https://hdl.handle.net/10481/22930 Sat, 18 Apr 2026 23:38:30 GMT 2026-04-18T23:38:30Z https://hdl.handle.net/10481/93531 Episodic postglacial deltaic pulses in the Gulf of Cadiz: implications for the development of a transgressive shelf and driving environmental conditions Carrión-Torrente, Álvaro; Lobo Sánchez, Francisco José; Puga Bernabeu, Ángel; Mendes, Isabel; Lebreiro, Susana; García, Marga; Van Rooij, David; Luján, María; Reguera, María Isabel; Antón, Laura The postglacial sea-level rise after the Last Glacial Maximum provided ideal conditions to study the transgressive sedimentary response to sudden shelf flooding driven by different rates of sea-level rise. In this study, a high-resolution seismic stratigraphic interpretation and sedimentological analysis were conducted on data from the northern Gulf of Cadiz continental shelf (SW Iberian Peninsula), in order to: 1) understand the succession of sedimentary processes during each shelf flooding episode and 2) explore the significance of variable rates of sea-level rise, sediment fluxes, and climatic conditions on the development of postglacial deposits. Four backstepping seismic postglacial transgressive units (PTUs; 4 to 1 from oldest to youngest) that are linked to the retreating mouth of the Guadiana River were interpreted. Together, these seismic units display a wedge-shape geometry, are located over the inner to middle shelf, and overlie a regional unconformity formed during the Last Glacial Maximum. Each PTU can be divided into several sub-units with distinctive seismic facies that have a similar stratigraphic organization. Each PTU contains lower sub-units that are composed of low-angle tangential-oblique clinoforms. The clinoforms are locally topped by a channelized sub-unit. The distal and/or lateral parts of the clinoforms are occasionally buried by sheet-like semitransparent subunits. The uppermost sub-units are present over the proximal and central parts of each seismic unit and are also sheet-like. PTUs can also be subdivided and described sedimentologically. Fine-grained sands with intercalated silty layers dominate the lower part of each PTU (lower clinoform sub-units). The upper part of each PTU (upper sheet-like sub-units) is characterized by reworked facies, composed of highly fragmented bioclasts within a mixture of silt and coarse to medium sand. Finally, mud deposits occur as a sediment drape over the PTUs. The internal structure of each PTU reveals several phases of development under a general process of transgressive submergence in which both coastal and marine deposits were formed and eventually preserved. The initial phase involved the development of coarse-grained deltas in shallow water, which were locally eroded by a network of distributary channels. In a transitional phase, the infilling of distributary channels and the offshore export of fine-grained sediments is related to a change in sediment sources, possibly triggered by enhanced hydrodynamic processes. The final phase involved the reworking of fluvio-deltaic sediments by shoreface processes to generate a sediment sheet. Age correlation with a suite of postglacial sea-level curves indicates that the formation of the postglacial transgressive deposits is bracketed between 14 ka and 9 ka. The studied deposits are related to a period of reduced sea-level rise, culminating in the Younger Dryas event (two oldest PTUs), and to phases of enhanced sea-level rise, such as Meltwater Pulse (MWP) 1B (two youngest PTUs). In spite of high rates of sea-level rise over MWP-1B, each PTU exhibits progradation and preservation of much of the delta. The preservation of progradational deltaic units is likely caused by increased sediment supply during progradational pulses. We suggest that those pulses of enhanced sediment fluxes during MWP-1B were strongly driven by the overall climatic conditions in the southwest of the Iberian Peninsula, probably resulting from enhanced rainfall runoff during humid periods and scarce land vegetation cover. Versión final del artículo en la web de la editorial https://hdl.handle.net/10481/93531 https://hdl.handle.net/10481/93415 Sedimentary dynamics and topographic controls on the tidal-dominated Zagra Strait, Early Tortonian, Betic Cordillera, Spain Puga Bernabeu, Ángel; Braga Alarcón, Juan Carlos; Aguirre Rodríguez, Julio; Martín Martín, José Manuel The approximately 350 m-thick stratigraphic succession of the Zagra Strait records an important oceanographic phase of basin interconnection between the Atlantic Ocean (Guadalquivir Basin) and the Mediterranean Sea through the Betic Cordillera (southern Spain) during the early Tortonian. The Zagra Strait developed as a narrow structurally controlled marine corridor. The sedimentary dynamics of the Zagra Strait were interpreted from the sedimentological features observed in six sections at well-exposed outcrops. Large-scale (>10 m high) compound dunes and compound–dune complexes moved parallel to the strait margins under strong tidal currents generated by tidal amplification