Calcarenitas con Microcodium del Paleoceno inferior en áreas hemipelágicas de la Zona Subbética, SE de España: isótopos de Sr, área fuente e implicaciones paleogeográficas

The Danian−early Selandian Olivares and Majalcorón formations are two calcarenite units rich in Microcodium remains that were accumulated in a marine hemipelagic setting of the Subbetic Zone (Betic Cordillera, southern Spain). Their outcrops are restricted to relatively small areas surrounded by uplifted Jurassic calcareous massifs, some of them with volcanic intercalations. The calcarenites contain lithoclasts of Lower Jurassic and lowermost Cretaceous age, and the 87 Sr/ 86 Sr isotopic ratios of the Microcodium remains suggest that they were originated in roots of plants that grew on Lower Jurassic carbonates. These facts entail that the Microcodium remains came from the calcareous massifs adjacent to their outcrops, the upper parts of which were subaerially exposed and colonized by Microcodium -producing plants during the Danian−early Selandian interval. The subaerial exposure of these massifs may have resulted from a coeval tectonic reactivation of Mesozoic syn-rift faults and folds, a eustatic sea level fall, or a combination of both processesLas formaciones Olivares y Majalcorón del Daniense-Selandiense inferior son unidades de calcarenitas ricas en restos de Microcodium acumuladas en un ambiente marino hemipelágico de la Zona Subbética (Cordillera Bética). Sus afloramientos están restringidos a áreas relativamente pequeñas rodeadas por elevados macizos de carbonatos jurásicos, algunos de ellos con intercalaciones volcánicas. Las calcarenitas contienen litoclastos del Jurásico Inferior y de la parte más baja del Cretácico, y los valores isotópicos 87 Sr/ 86 Sr de los restos de Microcodium sugieren que los mismos se originaron en raíces de plantas que crecían sobre carbonatos del Jurásico Inferior. Estos hechos implican que los restos de Microcodium proceden de los macizos carbonatados adyacentes a sus afloramientos, cuyas partes superiores estarían expuestas subaéreamente y colonizadas por plantas productoras de Microcodium durante el Daniense-Selandiense inferior. La exposición subaérea de dichos macizos pudo deberse a una reactivación tectónica de fallas y pliegues mesozoicos preexistentes, a un descenso eustático del nivel del mar, o a una combinación de ambos proceso

Tectonic control of the fluvio-palustrine cycles of the Campóo Group in the Aguilar Basin (Upper Tithonian-Berriasian, Palencia)

Los depósitos fluvio-palustres del Grupo Campóo se acumularon en la Cuenca limitada por fallas de Aguilar (N de Palencia) en condiciones de tectónica distensiva pulsante. El espacio de acomodación creado durante fases de aceleración tectónica de los cuatro pulsos principales reconocidos no fue compensado por aportes fluviales, causando la expansión de las zonas palustres.A la inversa, la reducción del espacio de acomodación durante las fases de desaceleración tectónica ocasionó la progresiva contracción y eventual desaparición de las zonas palustres. En la parte central y más subsidente de la cuenca, donde las condiciones fluviales fueron esporádicas, se acumuló una sucesión de calizas palustres de casi 500 m de espesor, una de las más potentes citadas hasta la fecha en la literatura geológicaThe fluvio-palustrine deposits of the Campóo Group were accumulated in the fault-bounded Aguilar Basin (N of Palencia province) under conditions of pulsating extensional tectonism. The accommodation space created during phases of accelerated tectonism of the four main pulses recognized was not compensated by fluvial input, resulting in the expansion of the palustrine zones. Conversely, the reduction of accommodation space during phases of tectonic slowdown caused the progressive contraction and eventual disappearance of the palustrine zones. In the central and most subsiding part of the basin, where fluviatile conditions were sporadic, a succession of palustrine limestones almost 500 m thick was accumulated, one of the thickest reported to date in the geological literatur

Characterization, significance and palaeoclimatic implications of the ferralithic soils of the Frontada Formation (upper Berriasien, Campóo Group, Basque-Cantabrian basin)

La Formación Frontada (Grupo Campóo) muestra numerosas estructuras relacionadas con la migración y precipitación de hierro en sus facies de orla aluvial distal y llanura de inundación. Estos rasgos pedogénicos están asociados con procesos de intenso lavado químico del sustrato y establecimiento de suelos hidromorfos. El análisis de estas estructuras ha permitido deducir cómo se generaron, y establecer un modelo genético para explicar su origen. Con base en ello, se han podido inferir unas condiciones climáticas de alta humedad y temperatura, similares al clima ecuatorial actual, bajo el cual se generaron los procesos de ferricretizaciónThe Frontada Formation (Campóo Group) presents an important amount of structures related to the migration and precipitation of iron in its alluvial floodplain sedimentary record. These pedogenical features are associated with processes of intense chemical weathering of the substrate and establishment of hydromorphic soils. The analysis of these structures has allowed us to deduce how they were generated, as well as to propose a genetic model to explain their origin. This model suggests a context of high climatic humidity and temperature, similar to the nowadays equatorial climate, under which the ferricretization processes occurre

