Eastern Ebro Basin Research Articles

Characterization of the marine‐air intrusion Marinada in the eastern Ebro sub‐basin

AbstractThe eastern Ebro basin is composed of an extensive irrigated plain, surrounded by rainfed slopes and wooden mountain ranges and open to the west to the agricultural western Ebro basin. The sea breeze generated at the coast is able to surmount the Catalan prelitoral range through its lowest heights, reaching the basin by its easternmost part. It is a well‐known feature in the region, called Marinada. A network of Automatic Weather Stations is used here to analyse a period of 19 years (2003–2021). A filtering procedure is developed which selects the events when the Marinada is present, based on detecting clear sky, weak wind conditions and the wind direction from the coast in the afternoon. The analysis of these days show that the Marinada propagates along the basin in the afternoon meanwhile observations of the specific humidity show a sudden increase as the temperature cools down, resulting on a cold and humid advection. It is also found that the timing of the arrival of the Marinada depends on the mesoscale/synoptical circulations already present in the region (westerlies or a thermal low).

A remarkable new paleotheriid (Mammalia) in the endemic Iberian Eocene perissodactyl fauna

ABSTRACT Equoid perissodactyls were diverse in the Eocene of the Iberian Peninsula, and those from the central and western Iberian basins (Mondego, Oviedo, Almazán, Duero, and Miranda-Treviño) and the eastern Ebro Basin (Ulldemolins area) were endemic, with the presence of six genera and 19 species (mainly Palaeotheriidae sensu stricto) that are unknown in the rest of western Europe. In this paper, a new endemic Eocene paleotheriid genus, Idiodontherium, gen. nov., is reported. The new genus includes two species: I. martindejesusi, from the upper middle Eocene (Bartonian) of Mazaterón (Almazán Basin, Soria, Spain) and I. astibiai, from the upper Eocene (Priabonian) site of Zambrana (Miranda-Treviño Basin, Álava/Araba, Spain). Idiodontherium exhibits an unusual dental pattern, which is characterized by an extreme shortening of the jugal series due to a great reduction of the premolar series, in combination with a long post-canine diastema. It is a small to medium-sized plagiolophine with thick enamel in comparison with other plagiolophine equoids of the same size. These new taxa exhibit peculiar dental features that could be associated with greater specialization of the diet.

The turtles from the upper Eocene, Osona County (Ebro Basin, Catalonia, Spain): new material and its faunistic and environmental context

Abstract. Eochelone voltregana n. sp. is a new marine cryptodiran cheloniid found at the Priabonian levels (latest Eocene) of the Vespella marls member of the Vic–Manlleu marls formation. It is the second cheloniid from Santa Cecília de Voltregà (Osona County, Spain), the first one being Osonachelus decorata from the same formation. Shell parameters indicate that the new species belongs to a branch of sea turtles including the Eocene Anglo–Franco–Belgian forms Argillochelys, Puppigerus and Eochelone (the shell of the latter was studied here for the first time) as well as Glarichelys from the Oligocene of Switzerland, all of them predating the worldwide living Miocene genera. The description of two other more littoral–continental Eocene species is given: Trionyx sp., from an older layer of the same formation; and the podocnemidid erymnochelyine, Cordichelys from a more basal layer of a middle Eocene (Lutetian) formation. The last one is identified as the only evidence of the Shweboemys subgroup in the European record, being distinct from the other known Osona County pleurodire Eocenochelus farresi, which is a member of the Erymnochelys group (same subfamily), from the younger Priabonian Sant Martí Xic layer. Thus, an update on the marine turtle fauna of the eastern Ebro Basin that variably opened in the east during Eocene times is provided. The turtles of Osona County belong to two suborders and five genera with three new species and extend the known distribution of their families (LSID urn:lsid:zoobank.org:act:48CE8676-7B82-4EF2-8165-27BEE90129F2).

