Aitor Payros

Did the Late Paleocene thermal maximum affect the evolution of larger foraminifers? Evidence from calcareous plankton of the Campo Section (Pyrenees, Spain)

The larger foraminifer turnover (LFT), which marks the base of the Ilerdian stage, may be related to the Late Paleocene Thermal Maximum (LPTM), or be at least nearly coeval with that climatic event. Thus, the impact of the LPTM may have been greater than hitherto realised, having also affected mid-latitude shallow-marine biota. This conclusion has been reached after a re-study of the calcareous plankton of the uppermost Paleocene and lowermost Eocene interval of the Campo section in the central southern Pyrenees. Campo is an important reference section because it contains larger foraminifers, planktic foraminifers and calcareous nannofossils, and their co-occurrence was used to intercalibrate their respective zonal schemes. Previous studies at Campo placed the onset of planktic foraminiferal Zone P5 near the base of the Ilerdian, and the calcareous nannofossil NP9/NP10 chronal boundary (sensu Bybell, L.M., Self-Trail, J.M., 1995. Evolutionary, biostratigraphic and taxonomic study of calcareous nannofossils from a continuous Paleocene/Eocene boundary section in New Jersey. US Geol. Surv. Prof. Pap. 1554, pp. 1‐36) not less than 150 m above the Ilerdian lower limit. By these estimates, the LPTM (known to have occurred in the middle part of Zone P5 and just before the NP9/NP10 boundary) would be an event much younger than the LFT. However, our reexamination of planktic foraminifers suggests that the base of the Ilerdian is probably situated at the middle of Zone P5 (a possibility proposed by Hillebrandt in 1965, but denied by later authors). For instance, Morozovella occlusa has been found for the first time in the Campo section. Its Last Appearance Datum (LAD), which in the Pyrenees was approximately coeval with that of Morozovella velascoensis (event used to place the top of Zone P5), has been identified in beds situated less than 70 m above the base of the Ilerdian. Such thickness represents a time span of a similar magnitude as the one which separated the LPTM and the LAD of M. occlusa in the deep-water hemipelagic succession of the Basque Basin, in the western Pyrenees. Autochthonous calcareous nannofossils are neither abundant nor well preserved in most of the studied interval, with Rhomboaster bramlettei (the marker of the base of Zone NP10) being extremely rare in lower and middle Ilerdian beds, a fact that makes it very difficult to fix the position of the NP9/NP10 boundary in the Campo section. However, the bases of zones NP9 and NP11 have been located, and they support the zonation with planktic foraminifers. These new data suggest that the LFT and the LPTM may have been coeval or nearly so, a possibility reinforced by correlation with sections of the Basque Basin. Specialists of larger benthic foraminifers can easily delineate the LFT in shallow water carbonate successions of the Tethys domain, and they propose to place the Paleocene/Eocene boundary at the base of the Ilerdian stage. On the other hand, the deep

Correlation of the Thanetian-Ilerdian turnover of larger foraminifera and the Paleocene-Eocene thermal maximum: confirming evidence from the Campo area (Pyrenees, Spain)

It has long been known that a major larger foraminifera turnover (LFT) occurred at the boundary between the Thanetian and Ilerdian stages, but its possible correlation with the Paleocene-Eocene thermal maximum (PETM) was unsuspected until the work of Baceta (1996), and has been controversial ever since. After summarizing the history of this controversy, we present information from three new sections that conclusively resolve the issue, all of them placed less than 2 km to the east of the classical Campo section in the southern Pyrenees. In these three sections, an up to 7 meter-thick intercalation of continental deposits rich in pedogenic carbonate nodules is sandwiched between uppermost Thanetian and lowermost Ilerdian shallow marine carbonates. The d13C composition of 42 pedogenic nodules collected from two of these sections (San Martin and La Cinglera) ranges between –11.4 and -14.3‰ and averages –12.9‰, values that conclusively represent the PETM and for the first time are recorded in sections where the LFT is clearly represented. Further, a high-resolution lithological correlation between Campo and the three new sections across the P-E interval unquestionably demonstrates that the lowermost marine beds with autochthonous specimens of Alveolina vredenburgi (a tell-tale of the LFT) are laterally interfingered –and are therefore coeval- with the nodule-bearing PETM continental deposits. On the basis of the new evidence, the temporal coincidence of the PETM and the LFT can no longer be doubted.

