Black Mn-Fe Crusts as Markers of Abrupt Palaeoenvironmental Changes in El Soplao Cave (Cantabria, Spain)

Gázquez, Fernando; Calaforra, J. M.; Forti, Paolo

doi:10.5038/1827-806x.40.2.8

Cited by 31 publications

(32 citation statements)

References 16 publications

(8 reference statements)

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“…Sometimes they form the base of speleothems, but they occasionally form part of stalactites, stalagmites or flowstones (Hill & Forti, 1997). "Fossilized" layers of Fe and Mn oxides inside other speleothems have only been described in a few studies (Peck, 1986;Gázquez et al, 2011).…”

Section: Metallic Oxides Precipitation As Solid Inclusionsmentioning

confidence: 99%

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Gypsum-carbonate speleothems from Cueva de las Espadas (Naica mine, Mexico): mineralogy and palaeohydrogeological implications

Gázquez¹,

Calaforra²,

Forti³

et al. 2012

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Some of the most outstanding hypogenic gypsum speleothems worldwide have been recently discovered in the Naica mines. The Cueva de las Espadas (Swords Cave), which lies at 120 m depth, hosts a rare type of speleothem called "espada" ("sword"). This study contributes to the understanding of the mineralogical composition of these singular speleothems, by means of their examination using micro-Raman spectroscopy, FT-IR spectroscopy and EDX microprobe. Our data revealed a complex mineralogy comprising a high-purity selenite core covered by several layers of calcite, aragonite and gypsum. Solid inclusions of polymetallic oxides (Mn-Pb-Zn) and graphite were also detected. The position of the water table during the genesis of the "espada" speleothems (over the past 60 kyr) was deduced from their mineralogy. Water level fluctuations at around -120 m depth led to environmental changes within the Cueva de las Espadas. The selenite core and gypsum layers were precipitated under biphasic (water-rock) conditions when the cave was submerged under hydrothermal water. The aragonite precipitation required triphasic (air-water-rock) conditions and occurred when the water table intercepted the cave, allowing the CO 2 exchange necessary for carbonate precipitation. Solid inclusions were trapped in an aerobic environment when the gypsum-aragonite boundary condition occurred. A thin calcite layer was precipitated under vadose conditions after the water table definitively moved out of the cave.

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Section: Metallic Oxides Precipitation As Solid Inclusionsmentioning

confidence: 99%

“…Over recent years, the mineralogy, morphology and genesis of this kind of speleothem has been studied in a variety of caves (Onac, 1996;Onac et al, 1997;White et al, 2009;Gázquez et al, 2011). Manganese oxides usually occur in caves as black crusts on the walls and floors.…”

Section: Metallic Oxides Precipitation As Solid Inclusionsmentioning

confidence: 99%

Gypsum-carbonate speleothems from Cueva de las Espadas (Naica mine, Mexico): mineralogy and palaeohydrogeological implications

Gázquez¹,

Calaforra²,

Forti³

et al. 2012

IJS

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“…Spectacular helictites and huge speleothems are the most relevant aesthetic features of this mining show-cave [12]. Other unusual speleothems have also been described, including amberine stalactites [13], flowstones containing layers of cemented detrital materials [14], black ferromanganese crusts and stromatolites [15,16], frostwork-type speleothems and moonmilk deposits [17], some of which were studied in our in situ survey.…”

Section: El Soplao Cavementioning

confidence: 96%

“…6) can be assigned to birnessite, which is a rather common mineral in subterranean environments [27,28]. The precipitation of this metal oxide in the El Soplao Cave is related to the mobilization of manganese from the host rock probably under phreatic anaerobic conditions and subsequent precipitation on the walls and floors of the cave as oxides when the water table fell and conditions were again oxygenic [15]. The oxidation of manganese was probably mediated by microorganisms (as suggested by the presence of fossil bacteria inside ferromanganese speleothems discovered in this cave in previous studies [16]).…”

Section: El Soplao Cavementioning

confidence: 99%

In situ Raman characterization of minerals and degradation processes in a variety of cultural and geological heritage sites

Gázquez

Rull

Sanz-Arranz

et al. 2017

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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We test the capabilities of in situ Raman spectroscopy for non-destructive analysis of degradation processes in invaluable masterpieces, as well as for the characterization of minerals and prehistoric rock-art in caves. To this end, we have studied the mechanism of decay suffered by the 15th-century limestone sculptures that decorate the retro-choir of Burgos Cathedral (N Spain). In situ Raman probe detected hydrated sulfate and nitrate minerals on the sculptures, which are responsible for the decay of the original limestone. In addition, in situ Raman analyses were performed on unique speleothems in El Soplao Cave (Cantabria, N Spain) and in the Gruta de las Maravillas (Aracena, SW Spain). Unusual cave minerals were detected in El Soplao Cave, such as hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O), as well as ferromanganese oxides in the black biogenic speleothems recently discovered in this cavern. In the Gruta de las Maravillas, gypsum (CaSO 4 ·2H 2 O) was identified for the first time, as part of the oldest cave materials, so providing additional evidence of hypogenic mechanisms that occurred in this cave during earlier stages of its formation. Finally, we present preliminary analyses of several cave paintings in the renowned "Polychrome Hall" of Altamira Cave (Cantabria, N. Spain). Hematite (Fe 2 O 3 ) is the most abundant mineral phase, which provides the characteristic ochre-reddish color to the Altamira bison and deer paintings. Thus, portable Raman spectroscopy is demonstrated to be an analytical technique compatible with preserving our cultural and natural heritage, since the analysis does not require physical contact between the Raman head and the analyzed items.

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“…Earlier known as psilomelan (now an obsolete term), romanèchite is a barium-containing manganese oxide, commonly occurring in caves in the composition of soft or hard dark brown to black ferromanganese coatings, crusts, nodules, and earthy deposits (Hill & Forti, 1997;Onac et al, 1997;White et al, 2009;Gázquez et al, 2011). The sample analyzed (VL-M05) was collected near the end of the Galeria d'en Pau, where it occurs as black earthy masses.…”

Section: Romanèchitementioning

confidence: 99%

Linking mineral deposits to speleogenetic processes in Cova des Pas de Vallgornera (Mallorca, Spain)

Onac¹,

Fornós²,

Merino³

et al. 2014

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Black Mn-Fe Crusts as Markers of Abrupt Palaeoenvironmental Changes in El Soplao Cave (Cantabria, Spain)

Cited by 31 publications

References 16 publications

Gypsum-carbonate speleothems from Cueva de las Espadas (Naica mine, Mexico): mineralogy and palaeohydrogeological implications

Gypsum-carbonate speleothems from Cueva de las Espadas (Naica mine, Mexico): mineralogy and palaeohydrogeological implications

In situ Raman characterization of minerals and degradation processes in a variety of cultural and geological heritage sites

Linking mineral deposits to speleogenetic processes in Cova des Pas de Vallgornera (Mallorca, Spain)

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