Testing the reliability of detrital cave sediments as recorders of paleomagnetic secular variations, Seso Cave System (Central Pyrenees, Spain)
Introduction
The classical theory of the acquisition of the characteristic magnetization in sediments (detrital remanent magnetization — DRM) was already proposed by Nagata (1961). The Earth's magnetic field imposes a torque on the magnetic particles, which tends to align them with the field therefore the magnetic grains align during deposition. However, for the last three decades the concept is being under consideration, in the light of, for example, the influence of postdepositional effects in the orientation of the magnetic moment of the particles due to e.g. physical compaction. As a result of postdepositional compaction, shallowing inclination errors have been documented in red beds (Tan and Kodama, 2002 and references therein). Therefore, the postdepositional effects on the magnetic particles can affect, and also delay, the final acquisition of the DRM, then the remanent acquisition is called postdepositional remanent magnetization (pDRM) and it can be influenced by many factors, among them: grain size, rate of deposition, bioturbation, diagenetic processes, and biochemical origin of new minerals (Abrajevitch and Kodama, 2009, Bilardello et al., 2013, Butler, 1992 and references therein).
In addition to the postdepositional modifications, the depositional effects such as the physical–chemical properties of the fluids and particles can also affect the alignment of the magnetic particles before they reach the sediment–water interface. Flocculation of particles during deposition affects the final alignment of the magnetic particles with the magnetic field. The influence of some depositional processes on flocculation has been studied in models and redeposition experiments considering salinity, composition of sediments, pH characteristics of the depositional environment or shape of particles (Bilardello et al., 2013, Katari et al., 2000, Mitra and Tauxe, 2009). These experiments suggest that the alignment of the magnetic particles with the magnetic field seems to be better for carbonate rich sediments, with lower clay content, therefore the former sediments are more suitable for relative paleointensity record (Spassov and Valet, 2012 and references therein).
The paleomagnetic record of continental sediments can be used as a chronological tool using the record of the inversions of the Earth's magnetic field. This inversions of the Earth magnetic field are marked for changes in the values of the paleomagnetic inclination, i.e. positive inclination and northern declination in normal polarity periods, to negative inclination and southern declination in reversal polarity periods, in the northern hemisphere. The sequence of inversions at local scale is then compared with the geomagnetic polarity time scale (GPTS) (Gradstein et al., 2004) for dating purposes. This is possible to apply in long sedimentary sequences and older than 780,000 years, when the last inversion from reverse to normal polarity chron occurs. In short sedimentary sequence (i.e., karstic sediments), the anchoring of one of the local polarity variations is necessary. The anchoring can be done with an independent dating technique i.e., relative dating linked to the speleogenesis of the cave, 14C, and optical stimulated luminescence among others. Otherwise, magnetostratigraphic dating can be problematic (Bosák et al., 2003). In younger sediments (< 780,000 years) polarity is always normal (except for at least 5 short excursions of the Earth's magnetic field, Channel, 2006) therefore changes in polarity are no longer valid for dating purposes. Then, the secular variations of the Earth's magnetic field are used as a chronological framework. Secular variations are short-term variations of the Earth's magnetic field that can be recorded at one location by changes in declination, inclination and intensity. However, the construction of secular variations curves is usually limited to the paleomagnetic data from archeomagnetic structures (kilns), which have been dated by other techniques. In particular, the catalog of secular variations in Iberia spans less than ~ 2000 years BP (Gómez-Paccard et al., 2006). There are examples where secular variation data have been used to date archeomagnetic artifacts when other dating technique is not available (Gómez-Paccard and Beamud, 2008). In addition to the actual data, there are also numerical models that reproduce the secular variations for the past (back to few million of years) based on archeomagnetic and paleomagnetic data of sediments (Korte and Constable, 2011, Korte et al., 2011, Pavón-Carrasco et al., 2009 among others).