Taphonomy and palaeoecology of the Oligocene flora from Cervera (Catalonia, Spain) and their implication in palaeoclimatic reconstruction

The Oligocene flora from Cervera (Eastern Ebro Basin, Catalonia) represents one of the most significant Paleogene palaeobotanical records of the Iberian Peninsula. This flora is studied here from the point of view of taphonomy and palaeoecology. Five plant-bearing beds have been found in the lacustrine facies of the Civit Member (Montmaneu Formation) and Talavera Formation. They contain three different taphonomic and palaeoecological assemblages: (1) an assemblage dominated by small leaves of Rhamnus and leaflets of Rhus and Mimosites, interpreted as wind transported, size-biased remains from open xerophytic woodlands located, away from the lake margins; (2) an assemblage composed of well-preserved whole leaves belonging to the Salicaceae, some species of the Myricaceae and helophytic stem portions without evidence of any selection or traction transport. These were probably supplied to the lake directly from the lakeshores by gravitational fall and would represent elements of a riparian forest; and (3) an assemblage formed by a few leaves belonging to the Lauraceae and some species of the Myricaceae that generally show marked tearing along the veins. These remains reached the lake through transport in river inlets and are assigned to a laurel forest possibly growing beyond the riparian community. This lauracean community would have grown in the lowlands of the Ebro foreland basin rather than at some altitude as suggested by previous authors. The ensemble of remains underwent flotation before being sedimented in the anoxic bottom of the lake centre.The taphonomic biases found in the Cervera leaf assemblages should be taken into account in future palaeoclimatic analyses based on leaf morphology. Specifically, the size-bias of leaves in assemblage 1, which is attributed to wind transport, could provide an exaggerated aridity signal if not corrected appropriately. Also the sampling bias of some previous collections from the same localities has resulted in an over-representation of large well-preserved leaves, mainly belonging to Lauraceae species, which lead to an inflated thermal indication if these were taken into account without determining their taphonomic constraints. This study highlights the need to perform taphonomic studies and define the taphofacies represented in a leaf assemblage before undertaking any palaeoclimatic analysis based on leaf physiognomy, such as CLAMP.

Taxonomy and palaeobiogeography of charophytes from the Upper Eocene-Lower Oligocene of the Eastern Ebro Basin (Catalonia, NE Spain)

ABSTRACT Eighteen charophyte species are documented from the Upper Eocene-Lower Oligocene transitional and terrestrial facies on the eastern Ebro Basin. The charophyte assemblage is composed of one Eurasian species, Lychnothamnus stockmansii (Grambast, 1957), fourteen species distributed throughout Europe (Harrisichara vasiformis form vasiformis-tuberculata Feist-Castel, 1977, Harrisichara lineata Grambast, 1957, Harrisichara tuberculata (Lyell, 1826), Nitellopsis (Tectochara) merianii (Al. Braun ex Unger, 1852), Lychnothamnus vectensis (Groves, 1926), L. grambastii (Feist-Castel, 1971), L. major (Grambast & Paul, 1965), Gyrogona caelata (Reid & Groves, 1921), Psilochara aff. acuta Grambast & Paul, 1965, Chara aff. antennata Grambast, 1958, C. rhenana Schwarz & Griessemer, 1994, C. microcera Grambast & Paul, 1965, Sphaerochara labellata Feist & Ringeade, 1977, Lamprothamnium sp.) and three species restricted to the Ebro Basin during the interval considered (Nodosochara jorbae Choi, 1989, Lychnothamnus lon...