at the strait entrance and exit. Dune distribution can be divided into three sectors with different palaeocurrent migration, lithological and topographical characteristics. The northern and central sectors were separated by a deep depression (>75 m water depth) where tidal currents were weaker and dunes were not generated. The southern sector records a relative decrease in current strength compared with the northern and central sectors, and a significant increase in the bioclastic content in the sediment. Terrigenous content generally increases towards the strait margins, and reciprocally, carbonates towards its axis. The closure of the Zagra Strait resulted from tectonic uplift of that part of the Betic Cordillera before the late Tortonian. https://hdl.handle.net/10481/93415 https://hdl.handle.net/10481/73453 Submarine landslide morphometrics and slope failure dynamics along a mixed carbonate-siliciclastic margin, north-eastern Australia Puga Bernabeu, Ángel Comparatively little work has been carried out on the morphology and distribution of submarine landslides onmixed carbonate-siliciclastic margins. The morphometric analysis of 84 open slope submarine landslides on the Great Barrier Reef (GBR) margin of north-eastern Australia provides useful insights into slope failure dynamics and frequency distribution of landslides on mixed margins. Our analysis has revealed that the slope area affected by failures (12.6% of the margin) is similar to siliciclastic-dominated passive margins, although the total volume of remobilized sediment (73 km3) is comparatively small. Landslide scars lie at shallower depths to the south of the margin (mean of 576 m vs 1517 m to the north) and there is good correlation between the depth at origin and depth at termination for the GBR landslides. The cumulative frequency distribution of volume, area and total length of the GBR landslides does not fit to common distributions (e.g., power law, logarithmic or exponential) for the entire dataset. Still, the cumulative frequency distribution of landslide dimensions can be statistically explained either by a power law similar to other passive margins, or by a lognormal distribution similar to some siliciclastic margins. Morphometric characteristics, such as the volume of sediment released per unit width and the probability function of volume distribution suggest that slope failures mainly involved relatively unconsolidated sediments. We find that the disintegration by debris flows was the dominant process along the entire GBR margin and that their spreading efficiency and mobility was relatively low. Margin stratigraphy, fluid overpressure at the base of the slope, and detachment surfaces at the boundary between different lithologies that separate sedimentary cycles may have preconditioned the slope to fail. This compilation provides a robust morphometric framework that allows comparison with existing and future slope failure databases, and lays the foundation for performing numerical simulations to assess the landslide-generated tsunamigenic hazards along the GBR margin. https://hdl.handle.net/10481/73453 https://hdl.handle.net/10481/49851 Holocene geochemical footprint from Semiarid alpine wetlands in southern Spain García-Alix Daroca, Antonio; Jiménez-Espejo, Francisco José; Jiménez Moreno, Gonzalo; Toney, Jaime, L; Ramos-Román, María J.; Camuera, Jon; Delgado Huertas, Antonio; Martínez Ruiz, Francisca; Queralt, Ignasi Here we provide the geochemical dataset that our research group has collected after 10 years of investigation in the Sierra Nevada National Park in southern Spain. These data come from Holocene sedimentary records from four alpine sites (ranging from ∼2500 to ∼3000 masl): two peatlands and two shallow lakes. Different kinds of organic and inorganic analyses have been conducted. The organic matter in the bulk sediment was characterised using elemental measurements and isotope-ratio mass spectrometry (EA-IRMS). Leaf waxes in the sediment were investigated by means of chromatography with flame-ionization detection and mass spectrometry (GC-FID, GC-MS). Major, minor and trace elements of the sediments were analysed with atomic absorption (AAS), inductively coupled plasma mass spectrometry (ICP-MS), as well as X-ray scanning fluorescence. These data can be reused by environmental researchers and soil and land managers of the Sierra Nevada National Park and similar regions to identify the effect of natural climate change, overprinted by human impact, as well as to project new management policies in similar protected areas. https://hdl.handle.net/10481/49851 https://hdl.handle.net/10481/23043 Sedimentación cíclica lagunar y bioconstrucciones asociadas en el Trías Superior Alpujarride Braga Alarcón, Juan Carlos; Martín Martín, José Manuel Este tipo de sedimentación cíclica lagunar, de edad Trías superior, aparece bien representada en la zona de los Alayos de Dílar (borde occidental de Sierra Nevada), en materiales dolomíticos pertenecientes a la Unidad Trevenque, siendo uno de los cortes más notorios