Quaternary waterlaid detrital sediments in karstic caves are very particular since their deposition is spatially restricted and highly controlled by several different sedimentation processes and speleogenesis. However, caves often house clastic sedimentary records containing valuable paleoenvironmental as well as chronological indicators. Sediments can be reworked from the cave material itself (internal or autochthonous origin), i.e. insoluble residue from bedrock, remobilization and deposition of sediments within the cave conduit; or they may come from the exterior (external or allochthonous origin) i.e: injection of allogenic soils by sinking streams, soil infiltration through joints and fractures, storm inwash of soils, piping failures or sinkhole collapses (Bosch and White, 2007, Ford and Williams, 2007). Stream deposits including sands, silts and clays are widespread clastic deposits in caves. Stream and pond deposits are common waterlaid clastic sediments in caves (Jennings, 1985) in interior sequences in a similar way to alluvial systems in surface (Bosch and White, 2007). Changes in the sedimentary facies indicate changes in the processes of deposition of particles with time. Although these waterlaid detrital sediments have suitable characteristics for paleomagnetic analysis, very scarce information on this indicator is available at the moment. Only some attempts to study paleomagnetism in Pleistocene–Holocene detrital sequences are reported (Faust et al., 2004, Gómez-Paccard et al., 2013, Zielhofer et al., 2008, Noel et al., 1984) and some correspond to cave sediments (Creer and Kopper, 1974, Creer and Kopper, 1976, Noel, 1986, Noel and St. Pierre, 1984, Turner and Lyons, 1986). More recently, the recording of inversions of the paleomagnetic field is analyzed in old cave sediments for dating purposes (Bosák et al., 2003, Chazan et al., 2008, Herries and Shaw, 2011, Musgrave and Webb, 2003, Sasowsky et al., 1995, Stock et al., 2005). These studies indeed confirm that the sediments within caves can record the polarity of the Earth's magnetic field.
Our study is focused on the paleomagnetic signature of a Holocene waterlaid detrital sequence housed in the Seso Cave System (West-Central Pyrenees). The purpose of this study is to compare the results of the calculated characteristic component to: i) the known secular variation data of Iberia for the last 2000 years (Gómez-Paccard et al., 2006), ii) three global geomagnetic field models, ARCH3k.1, CALS3k.4 and CALS10k.1b (Donadini et al., 2006, Korhonen et al., 2008, Korte and Constable, 2011, Korte et al., 2011) iii) Pavón-Carrasco et al. (2009) regional geomagnetic model for the last 3000 years (SCHA.DIF.3K) in order to qualitatively measure the accuracy of the recording of the Earth's magnetic field in two distinct cave deposits (pond and stream sediments) analyzing for that purpose discrete samples and using the two standard demagnetizing methods (alternating field and thermal).
Section snippets
The Seso Cave System
The Seso Cave System (SCS) is located near Boltaña (Huesca), in the eastern limb of the Boltaña anticline (Bartolomé et al., 2011, Mas and Fuertes, 2007), which represents the structural boundary between the South Pyrenean Central Unit to the east and the Jaca-Pamplona basin to the west, in the southern Pyrenees (Séguret, 1972, Soto and Casas, 2001) (Fig. 1A). The Eocene marls and limestones (Boltaña Formation) host the SCS. It is basically a pseudokarstic cave system developed by piping
Methods
Only one stratigraphic profile was described and interpreted because of the reduced size of the detrital sedimentary deposits in the Seso Cave System. Several proposals of classification of clastic sediments in caves were made by Jennings (1985), White (1988), Bosch and White (2007) and Ford and Williams (2007). In this study we use the nomenclature by Jennings (1985). Thus clastic cave sediments include i) breakdown, weathering and mass movement deposits and ii) stream and pond deposits.
Stratigraphy of the waterlaid detrital record
The sedimentological characteristics of the studied sequence allow dividing the infilling of the detrital record from Seso Cave into five sedimentological units that correspond to two main sedimentary environments (Fig. 2).
