Examinando por Autor "Nieto, L.M."

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A lower Valanginian coral fauna from the South Iberian Palaeomargin (Internal Prebetic, SE Spain)
(Paleontological Society, 2021-02) Lösser, H.; Nieto, L.M.; Castro, J.M.; Reolid, M.
From the Lower Valanginian of the Sierra de Cazorla (Internal Prebetic, SE Spain), a coral fauna is taxonomically described. The fauna encompasses 51 species in 29 genera. One genus and three species are described as new. The most speciesrich are the superfamilies Cyclolitoidea and Stylinoidea. The faunal composition is ambivalent and encompasses typical Jurassic taxa, such as members of the families Amphiastraeidae, Rhipidogyridae, Solenocoenidae and Stylinidae, but also typical Cretaceous elements such as the genera Confusaforma, Floriastrea and Holocoenia (which also have their first occurrence in the Valanginian studied fauna). Four Jurassic genera show a range extension into the Early Valanginian: Alloiteaucoenia, Bilaterocoenia, Hykeliphyllum and Miscellosmilia. Other genera still survived into the Late Valanginian (Placogyra, Rhipidogyra and Solenocoenia) but became extinct. A palaeobiogeographic analysis shows relationships of the studied fauna to the Tithonian and the Kimmeridgian of the northern Tethys on one hand, and the Hauterivian of the Paris Basin and the Puebla Basin (Mexico) on the other. Nineteen species of the studied fauna remained in open nomenclature; the majority of them probably represent new species.
An integrated analysis (microfacies and ichnology) of a shallow carbonate-platform succession: upper Aptian, Lower Cretaceous, Betic Cordillera
(Springer, 2017-11-27) Nieto, L.M.; Reolid, M.; Rodríguez-Tovar, F.J.; Castro, J.M.; Molina, J.M.; Ruiz-Ortiz, P.A.
Four lithofacies and 12 microfacies types recognized in an upper Aptian section in the Sierra de Bedmar-Jódar (Prebetic of Jaén) represent shallow lagoonal environments (marl and marly limestone) and sand bars that delimited the lagoon. The lagoonal facies reflect subtidal restricted water circulation with low energy. The sand bar facies (intertidal environment) have upper surfaces that show the effects of supratidal and subaerial conditions. The presence of early fractures in particular lithofacies shows the importance of local synsedimentary tectonics during sedimentation. Thalassinoides, ?Arenicolites, Diplocraterion, Circolites, Gastrochaenolites and Trypanites are recorded in different beds of this section, reflecting various states of substrate consistency, in the form of firmground, hardground, and rockground. Whereas firmground conditions were dominant in the lower part of the section, hardgrounds and rockgrounds are mainly present in the upper part of the section. Four types of shallowing-upward elementary sequence are recognized. All the sequences show at the base mudstone or wackestone microfacies representing a lagoonal environment, overlain by sand-bar grain-pack-stone facies corresponding to a bar bounding the lagoon. The factors that controlled their development were carbonate production and tectonic movements.
Assessment of geodiversity at the confluence of different geological domains and delimitation of natural protected areas (examples from Southern Spain)
(Springer, 2023-06-24) Nieto, L.M.; Fernández, T.; Leiva-Lozano, J.E.
Geodiversity and biodiversity have been assessed in an area of the province of Jaén (Southern Spain), the first one from the consideration of partial indices based on lithology, geomorphology, pedology, hydrology, palaeontology, mineralogy and geosites; biodiversity is also regarded from previous data, considering a biodiversity index and endangered species index. This area shows the contact between the Guadalquivir Basin and the Betic External Zones. In addition, several natural protected areas have been defined, among which the Cazorla, Segura and Las Villas Natural Park (where mainly Prebetic materials outcrop) and the Sierra Mágina Natural Park (made up of Subbetic materials) stand out. The high and very high values of geodiversity have been located in an area where mainly Subbetic materials outcrop, including the Sierra Mágina Natural Park, and which coincides to a large extent with the front of the Betic External Zones and its contact with the Guadalquivir Basin. However, the Cazorla, Segura and Las Villas Natural Park is outside this area of high or very high geodiversity. Both natural parks fit well in areas where biodiversity and endangered species are important. These differences between the geodiversity values and the boundaries of these natural areas allow suggesting that, for delimitation of any natural protected area, its boundaries should be defined based on knowledge of the geodiversity and biodiversity of the region where the natural area is located.
Assessment of geodiversity in the southern part of the Central Iberian Zone (Jaén Province): usefulness for delimiting and managing natural protected areas
(Springer, 2020-02-03) Fernández, A.; Fernández, T.; Pereira, D.I.; Nieto, L.M.