Correlation of the Thanetian-Ilerdian turnover of larger foraminifera and the Initial Eocene thermal maximum (IETM) confirming evidence from the Campo area (Pyrenees, Spain)

Abstrac

Río Gor, Guadix region, Granada province: a new reference section for the Subbetic lower Paleogene

La recientemente descubierta sección de Río Gor es mucho más expandida y completa que la clásica sección de Alamedilla, a menudo considerada la sección más representativa de la sucesión del Paleógeno inferior de la Zona Subbética (Cordillera Bética). La sección de Río Gor, por tanto, ofrece mejores perspectivas que Alamedilla para testar la aplicabilidad de los criterios recientemente adoptados en la Cuenca Vasca para marcar las bases de los pisos globales Selandiense, Thanetiense y Luteciense, y para localizar y analizar el registro de eventos hipertermales típicos de este intervalo geológico. Este trabajo describe la litoestratigrafía de la nueva sección, junto con una zonación biostratigráfica preliminar basada en foraminíferos planctónicos, y discute futuras líneas de investigación para explotar su potencialThe recently discovered Río Gor section has been found to be far more expanded and complete than the classic Alamedilla section, often considered the most representative section of the lower Paleogene succession of the Subbetic Zone (Betic Cordillera). The Río Gor section, therefore, offers better prospects than Alamedilla to test the applicability of the criteria recently adopted in the Basque Basin to pinpoint the bases of the Selandian, Thanetian and Lutetian global stages, and to locate and analyze the signature of hyperthermal events typical of this geological interval. This paper describes the lithostratigraphy of the new section, together with a preliminary biostratigraphic zonation based on planktonic foraminifera, and discusses future lines of research to fully exploit its potentia

Middle Eocene Rhodoliths from Tropical and Mid-Latitude Regions

During the greenhouse conditions prevailing in the early–middle Eocene, larger benthic foraminifers (LBF) spread out on carbonate platforms worldwide while rhodolith beds were scarcely represented. This reduction in rhodolith beds coincided with a relative decrease in coralline algal diversity and with a drastic decline of coral reef abundance. Middle Eocene rhodoliths from two tropical (San Jacinto Fold Belt in northern Colombia and Bahoruco Peninsula in the Dominican Republic) and two mid-latitude (Salinas Menores Ravine and Sierra del Zacatín in Southern Spain) localities were studied. Rhodolith rudstones in the tropical areas accumulated on relatively deep (several tens of meters) platform environments and were also redeposited in deeper settings downslope. In Salinas Menores, rhodoliths are dispersed in planktic foraminifer-rich marls. Miliolids are common in the infilling of constructional voids in these rhodoliths, indicating that they originally grew in shallow-water inner-shelf settings and afterwards they were transported to deeper environments. In Sierra del Zacatín, rhodoliths are scarce and coralline algae mainly occur as crusts attached to and intergrowing with corals. Here, LBF dominated shallow-water carbonate platforms. In terms of taxonomic composition, coralline algae of the order Hapalidiales are the most abundant in the study areas, followed by Sporolithales. The order Corallinales is poorly represented except in Salinas Menores, where it is relatively abundant and diverse. The impact of high temperatures due to high levels of atmospheric CO2 during the Eocene and widespread oligotrophic conditions, which favored formation of LBF-rich lithofacies, might account for the low abundance of rhodolith beds at mid and high latitudes. In contrast, the more productive equatorial regions would have favored the formation of rhodolith beds.This research was funded by Research Group RNM-190 of the Junta de Andalucía (JA and JCB), MINECO/FEDER-UE project CGL2015-65404-R and by the Consolidated Research Group IT930-16 of the Basque Government (VP and XOE)

Integrative stratigraphy and climatic events of a new lower paleogene reference section from the betic cordillera: Río gor, Granada province, se Spain

Research interest in the early Paleogene was greatly enhanced after the recognition of several short-lived warming events in that period (hyperthermals), considered ancient analogues of the ongoing warming of the Earth climate. In the Caravaca and Alamedilla sections, the previously most studied lower Paleogene sections of the Subbetic Zone (Betic Cordillera), only the most prominent of these hyperthermals had been located, the so-called Paleocene/Eocene Thermal Maximum. The Río Gor section, though less studied, is found to comprise a lower Paleogene succession that is more expanded and complete than Caravaca and Alamedilla; it contains record of the Early Late Paleocene and Paleocene/Eocene Thermal Events, and at least one additional Eocene hyperthermal, thus offering an excellent opportunity to study these climatic events in the Subbetic Zone. Study of the Río Gor section is still in progress, this paper summarizing the state-of-the art of ongoing research

Redefinition of the Ilerdian Stage (early Eocene)

