Tufa Layers Research Articles

Pleistocene freshwater ostracods from the Homo erectus site at Bilzingsleben, Germany—Review of historic collection and unpublished manuscript material for palaeoenvironmental reconstruction

AbstractWe provide a review of micropalaeontological research on Ostracoda from the Middle Pleistocene (MIS 11, Holstein interglacial) hominin site Bilzingsleben in Thuringia in Central Germany from 1963 to the 1990s. Samples from four sections inside and six search pits outside the excavation area were investigated and, in total, 49 ostracod species were identified. The ostracod assemblages of the sections mirror the complex and small‐scale palaeoenvironmental evolution of the site from a seeping‐spring to fluviatile, lacustrine and finally seeping‐spring habitat in which a massive tufa layer formed and prevented erosion of the sediments beneath. Pleistocene index fossils are represented by Ilyocypris quinculminata from search pit 3/sample 9933 and Scottia browniana from section 70. Both species indicate the age dating of MIS 11 for the tufa deposit. The results of this study facilitate new insights into site formation processes, enable refinement of the interpretation of the archaeological record and shed light on the question: Does the find‐bearing layer at the Bilzingsleben site contain in situ remains of a camp site of Homo erectus or not? Our results suggest that the site is not unaffected at least.

Insights into Alpine-Karst-Type Tufa Deposits in Geological Environmental Records: A Case Study of the Calcareous Tufa Profile of the Jiuzhaigou Natural Reserve on the Eastern Margin of the Tibetan Plateau

To study the geological environmental records of alpine-karst-type tufa deposits in the eastern margin of the Tibetan Plateau, the calcareous tufa profile exposed by the “8.8” Jiuzhaigou earthquake was taken as the research object and combined with a field geological investigation. Further, the petrography, sedimentology, chronology, and elemental geochemistry of the calcareous tufa were studied and analyzed. The results show the following. (1) The Sparkling Lake calcareous tufa profile was deposited under the background of a warm and humid climate during the Holocene. The growth pattern follows a bottom-to-top deposition. (2) At 750 ± 30–300 ± 30 aB.P., the calcareous tufa layers were gray-black as a whole, and the changes in mineral composition and elemental geochemistry indicate a fluctuating upward trend for temperature and precipitation during this period. (3) The formation of two sets of black peat layers in the upper part of the tufa calcareous profile is due to the synergistic action of multiple factors caused by strong tectonic activity. In conclusion, the deposition mechanism of the calcareous tufa in Jiuzhaigou was controlled by paleoclimate hydrology and glaciation for a long time, while strong tectonic activity over a short period of time considerably changed the color, structure, element content, and mineral composition of the calcareous tufa.

Non-Linear Clumped Isotopes from DIC Endmember Mixing and Kinetic Isotope Fractionation in High pH Anthropogenic Tufa

Clumped isotope values (Δ47) of carbonates forming in high pH conditions do not correspond to mineral precipitation temperatures due to certain effects including kinetic isotope fractionation and dissolved inorganic carbon (DIC) endmember mixing. Field-based archives of these carbonate environments are needed to evaluate and quantify these effects accurately. In this study, we measure the clumped isotope values of anthropogenic carbonates for the first time. Tufa layers were analyzed from samples precipitating in a high pH (>10) stream that drains a major slag heap in north east England. Δ47 values are 0.044‰–0.183‰ higher than expected equilibrium values. Non-linear distribution of clumped isotope data is diagnostic of DIC endmember mixing, rather than partial equilibration of DIC. Episodic dilution of hydroxide-rich stream waters by equilibrated rainfall surface runoff provides the mechanism by which mixing occurs. Δ47 values are ~0.010‰–0.145‰ higher than linear clumped isotope mixing profiles, suggesting that the majority of Δ47 increase results from a combination of endmember non-linear mixing effects and an atmosphere-hydroxide sourcing of DIC. The diagnostic trends and variation in clumped isotope values present in these results demonstrates the potential of anthropogenic carbonate systems as a useful archive for studying and quantifying kinetic effects in clumped isotopes.

Early and mid-Holocene hydroclimate change recorded in tufa deposits in the Jiuzhaigou gully, eastern Tibetan Plateau

Rhythmic nature of tufa deposits and analysis of hydrochemical proxies offer the potential to reconstruct the history of regional palaeo-hydrological and palaeo-climatic change. This paper investigates the tufa deposits of Sparkling Lake in the Jiuzhaigou gully of the eastern Tibetan Plateau (ETP). Detailed analysis of mineral composition, major elements and stable isotope (δ13C, δ18O) distinguished seven “dirty tufa layers” that are characterized by quartz-rich sediments, high kaolinite and high K, Na and Al. Compared with clean tufa deposits, dirty components in the tufa deposits were a result of surface soil erosion activity during strong monsoon rainfall periods within the catchment. The chronology of tufa deposits is established by using radiocarbon (14C) dating of organic material from the dirty tufa layers. Seven flood-rich periods and eight flood-poor periods during the early and mid-Holocene were recorded by the dirty tufa layers interbedded with clean tufa layers in the Jiuzhaigou gully. The tufa records are more sensitive response to regional hydroclimate change, in comparison with the peat, lake sediments and stalagmite records. The low values of δ18O and δ13C in the dirty tufa layers indicate the flood-rich periods (10310–8390, 7120, 6910, 6340, 5900, 5620, 5020 a BP) were mainly triggered by strong monsoon rainfall events during early and mid-Holocene. Considering the chronological uncertainties and sampling resolution, some other abrupt climate events (i.e, 8200 a BP and 5500 a BP) may be also recorded in the tufa deposits. These results greatly improve our understanding of hydroclimate change in the ETP during the early and mid-Holocene.