Loess and soils in the eastern Ebro Basin

Wind-blown sandy and silty deposits were formed during the late Quaternary in the NE Iberian Peninsula. They are the most significant in the West Mediterranean region, together with those described in the Tagus River basin (Iberian South Subplateau), forming small scattered patches across parts of the SE Ebro Depression and SW Catalan Mediterranean Range. Two major depositional environments are distinguished. The first (largest) outcrop covers the lower Ebro reaches on the SE border of the Ebro Depression, the Prelitoral Coastal Range and the Móra d'Ebre Basin. A second outcrop, to the north, consists of a few patches scattered over a wide amphitheatre surrounding the western tributaries of the Segre River, from the wind-exposed Segrià platforms to the Almenara Range in its northernmost part. They consist of highly sorted fine sands and silts, 1–12 m thick (though most typically 3–4 m thick), and coarser than typical loess. They are highly uniform, lack any sedimentary structures and are pale ochre. The deposits are calcareous (30–45% CaCO3), basic to alkaline and with some soluble salts.Five selected sequences of primary loess (namely Mas de l'Alerany, Tivissa, Guiamets, Batea and Almenara) were studied to ascertain deposit characteristics and soil development. All sections show a consistent vertical granulometric variability that may be attributed to wind intensity changes, and hinders the recognition of spatial particle size distribution. Pedogenesis is mostly related to calcium carbonate redistribution, which accumulates as nodules, large rhizocretions or biogenic calcite. Secondary gypsum (Batea and Almenara sequences) is probably related to primary gypsum blown from the source areas that was redistributed by leaching and precipitation at the bottom of the profiles. In a few places (Mas de l'Alerany outcrop) a fersialitic, rubefacted-recalcified soil indicates the presence of an older generation of loess. While the dominant WNW winds and particle coarseness suggest that the loess originates from nearby alluvial fans and fluvial plains, the presence of gypsum and Mg anomalies may be evidence of more distant sources of the Central Ebro Depression and Ondara-Corb alluvial fans.Optical Stimulated Luminiscence (OSL) ages for the more recent deposits (Guiamets, Batea, Almenara) are between 18 and 34 ka, while the old Mas de l'Alerany sequence is more than 115 ka. These ages indicate loess deposition during the last cold phases of the Quaternary and with pedogenesis occuring during warm interglacial periods.

An exceptional cheloniid turtle, Osonachelus decorata nov. gen., nov. sp., from the Eocene (Bartonian) of Catalonia (Spain)

Osonachelus decorata nov. gen., nov. sp., is the first named chelonioid turtle from the Iberian Peninsula. This Eocene turtle was found in the marine sediments of the Vespella Marls Member (Vic-Manlleu Marls Formation, upper Bartonian) that occur in the Osona county (eastern Ebro Basin, Province of Barcelona, Catalonia, Spain). The area is rich in invertebrate, fish, and plant fossils but various vertebrates, including several chelonian taxa, have remained unpublished. This paper is the first dedicated to the fossil turtles of this area. Osonachelus nov. gen. is a large turtle with an impressive, massive skull revealing a specialized diet, a large and well-fenestrated shell (well ornamented dorsally and much lightened ventrally), and large paddles for high-sea locomotion. It is phylogenetically located among relatively advanced cheloniids, just basal to modern forms. Although apparent similarities in shell morphology exist with Allopleuron from the Maastrichtian of Holland, Osonachelus nov. gen. is distinct due to its masticatory apparatus, less usual among cheloniids and seemingly closer to that of the Lutetian Eochelone from Belgium. Based on the deeply concave and smooth lower jaw symphysis, its diet probably consisted of soft animals or plants rather than hard-food items. Therefore, it occupied a specialized ecological niche that is unique for the Eocene of the Iberian Peninsula.

Calibration of Eocene-Oligocene charophyte biozones in the Eastern Ebro Basin (Catalonia, Spain)

