisms. Here we report the presence of 11 fish-specific proteins (and several isoforms) in Miocene (ca. 14.8-14.6 Ma) phycid hake otoliths. These fossil otoliths were preserved in water-impermeable clays and exhibit microscopic and crystallographic features indistinguishable from modern representatives, consistent with an exceptionally pristine state of preservation. Indeed, these fossil otoliths retain ca. 10% of the proteins sequenced from modern counterparts, including proteins specific to inner ear development, such as otolin-1-like proteins involved in the arrangement of the otoliths into the sensory epithelium and otogelin/otogelin-like proteins that are located in the acellular membranes of the inner ear in modern fish. The specificity of these proteins excludes the possibility of external contamination. Identification of a fraction of identical proteins in modern and fossil phycid hake otoliths implies a highly conserved inner ear biomineralization process through time.
Five types of reefs are described from the northern and southern parts of the Azrou-Khenifra Basin generated by the interactions of microbes and coral communities. The type 1 microbial reefs grew in ...both shallow- and deep-water settings, with a strong control by glacioeustasy. Type 2 microbial reefs developed in more tranquil periods, associated with common intermounds, and where only a single major regressive-transgressive sequence is recognised. Type 3 microbial reefs developed in constant deeper water conditions, generated by higher rates of subsidence in the basin, and creating an overall deepening-upward sequence. Type 4 microbial reefs recognised in the northern part of the basin have no clear counterparts in southern outcrops, but they are likely the capping strata observed in the latter area. Rugose corals allow to define a Type 5 reef, unrelated to microbial facies, and are recorded in oolitic-bioclastic backshoals or quiet inner platform settings. The presence of similar reefs in both the northern and southern parts of the basin demonstrates that conditions were not as different as previously proposed, and a lithostratigraphical, environmental uniformity occurs, which permits the analysis of different subsidence rates and glacioeustastic influence. In the Azrou-Khenifra Basin, the reefs, as well as other regional features, suggest that the basin, overall, evolved from an extensional tectonic regime during the early Brigantian into a complex extensional or compressional regime during the early Serpukhovian, passing into a predominantly compressional phase during the late Serpukhovian in a polyphase tectonic inversion during the onset of the Variscan Orogeny in the region.
In southern France, including the southern Montagne Noire and Mouthoumet Massif, foraminifers allow describing a biostratigraphical zonation for different formations included in those areas. ...Carbonate platforms are developed from the latest Tournaisian to the lower part of the late Viséan. In between, up to six additional zones have been recognized. The foraminiferal study also includes the first formal description of early Viséan foraminifers from the Vieussan area, a metamorphic area north of the main Mississippian stratigraphic sections of the Mont Peyroux nappe and écailles de Cabrières, as well as the dating of some preserved carbonates of the Mouthoumet Massif. Global foraminiferal guides are used for the definition of the zones, as well as other taxa considered as regional markers, but their detailed study might also be used for more continental to global level correlations. Lapparentidiscus irregularis nov. sp. and Ugurus intermedius nov. sp. are described.
Corals are significant components of fossil marine communities and important for paleoenvironmental reconstructions throughout the Phanerozoic. Despite their abundance and diversity in Paleozoic ...rocks, the presence, and criteria for the recognition of primary, biogenic skeletal structures is highly controversial. The aim of this study is a multilevel analysis of the diverse morphological elements that form well-preserved specimens of the Carboniferous Multithecopora tabulate coral skeleton. Results indicate that samples are minimally altered by diagenesis, but most importantly that skeletal structures are biogenic in nature, and similar to those of modern and fossil carbonate-producing organisms. Nano- and microcrystals form a complex framework of different domains of crystal morphologies that comprise the bulk of the skeleton in Multithecopora. These domains are thought to be the possible phenotypic response of the genotype of these corals, and had a structural importance during the life of the organism. Overall, this study sheds light for a better understanding on the controversy that exists about the biogenic or abiogenic origin of the Paleozoic coral microstructures.
•Use of mineral characterization techniques in skeletons of Paleozoic corals.•First record of original nanotexture in Paleozoic corals by AFM.•Crystallographic study by EBSD of auloporid corals.•Diagenetic evaluation of skeletal structures in auloporid corals.•Establishment of new criteria to recognize original structures in Paleozoic corals.
The Luna Valley complex geosite (northwestern Spain) is a region of geoheritage significance located in an area with high environmental value. Geological studies began in the mid-20th century and ...continue to provide scientific data of significant relevance to the knowledge regarding the Palaeozoic stratigraphy of northern Gondwana and the tectonics of the Variscan orogen. This region also has high value for geoeducation, being visited regularly by both students and the general public. Educational use of the area has promoted the creation of several publicly available materials and activities that include trails, guides, displays and brochures, as well as the development of a small museum. However, over time, weathering; the abandonment of rural life; and the intensive, uncontrolled, and careless use of this region as a geosite for scientific and educational purposes has led to significant degradation and the consequent loss of its geoheritage value. This paper describes the geology of five key geosites in the Luna Valley. This is followed by a review of the promotional initiatives carried out in the area. These data, along with our knowledge of the area, allow us to develop a heritage analysis that includes the main geological interests, conservation status and some key management issues for each of these five individual sites. Several recommendations aim to control the physical degradation of the geosites, encourage their regular monitoring and the updating of the outreach materials using virtual tools, and promote the involvement of the local population in the conservation of this unique site.