The Ilerdian Stage was created by Hottinger and Schaub in 1960 to accommodate a significant phase in the evolution of larger foraminifera not recorded in the northern European basins, and has since been adopted by most researchers working on shallow marine early Paleogene deposits of the Tethys domain. One of the defining criteria of the stage is a major turnover of larger foraminifera, marked by the FO's of Alveolina vredenburgi (formerly A. cucumiformis) and Nummulites fraasi. There is now conclusive evidence that this turnover was coeval with the onset of the Carbon Isotope Excursion (CIE) and, consequently, with the Paleocene-Eocene (P-E) boundary, a temporal correspondence that reinforces the usefulness of the Ilerdian as a chronostratigraphic subdivision of the early Eocene in a regional context. However, in addition to the paleontological criteria, the definition of the Ilerdian was also based on the designation of two reference sections in the southern Pyrenees: Tremp (stratotype) and Campo (parastratotype). In both sections, the base of the stage was placed at the lowest marine bed containing A. vredenburgi specimens. Using the CIE as a correlation tool we demonstrate that these two marine beds occur at different chronological levels, being older in Campo than in Tremp. Further, we show that both beds are in turn younger than the lowest strata with Ilerdian larger foraminifera at the deep-water Ermua section in the Basque Basin (western Pyrenees). Since the age of stage boundaries must be the same everywhere, the choice of these stratotype sections was misleading, since in practice it resulted in the Ilerdian being used as a facies term rather than as a chronostratigraphic unit. To eliminate that conflict, and yet be respectful with established tradition, we propose to redefine the Ilerdian Stage following a procedure similar to the one used by the International Commission on Stratigraphy to establish global chronostratigraphic standards, namely: by using a "silver spike" to be placed in the Tremp section at the base of the Claret Conglomerate, a widespread lithological unit that in the Tremp Graus Basin coincides with the onset of the CIE. The redefined regional Ilerdian Stage becomes thus directly correlatable to the lower part of the global Ypresian Stage, as currently defined by the International Commission on Stratigraphy

The Global Stratotype Section and Point (GSSP) for the base of the Lutetian Stage at the Gorrondatxe section, Spain

The GSSP for the base of the Lutetian Stage (early/ middle Eocene boundary) is defined at 167.85 metres in the Gorrondatxe sea-cliff section (NW of Bilbao city, Basque Country, northern Spain; 43º22'46.47" N, 3º 00' 51.61" W). This dark marly level coincides with the lowest occurrence of the calcareous nannofossil Blackites inflatus (CP12a/b boundary), is in the middle of polarity Chron C21r, and has been interpreted as the maximumflooding surface of a depositional sequence that may be global in extent. The GSSP age is approximately 800 kyr (39 precession cycles) younger than the beginning of polarity Chron C21r, or ~47.8 Ma in the GTS04 time scale. The proposal was approved by the International Subcommission on Paleogene Stratigraphy in February 2010, approved by the International Commission of Stratigraphy in January 2011, and ratified by the International Union of Geological Sciences in April 2011.Published86-1082.2. Laboratorio di paleomagnetismoJCR Journalrestricte

The Global Stratotype Sections and Points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages at Zumaia, Spain

The global stratotype sections and points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages have been defined in the coastal cliff along the Itzurun Beach at the town of Zumaia in the Basque Country, northern Spain. In the hemipelagic section exposed at Zumaia the base of the Selandian Stage has been placed at the base of the Itzurun Formation, ca. 49 m above the Cretaceous/ Paleogene boundary. At the base of the Selandian, marls replace the succession of Danian red limestone and limestone-marl couplets. The best marine, global correlation criterion for the basal Selandian is the second radiation of the important calcareous nannofossil group, the fasciculiths. Species such as Fasciculithus ulii, F. billii, F. janii, F. involutus, F.pileatus and F. tympaniformis have their first appearance in the interval from a few decimetres below up to 1.1 m above the base of the Selandian. The marker species for nannofossil Zone NP5, F. tympaniformis, first occurs 1.1 m above the base. Excellent cyclostratigraphy and magnetostratigraphy in the section creates further correlation potential, with the base of the Selandian occuring 30 precession cycles (630 kyr) above the top of magnetochron C27n. Profound changes in sedimentology related to a major sea-level fall characterize the Danian-Selandian transition in sections along the margins of the North Atlantic. The base of the Thanetian Stage is placed in the same section ca. 78 m above the Cretaceous/Paleogene boundary. It is defined at a level 2.8 m or eight precession cycles above the base of the core of the distinct clay-rich interval associated with the Mid-Paleocene Biotic Event, and it corresponds to the base of magnetochron C26n in the section. The base of the Thanetian is not associated with any significant change in marine micro-fauna or flora. The calcareous nannofossil Zone NP6, marked by the first occurrence of Heliolithus kleinpelli starts ca. 6.5 m below the base of the Thanetian. The definitions of the global stratotype points for the bases of the Selandian and Thanetian stages are in good agreements with the definitions in the historical stratotype sections in Denmark and England, respectively