J. Serra-Kiel’s research while affiliated with Museu de Ciències Naturals de Barcelona and other places

A detailed sedimentological and magnetostratigraphic analysis of three selected sections of the Eocene carbonate platforms of the South Pyrenean Jaca-Pamplona foreland basin has been carried out in the Aragonese External Sierras (Huesca, Spain). The stratigraphic record spans from the middle-late Lutetian (Chron 20r, SBZ15) to the Bartonian (Chron 18r, SBZ17). The Lutetian-Bartonian transition was characterized by a major paleogeographic change, from a turbiditic foredeep with associated peripheral carbonate ramps to deltaic sedimentation. In most of the outcrops of the External Sierras, the peripheral carbonate platforms (Guara Formation) are overlained by prodelta and outer ramp marls (Arguis Formation). The drowning unconformity between these two formations in the outcrops located in the westernmost tip of the External Sierras is documented herein for the first time. In this area, the Guara Formation is overlain by glauconitic limestones deposited in a carbonate ramp setting. Between these units a characteristic unconformity is observed, with hard-ground formation and local evidence of subaerial exposure in the shallowest domains of the study area. The abundant glauconite found on top of this unconformity records a starvation period in the basin, followed by the development of a new carbonate ramp system during Bartonian times (Santo Domingo Member of the Arguis Formation). Magnetostratigraphic and sedimentological data show that tectonic tilting occurred in latest Lutetian times, prior to the drowning process. This suggests the influence of the flexural subsidence in the cratonic margin of the foreland as a result of the advance of a basement thrust in the hinterland. Nevertheless, the correlation of the uppermost Lutetian drowning unconformity with a basinwide regional sea level rise, which may have further been global, suggests an interplay between tectonic and eustatic processes in the drowning of the late Lutetian South Pyrenean carbonate ramps. In this work we point out a narrowing of the carbonate ramp, together with a relative sea level rise, as the processes responsible for the drowning of the Upper Guara Mb carbonate ramp. These processes could be responsible for the development of drowning unconformities in cratonic margins of other foreland basins. As carbonate ramps have a high sediment production potential, the narrowing of the carbonate factory could provide the conditions for the drowning of the carbonate ramp system in a subsequent sea level rise.

Here, the larger foraminifera found in MiddleEocene-Early Miocene rocks from Dhofar (Oman) andSocotra Island (Yemen) are studied in detail. The architecturalanalysis leads to the description of five new genera and ninenew species: five agglutinated foraminifera, Pseudolituonellarobineti n. sp., Socotraella ashawqi n. gen. n. sp.,Pseudoaccordiella ayaki n. gen. n. sp., Barattolites andhurin. sp., and Rogerella aydimi n. gen. n. sp.; and four porcellaneousforaminifera, Idalina grelaudae n. sp., Idalina pignattiin. sp., Macetadiscus incolumnatus n. gen. n. sp., andOmanodiscus tenuissimus n. gen. n. sp. The larger foraminiferaidentified in a composite section located in westernDhofar, in the Shuwaymiyah section located in easternDhofar, and in the Wadi Ayak section located on SocotraIsland have facilitated the identification of the following largerforaminifera zones: SBZ 14–SBZ 15 (middle Lutetian), SBZ16 (late Lutetian), SBZ 17 (Bartonian), SBZ 18 (latestBartonian-earliest Priabonian) , SBZ 19–SBZ 20(Priabonian), SB 21–SB 22A (Rupelian), SB 22B–SB 23(Chattian), and SB 24 (Aquitanian). All these data permit toassess the age of the following lithostratigraphic units:Dammam Fm.—Andhur Mb. lower Lutetian?-middleLutetian age (SBZ 13?–SBZ 14 partim), Qara Mb. middleLutetian (SBZ 14–SBZ 15), and Uyun Mb. upper Lutetian(SBZ 16); Aydim Fm.—Heiron Mb. Bartonian (SBZ 17),Moosak Mb. upper Bartonian-Priabonian (SBZ 18–SBZ 20),Tagut Mb. Priabonian (SBZ 19–SBZ 20), and Haluf Mb.Priabonian (SBZ 19–SBZ 20) to lower Rupelian (SBZ 21)on Socotra Island; Ashawq Fm. Rupelian (SB 21–SB 22A);and Mughsayl Fm. Chattian-Aquitanian (SB 23–SB 24).

In the northern part of the Bahariya Depression (Western Desert, Egypt) the Eocene carbonate succession , unconformably overlying the Cretaceous deposits, consists of three main stratigraphic units; the Naqb, Qazzun and El Hamra formations. The Eocene carbonates are relevant as they locally host a large economic iron mineralization. This work revises the stratigraphic attribution of the Eocene formations on the basis of larger benthic foraminifers from both carbonate and ironstone beds. Eight Nummulites species spanning the late Ypresian e early Bartonian (SBZ12 to SBZ17) were identified, thus refining the chronostratigraphic framework of the Eocene in that region of Central Egypt. Moreover, additional sedimentological insight of the Eocene carbonate rocks is presented. The carbonate deposits mainly represent shallow marine facies characteristic of inner to mid ramp settings; though deposits interpreted as intertidal to supratidal are locally recognized. Dating of Nummulites assemblages from the youngest ironstone beds in the mines as early Bartonian provides crucial information on the timing of the hydrothermal and meteoric water processes resulting in the formation of the iron ore mineralization. The new data strongly support a post-depositional, structurally-controlled formation model for the ironstone mineralization of the Bahariya Depression.

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.