A charophyte biozonation for the transitional and continental Upper Eocene-Lower Oligocene record in the eastern margin of the Ebro Basin is performed and calibrated using magnetostratigraphic data. This study has been based on intensive sampling collected along five composite sections. The Harrisichara vasiformis-tuberculata European biozone has been renamed to H. lineata biozone, since the former index-species was a poorly characterised morphotype with a non-valid species name. This biozone is represented in the transitional Sant Boi Formation and the lowermost part of the Artés Formation in the northeastern sector of the basin, within the normal part of chron C16. The Harrisichara tuberculata European superzone encompasses most of the continental Artés Formation in the northeastern sector and the Margalef Formation in the southeastern sector of the basin ranging from chron C16n.2n (~35.5 Ma) to chron C12r (~31.5 Ma). Included within the Harrisichara tuberculata superzone, the Lychnothamnus vectensis European biozone was redefined as the interval between the first occurrence of Lychnothamnus vectensis and the first occurrence of Lychnothamnus pinguis. Redefinition of the Lychnothamnus vectensis biozone implies that its basal limit does not coincide with the basal limit of the Harrisichara tuberculata superzone, as previously believed. The absence of L. pinguis in the Ebro Basin, and probably in all Southern Europe, results in a local Lychnothamnus vectensis biozone for that area including the total distribution range of this index species. Magnetostratigraphic correlation suggests that this biozone ranges in the Ebro Basin from chron C13r (~34.5 Ma) to chron C13n (~33.5 Ma) including the Eocene-Oligocene boundary. Anew local Harrisichara tuberculata-Nodosochara jorbae assemblage zone was defined at the base of Harrisichara tuberculata superzone coinciding with the base of the Artés Formation in the northeastern sector, ranging between chron C16n.2n and chron C13r. The Lychnothamnus major European biozone encompasses the lower part of the continental Albi Formation in the southeastern sector of the basin within chron C12r. The lower limit of the Chara microcera European biozone is recorded in the Tàrrega Formation. Litho- and magnetostratigraphic correlation suggests that the lower limit of this biozone belongs to the uppermost part of chron C12r (~31 Ma). Comparisons with homologous data from the classical Upper Eocene-Lower Oligocene Solent Group in the Hampshire Basin (Isle of Wight, UK) suggest that the lower limit of the Harrisichara tuberculata superzone is isochronous in Europe but was recorded earlier in the Ebro Basin than in the Hampshire Basin due to more appropriate palaeoecological conditions.

The Bartonian-Priabonian marine record of the eastern South Pyrenean foreland basin (NE Spain): a new calibration of the larger foraminifers and calcareous nannofossil biozonation

This study presents a combined biostratigraphic (calcareous nannofossils, larger foraminifers) and magnetostratigraphic study of the Middle and Late Eocene marine units of the Igualada area, eastern Ebro Basin. The studied sections of Santa Maria de Miralles and La Tossa encompass the complete marine succession of the Santa Maria Group, where assemblages rich in larger foraminifers have been studied since the early 1950's. A total of 224 paleomagnetic sites and 62 biostratigraphic samples were collected along a 1350m-thick section that ranges from chron C20n to chron C16n (~43Ma to ~36Ma). The resulting magnetostratigraphy-based chronology challenges existing chronostratigraphic interpretations of these units and results in a new calibration of the biostratigraphic zonations. The base of calcareous nannofossil Zone NP19-20 is pinned down to an older age than its presently accepted attribution, whereas the time span assigned to Zone NP18 is significantly reduced. A revised calibration of larger foraminifers indicates that Zone SBZ18, formerly assigned exclusively to the late Bartonian, extends its range to the earlymost Priabonian, the Bartonian stage being almost entirely represented by Zone SBZ17. A division of Zone SBZ18 into two subzones is proposed.

Charophyte palaeoecology in the Upper Eocene of the Eastern Ebro basin (Catalonia, Spain). Biostratigraphic implications

A micropalaeontological study of the non-marine Upper Eocene of the north eastern Ebro Basin (Catalonia, Spain) was carried out to clarify the palaeoecology of well-known charophyte species that are widely recognised as significant in charophyte biostratigraphy. Autochthonous specimens of the biozone index-species Harrisichara vasiformis-tuberculata were found in marlstones from the Sant Boi Formation (middle part of the Priabonian), which are associated with brackish water ponds laterally related to paralic marshes. In contrast, laterally equivalent assemblages found in white laminated marls from stable freshwater lakes were devoid of the index species and were dominated by Harrisichara lineata. Three more charophyte assemblages are reported from the continental Artés Formation (Stephanochara vectensis biozone, Upper Priabonian). Assemblages dominated by the species Nodosochara jorbae, reported only from Iberia at that age, occur in marlstones related to freshwater, temporary and turbid lakes within flood plains in medial fluvial fan environments. However, Lychnothamnus grambastii dominates locally in similar environments with higher organic matter content. Laterally equivalent assemblages from freshwater perennial lakes in distal alluvial fan facies were dominated by the biozone index-species Harrisichara tuberculata.These results provide evidence that important charophyte index species of the European charophyte biozonation were controlled by palaeoenvironmental factors such as water salinity, lake level changes or terrigenous input to the lakes. In consequence, these species should be used with caution in biostratigraphic studies, taking into account that their presence or absence may be palaeoecologically driven.

