Insights into speleothems from lava tubes of the Galapagos Islands (Ecuador): mineralogy and biogenecity

Different types of hard and soft speleothems (stalactites, stalagmites, columns, crusts, flowstones, micro-gours and botryoidal coralloids) have been observed throughout lava tubes in the Galapagos archipelago, Ecuador. Three lava tubes were studied in this work: Gallardo and Royal Palm volcanic caves (Santa Cruz Island) and Sucre Cave (Isabela Island). The studied speleothems were mainly formed by opal, calcite and clay minerals, including plagioclase and pyroxenes from the basaltic host rock. Rarely, iron oxides, gypsum were found in some speleothems, which were interpreted as alteration products of the primary volcanic materials. Field emission scanning electron microscopy revealed abundant filamentous 17th International Vulcanspeleology Symposium 2 bacteria, and reticulated filaments similar to those recently observed in others lava tubes around the world. These filaments are associated with EPS and mineral deposits rich in Si, Ca or Fe. The identified minerals and the evidence of biosignatures suggest a biological contribution to speleothem development within Gallardo, Royal Palm and Sucre lava tubes

Bunker Cave stalagmites: an archive for central European Holocene climate variability

Holocene climate was characterised by variability on multi-centennial to multi-decadal time scales. In central Europe, these fluctuations were most pronounced during winter. Here we present a record of past winter climate variability for the last 10.8 ka based on four speleothems from Bunker Cave, western Germany. Due to its central European location, the cave site is particularly well suited to record changes in precipitation and temperature in response to changes in the North Atlantic realm. We present high-resolution records of δ18O, δ13C values and Mg/Ca ratios. Changes in the Mg/Ca ratio are attributed to past meteoric precipitation variability. The stable C isotope composition of the speleothems most likely reflects changes in vegetation and precipitation, and variations in the δ18O signal are interpreted as variations in meteoric precipitation and temperature. We found cold and dry periods between 8 and 7 ka, 6.5 and 5.5 ka, 4 and 3 ka as well as between 0.7 and 0.2 ka. The proxy signals in the Bunker Cave stalagmites compare well with other isotope records and, thus, seem representative for central European Holocene climate variability. The prominent 8.2 ka event and the Little Ice Age cold events are both recorded in the Bunker Cave record. However, these events show a contrasting relationship between climate and δ18O, which is explained by different causes underlying the two climate anomalies. Whereas the Little Ice Age is attributed to a pronounced negative phase of the North Atlantic Oscillation, the 8.2 ka event was triggered by cooler conditions in the North Atlantic due to a slowdown of the thermohaline circulation

The ribbed drapery of the Puerto Princesa Underground River (Palawan, Philippines): morphology and genesis

During the 2011 speleological expedition to the Puerto Princesa Underground River (Palawan, Philippines) a drapery characterized by several close-to-horizontal ribs has been noticed. Even without sampling and analyzing its internal growth layers, a detailed morphological study allowed to present a possible genetic model. The presented model helps to explain its evolution, which is mainly controlled by variation in water flow as a consequence of the Palawan climate. When validated by further analyses, the same genetic mechanism could define also the evolution of the very common but still unexplained complex flowstones, which exhibit several close-to-horizontal steps, widenings and narrowings along their growth axis

Direct specific isotopic analysis of compounds released by pyrolysis (Py-CSIA): Novel applications in paleoenvironmental studies

Poster J.03 presentado en el The 40th International Symposium on Capillary Chromatography and 13th GCxGC Symposium May 29-June 03, (2016) Riva del Garda Fierecongressi, Riva del Garda, Italyisotopic analysis (Py-CSIA) and analytical pyrolysis (Py-GC/MS) opens new windows of information and is particularly useful to study solid materials that are not soluble and therefore not amenable by conventional GC/MS techniques. Py-CSIA is a rather novel hyphenated technique that combines the chromatographic separation of compounds released by pyrolysis (Py-GC) with an isotope ratio mass spectrometer (IRMS). The technique allows the measurement of stable isotope proportions i.e., δ13C, δ15N and δ2H, δ18O in specific compounds released by pyrolysis. The sample preparation is minimized and a molecular fingerprinting of the material is achieved.N

First data on testate amoebae in speleothems of caves in igneous rocks

[Abstract] The testate amoebae form part of the habitual troglobios in caves developed in igneous rocks (plutonic and volcanic) where the little light, the persistence of humidity, the availability of silica and organic matter allow these protozoa to develop their biological cycle. This work presents a first inventory of species of amoebae testate identified in caves in igneous rocks from different parts of the World

Organic geochemistry and mineralogy suggest anthropogenic impact in speleothem chemistry from volcanic show caves of the Galapagos

The network of lava tubes is one of the most unexploited natural wonders of the Galapagos Islands. Here, we provide the first morphological, mineralogical, and biogeochemical assessment of speleothems from volcanic caves of the Galapagos to understand their structure, composition, and origin, as well as to identify organic molecules preserved in speleothems. Mineralogical analyses revealed that moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves were composed of calcite, opal-A, and minor amounts of clay minerals. Extracellular polymeric substances, fossilized bacteria, silica microspheres, and cell imprints on siliceous minerals evidenced microbe-mineral interactions and biologically-mediated silica precipitation. Alternating depositional layers between siliceous and carbonate minerals and the detection of biomarkers of surface vegetation and anthropogenic stressors indicated environmental and anthropogenic changes (agriculture, human waste, and cave visits) on these unique underground resources. Stable isotope analysis and Py-GC/MS were key to robustly identify biomarkers, allowing for implementation of future protection policies

Multitechnique characterization of secondary minerals near HI-SEAS, Hawaii, as Martian subsurface analogues

Secondary minerals in lava tubes on Earth provide valuable insight into subsurface processes and the preservation of biosignatures on Mars. Inside lava tubes near the Hawaii-Space Exploration and Analog Simulation (HI-SEAS) habitat on the northeast flank of Mauna Loa, Hawaii, a variety of secondary deposits with distinct morphologies were observed consisting of mainly sodium sulphate powders, gypsum crystalline crusts, and small coralloid speleothems that comprise opal and calcite layers. These secondary deposits formed as a result of hydrological processes shortly after the formation and cooling of the lava tubes and are preserved over long periods of time in relatively dry conditions. The coralloid speleothem layers are likely related to wet and dry periods in which opal and calcite precipitates in cycles. Potential biosignatures seem to have been preserved in the form of porous stromatolite-like layers within the coralloid speleothems. Similar secondary deposits and lava tubes have been observed abundantly on the Martian surface suggesting similar formation mechanisms compared to this study. The origin of secondary minerals from tholeiitic basalts together with potential evidence for microbial processes make the lava tubes near HI-SEAS a relevant analog for Martian surface and subsurface environments.</p