Biostratigraphic and magnetostratigraphic intercalibration of latest Cretaceous and Paleocene depositional sequences from the deep-water Basque basin, western Pyrenees, Spain

Abstract Latest Cretaceous (Late Maastrichtian) and Paleocene depositional sequences from the deep-water Basque basin have been calibrated with published [1,2] and newly acquired magnetostratigraphic data. Sequences mostly consist of hemipelagic marls and limestones, and their relative ages are well constrained with planktic foraminifera. They accumulated during a phase of tectonic tranquillity and reduced clastic input into the basin, and therefore they can be attributed to eustatic sea-level changes with reasonable confidence. On the basis of the planktic foraminifera zonation, a good match has been observed previously between the depositional sequences of the Basque basin and specific sea-level cycles of the 1988 version of the Exxon Global Cycle Chart (GCC) [3]. Here, a new attempt at correlation using their respective magnetostratigraphic data has failed to confirm such a match. The disagreements observed may indicate that, for the studied interval, (1) the current planktic foraminifera biostratigraphy lacks the necessary level of resolution to ensure synchrony between sequences of different basins, and/or (2) the magnetostratigraphy of the GCC needs to be revised. Whatever the case, the new findings lend support for some criticism on the use of the GCC for interregional correlations.

Redefinition of the Ilerdian Stage (early Eocene)

The Ilerdian Stage was created by Hottinger and Schaub in 1960 to accommodate a significant phase in the evolution of larger foraminifera not recorded in the northern European basins, and has since been adopted by most researchers working on shallow marine early Paleogene deposits of the Tethys domain. One of the defining criteria of the stage is a major turnover of larger foraminifera, marked by the FO’s of Alveolina vredenburgi (formerly A. cucumiformis) and Nummulites fraasi. There is now conclusive evidence that this turnover was coeval with the onset of the Carbon Isotope Excursion (CIE) and, consequently, with the Paleocene-Eocene (P-E) boundary, a temporal correspondence that reinforces the usefulness of the Ilerdian as a chronostratigraphic subdivision of the early Eocene in a regional context. However, in addition to the paleontological criteria, the definition of the Ilerdian was also based on the designation of two reference sections in the southern Pyrenees: Tremp (stratotype) and Campo (parastratotype). In both sections, the base of the stage was placed at the lowest marine bed containing A. vredenburgi specimens. Using the CIE as a correlation tool we demonstrate that these two marine beds occur at different chronological levels, being older in Campo than in Tremp. Further, we show that both beds are in turn younger than the lowest strata with Ilerdian larger foraminifera at the deep-water Ermua section in the Basque Basin (western Pyrenees). Since the age of stage boundaries must be the same everywhere, the choice of these stratotype sections was misleading, since in practice it resulted in the Ilerdian being used as a facies term rather than as a chronostratigraphic unit. To eliminate that conflict, and yet be respectful with established tradition, we propose to redefine the Ilerdian Stage following a procedure similar to the one used by the International Commission on Stratigraphy to establish global chronostratigraphic standards, namely: by using a “silver spike” to be placed in the Tremp section at the base of the Claret Conglomerate, a widespread lithological unit that in the Tremp Graus Basin coincides with the onset of the CIE. The redefined regional Ilerdian Stage becomes thus directly correlatable to the lower part of the global Ypresian Stage, as currently defined by the International Commission on Stratigraphy.