Tectonic and climatic controls on the sequential arrangement of an alluvial fan/fan‐delta complex (Montserrat, Eocene, Ebro Basin, NE Spain)

AbstractA magnetostratigraphy‐based chronological framework has been constructed in the Eocene sediments of the Montserrat alluvial fan/fan‐delta complex (southeast Ebro Basin), in order to unravel forcing controls on their sequential arrangement and to revise the tectonosedimentary history of the region. The palaeomagnetic study is based on 403 sites distributed along an 1880‐m‐thick composite section, and provides improved temporal constraints based on an independent correlation to the geomagnetic polarity time scale. The new chronological framework together with sequence stratigraphy and geohistory analysis allow us to investigate the interplay between factors controlling the sequential arrangement of the Montserrat complex at the different temporal scales and to test for orbitally driven climate forcing. The results suggest that the internal stacking pattern in transgressive and regressive sequences sets within the more than 1000‐m‐thick Milany Composite Megasequence can be explained as the result of subsidence‐driven accommodation changes under a general increase of sediment supply. Composite sequences (tens to hundreds of metres thick) likely reflect orbitally forced cyclicity related to the 400‐kyr eccentricity cycle, possibly controlled by climatically induced sea‐level fluctuations. This study also provides new insights on the deformational history of the area, and shows a correlation between (tectonic) subsidence and forelimb rotation measured on basin‐margin deformed strata. Integration of subsidence curves from different sectors of the eastern Ebro Basin allows us to estimate the variable contribution of tectonic loads from the two active basin margins: the Catalan Coastal Ranges and the Pyrenees. The results support the presence of a double flexure from Late Lutetian to Late Bartonian, associated with the two tectonically active margins. From Late Bartonian to Early Priabonian the homogenization of subsidence values is interpreted as the result of the coupling of the two sources of tectonic load.

Study of Mesobeta Basin Flows by Remote Sensing

If no well-defined synoptic pressure gradients exist over a basin, flows can develop at a variety of scales, the main generators of circulations being spatial thermal differences. These dynamics are studied for the eastern Ebro basin, at the north-eastern part of the Iberian Peninsula, almost isolated from the surrounding areas by mountain ranges. The main tool for the study is the new RASS-Sodar by Scintec, the WindRASS, which combines sound and radio waves to provide profiles of wind and virtual temperature up to 360 m above the ground in the present configuration. One year of operation shows that low-level jets are found routinely, their maximum speed being at a height below 500 m above ground level. The jets are from a constant direction for several hours over the whole observed column, with rapid transitions between these periods. They allow for efficient heat transport at the basin scale and are good producers of vertical mixing due to the strong wind shear. In summer the irrigated plain has larger thermal contrast with the dry slopes, and the winds are stronger than in winter, when katabatic flows can develop at night and usually radiation fog appears and may last for days.

The age of the “Grande Coupure” mammal turnover: New constraints from the Eocene–Oligocene record of the Eastern Ebro Basin (NE Spain)

The Grande Coupure represents a major terrestrial faunal turnover recorded in Eurasia associated with the overall climate shift at the Eocene–Oligocene transition. During this event, a large number of European Eocene endemic mammals became extinct and new Asian immigrants appeared. The absolute age of the Grande Coupure, however, has remained controversial for decades. The Late Eocene–Oligocene continental record of the Eastern Ebro Basin (NE Spain) constitutes a unique opportunity to build a robust magnetostratigraphy-based chronostratigraphy which can contribute with independent age constraints for this important turnover. This study presents new magnetostratigraphic data of a 495-m-thick section (Moià-Santpedor) that ranges from 36.1 Ma to 33.3 Ma. The integration of the new results with previous litho- bio- and magnetostratigraphic records of the Ebro Basin yields accurate ages for the immediately pre- and post-Grand Coupure mammal fossil assemblages found in the study area, bracketing the Grande Coupure to an age embracing the Eocene–Oligocene transition, with a maximum allowable lag of 0.5 Myr with respect to this boundary. The shift to drier conditions that accompanied the global cooling at the Eocene–Oligocene transition probably determined the sedimentary trends in the Eastern Ebro Basin. The occurrence and expansion of an amalgamated-channel sandstone unit is interpreted as the forced response of the fluvial fan system to the transient retraction of the central-basin lake systems. The new results from the Ebro Basin allow us to revisit correlations for the controversial Eocene–Oligocene record of the Hampshire Basin (Isle of Wight, UK), and their implications for the calibration of the Mammal Palaeogene reference levels MP18 to MP21.

