Options
Alegret, L.
Loading...
Preferred name
Alegret, L.
4 results
Now showing 1 - 4 of 4
- PublicationRestrictedReassessing the Bartonian unit stratotype at Alum Bay (Isle of Wight, UK): an integrated approach(2021)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; The Global Stratotype Section and Point (GSSP) for the base of the Bartonian, currently remains undefined. The Bartonian unit stratotype is located at the Barton coastal section in the Hampshire Basin, on the South Coast of the UK. The base of the “Barton beds” was originally placed at the lowest occurrence of Nummulites prestwichianus, and this is still the basis of the recognition of the unit Bartonian Stage as a formal chronostratigraphic unit of the Paleogene. However, this biostratigraphic marker is not widely applicable elsewhere. The base of the lithostratigraphic unit, the Barton Clay Formation, also extends below this level creating further complication. The parastratotype section is located at Alum Bay, 7 km away, on the Isle of Wight. Despite a number of studies carried out in 1970s and ‘80s on both sections, global correlation remains problematic. Here we present an integrated (micropalaeontological, stratigraphic, palaeomagnetic) study of the Lutetian-Bartonian transition at Alum Bay, and aim at improving the stratigraphy of this section to better define the base of the Bartonian and contribute towards a decision on the GSSP.163 24 - PublicationRestrictedEvidences of an abrupt environmental disruption during the Mid Paleocene Biotic Event (Zumaia section, W Pyrenees)(2007)
; ; ; ; ; ; ; ;Bernaola, G.; Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado de correos 644, 48080 Bilbao, Spain ;Baceta, J. I.; Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado de correos 644, 48080 Bilbao, Spain ;Orue-Etxebarria, X.; Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado de correos 644, 48080 Bilbao, Spain ;Alegret, L.; Área de Estratigrafía, Departamento de Ciencias de la Tierra, Universidad de Zaragoza, E-50009 Zaragoza, Spain ;Martín-Rubio, M.; Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado de correos 644, 48080 Bilbao, Spain ;Arostegui, J.; Departamento de Mineralogía y Petrología, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado de correos 644, 48080 Bilbao, Spain ;Dinarès-Turell, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; ; ; An abrupt environmental disruption occurred in the photic zone and at the seafl oor during the mid-Paleocene biotic event (MPBE). Calcareous nannoplankton, planktic foraminifer, and benthic foraminifer assemblages at Zumaia section (western Pyrenees) underwent a rapid and remarkable transformation. The major calcareous plankton assemblage changes suggest a shift from relatively cooler mesotrophic to warmer, more oligotrophic conditions, indicating a disturbed environment due to the warming of the ocean. Benthic foraminifer assemblages were also signifi cantly affected by the MPBE; diversity of the assemblages and buliminids show net decline and the low food and opportunistic taxa increase in abundance. The reorganization of the planktic ecosystem possibly involved changes in the food fl ux (type and quantity) to the seafl oor, thus triggering changes in the benthic communities. A 1‰ negative δ13C shift and a 30% carbonate content decrease are recorded in connection with the biotic event. This suggests that during the MPBE, as in the Paleocene- Eocene Thermal Maximum (PETM), an input of a large mass of isotopically depleted carbon into the ocean and atmosphere could have lowered the deep-sea pH, triggering a rapid shoaling of the lysocline and contributing to greenhouse warming. The MPBE was short lived: according to the counting of limestone-marl couplets, the stratigraphic expression of precession cycles throughout the Zumaia section, the MPBE lasted for ~52–53 k.y., with the core of the event representing ~10–11 k.y. The Zumaia section is the fi rst land-based locality in which the MPBE is recognized and described in detail. Due to its expanded character and excellent paleontological record, this section may prove to be a global reference section for the study of this shortlived event.179 21 - PublicationRestrictedThe Global Stratotype Sections and Points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages at Zumaia, Spain(2011-12)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Schmitz, B.; Department of Geology, Lund University, SE-22362 Lund, Sweden ;Pujalte, V.; Department of Stratigraphy and Paleontology, University of the Basque Country, E-48080 Bilbao, Spain ;Molina, E.; Department of Earth Sciences, Zaragoza University, E-50009 Zaragoza, Spain ;Monechi, S.; Department of Earth Sciences, Florence University, 50121 Florence, Italy ;Orue-Etxebarria, X.; Department of Stratigraphy