XXIII JORNADAS DE LA SOCIEDAD ESPAÑOLA DE PALEONTOLOGÍA Caravaca de la Cruz 3-6 de Octubre de 2007 LIBRO DE RESÚMENES XXIII JORNADAS DE LA SOCIEDAD ESPAÑOLA DE PALEONTOLOGÍA Caravaca de la Cruz 3-6 de Octubre de 2007 LIBRO DE RESÚMENES Editores: Juan C. Braga Antonio Checa Miguel Company Instituto Geológico y Minero de España y Universidad de Granada 2007 XXIII Jornadas de la Sociedad Española de Paleontología (Caravaca de la Cruz, 3-6 de Octubre de 2007). Libro de Resúmenes Editores: Juan C. Braga, Antonio Checa y Miguel Company Edita: Instituto Geológico y Minero de España y Universidad de Granada Imprime: Copicentro Granada S.L., Granada I.S.B.N.: 84-96856-20-8 Depósito legal: GR-2081/2007 Ejemplo de cita: Andrade Olalla, A. y Calonge García, A. Aprendizaje combinado como propuesta en la Convergencia Europea para la enseñanza de la Paleontología. In: XXIII Jornadas de la Sociedad Española de Paleontología (Caravaca de la Cruz, 3-6 de Octubre de 2007). Libro de resúmenes (Eds.: J.C. Braga, A. Checa y M. Company). Instituto Geológico y Minero de España y Universidad de Granada, 13-14. XXIII Jornadas de la Sociedad Española de Paleontología (Caravaca de la Cruz, 3-6 de Octubre de 2007) ORGANIZAN: • Sociedad Española de Paleontología • Universidad de Granada PATROCINA: • Excelentísimo Ayuntamiento de Caravaca de la Cruz COLABORAN: • Consejería de Educación y Cultura de la Región de Murcia • Instituto Geológico y Minero de España • Programa Internacional de Geociencias. IGCP-Unesco • Asociación Cultural Paleontológica Murciana • Centro de Profesores y Recursos de Cehegín • IES San Juan de la Cruz de Caravaca • CajaGranada XXIII Jornadas de la Sociedad Española de Paleontología. Libro de Resúmenes Conferencias invitadas 1 XXIII Jornadas de la Sociedad Española de Paleontología. Libro de Resúmenes 2 XXIII Jornadas de la Sociedad Española de Paleontología. Libro de Resúmenes Major environmental change events during the Mesozoic and the recycling of carbon through Earth history Hesselbo, S.P. Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR The record of Mesozoic geological history is characterized by several major environmental change events. These are commonly characterized by biotic mass extinction and ocean anoxia, and they coincide with voluminous flood basalt volcanism. Much of the world’s current hydrocarbon reserves are sourced from sediment laid down during these events, and an understanding of the mechanisms linking biotic change, carbon-cycle processes, and palaeoclimate, provides a crucial context for present-day forcing of environmental change by fossil-fuel burning. The most significant environmental change events in the Mesozoic were at the Permian–Triassic and Triassic–Jurassic boundaries, in the Early Toarcian, in the Early Aptian, and at the Cenomanian–Turonian boundary. In almost all cases the events are associated with both negative and positive carbon-isotope anomalies, signifying major perturbations to the carbon cycle. The Early Toarcian (Early Jurassic) Oceanic Anoxic Event (OAE) has a particularly good record in NW Europe. Here, Early Toarcian strata are commonly laminated and/or rich in marine organic matter. Extinction affected the benthic and necktobenthic fauna, suggesting that water column and sea-floor anoxia was a principal cause of the local extinction patterns. However, there are rather few data for this event from other regions, and recently several workers have challenged the notion that the Early Toarcian was globally significant, and have instead postulated that the environmental deterioration was diachronous over timescales of several million years. If this were true, global processes resulting from flood basalt volcanism could not easily provide an explanatory framework. Of the Early Toarcian sections in NW Europe, that at Peniche, in the Lusitanian Basin of Portugal, is particularly informative. This relatively expanded section serves as a candidate GSSP for the base of the Toarcian stage. The sediments were deposited on a distal carbonate ramp, but closely adjacent to the footwall of a major basement uplift, the Berlengas–Farilhões Platform, which lay ~10-15 km to the west. The basement platform supplied coarse siliclclatic sediment and organic detritus of local terrestrial origin. Thus the strata at Peniche contain a mixture of materials from marine and non-marine sources. Carbon-isotope analysis (Hesselbo et al., 2007) of the carbonate at a very high resolution, and of woody organic matter, show that these two materials show almost identical patterns of isotopic evolution, even though one is sourced from calcareous plankton in the surface waters of the basin, and the other is from carbon taken directly from the Early Jurassic atmosphere. Localized