Mineralogical data on bat guano deposits from three Romanian caves

Mineralogical studies performed on crusts, nodules and earthy masses from the Romanian caves Gaura cu Muscă, Gaura Haiducească and Peștera Zidită have revealed the presence of three different phosphate associations. The minerals have been identified by means of X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Five phosphates have been identified in the samples, with hydroxylapatite the only common mineral in all the three caves. Brushite, taranakite, leucophosphite and variscite are the other phosphates identified. Associated minerals include gypsum, calcite, quartz and illite-group minerals. Aside from differences in the lithology, the occurrences of the different phosphate minerals indicate variable pH and humidity conditions near or within the guano accumulations

Mineralogy of Iza Cave (Rodnei Mountains, N. Romania)

The secondary minerals from Iza Cave result from the interactions of karst water and/or cave atmosphere over a variety of sedimentary and metamorphic rocks. The cave passages expose at various extents Eocene limestones and conglomerates, Oligocene black shales, Upper Precambrian micaschists, marble and dolomitic marble and associated ore deposits. Twelve secondary minerals identified in the cave (carbonates, sulfates, phosphates, oxides and hydroxides, and silicates) are presented in this study. Calcite, aragonite, gypsum, brushite and hydroxylapatite are the components of common speleothems in the limestone, dolomite and conglomerate areas of the cave. Ankerite crusts are related to areas with pyrite mineralization within the metamorphic carbonate rocks. Goethite, jarosite, hematite and gypsum form various speleothems in the sectors within micaschists and conglomerates. Large weathering deposits occurring in passage areas developed within micaschists consist of illite, kaolinite, jarosite, goethite, gypsum and alunite. The extent of the weathering deposits occurring on non-karst rocks in the underground environment makes this cave a particularly interesting site for studies of water-rock interactions

A radiocarbon dated bat guano deposit from N.W. Romania: Implications for the timing of the Little Ice Age and Medieval Climate Anomaly

There is considerable interest in the potential of bat guano as an alternative record of palaeoclimate in regions that are devoid of more commonly utilised archives. In this study, designed originally to evaluate the potential of cave hosted bat guano to preserve temporal variations in the flux of cosmogenic 36Cl, it was found that the guano depositional history is strongly linked to climatic conditions. Radiocarbon measurements on a 2.7 metre long core of bat guano from Măgurici Cave, N.W. Romania indicate a maximum depositional age of 1195 AD for the base of the core. Deposition of the lowermost portion of the accumulation occurred during the Medieval Climate Anomaly. The cave roost was subsequently devoid of bats during a regional cold phase linked to the Little Ice Age, with bats returning when local temperatures increased. The rate of guano accumulation then appears to increase in tandem with anthropogenic warming. This indicates that bat occupation at this roost site in Măgurici Cave is strongly linked to regional climate variability, with habitation during warm periods, possibly associated with the abundance of insects upon which the bats feed. Comparison of large peaks in anthropogenic 14C and 36Cl production associated with nuclear weapons testing indicates downward migration of 36Cl, probably reflecting post-depositional migration within the guano deposit. Elevated 36Cl/Cl at the top of the core in comparison with modern atmospheric values may indicate recycling of bomb 36Cl in vegetation. Therefore, we show that while bat guano contains abundant atmospherically-derived chloride it has severe limitations as a potential archive of atmospherically-derived 36Cl (a solar proxy), because of post-depositional mobility. However, separation of organically bound chloride, or the use of an alternative cosmogenic isotope 10Be, in bat guano, may offer an unexploited solar proxy that contains contemporaneous environmental signals, such as stable isotopes (e.g. δ13C) and pollen, in association with radiocarbon dating

Lateglacial-Middle Holocene Stable Isotope Records in Two Coeval Stalagmites from the Bihor Mountains, NW Romania

Oxygen and carbon stable isotope records of two stalagmites from NW Romania provide a continuous climatic record between 14.8 and 5.6 ka BP. The chronology is established by 21 TIMS uranium series ages. Uncertainties in the isotope chronology range between ±20 and ±100 yr. The d18 O values are positively correlated with temperature, whereas d13 C fluctuations suggest changes in soil CO2 production. Lateglacial deposition of both stalagmites started at ~14.8 ka BP. The d18 O records subsequently show a slow decline in temperatures until 12.6 ka BP. Three warmer periods with increased soil productivity occurred at 14.5-13.9 ka BP, 13.6-13.2 ka BP, and 12.9-12.6 ka BP. Lower d18 O and high d13 C values between 12.6 and 11.4 (11.7) ka BP indicate a cold and dry climate during the Younger Dryas (GS-1). During the Early Holocene, three short cold intervals are marked on the d18 O profiles at 11.0-10.6, 10.5-10.2 and 9.4-9.1 ka BP. For the remainder of the Holocene sequence, the d18 O records show less variation between 9 and 7.8 ka BP and gradual warming from 7.6-5.6 ka BP. The speleothem records correlate with the Greenland ice core records and with other proxies throughout Europe and the North Atlantic region

Palaeoenvironmental information from the palynology of an 800 year old bat guano deposit from Măgurici Cave, NW Transylvania (Romania)

Pollen analysis of a 270 cm deep guano deposit from Măgurici Cave (NW Romania) was performed to understand the vegetation dynamics and the influence of deforestation and farming activities that unfolded in the Transylvania area over the past 800 years. The study discusses the value of cave guano as a source of palaeoclimate data and tests if guano sequences record the same signals as other proxies (tree rings, speleothems, lakes or peat). The pollen record extracted from Măgurici Cave guano is consistent with the known vegetation history during the Late Subatlantic period, exhibiting two climate events: the Medieval Climate Anomaly and the Little Ice Age. Human influence on vegetation is also revealed, especially in modern times, by the decrease of arboreal pollen, the increase of herbaceous taxa related to grazing and the occurrences of cereals. Cave bat guano is emphasized as a source of valuable palaeoclimate data, especially in areas where no conventional archives are available

Lateglacial-Middle Holocene Stable Isotope Records in Two Coeval Stalagmites from the Bihor Mountains, NW Romania

Oxygen and carbon stable isotope records of two stalagmites from NW Romania provide a continuous climatic record between 14.8 and 5.6 ka BP. The chronology is established by 21 TIMS uranium series ages. Uncertainties in the isotope chronology range between ±20 and ±100 yr. The d18 O values are positively correlated with temperature, whereas d13 C fluctuations suggest changes in soil CO2 production. Lateglacial deposition of both stalagmites started at ~14.8 ka BP. The d18 O records subsequently show a slow decline in temperatures until 12.6 ka BP. Three warmer periods with increased soil productivity occurred at 14.5-13.9 ka BP, 13.6-13.2 ka BP, and 12.9-12.6 ka BP. Lower d18 O and high d13 C values between 12.6 and 11.4 (11.7) ka BP indicate a cold and dry climate during the Younger Dryas (GS-1). During the Early Holocene, three short cold intervals are marked on the d18 O profiles at 11.0-10.6, 10.5-10.2 and 9.4-9.1 ka BP. For the remainder of the Holocene sequence, the d18 O records show less variation between 9 and 7.8 ka BP and gradual warming from 7.6-5.6 ka BP. The speleothem records correlate with the Greenland ice core records and with other proxies throughout Europe and the North Atlantic region