Closing and continentalization of the South Pyrenean foreland basin (NE Spain): magnetochronological constraints

ABSTRACTThis paper presents new magnetostratigraphic results from a 1100‐m‐thick composite section across the marine to continental sediments of the central part of the SE margin of the Ebro basin (NE Spain). Integration with existing marine and continental biochronological data allows a robust correlation with the geomagnetic polarity time scale. The resulting absolute chronology ranges from 36.3 to 31.1 Ma (Priabonian to Rupelian), and yields an interpolated age of ∼36.0 Ma (within chron C16n.2n) for the youngest marine sediments of the eastern Ebro basin. This age is in concordance with a reinterpretation of earlier magnetostratigraphic data from the western South Pyrenean foreland basin, and indicates that continentalization of the basin occurred as a rapid and isochronous event. The basin continentalization, determined by the seaway closure that resulted from the uplift of the western Pyrenees, was probably coincident with a mid‐amplitude eustatic sea level low with a maximum at 36.2 Ma. The base level drop that followed the basin closure and desiccation does not appear associated to a significant sedimentary hiatus along the margins, suggesting a late Eocene shallow marine basin that rapidly refilled and raised its base level after the seaway closing. Rapid basin filling following continentalization predates the phase of rapid exhumation of the Central Pyrenean Axial Zone from 35.0 to 32.0 Ma, determined from the thermochronology data. It is possible then that sediment aggradation at the front of the fold‐and‐thrust belt could have contributed to a decrease in the taper angle, triggering growth of the inner orogenic wedge through break‐back thrusting and underplating. Contrasting sedimentation trends between the western and eastern sectors of the South Pyrenean foreland indicate that basin closing preferentially affected those areas subjected to sediment bypass towards the ocean domain. As a result, sediment ponding after basin closure is responsible for a two‐fold increase of sedimentation rates in the western sector, while changes of sedimentation rates are undetected in the more restricted scenario of the eastern Ebro basin.

Erratum

SedimentologyVolume 54, Issue 2 p. 481-481 Free Access Erratum First published: 13 March 2007 https://doi.org/10.1111/j.1365-3091.2007.00867.xAboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat In Sáez et al. (2006), the frames of three units in the key of Fig. 1B were incorrect. The corrected figure is reproduced below. Figure 1Open in figure viewerPowerPoint (B) Schematic map of the Upper Eocene–Lower Oligocene units in the central area of the eastern Ebro Basin. The Llobregat upper river valley and a lateral ramp associated with the Pedraforca Nappe coincide with the approximate location of the palaeovalley that fed the Cardona-Súria fluvial fan. The upper Cardener river valley and a lateral ramp associated with the Montsec Nappe coincide with the approximate location of the palaeovalley that fed the Solsona-Sanaüja fluvial fan. Reference Sáez A., Anadón P., Herrero M.J., Moscariello, A. (2006) Variable style of transition between Palaeogene fluvial fan and lacustrine systems, southern Pyrenean foreland, NE Spain. Sedimentology, 54, 367– 390. Web of Science®Google Scholar Volume54, Issue2April 2007Pages 481-481 FiguresReferencesRelatedInformation

Variable style of transition between Palaeogene fluvial fan and lacustrine systems, southern Pyrenean foreland, NE Spain

