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

K/T muga euskokantauriar arroan

Kretazeo eta Tertziarioaren arteko mugan gertatu zen suntsipen masiboak Lurreko espezieen hiru laurden baino gehiago desagertarazi zuen eta gaur egun zientzia-eremu ezberdinetako zientzialarien interesa suspertzen du; haien artean paleontologoak, geokimikoak, astrofisikoak eta abarrak. Ikertzaileok, Biziaren historiaz gain Lur planetaren eboluzioaz arduratzen dira. Euskokantauriar Arroan K/T muga ebaki anitzetan gorde da, Kretazeoaren amaierako krisiari buruzko ikerketak garatzeko leku aparta izanik

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

Haizeolak eta burdin hobiak Euskal Herrian

Urteetan zehar Baskonian eta inguruetan, Zientzia eta Teknologia Fakultateko jakintza alor anitzeko irakasle talde batek, egindako lanei esker, frogatu du haizeola kopuru handia gelditzen dela, orain arte esan denaren aurka; hala ere hainbat eta hainbat haizeola deseginda daude. Haizeola hauen labeak tamaina handiko egitura edo kubetak dira, kono-enbor eiteduna edo udare formadunak. Egitura hauek aspalditik karabiekin nahasiak, hauetatik bereizten dira, batez ere, beheko aldean duten kanal baten bidez kanpoko aldearekin loturik daudelako. Halaber, labearen barnea tarteka burdin zepak dituen buztinezko geruza batez estalia agertzen da. Zepak dentsoak dira eta Fe, Si eta Al eduki handia dute (fayalita, wustita eta herzinita mineral gisan). Honek adierazten du baxua zela metala ateratzeko prozesuaren errendimendua. Mendi lepoetan eta erreka batetik gertu kokatzen ohi dira, Behe Kretazeoko arrokez osaturiko zonaldeetan eta, hein txikiagoan Paleozoikoko arrokez osaturiko zonaldeetan ere. Aipagarria litzateke era berean haizeola hauen eta -ola aurrizki edo atzizkia duten toponimoen arteko harremana ere

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

Los miembros calciclásticos de la Formación Anotz (Eoceno de Navarra, W Pirineos): ejemplo de resedimentación en taludes de rampas carbonatadas

The four calciclastic members of the Lower-Middle Eocene Anotz Formation in the western Pyrenees, considered by some previous authors of shallow-marine origin because of their large size, massive appearance and abundant content of shallow-water fossils, are here re-interpreted as deep-marine, resedimented deposits. Eight different calciclastic facies have been recognized, all formed by sediment gravity flows derived from an adjacent shallow-water ramp to the west, showing that high-energy marine currents swept the shallow ramp and shed loose grains as sustained sediment gravity flow off to the ramp slopes. This example shows the need of careful petrosedimentological analyses to correctly address the depositional setting of calciclastic accumulationsLos cuatro miembros calciclásticos de la Formación Anotz del Pirineo occidental (Eoceno inferior-medio), que fueron interpretados previamente como depósitos marinos someros en base a sus grandes dimensiones, su apariencia masiva y su alto contenido en fósiles de aguas someras, se reinterpretan aquí como depósitos marinos profundos resedimentados. Se han reconocido ocho facies calciclásticas diferentes, todas formadas por flujos gravitacionales de sedimentos derivados desde una rampa carbonatada somera situada al oeste, lo que indica que la rampa somera era afectada por corrientes marinas energéticas que suministraron sedimento al talud mediante frecuentes flujos gravitacionales. Este ejemplo evidencia la necesidad de realizar análisis petrosedimentológicos detallados para establecer correctacmente el ambiente deposicional de acumulaciones calciclástica