On the age of the Early/Middle Eocene boundary and other related events: cyclostratigraphic refinements from the Pyrenean Otsakar section and the Lutetian GSSP

An integrated bio-, magneto- and cyclostratigraphic study of the Ypresian/Lutetian (Early/Middle Eocene) transition along the Otsakar section resulted in the identification of the C22n/C21r chron boundary and of the calcareous nannofossil CP12a/b zonal boundary; the latter is the main correlation criterion of the Lutetian Global Stratotype Section and Point (GSSP) recently defined at Gorrondatxe (Basque Country). By counting precession-related mudstone–marl couplets of 21 ka, the time lapse between both events was calculated to be 819 ka. This suggests that the age of the CP12a/b boundary, and hence that of the Early/Middle Eocene boundary, is 47.76 Ma, 250 ka younger than previously thought. This age agrees with, and is supported by, estimates from Gorrondatxe based on the time lapse between the Lutetian GSSP and the C21r/C21n boundary. The duration of Chron C21r is estimated at 1.326 Ma. Given that the base of the Eocene is dated at 55.8 Ma, the duration of the Early Eocene is 8 Ma, 0.8 Ma longer than in current time scales. The Otsakar results further show that the bases of planktonic foraminiferal zones E8 and P10 are younger than the CP12a/b boundary. The first occurrence of Turborotalia frontosa , being approximately 550 ka older that the CP12a/b boundary, is the planktonic foraminiferal event that lies closest to the Early/Middle Eocene boundary. The larger foraminiferal SBZ12/13 boundary is located close to the CP12a/b boundary and correlates with Chron C21r, not with the C22n/C21r boundary.

An early Lutetian carbon‐cycle perturbation: Insights from the Gorrondatxe section (western Pyrenees, Bay of Biscay)

turbidites and kaolinite, a 3‰ decline in the bulk d 13 C record, a >1‰ decline in benthic foraminiferal d 13 C followed by a gradual recovery, a distinct deterioration in foraminiferal preservation, high proportions of warm-water planktic foraminifera and opportunistic benthic foraminifera, and reduced trace fossil and benthic foraminiferal diversity, thus recording a significant environmental perturbation. The onset of the perturbation correlates with the C21r-H6 event recently defined in the Atlantic and Pacific oceans, which caused a 2C warming of the seafloor and increased carbonate dissolution. The perturbation was likely caused by the input of 13 C-depleted carbon into the ocean-atmosphere system, thus presenting many of the hallmarks of Paleogene hyperthermal deposits. However, from the available data it is not possible to conclusively state that the event was associated with extreme global warming. Based on our analysis, the perturbation lasted 226 kyr, from 47.44 to 47.214 Ma, and although this duration suggests that the triggering mechanism may have been similar to that of the Paleocene-Eocene Thermal Maximum (PETM), the magnitude of the carbon input and the subsequent environmental perturbation during the early Lutetian event were not as severe as in the PETM.

Bird and Mammal Footprints From the Tertiary of Navarre (Western Pyrenees)

A rich variety of vertebrate footprints is known from a number of Upper Eocene to Lower Miocene localities of Navarre (western Pyrenees). The sediments were deposited in a wide range of depositional environments, from marginal marine to diversified terrestrial. Abundant bird tracks have been found in the coastal deposits of the Upper Eocene Liedena Sandstone of the Yesa and Itzagaondoa areas. Ciconiiformes-like (Leptoptilostipus pyrenaicus) and Charadriiformes-like (Charadriipeda ichnospp.) footprints have been recognized. Mammal ichnites have been discovered in the Oligocene and Lower Miocene deposits of Navarre. Equoid perissodactyl ichnites similar to those of Plagiolophustipus occur in the Oligocene fluviatile rocks of the Mués Sandstone of Olexoa and the Rocaforte Sandstone near Oibar and Sada. Trackways of entelodontids (Entelodontipus) are known in fluviatile-palustrine beds of the Oligocene Mués Sandstone of Olkotz. Additionally, bird (Charadriiformes-like) tracks are known in fluviatile-palustrine floodplain deposits of the Lower Miocene Ujué Formation of Los Arcos. In the same area, the Desoio and Los Arcos outcrops have also yielded perissodactyl trackways of possible Equoidea. Trackways of rhinocerotids (?) and artiodactyls (possibly Pecoripeda) are described from the Lower Miocene (Ramblian) palustrine limestones marginal to the Lerín Formation of Kaparroso and from alluvial fan deposits of the Uncastillo-Perdón Formation of Altzorritz, respectively.