AbstractTwo Palaeogene fluvial fan systems linked to the south‐Pyrenean margin are recognized in the eastern Ebro Basin: the Cardona–Súria and Solsona–Sanaüja fans. These had radii of 40 and 35 km and were 800 and 600 km2 in area respectively. During the Priabonian to the Middle Rupelian, the fluvial fans built into a hydrologically closed foreland basin, and shallow lacustrine systems persisted in the basin centre. In the studied area, both fans are part of the same upward‐coarsening megasequence (up to 800 m thick), driven by hinterland drainage expansion and foreland propagation of Pyrenean thrusts. Fourteen sedimentary facies have been grouped into seven facies associations corresponding to medial fluvial fan, channelized terminal lobe, non‐channelized terminal lobe, mudflat, deltaic, evaporitic playa‐lake and carbonate‐rich, shallow lacustrine environments. Lateral correlations define two styles of alluvial‐lacustrine transition. During low lake‐level stages, terminal lobes developed, whereas during lake highstands, fluvial‐dominated deltas and interdistributary bays were formed. Terminal lobe deposits are characterized by extensive (100–600 m wide) sheet‐like fine sandstone beds formed by sub‐aqueous, quasi‐steady, hyperpycnal turbidity currents. Sedimentary structures and trace fossils indicate rapid desiccation and sub‐aerial exposure of the lobe deposits. These deposits are arranged in coarsening–fining sequences (metres to tens of metres in thickness) controlled by a combination of tectonics, climatic oscillations and autocyclic sedimentary processes. The presence of anomalously deeply incised distributary channels associated with distal terminal lobe or mudflat deposits indicates rapid lake‐level falls. Deltaic deposits form progradational coarsening‐upward sequences (several metres thick) characterized by channel and friction‐dominated mouth‐bar facies overlying white‐grey offshore lacustrine facies. Deltaic bar deposits are less extensive (50–300 m wide) than the terminal lobes and were also deposited by hyperpycnal currents, although they lack evidence of emergence. Sandy deltaic deposits accumulated locally at the mouths of main feeder distal fan streams and were separated by muddy interdistributary bays; whereas the terminal lobe sheets expand from a series of mid‐fan intersection points and coalesced to form a more continuous sandy fan fringe.

Interplay between tectonics, climate, and fluvial transport during the Cenozoic evolution of the Ebro Basin (NE Iberia)

Three‐dimensional modeling that integrates fluvial sediment transport, crustal‐scale tectonic deformation, and lithospheric flexural subsidence is carried out to simulate the landscape and drainage evolution of the Ebro sedimentary basin (NE Iberia). The Ebro Basin underwent a long period of closed intramountain drainage as a result of tectonic topography generation at the Pyrenees, the Iberian Range, and the Catalan Coastal Range. In the late Oligocene, the Catalan Coastal Range underwent extension leading to the formation of the Valencia Trough (NW Mediterranean), but the Ebro Basin remained closed for nearly 15 Myr more before the Ebro River cut through the remnants of the topographic barrier. This drainage opening caused widespread basin incision that shaped spectacular outcrops of the syntectonic and posttectonic infill. Here we investigate the processes controlling these major drainage changes. The modeling results, constrained by a large data set on the tectonic and transport evolution of the area, predict a closed phase characterized by a large lake in the central eastern Ebro Basin. Dry climatic conditions probably lowered the lake level and contributed, together with rift flank uplift, to prolong this endorheic basin stage. The age and amount of reworked sediment after the opening are consistent with an onset of basin incision between 13 and 8.5 Ma as a result of lake capture by escarpment erosion and lake level rise associated with sediment accumulation and wetter climatic conditions. Sea level changes in the Mediterranean had no major impact in the large‐scale drainage evolution of the Ebro Basin.

Effects of rate and nature of synkinematic sedimentation on the growth of compressive structures constrained by analogue models and field examples