and Paleontology, University of the Basque Country, E-48080 Bilbao, Spain ;Speijer, R. P.; Department of Earth and Environmental Sciences, K.U. Leuven, B-3001 Leuven, Belgium ;Alegret, L.; Department of Earth Sciences, Zaragoza University, E-50009 Zaragoza, Spain ;Apellaniz, E.; Department of Stratigraphy and Paleontology, University of the Basque Country, E-48080 Bilbao, Spain ;Arenillas, I.; Department of Earth Sciences, Zaragoza University, E-50009 Zaragoza, Spain ;Aubry, M. P.; Department of Geology, Rutgers University, Piscatatway, NJ 08854 USA. ;Baceta, J. I.; Department of Stratigraphy and Paleontology, University of the Basque Country, E-48080 Bilbao, Spain ;Berggren, W. A.; Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA ;Bernaola, G.; Department of Mining and Metallurgic Engineering and Material Sciences, University of the Basque Country, E-48901 Barakaldo, Spain ;Caballero, F.; Department of Stratigraphy and Paleontology, University of the Basque Country, E-48080 Bilbao, Spain ;Clemmensen, A.; Department of Earth Sciences, Århus University, DK-8000 Århus C, Denmark ;Dinarès-Turell, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Dupuis, C.; Laboratoire de Géologie Fondamentale et Appliquée, Faculté Polytechnique de Mons, B-7000 Mons, Belgium ;Heilmann-Clausen, C.; Department of Earth Sciences, Århus University, DK-8000 Århus C, Denmark ;Orús, A. H.; Eguzkialde 13, E-20271 Irura, Gipuzkoa, Spain ;Knox, R.; British Geological Survey, Kingsley Durham Centre, Keyworth, Nottingham NG12 5GG, United Kingdom ;Martín-Rubio, M.; Department of Mining and Metallurgic Engineering and Material Sciences, University of the Basque Country, E-48901 Barakaldo, Spain ;Ortiz, S.; Department of Earth Sciences, Zaragoza University, E-50009 Zaragoza, Spain ;Payros, A.; Department of Stratigraphy and Paleontology, University of the Basque Country, E-48080 Bilbao, Spain ;Petrizzo, M. R.; Department of Earth Sciences, Milano University, 20133 Milano, Italy ;von Salis, K.; Via Maistra 9, CH-7513 Silvaplana, Switzerland ;Sprong, J.; Department of Earth and Environmental Sciences, K.U. Leuven, B-3001 Leuven, Belgium ;Steurbaut, E.; Department of Paleontology, Royal Belgian Institute of Natural Sciences, B-1000 Brussels, Belgium ;Thomsen, E.; Department of Earth Sciences, Århus University, DK-8000 Århus C, Denmark; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; 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.293 30 - PublicationRestrictedThe Global Stratotype Section and Point (GSSP) for the base of the Lutetian Stage at the Gorrondatxe section, Spain(2011-06)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Molina, E.; Departamento de Ciencias de la Tierra, Universidad de Zaragoza, E-50009 Zaragoza, Spain ;Alegret, L.; Departamento de Ciencias de la Tierra, Universidad de Zaragoza, E-50009 Zaragoza, Spain ;Apellaniz, E.; Departamento de Estratigrafía y Paleontología, Universidad del País Vasco, E-48080 Bilbao, Spain ;Bernaola, G.; Departamento de Estratigrafía y Paleontología, Universidad del País Vasco, E-48080 Bilbao, Spain ;Caballero, F.; Departamento de Estratigrafía y Paleontología, Universidad del País Vasco, E-48080 Bilbao, Spain ;Dinarès-Turell, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Hardenbol, J.; Global Sequence, Chronostratigraphy Inc., 826, Plainwood Drive, Houston, Texas 77079-4227, USA ;Heilmann-Clausen, C.; Department of Earth Sciences, Aarhus University, Dk-8000, Aarhus C, Denmark ;Larrasoaña, J. C.; Instituto Geológico y Minero de España, Unidad de Zaragoza, E-50006, Zaragoza, Spain ;Luterbacher, H.; Museo Geológico, Seminario Conciliar, E-08007, Barcelona, Spain ;Monechi, S.; Dipartimento di Scienze della Terra, Università di Firenze, I-50121 Firenze, Italy ;Ortiz, S.; Departamento de Ciencias de la Tierra, Universidad de Zaragoza, E-50009 Zaragoza, Spain and Department of Earth Sciences, University College London, WC1E 6BT, London, UK ;Orue- Etxebarria, X.; Departamento de Estratigrafía y Paleontología, Universidad del País Vasco, E-48080 Bilbao, Spain ;Payros, A.; Departamento de Estratigrafía y Paleontología, Universidad del País Vasco, E-48080 Bilbao, Spain ;Pujalte, V.; Departamento de Estratigrafía y Paleontología, Universidad del País Vasco, E-48080 Bilbao, Spain ;Rodríguez-Tovar, F. J.; Departamento de Estratigrafía y Paleontología, Universidad de Granada, E-18002 Granada, Spain ;Tori, F.; Dipartimento di Scienze della Terra, Università di Firenze, I-50121 Firenze, Italy ;Tosquella, J.; Departamento de Geodinámica y Paleontología, Universidad de Huelva, E-21071 Huelva, Spain ;Uchman, A.; Institute of Geological Sciences, Jagiellonian University, Kraków, Pl-30063, Poland; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; 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 2011.227 32