ALBERT

Description: Anharmonic solid neon entropy calculated from harmonic vibration spectrum and geometric mean frequency

Description: Solid Ne isotopes specific heat at constant pressure and volume, entropy, enthalpy and Gruneisen parameters

Description: Isotope effects in specific heat of solid neon

Description: Westward extentsion by continental of the Alboran Sea platelet in the early Neogene initiated large slump-block movements along the Iberic and Moraccan continental margins. Extensive allochthonous salt may underlye and serve as a lubricant for gravity-driven translation whose overall movement may exceed 400 km. Mobile, Late Cretaceous-Paleogene salt, Deposited in a paleo-basin with a western limit of 10°W to 12°W, appears to have become diapiric. The migrating blocks and associated down-dip debris-flows may be the trapping mechanisim for hydrocarbons. Migrating debris covers and area as great as 90,000 km 2 with potential reserves riveling the Gulf of Mexico sub-salt play. This complex geologic evolution apparently began as the Gibraltar Arc moved westward in the Neogene, and caused an overthrust that formed an accretionary wedge onto the Gulf of Cadiz. The westward Gibraltar Arc migration margins, which initiated farther westward migration of gravity-driven continental and salt-floored blocks. Ultimate emplacement was over oceanic crust. As the continental blocks migrated, normal listric faulting along the present continental shelf of the Gulf of Cadiz developed, thus accomodating upper Miocene (past 19 Ma) tectonics and deposition. Multiple stacking of thrusting wedges occurred at the foot of the rotated continental blocks. Lateral migration can generate compression zones that, in turn, can provide extensive fracturing, faulting, and jointing, suitable for further petroleum storage. This is the first proposed ocean basin hydrocarbon province based on long-distance allochthon/mass-wasting migration.

Description: A detailed, high-resolution stratigraphic analysis of the Mediterranean Outflow contourite system at the continental slope of the Gulf of Cadiz has been carried out through the correlation between a dense network of seismic reflection profiles (sparker, airgun, 3.75 kHz and parametric echosounder — TOPAS), Calypso giant piston and standard gravity cores. From such correlation we determine a stacking pattern constituted by four main seismic units (a–d) that are internally structured into ten subunits. Each subunit shows a single sequence formed by transparent seismic facies at the base to smooth, parallel reflectors of moderate to high amplitude facies at the top, being well correlated in the cores with a coarsening-upward sequence. The latest Pleistocene–Holocene deposits form glacial/interglacial depositional sequences related to cycles with a frequency range below the Milankovitch band that corresponds to millennial timescale climatic changes such as Dansgaard–Oeschger (1.5 ka) and Bond Cycles (10–15 ka). Oxygen isotope records of planktonic foraminifera and the occurrence of ice-rafted debris (IRD) in the most recent contourite subunits show clear evidence of the influence of the North Atlantic climatic conditions, especially the climatic Heinrich events (H) in the slope sedimentation of the Gulf of Cadiz and then in the circulation of the Mediterranean Outflow Water (MOW). The coarser contourite deposits are mostly associated with the Last Glacial Maximum, Younger Dryas and Heinrich events on the central area of the middle slope. During globally cooler conditions, the MOW was denser so that it was more active in deeper areas than today. On the other hand, during warm periods the MOW became less dense favoring an increased intensity of the MOWon the distal area of the upper slope. Therefore, spatial and vertical fluctuations of the MOW contourite system are strongly affected by global climate and oceanographic changes, being clearly influenced by iceberg discharges and probably also, by the resumption of thermohaline circulation in the North Atlantic Ocean during ice melting periods.