Abstract Compressive basins show various geometries of growth structures. In this paper, we examine the effects of the rate and nature of synkinematic sedimentation by comparing analogue models and field examples. We performed different types of experiments in order to simulate various natural conditions, the parameters tested including the rate of synkinematic sedimentation and the presence of a potential décollement layer deposited during deformation. Modelling techniques are similar to those usually used for experiments on brittle-ductile systems made of sand and silicone putty. To study the influence of the synkinematic sedimentation rate, we used sets of experiments with different velocity ratios R between the rate of sedimentation ( V s ) and the rate of uplift of the top of the structure ( V u ). In standard experiments, we deposited only sand during deformation. In all experiments, growth folds and growth faults developed. The geometry of growth folds changes from a steep anticline for R =1, to a rounded broken anticline when R exceeds 2. The geometry of growth reverse faults changes: from segments which initiate with a dip angle of about 30°, but then flatten or steepen, for R =1/2 and for R =1, respectively. For some sets of experiments, a thin silicone layer deposited instead of sand at some stage of sedimentation simulated the introduction of potential décollement layers. When a change in the nature of synkinematic sedimentation occurs between the two flanks of a fold, a fault develops in the flank where brittle material dominates. The direction of growth folds forming during compression in front of a ramp and above a décollement layer is parallel to the ramp and oblique to the direction of bulk shortening. Good correlations are observed between experimental geometries and field examples from the southern Pyrenees (Eastern Ebro Basin and Jaca Basin, Spain) and the Apennines (Italy).

Sedimentology and isotopic composition of Upper Palaeocene to Eocene non‐marine stromatolites, eastern Ebro Basin, NE Spain

ABSTRACTStromatolites are abundant in Upper Palaeocene to Eocene fluvial deposits from the Eastern Ebro Basin, whereas they are scarce in the lacustrine facies. The fluvial stromatolites display a variety of growth forms: oncoids, domes, laminated crusts and locally irregular bioherms. These morphologies are related to the hydrological behaviour of the fluvial systems. Elongate domes, dome heads and ovoid to subspherical oncoids accreted in flowing water. Laminated crusts and small‐sized cylindrical to lenticular oncoids formed during low‐discharge and ponding phases. In the lacustrine environments only small‐sized ovoid oncoids occur.The main characteristics of the Ebro Basin non‐marine stromatolites are: (1) laminations and concentric banding exhibited by all morphologies; (2) the occurrence of well‐preserved cyanobacterial filaments in several laminae, suggesting that these microbiotas are the major contributors in growth; (3) the asymmetrical growth of cortices in domes and oncoids with polar thickening on the upper side suggesting in situ growth under low energy conditions.δ13C values of carbonate stromatolites range from ‐ 11.3%o (Late Palaeocene) to — 4.4%o (Middle‐Late Eocene). During the Late Palaeocene, under tectonically quiescent conditions, the δ13C values mainly reflect the influence of soil‐derived CO2. During the Eocene, the progressive uplift of the surrounding catchment areas led to an increase of exposures of Mesozoic rocks. Consequently, the δ13C values of the Eocene stromatolites reflect the influence of the CO2 derived from the dissolution of Mesozoic marine carbonates.There is a 2.5%o shift in δ18O values of stromatolites from the Late Palaeocene to Middle‐Late Eocene which is consistent with the variation in δ18O of precipitation due to changes in altitude of the catchment area during this time.The isotopic values of all Middle‐Upper Eocene laminated crust samples show distinct covariant trends, suggesting that these stromatolites were formed either in ponding zones of fluvial channels or in disconnected pools developed during low‐discharge episodes.

Preliminary palynological data on floristic and climatic changes during the Middle Eocene-Early Oligocene of the eastern Ebro Basin, northeast Spain

Variations in pollen spectra observed in sediments from the middle Bartonian-Lower Oligocene of Igualada, Ebro Basin (northeast Spain), have permitted the identification of general trends in floristic and climate change. Detailed investigations of the biological affinities of certain fossil pollen have revealed a number of plant genera previously unidentified in the fossil record. The floral diversity and ecological characteristics of the pollen taxa indicates that the middle Bartonian vegetation of the eastern Ebro Basin was characterised by a complex mangrove swamp reflecting warm climatic conditions. During the Priabonian, the greater variety of herbaceous plants suggests the existence of a more open vegetation correlated with the change to a climate with a dry season. During the Priabonian the diversification of Caesalpiniaceae indicates African influence. During the Late Eocene taxa interpreted as indicators of a dry climate are identified, while those indicating humid climatic conditions disappear. Dry climatic conditions characterise the Lower Oligocene, as indicated by the abundance of cupressacean pollen interpreted as evidence of a sclerophyllous forest. A slight climatic cooling is also revealed by the presence of some microthermal taxa.