el del Picacho Alto, donde el conjunto supera los 500 m. de potencia (fig. 1). Todo él corresponde a una sucesión cíclica cuyo patrón general, de muro a techo, es el siguiente: 1) biomicrita («floatstone») de Dasycladáceas; 2) «bafflestone» de Solenoporáceas; 3) «boundstone» de serpúlidos —Tubyphites— algas encostrantes tipo Spongiostromata-cementos, y 4) facies de brechas (fig. 2). La potencia de los ciclos varía de 1 a 10 m. Las facies de Dasycladáceas suelen tener de 0,5 a 2 m.; la de Solenoporáceas de O a 1 m. (no siempre está representada) (lám. Ia y lám. IIb); los «boundstones» (bioconstrucción s.str.) de 0,5 a 5 m. y las brechas de O a 3 m. Las biomicritas de Dasycladáceas incorporan frecuentemente pequeños bivalvos y gasterópodos. En los «baffles» de Solenoporáceas de los ciclos más basales aparecen a veces, aunque muy raramente, corales y esponjas (lám. IIc y d). Los «boundstones» corresponden generalmente a asociaciones de serpúlidos y Tubiphytes que desarrollan formas arborescentes intrincadas (lám. Ib y lám. IIa). En las brechas, a los clastos de la bioconstrucción se les añaden en ocasiones elementos de las otras facies, todos ellos trabados entre sí por micrita. En la parte alta de las brechas dicha matriz micrítica puede incluir abundantes Dasycladáceas. El conjunto sedimentario se interpreta como depósitos de «lagoon» en sentido amplio. La sucesión Dasycladáceas-Solenoporáceas-bioconstrucción refleja un progresivo hundimiento del fondo de éste. Las facies de brechas situadas al techo de los ciclos marcan un cambio brusco en las condiciones de sedimentación y corresponden a una fase de destrucción ligada probablemente a emersión. La sedimentación cíclica puede estar condicionada por variaciones de tipo eustático relacionadas presumiblemente con el depósito contemporáneo de las evaporitas de facies Keuper en el Trías germánico. Las bioconstrucciones aquí desarrolladas son muy similares a las que aparecen en otros cortes de la Unidad Trevenque (corte de los Cahorros de Monachil), si bien lo hacen en contextos paleogeográficos algo diferentes (lagoon en el caso de los Alayos frente a plataforma externa en el caso del corte de los Cahorros). La revisión detallada de la flora que aparece en estos últimos cortes (Cahorros y Picacho Alto) y otros cercanos (Pico de la Carne, Picos de la Dehesilla), nos lleva a proponer una edad para dichas construcciones similar (Noriense).; This type of Upper Triassic cyclic lagoonal sedimentation appears well represented in the «Picacho Alto» section in the «Alayos de Dilar» area (northwestern Sierra Nevada), within dolomitic materials belonging to the Trevenque Unit (Alpujarride Complex, Betic Cordillera) (fig. 1). The whole section is more than 500 m. thick and corresponds to a repetitive cyclic succession in which the general sequence, for one cycle in particular, consists of, in ascending order (fig. 2): 1) Dasycladacean floatstones; 2) Solenoporacean bafflestones (Pl. Ia & IIb); 3) serpulid —Tubiphytes— Spongiostromata algae-cement boundstones; 4) breccias. The thickness of the Dasycladacean facies ranges from 0,5 to 2 m.; that of the Solenoporacean facies from 0 to 1 m. (not always is represented); that of the boundstones (bioconstructions s. str.) from 0.5 to 5 m. and that of the breccias from 0 to 3 m. The total thickness of the sequence changes between 1-10 m. Small bivalves and gastropods are often incorporated in the Dasycladacean biomicrites. Solitary corals and sponges (Pl. IIc & d) very rarely occur within the Solenoporacean facies of the lowermost cycles. Serpulid and Tubíphytes associations develop intrincated branching growths (Pl. Ib & IIa) that form the bulk of the boundstones. The clasts of the breccias are mainly from the boundstones although, in places, fragments of the other facies appear sporadically as well, all embedded in micrite. This micrite may contain some dasyclad remains in its uppermost part. The whole sequence is considered as «lagoonal» in a very broad sense, the Dasycladacean-Solenoporacean-serpulid/alga/cement bioconstruction succesion reflecting a progressive deepening of the bottom of the «lagoon». The breccias at the top of the cycles correspond to a destruction phase, and reveal a brusque change in sedimentation conditions that probably resulted in emersion. The cyclic sedimentation seems to be related with sea level eustatic oscillations presumably linked to the contemporaneus deposition of the Keuper evaporites in adjacent areas. The bioconstructions here studied are very similar to those outcropping in other Trevenque Unit sections (e. g., Cahorros de Monachil), although they settled down in a very different paleogeographical context («lagoon» in the studied section against outer platfrom/platform edge in the Cahorros). From a detailed revision of the flora appearing in both sections (Cahorros-Picacho Alto) and others placed nearby (Pico de la Carne, Picos de la Dehesilla), the same age (Norian) is proposed for ah the above-mentioned bioconstructions. https://hdl.handle.net/10481/23043