Revision of several important Carboniferous stratigraphic successions in basins in the Saharan Platform allows us to propose distinct biostratigraphical boundaries for the upper Viséan, lower and ...upper Serpukhovian and lower Bashkirian, with the latter boundary separating upper Mississippian from lower Pennsylvanian strata. The boundaries are not only defined primarily by foraminifers but also incorporate ammonoid and conodont data. This study shows that the positioning of some boundaries differs significantly from previous studies in the region.
For the studied interval, it can be recognized that two well-defined tectonic events were widespread in the entire Sahara Platform: a mostly late Viséan event and a latest Serpukhovian–early Bashkirian event. Both tectonic events show a marked tendency to become younger eastward, and they are compared to the intra-Viséan phase of the Variscan Orogeny and the main phase of this orogeny, respectively.
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•Carboniferous basins in northern Gondwana constituted a large shallow-water platform.•Biostratigraphic revision aids precise correlation of late Mississippian–early Pennsylvanian.•Two tectonic events migrating in age eastward are linked to the Variscan Orogeny.
A new early Visean coral assemblage has been recorded from turbidite facies in the southern part of the Azrou-Khenifra Basin, northwest of Khenifra, central Morocco. The newly discovered Ba Moussa ...West (BMW) coral fauna includes
Siphonophyllia khenifrense
sp. nov.,
Sychnoelasma urbanowitschi
,
Cravenia lamellata
,
Cravenia tela
,
Cravenia rhytoides
,
Turnacipora megastoma
and
Pleurosiphonella crustosa
. The early Visean age of the coral assemblage is supported by foraminiferal and conodont data, with the recognition of the basal Visean MFZ9 Zone. This confirms that the first transgression in the Azrou-Khenifra Basin was during the earliest Visean. The allochthonous coral assemblage was recovered from coarse-grained proximal limestone debris flow and turbidite beds within a fault-bounded unit, lying to the west of a thrust syncline containing upper Visean limestones. No evidence exists of the former early Visean shallow-water platform from which the corals were derived. All other in situ platform carbonate rocks around the southern margin of the Azrou-Khenifra Basin are probably of late Visean (Asbian–Brigantian) age. The early Visean Ba Moussa West coral fauna can be compared with that at Tafilalt in eastern Morocco, as well as in other Saharian basins of Algeria. Many of the genera and species in the Ba Moussa West assemblage are identical to those in NW Europe, with which it must have had marine connections. The new rugose species described,
Siphonophyllia khenifrense,
is probably endemic to North Africa. Its ecological niche in NW Europe was occupied by
S. cylindrica
or
S.
aff.
garwoodi
.
En la naturaleza, el ion uranilo se asocia comúnmente a arseniatos, fosfatos y vanadatos; uno de los orígenes secundarios másfrecuentes del uranio está asociado a fosfatos cálcicos biogénicos. En ...este estudio se han caracterizado minerales de uranio con espectroscopia de reflectancia VNIR-SWIR de laboratorio (400-2500 nm). Entre las muestras estudiadas se han incluido los minerales secundarios de uranio: metatorbernita, metautunita y metauranocircita, así como fosfatos cálcicos (biogénicos e inorgánicos) y fósiles coexistentes con mineralizaciones de metatyuyamunita encontrados en el yacimiento de vertebrados del Mioceno inferior de Córcoles (Cuenca del Tajo, Guadalajara, España). Este yacimiento representa un ejemplo de la formación de minerales secundarios de uranio de tipo fosfatos. Su origen es el resultado de la interacción de los fósiles con aguas subterráneas u otros fluidos mineralizadores portadores de uranilo (UO22+) durante la diagénesis. Los minerales con uranilo muestran rasgos de absorción a 1100, 1330 y 1672 nm atribuidos a los aniones uranilo. Dada la escasa información preexistente, la caracterización de los minerales que contienen uranio aporta valiosa información con gran potencial para ser aplicada en teledetección. Los datos obtenidos pueden ser de utilidad en la exploración, caracterización y/o protección de los yacimientos de uranio.
Variations in the geochemical signatures of fossil brachiopod shells may be due to diagenesis and/or biological processes (i.e., 'vital effects'). It is critical to characterise them in order to ...identify reliable shell areas suitable for paleoclimate studies. This investigation contributes to an in-depth understanding of geochemical variations in
sp. shells (SW Spain, Serpukhovian age), throwing light onto the Late Paleozoic Ice Age interpretation. Microstructural, crystallographic, cathodoluminescence and geochemical (minor and trace elements, δ
O, δ
C, and strontium isotopes) characterisations have been performed on the tertiary layer of the ventral valve, to assess the preservation state. Poorly preserved areas exhibit microstructural and geochemical changes such as recrystallisation, fracturing and higher Mn and Fe enrichment. Moreover, these areas have a higher dispersion of ⁸⁶Sr, ⁸⁷Sr, δ
O and δ
C than well-preserved areas. Three structural regions have been identified in well-preserved areas of the ventral valve by differences in valve curvature and thickness, such as the umbonal and thick and thin regions. These regions have different proportions of Mg, S, Na, δ
O, and δ
C, which are interpreted as 'vital effects' and probably related to growth-rate differences during shell growth. The
tertiary layer seems the most suitable for paleoclimate studies, because it retains the original microstructure and geochemical composition.
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