To explore the relationship between geodiversity and borders of natural protected areas, we studied the northern part of Jaén Province (southern Spain), where the southern sector of the Central Iberian Massif, the Betic Cordillera and the Guadalquivir foreland basin come together. Moreover, several natural protected areas (NPAs) are located here. To approach the topic, we defined the geodiversity index as the sum of partial indices: lithological, geomorphological, palaeontological, pedological, minerals, hydrology and geosites. This made it possible to derive a map of the geodiversity index and a map of geodiversity gradient. Analysis of their distribution shows that almost 80% of the territory has values of medium, high and very high geodiversity, but these zones are situated outside the borders of the NPAs. A similar study considering two biological indices (endangered species and biodiversity) shows a good correlation between the limits of NPAs and the higher values of these indices. Thus, an absence of correlation between the geodiversity index and biological indices is clearly detected. These results are not in agreement with the definition of NPAs in the current Spanish laws of nature conservation.
Early development and OAE 1a-linked demise of a carbonate platform in the western Tethys: Lower Cretaceous of Sierra Mariola (South Iberian Paleomargin, SE Spain)
(Elsevier, 2024) Martínez-Rodríguez, R.; Castro, J.M.; de Gea, G.A.; Nieto, L.M.; Ruiz-Ortiz, P.A.; Skelton, P.W.
A carbonate platform succession of early Aptian age is described from the Sierra Mariola, which is located within the Prebetic Zone of the Betic External Zones (BEZ) of the Southern Iberian Palaeomargin, in SE Spain. The facies and stratigraphic architecture of the studied succession are described and analysed from multiple logged sections to characterize different depositional environments. The cyclic stacking of facies observed suggests a possible orbital forcing of climate transmitted to sedimentation. Superbundles are recognized describing two sequences of Regressive-Transgressive (R-T) evolution. Analysis of carbon-isotope data identifies both the interval before the hyperthermal event of the early Aptian Oceanic Anoxic Event (OAE 1a) and the onset of the latter event, with an abrupt change in sedimentation marking the demise of the carbonate platform. The field outcrop thus preserves a record of the transition from a greenhouse world to a hothouse event.
Evolution from carbonate platform to pelagic environments in the South Iberian Paleomargin (Pliensbachian-Early Toarcian, Early Jurassic): carbonate features and isotope geochemistry
(MDPI, 2023-10-29) Nieto, L.M.; Molina, J.M.; Ruiz-Ortiz, P.A.; Fraguas, A.; Reolid, M.
This paper studies ten Subbetic (Betic External Zones) stratigraphic sections spanning the Pliensbachian–early Toarcian time interval. Eight lithofacies were distinguished: crinoidal limestones, peloidal limestones, breccias, cherty limestones, nodular limestones, hardground surfaces and condensed levels, marls and marly limestone alternance, and dark marls. The biostratigraphy matches data from ammonite and calcareous nannofossil zonations. In addition, we analyzed C and O isotopes from bulk samples from three of the studied sections in which the lower Toarcian sedimentation crops out. The demise of the Lower Jurassic shallow platform developed in the South Iberian Paleomargin was a complex process driven by rifting, which led to tilted blocks giving way to different sedimentary environments. The tectonic stages occurred in the Sinemurian–Pliensbachian transition (R1), toward the lower part of the Ibex Zone (FO of the Biscutum grande, R2), in the Ibex– Davoei zones boundary (FO of Lotharingius barozii, R3), in the lower–upper Pliensbachian (R4), and in the lower boundary of the NJT4d nannofossil Subzone (R5) (Lavinianum Zone, upper Pliensbachian). After this last phase, sedimentation became pelagic in origin throughout the basin, represented by the sections studied. However, the isotope data show no clear record of the different C-isotopic events, though the Davoei–Margaritatus Event, the late Pliensbachian Event, and the Pliensbachian–Toarcian Boundary Event (PTBE) could be cautiously identified. These geochemical features are explained by the convergence of marine currents from Panthalassa (through the Hispanic Corridor) and Tethys.
Geodiversity as a tool for the nature conservation
(IntechOpen, 2024) Nieto, L.M.
Geodiversity and biodiversity are the two fundamental components of Nature that must be analyzed simultaneously for good management of the natural environment. Geodiversity, including geomorphodiversity, has values that make it possible to define the geosystem services on the basis of which it is possible to establish protocols for the sustainable development of the territory analyzed. Both the values of geodiversity and the geosystem services they provide are key elements for the definition of Natural Protected Areas (NPAs). Furthermore, it is also necessary to consider the assessment of the geodiversity and geomorphodiversity of the territory under consideration, so that a zoning can be established in terms of the geodiversity index (geodiversity/ geomorphodiversity gradient) that favors the establishment of specific geoconservation protocols according to the value of these indices. In addition, NPAs should be considered as elements belonging to a network in which the different natural systems of the territory in which the network is defined are represented. In the case of geodiversity or geomorphodiversity, the network must be supported by the definition of geological contexts, representative of the major geological units that are observable in the territory.