Unit 1 (100 cm thick) is mainly composed of light gray and brownish laminated marls. Carbonate induration (calcrete) appears in the lower section. This unit corresponds to pond deposits (Jennings, 1985) and relates to the transport as suspended load of the autochthonous marls
Discussion
The waterlaid detrital deposit of the Seso Cave System records unique environmental characteristics that can be reconstructed by the hydrological changes and variations recorded in the depositional environments. In addition, the detrital sedimentary sequence remains and can be observed, thanks to the erosion of part of the profile due to the later water incision of the clastic deposit.
Conclusions
The waterlaid detrital cave sedimentary record in the Seso Cave System is composed of two different type deposits: a first autochthonous pond sediments and a second allochthonous stream deposits covering from 2080 to 650 cal yr BP. The main change in the sedimentary sequence took place at the end of the Roman Period when the general decrease in humidity produced a reduction of water inside the cave thus diminishing the importance of in-cave piping processes in the accumulation of the sediments.
Acknowledgments
BOU acknowledges the JAEdoc Programme of CSIC, partly financed by the European Social Fund. All authors thank the financial support of the Instituto de Estudios Altoaragoneses, of the projects CGL2009-10455/BTE, HIDROPAST CGL2010-16376 (MICINN and FEDER), ORDESA (Autonomous Organism of National Parks), and the PaleoQ Group (Universidad de Zaragoza-Gobierno de Aragón). We are also indebted to Jaume Mas-Moiset and Xavier Fuertes from the Grup d'Espeleologia de Badalona (GEB) for the cartography
References (59)
- et al.
Biochemical vs. detrital mechanism of remanence acquisition in marine carbonates: a lesson from the K–T boundary interval
Earth Planet. Sci. Lett.
(2009) - et al.
Role of spherical particles on magnetic field recording in sediments: experimental and numerical results
Phys. Earth Planet. Inter.
(2013) - et al.
Radiometric dating of the Earlier Stone Age sequence in excavation I at Wonderwerk Cave, South Africa: preliminary results
J. Hum. Evol.
(2008) - et al.
High-resolution fluvial record of late Holocene geomorphic change in northern Tunisia: climatic or human impact?
Quat. Sci. Rev.
(2004) - et al.
Recent achievements in archaeomagnetic dating in the Iberian Peninsula: Application to four Spanish structures
Journal of Archaeological Science
(2008) - et al.
Environmental response of a fragile, semiarid landscape (Bardenas Reales Natural Park, NE Spain) to Early Holocene climate variability: a paleo- and environmental-magnetic approach
Catena
(2013) - et al.
Palaeomagnetic analysis of the Sterkfontein palaeocave deposits: implications for the age of the hominid fossils and stone tool industries
J. Hum. Evol.
(2011) - et al.
A reassessment of post-depositional remanent magnetism: preliminary experiments with natural sediments
Earth Planet. Sci. Lett.
(2000) - et al.
Reconstructing the Holocene geomagnetic field
Earth Planet. Sci. Lett.
(2011) - et al.
Improving geomagnetic field reconstructions for 0–3 ka
Phys. Earth Planet. Inter.
(2011)
Land surface temperature changes in Northern Iberia since 4000 yr BP, based on d13C of speleothems
Glob. Planet. Chang.
Full vector model for magnetization in sediments
Earth Planet. Sci. Lett.
The Medieval Climate Anomaly in the Iberian Peninsula reconstructed from marine and lake records
Quat. Sci. Rev.
Holocene alluvial morphopedosedimentary record and environmental changes in the Bardenas Reales Natural Park (NE Spain)
Catena
Detrital magnetizations from redeposition experiments of different natural sediments
Earth Planet. Sci. Lett.
Comparison of U–Th, paleomagnetism, and cosmogenic burial methods for dating caves: implications for landscape evolution studies
Earth Planet. Sci. Lett.
Late Pleistocene and Holocene alluvial archives in the Southwestern Mediterranean: changes in fluvial dynamics and past human response
Quat. Int.
La cueva de Seso (Boltaña, Huesca): aproximación geomorfológica y espeleogénesis holocena
El papel del piping en la espeleogénesis del sistema endokárstico de Seso (Pirineo central, Huesca)
Geogaceta
Flexible paleoclimate age–depth models using an autoregressive gamma process
Bayesian Anal.