atmospheric carbon-isotope anomalies are conceivable, if one postulates an intense persistent local source of isotopically very light carbon, but close parallelism between surface marine and terrestrial isotope curves through the whole section would be extremely unlikely in these circumstances. The reality of the atmospheric signal cannot be doubted and that implies that the isotope anomalies, and associated phenomena, are of global significance. The large carbon-isotope anomalies have particular value for stratigraphic correlation. As a result, data on environmental change in the Portugese section can be compared precisely with data from anoxic organic-rich shale of the Jet Rock, exposed on the coast of Yorkshire, UK, where other isotopic proxies indicate high surface-water temperatures (oxygen isotopes) and extreme rates of continental weathering (osmium 3 XXIII Jornadas de la Sociedad Española de Paleontología. Libro de Resúmenes isotopes). Such observations indicate that increased deep-water gravity flow sedimentation during the OAE in sections such as Peniche, were caused by sediment supply increase rather than localized sea-level fall. It is also possible to establish correlations into sections that are rather poorly constrained by biostratigraphic data, such as paralic facies. For example, the negative carbon-isotope excursion of the levisoni Zone can also be recognized in particulate woody organic matter in marginal-marine sections of Bornholm, eastern Denmark. The sediments also contain well-preserved fossil leaves that provide evidence of high atmospheric carbon-dioxide content co-incident with the excursion. In principle, it should be possible to distinguish the isotopic signature in non-marine facies in other parts of the world, although this has not yet been achieved for the Toarcian. A clear temporal link to flood basalt volcanism is established for the Toarcian OAE (i.e. with the Karoo-Ferrar large igneous province), and for other similar events. It has been suggested that greenhouse gas from volcanoes induced a warming of the atmosphere and ocean waters, which led to dissociation of oceanic gas hydrates, and release of isotopically light methane into the atmosphere. Further extreme environmental change is inferred in a positive feedback loop that was eventually brought to an end by increased organic carbon burial. However, other authors have argued that the size of the gas hydrate reservoir would have been insufficient to drive environmental change on the scale observed whilst at the same time matching the amplitude of the carbon-isotope excursion. An alternative recently suggested mechanism that links magmatic baking of organic-rich sediments in the intrusive complexes underlying flood basalt provinces possibly provides a more parsimonious explanation for these events. Such a mechanism is closely analogous in scale, and perhaps also in tempo, to our present-day liberation of carbon from fossil fuels. References Hesselbo, S.P., Jenkyns, H.C., Duarte, L.V. & Oliveira, L.C.V. 2007. Carbon-isotope record of the Early Jurassic (Toarcian) Oceanic Anoxic Event from fossil wood and marine carbonate (Lusitanian Basin, Portugal). Earth and Planetary Science Letters, 253, 455-470, doi: 10.1016/j.epsl.2006.11.009. 4 XXIII Jornadas de la Sociedad Española de Paleontología. Libro de Resúmenes Plancton calcáreo, biomarcadores y la naturaleza de la extinción masiva finicretácica Lamolda, M. A. Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Universidad de Granada, Campus de Fuentenueva, 18002 Granada; [email protected] La extinción del final del Período Cretácico es uno de los eventos que suscita mayor interés tanto en la comunidad académica como a nivel popular. Sin duda es el evento sobre el que hay un mayor número de trabajos durante los últimos 25 años y no por ello su interés ha disminuido. Sus registros estratigráfico y paleontológico han desvelado muchas evidencias sobre la importancia de la extinción a nivel global, aunque no con iguales consecuencias biogeográficas ni taxonómicas. El tema que más controversia ha generado ha sido el de su modo de desarrollo, es decir: ¿fue una extinción catastrófica ó por el contrario lo fue gradual? Otro tema controvertido es si esa extinción masiva estuvo ligada a una sola causa, p. ej.: el impacto con la Tierra de un cuerpo extraterrestre, o bien fue el efecto de diversas causas concurrentes no necesariamente cohetáneas. Los organismos planctónicos con endoesqueleto calcáreo: foraminíferos y nanoflora eran unos grupos diversificados según nos muestra su registro en el Maastrichtiense superior, evidencia de un ecosistema estable y complejo. Tras la extinción quedaron reducidos a unos pocos componentes oportunistas, con registros de abundancia absoluta