The Upper Eocene South Pyrenean Coastal deposits (Liedena sandstone, navarre): Sedimentary facies, benthic formanifera and avian ichnology

SummaryDuring the 1960s and the 1970s the Liedena Sandstone was a type deposit for “flysch-like facies” (sandstone and lutite alternations) of coastal sedimentary systems. However, the depositional system of these beds was never accurately defined. The sedimentological analysis along 100 km of outcrops in the western part of the South Pyrenean Zone (Navarre) allows these peculiar facies to be assigned to a mixed intertidal flat. Furthermore, sandy beach facies, different types of heterolithic, backbarrier deposits and conglomeratic, fluviatile facies have been recognized associated with these intriguing deposits. Generally, a northwestward-facing barrier-island system or wave-dominated delta was the likely depositional environment.The benthic foraminiferal assemblage in the intertidal deposits exhibits the typical characteristics of a marginal marine environment: extremely high dominance of one species (Pararotalia inermis), low species diversity, and a hyaline dominance with discrete amounts of miliolids. Furthermore, the most abundant species indicates that the Liedena Sandstone was deposited during the Late Eocene.Abundant footprints of aquatic birds are known in the tidal flat deposits. Six morphotypes have been distinguished: two (types 1 and 2) are ciconiforme-like; type 1 is here assigned to a new ichnotaxon,Leptoptilostipus pyrenaicus and is one of the oldest occurrences of Ciconiiforme-like ischmites in the fossil record. Two other morphotypes (5 and 6) are similar to those of the Charadriiformes and are refeered to asCharadriipeda. Finally, the affinities of the two remainder morphotypes (3 and 4) are unclear, they could have been made by Charadriiformes.Synsedimentary tectonic activity controlled the evolution of the depositional system, as the area of deposition of the Liedena Sandstone was progressively incorporated into the active thrust sheets of the Pyrenean Orogen during the Late Eocene. The structural uplift and the large amount of sediments derived from the adjacent highlands induced progradation of the depositional system and the definitive retreat of the sea from the South Pyrenean Zone.

Early Eocene climatic optimum: Environmental impact on the North Iberian continental margin

The early Eocene climatic optimum, which constituted the peak of the long-term early Cenozoic global warming, had a significant impact on the environmental evolution of terrestrial and oceanic areas. Surprisingly, however, its influence on continental margins is poorly known. New insights are provided from a sedimentological, stable isotope, mineralogical, and micropaleontological study of an 1100-m-thick Lower-Middle Eocene deep-marine succession that accumulated on the North Iberian continental margin. The early Eocene climatic optimum is represented by a 410-m-thick interval characterized by scarcity of hemipelagic limestones, abundance of dark marls, which record a reduction in calcium carbonate content and an increase in kaolinite, and the occurrence of conspicuous red layers with high siderite and pyrite content. Series of stratigraphically significant events frame the early Eocene climatic optimum. Based on this analysis, the environmental influence of the early Eocene climatic optimum started at 52.6 Ma and lasted ~2.3 m.y. Its onset is marked by rapid drops in δ13C and δ18O, which record the addition of 13C-depletedcarbon into the ocean-atmosphere system for 80 k.y. and a concomitant warming. A hotter climate and a perennial rainfall regime increased the supply of terrestrial clays, organicmatter, and iron oxides into the sea. Eventually, these changes affected the deepsea bottom 270 k.y. after the onset of the early Eocene climatic optimum, creating conditions in which opportunistic benthic foraminifera thrived, and leading to increased methanogenesis in the subsurface, which caused the formation of siderite. A subsequent gradual recovery culminated abruptly at 50.3 Ma with a global cooling episode, which is locally recorded by the accumulation of lowstand resedimentation deposits.