Magnetostratigraphy of cave sediments: application and limits
Stud. Geophys. Geod.
Lithofacies and transport of clastic sediments in karstic aquifers
Alluvial fans and near surface subsidence in Western Fresno County, California
U. S. Geol. Surv. Prof. Pap.
Paleomagnetism: Magnetic Domains to Geologic Terranes
Paleomagnetic dating of cave paintings in Tito Bustillo Cave, Asturias, Spain
Sci. New Ser.
Secular oscillations of geomagnetic-field recorded by sediments deposited in caves in mediterranean region
Geophys. J. R. Astron. Soc.
Remasoft 3.0 a user-friendly paleomagnetic data browser and analyzer
Trav. Géophys.
Late Brunhes polarity excursions (Mono Lake, Laschamp, Iceland Basin and Pringle Falls) recorded at ODP Site 919 (Irminger Basin)
Earth Planet. Sci. Lett.
Database for Holocene geomagnetic intensity information
EOS Trans. Am. Geophys. Union
Cited by (5)
Effects of glaciation on karst hydrology and sedimentology during the Last Glacial Cycle: The case of Granito cave, Central Pyrenees (Spain)
2021, CatenaCitation Excerpt :In the Pyrenees, clastic deposits in caves are common but there have been few sedimentological studies. Previous studies on cave sediments in the Pyrenees include the pioneer work of Robert, (1981) highlighting the variety and singularity of the clastic sediments in the Granito cave, Oliva-Urcia et al., (2014) in Seso cave, Quinif and Maire, (1998) in the Northwestern Pyrenees, and, more recently, by Aranburu et al., (2015) and Arriolabengoa et al., (2018, 2020) in the southwestern Pyrenees. To analyse and interpret the sedimentary fill of the Granito cave we integrated: 1) the geomorphic mapping of the surroundings of the cave, with emphasis on glacial sediments in the Ara River valley, to identify the clastic sediment source to the cave; 2) a detailed sedimentological and geochemical characterization of cave deposits (speleothems and detritic sequences) together with their chronology associated to landscape and environmental changes.
Reconstructing the sedimentary history of Lezetxiki II cave (Basque Country, northern Iberian Peninsula) using micromorphological analysis
2018, Sedimentary GeologyCitation Excerpt :We therefore deduce that these deposits could have formed from inwash events, when part of the soil in the surroundings areas was eroded and transported into the cave through small entrances or shaft drains (Bosch and White, 2007). This type of process is more common during periods of low vegetation cover, when soil erosion is greater and materials can be remobilised (Courty and Vallverdú, 2001; Oliva-Urcia et al., 2014). The flow responsible for this could also have been hyperconcentrated in sediment, resulting in poor sorting of the microfabric (Courty and Vallverdú, 2001; Oliva-Urcia et al., 2014).
Upper pleistocene interstratal piping-cave speleogenesis: The seso cave system (central pyrenees, northern spain)
2015, GeomorphologyCitation Excerpt :Calcite growth occurs today in SCS as indicated by the active precipitation on artificial substrates revealed by an ongoing cave monitoring survey. The main morphological feature observed in the lower gallery (Fig. 3B) is a more than 2.4 m thick Late Holocene layered sedimentary deposit (Bartolomé et al., 2013; Oliva-Urcia et al., 2014). It is composed of autochthonous lutites coming from erosion of the hosting marl and deposited in pond cave environments, and allochthonous lutites and sands derived from soil and external weathered marls introduced into the cave by runoff and streams related to rainfall episodes.
Fossil remains in karst and their role in reconstructing Quaternary paleoclimates and paleoenvironments
2014, Quaternary InternationalMagnetic fabric and archaeomagnetic analyses of anthropogenic ash horizons in a cave sediment succession (Crvena Stijena site, Montenegro)
2021, Geophysical Journal International
- 1
Tel.: + 34 976369393x880056; fax: + 34 976 716 019.