Palustrine sediments between two isolated shallow carbonate platforms (Aptian-Albian transition, Prebetic of Jaén, South Spain)
(MDPI, 2022-01-20) Nieto, L.M.; Molina, J.M.; Ruiz-Ortiz, P.A.; Castro, J.M.; Reolid, M.; de Gea, G.A.
During the Aptian-Albian transition, an extensional phase of the Central Atlantic which affected the Prebetic carbonate platform (South Iberian Continental Margin, northwestern margin of the Tethys) occurred. A graben morphology was developed in the platform coeval to a relative sea level fall. As a consequence, palustrine facies characterized by rhizoliths and some pond deposits of black lutites were established. Over these palustrine sediments, a second shallow carbonate platform was built during the early Albian. However, this process was not abrupt, as several levels with orbitolines and rudists were deposited intercalated between the continental facies, recording the transition to a new shallow marine carbonate platform developped during the Early Albian. The presence of these continental palustrine sediments between two episodes of shallow carbonate platform is described for the first time in the Prebetic. The demise of an upper Aptian isolated shallow carbonate platform drove to the deposition of these palustrine sediments in an extensional tectonic regime.
Progradation of a shallow carbonate platform developed on a fault-block in the Western Tethys (lower Aptian, Sierra de Bedmar-Jódar, Prebetic of Jaén, Spain)
(Springer, 2023-04-10) Martínez-Rodríguez, R.; Nieto, L.M.; Castro, J.M.; de Gea, G.A.; Ruiz-Ortiz, P.A.; Molina, J.M.; Skelton, P.W.
The Middle Member of the Llopis Fm in the Sierra de Bedmar-Jódar Unit of the Prebetic Zone of Jaén (southern Spain) was deposited on a shallow-marine platform of the Southern Iberian Continental Margin during the earliest Aptian. Detailed field logging of nine stratigraphic sections and facies mapping have allowed seven lithofacies associations (L1–L6) to be distinguished, one siliciclastic (L1) and five carbonate facies (L2–6). The succession is composed of eight consecutive elemental sequences of lithofacies associations L1–L6. Each elemental sequence is interpreted as representing one episode of shallowing-upwards carbonate deposition in a very shallow platform-lagoon that was bounded shoreward by clastic/ooid bars and passed seaward either to stromatoporoid bioconstructions (bioherms and biostromes) or rudist biostromes. The successive elemental sequences show north-eastward progradational geometries. Three phases of platform development are identified: (1) installation of the shallow platform; (2) development of a lagoon bounded by a stromatoporoid barrier and (3) development of an Urgonian-type platform dominated by rudists. During the early Aptian, the Bedmar-Jódar platform was partially isolated from the rest of the Prebetic platform and showed overall progradation towards the NE, in contrast to the general south-eastward progradational trend of the Prebetic platform. Sedimentation was controlled by rift-generated extensional tectonics that resulted in tilting of the platform block, causing the deviation of progradation from the general trends of the Prebetic Platform. In addition, climatic influence is inferred from the presence of siliciclastic sediments derived from weathering of the hinterland, which restricted the carbonate factory.
Tracking magmatism and oceanic change through the early Aptian Anoxic Event (OAE 1a) to the late Aptian: insights from osmium isotopes from the westernmost Tethys (SE Spain) Cau Core
(Elsevier, 2021-09-29) Martínez-Rodríguez, R.; Selby, D.; Castro, J.M.; de Gea, G.A.; Nieto, L.M.; Ruiz-Ortiz, P.A.
Some of the major Carbon cycle perturbations of the Phanerozoic occurred during the Aptian, in relation to magmatism. The highest temperatures reconstructed for the Cretaceous Period correspond to the Oceanic Anoxic Event of the early Aptian (OAE 1a), an episode of accelerated global change. Here we present a chemostratigraphic study based on osmium isotopes integrated with high-resolution Carbon-Oxygen stable isotope data from the Cau Core (Western Tethys, SE Spain), including a 6.4 Ma record from the early to the late Aptian. This high resolution study of the continuous and expanded Cau section permits a thorough understanding of the duration of the Aptian events, as well as an evaluation of the mechanisms triggering the abrupt changes of the global carbon and osmium cycles and their interdependence. Here we show that the Large Igneous Province (LIP) Aptian magmatism initiated 550–750 kyr prior to the OAE 1a, and persisted for 1.4 Myr after the event, influencing the composition of seawater for 2.8 Myr. We show a continuous Os isotope record encompassing the OAE 1a and the late Aptian for the first time, and demonstrate that the recovery from the exceptionally unradiogenic composition of seawater Os produced by the dominance of the Ontong Java Plateau volcanism, was slow. Our results demonstrate the different time duration of some events, and the asynchronous relationship between the carbon and osmium cycles

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Examinando por Autor "Nieto, L.M."