Upper Paleocene—lower Eocene strata of the western Pyrenees, Spain: A shelf-to-basin correlation

High resolution studies across the P/E boundary in the western Pyrenees have been so far restricted to deep-water successions, in spite of the fact that the bulk of available lower Paleogene outcrops are of shallow-water facies (Fig. 1). For that reason, while both the benthic extinction event (BEE) and the carbon isotopic excursion (CIE) have been pinpointed in basinal deposits (Schmitz et al. 1997 and in prep.), the effects of these P–E events in the shallow domain are poorly known. One possible reason for that situation is the difficulty to establish biostratigraphic correlations between shallow and deep-water deposits, which are typified by different and mutually exclusive fossil groups and, indeed, even by different chronostratigraphic scales (Ilerdian-Cuisian vs. late Thanetian-Ypresian). Interestingly, shallowand deep-water fossils are found together in the base-of-slope setting (Fig. 1), potentially a key zone to intercalibrate the different biostratigraphic scales. However, results of such intercalibration have been considered unreliable because of the resedimented nature of the largest foraminifera occurring in such a setting. In this paper we report an attempt at correlation between upper Paleocene–lower Eocene shallowand deep-water successions, which is primarily based on objective lithostratigraphic criteria. Our database is comprised of nearly continuous cores from two boreholes (“Perraran” and “Las Cequias”) and of five outcrop sections (“Leortza”, “Korres”, “Ermua”, “Zumaia” and “Ibaeta”, Fig. 1), which allow the reconstruction of a complete shelf-tobasin transect. Details of the outcrop sections have already been published (e.g. Orue-Etxebarria et al. 1996; Schmitz et al. 1997), while the borehole information is presented here for the first time. Four units have been recognized in the three settings for the Thanetian–early Ypresian interval (A, B, C, and D). Their sedimentary structures, fossil content, and other parameters change depending on their specific setting. However, their respective gross lithological features and vertical trends are very similar everywhere (Fig. 2 and below). These units are separated in the shelf and base-of-slope settings by sharp erosional boundaries, which pass into correlative conformities in the basinal setting. Unit A is thick (55 to 120 m) and largely made up of marls and limestones, its carbonate content increasing upward in all sections. In the shelf setting it is made up of the following facies: A1, sandy lutites, grading up into bioclastic marlstones (littoral deposits); A2, marly limestones (wackestones) and highly bioturbated marlstones, occasionally including discocyclinids and nummulitids (shallow-water, open marine deposits); A3, bioclastic grainstones with coralgal mounds (reefal deposits); A4, limestones (packstones and wackestones) rich in miliolids and alveolinids (backreef/lagoonal deposits). In the base-of-slope setting two parts are recognized in Unit A, the lower one composed of mud-supported carbonate breccias (“muddy debrites”), marls and thin-bedded mixed carbonate-siliciclastic turbidites, the upper one comprised of coarseand fine-grained carbonate turbidites alternating with hemipelagic marls and limestones. In the basinal setting Unit A is mostly made up of hemipelagic marls and limestones, plus occasional thin-bedded carbonate turbidites, with marls predominating in the lower part and limestones in the upper one. Unit B (20–40 m) has a mixed carbonate-siliciclastic character. In the shelfal setting it begins with sandy grainstones that grade upward into sandstones with a low carbonate content. The unit is capped by a carbonate sub-unit of bioclastic grainstones, which is partially or totally missing (eroded out) in the boreholes. Largest foraminifera are abundant throughout the unit, demonstrating the persistence of shallow marine conditions during its deposition. In the base-of-slope, the lower part of Unit B is formed by carbonate breccias and turbidites, the middle part by alternating mixed carbonate-siliciclastic turbidites and hemipelagic marly limestones, and the upper part by a comparatively thin sub-unit (c. 2 m) of hemipelagic limestones and carbonate turbidites. The onset of the CIE occurs just above this upper subunit (Schmitz et al. in prep.). In the basinal setting, the lower part of Unit B is made up of hemipelagic marls and limestones, plus thin-bedded turbidites of mixed composition, the middle part is dominated by hemipelagic marls with intercalations of thin-bedded siliciclastic turbidites, while the upper part is a thin sub-unit (c. 1 m) of hemipelagic limestone with just one thin-bedded carbonate turbidite. The BEE and the CIE have been located in Zumaia just above this sub-unit (Schmitz et al. 1997). Unit C (4–25 m) has a siliciclastic composition. In the shelfal setting it is mostly composed of cross-bedded sands and gravelly sands, but also includes intercalations of red or dark-grey lutites. Its features, and the conspicuous absence of marine fossils, indicate terrestrial depositional conditions. In the base-of-slope, Unit