Description: Expedition SO175 using FS Sonne aimed for a multidisciplinerary geoscientific approach with an international group of researchers. Methods covered the entire span from geophysical data acquisition (seafloor mapping, echography, seismic reflection), sediment coring at sites of active fluid venting, in situ heat flow measurements across the entire length of the Gibraltar thrust wedge, the deformation front, landslide bodies, and mud volcanoes, and finally the deployment of a long-term pore pressure probe. Video-supported operations helped to identify fluid vent sites, regions with tectonic activity, and other attractive high priority targets. Qualitative and quantitative examinations took place on board and are continued on land with respect to pore pressure variation, geomicrobiology, sediment- and fluid mobilization, geochemical processes, faunal assemblages (e.g. cold water corals), and gas hydrates (flammable methane-ice-crystals). Main focus of the expedition has been a better understanding of interaction between dynamic processes in a seismically active region region with slow plate convergence. In the context of earthquake nucleation and subduction zone processes, the SO175 research programme had a variety of goals, such as: • To test the frictional behaviour of the abyssal plain sediments. • To explore the temperature field of the 1755 thrust earthquake event via heat flow measurements. • To assess the role of fluid venting and gas hydrate processes control slope stability and mud volcanic activity along the Iberian continental margin. • To measure isotope geochemistry of pore waters and carbonates of deep fluids. • To quantify microbial activity in Gibraltar wedge sediments. • To test whether microseismicity in the area corresponds to in situ pore pressure changes. • To find out if enhanced heat flow max be indicative of active subduction. Initial tentative results during the cruise suggest that there is a component of active thrusting at the base of the wedge, as attested by heat flow data. Based on mostly geochemical evidence, mud volcanism was found less active than previously assumed. Highlights from post-cruise research include the successful deployment of the long-term station and high frictional resistance of all incoming sediment on the three abyssal plains.

Description: The Alpine orogeny is well recorded onshore and offshore by tectonic inversion of the Mesozoic rift basins. Large scale linear seamounts (more than 250 km long and with up to 5 km of uplift) involving oceanic and continental lithosphere were carried on top of thrusts, such as the Gorringe seamount and the Estremadura Spur in the SouthWest and West Iberia Margin, respectively. The SouthWest Iberia Margin also recorded the westward migration of the Gibraltar Oceanic slab as the westwards propagation of the Neo-Tethys subduction. Rotation of the tectonic compression from NW-SE to WNW-ESE inPliocene times caused the development of large scale dextral wrench faults as the present day Africa-Iberia plate boundary. Neotectonics of this plate boundary caused large to mega-scale destructive earthquakes and tsunamis.

Description: A joint study and mapping of the morphological features and architecture of the Galicia margin based on high-resolution multibeam bathymetry data and multichannel seismic profiles, provides new insights of the margin morphostructure. Tectonic processes are the major control of the margin's morphology, where the imprint of the North Atlantic rifting and opening and later subduction of the Bay of Biscay and compressional events are still well preserved. The West Galicia margin, which is up to 350 km wide, is composed from east to the west of inner, transitional and outer sectors. The inner sector shows a graded upper slope strongly dissected by a system of submarine canyons and valleys that flow into the 170 km long and 40–60 km wide NW-SE Valle Inclán Valley. The transitional sector, which is up to 75 km wide, displays a smooth relief dominated by landslides and giant craters. Finally, the outer sector is characterised by several banks, N-S sub-parallel ridges and elongated valleys that project seaward over 200 km (i.e., Galicia Bank, Half-Graben, Deep Galicia margin and Peridotite Ridge domains). The North Galicia margin is characterised by a system of terraces up to 30 km wide, that form a stepped slope followed by an abrupt lower slope affected by large-scale rotational failures. The Galicia margin constitutes an exceptional area within the Atlantic margins for identifying different morphostructure styles that characterised the main stages of the margin's evolution along the Wilson cycle. The Galicia margin hosts the transition between two end-members of continental margin styles: a western hyperextended rifted margin (being the conjugate with the Newfoundland margin during the Late Jurassic) and a northern convergent margin (now fossilised) associated with the partial subduction of the southern sector of the Bay of Biscay underneath the North Iberian margin, which occurred in Paleocene-Eocene times. Thus, the morphostructure of the West Galicia margin still reflects the detached fault systems and tilted blocks that resulted from the Mesozoic North Atlantic rifting. Furthermore, the Coruña and Jean Charcot seamounts, which are adjacent to the Galicia margin, correspond to spreading ridges formed by the simultaneous opening of North Atlantic Ocean and the Bay of Biscay in the Upper Cretaceous. The rest of the terraced morphology of the North Galicia margin is derived from extensional faults caused by an overriding of the Iberian plate in relation to the subduction of the Bay of Biscay oceanic crust during Cenozoic times. Since the late Neogene, compressional tectonics resulting from the reorganisation of the Eurasia/Iberia and Africa plates is also reflected on the present-day morphology as the following: (i) an elevation of the Biscay Abyssal Plain up to 150 m over the Iberia Abyssal Plain; (ii) deep-seated landslides associated with an uplift of the Galicia Bank; and (iii) an orientation of submarine canyons along NW-SE strike slip faults.