Giant tufas of Lake Van record lake-level fluctuations and climatic changes in eastern Anatolia,Turkey

Lake Van, the largest soda lake in the world, is a key area where climatic changes are recorded by well-preserved sedimentary successions. In spite of the existence of such sequences, the ancient lake levels are still under debate. Here, we present U/Th ages of tufa layers exposed along the northern margin of the lake near the town of Adilcevaz. Tufa are interpreted to form during humid and temperate climate conditions in the contact zone between the highly alkaline lake water – rich in bicarbonate and carbonate ions – and calcium-rich groundwater. These contact zones most likely appear near shore. Thus, U/Th ages and altitude of the tufa present minimum ancient lakestands. The tufas obtained in our study are dated between 112.7 and 19.3 ka. They are interpreted to record two transgressional intervals, the first starting at 1701 meters above sea level (masl) altitude at 112.7 ka reaching 1706 masl at 72.5 ka (based on three U/Th ages). The second transgression starts at the present Lake Van level of 1646 masl at 30.1 ka, reaching 1725 masl at 19.3 ka (based on 15 U/Th ages). Comparison with climate proxies reveals that the first transgression was caused by intensified precipitation accompanied by warming, while the second transgression was triggered mainly by warming that initiated melting of glaciers. The lake-level fluctuations described here are almost in line with the ones gathered from dated lake terraces but contradict lake-level reconstruction based on pore water salinity.

Geomorphological and geophysical investigations for the characterization of the Roman Carsulae site (Tiber basin, Central Italy)

This paper aims to bring to light the possible linkage between karstic phenomena and the human occupation of the Roman site of Carsulae (Tiber basin, Central Italy). Dolines are a typical morphological expression of karst rocks' dissolution and collapse and, usually, they represent a potential hazard for human activities and, in particular, in the care and maintenance of cultural heritage sites. In this study, we observed that the development of a subsidence doline caused severe damage to some archaeological structures at the Carsulae monumental site. According to the results obtained in our investigation, three sites at least with karst dissolution phenomena in the shallow calcareous tufa layer have been identified. One of them subsided probably in Roman times and produced a sharp deformation of the decumanus. In order to understand the evolution of this territory an integrated geomorphological and geophysical survey was carried out. The combination between the information derived from different geophysical techniques, such as: Electrical Resistivity Tomography (ERT), Frequency-Domain Electromagnetism (FDEM), and Ground Penetrating Radar (GPR) clearly pointed out that the calcareous tufa layer is characterized by an irregular geometry and this resulted in the investigated area being affected by karst dissolution in several parts.Four boreholes opportunely located, provided direct information about the depth and the alteration of the calcareous tufa basement and precious calibration data for the geophysical methods.This study contributes to improving our knowledge on the evolution of the Carsulae archaeological site providing a new insight into the adaptation of ancient human societies in this problematic territory.

Distribution of rotifers and other meiofauna in the bryophytes and hyporheic zone of a karst hydrosystem – an example of a nested community

The meiofauna assemblages inhabiting the bryophyte-covered tufa barriers were investigated in the barrage system of Plitvice Lakes (Croatia). The main aims of the present study were: (1) to analyse the structure of the rotifer community and other meiofaunal communities in the bryophytes and the hyporheic tufa zone; and (2) to determine the influence of food sources on the meiofauna. Our results indicate that meiofauna were a constant and abundant component in bryophytes and tufa. Of the nine identified groups (Catenulida, Gastrotricha, Nematoda, Rotifera, Hydrachnidia, Oligochaeta, Copepoda, Tardigrada and Chironomidae (Diptera)), rotifers (50%) and nematodes (40%) were most abundant. Rotifers were the most diverse meiofaunal group and reached their highest numbers within the bryophytes. Also, the highest amount of ultrafine particulate organic matter, as a potential food source for rotifers, was recorded in this layer. Nematodes were the dominant meiofaunal group in deeper tufa layers. They are an omnivorous trophic group and different food sources (such as phytal remains or other meiofauna) were available in tufa layers. Meiofaunal assemblages were significantly nested and their composition was under the influence of community established in surface bryophyte mats. Information on these often overlooked faunal groups is essential for estimates of overall abundance, species richness and productivity in freshwater ecosystems.

Geochemistry of deposits from spring-fed fens in West Pomerania (Poland) and its significance for palaeoenvironmental reconstruction

The cupolas of the spring-fed fens at Bobolice and Ogartowo (West Pomerania, Northern Poland) are composed of alternating peat and calcareous tufa layers. The geology of those two fens, together with the geochemistry of their deposits and radiocarbon dating results, made it possible: (1) to determine the source of water and mineral matter, and (2) to reconstruct the main stages in their development. The distinguished five main stages of development of the fens (four at Ogartowo) reflected varying depositional environments resulting, among other things, from the proportion of groundwater supply and its physico-chemical properties. On the basis of principal components analysis, the sources supplying elements of the peat-tufa rhythmite were found to be chemical denudation and sedentation of peat deposits, while mechanical denudation and atmospheric supply were considerably less important. The geochemistry of deposits was also influenced by local conditions of the geochemical environment, such as its pH, redox potential, CO2 content in water, and the occurrence of organic matter.

A combined geological, hydrochemical, and geophysical approach to understanding a disease contamination hazard in groundwaters at a state fish hatchery

At the Midway, Utah, USA fish hatchery, a groundwater development program was conducted to help transition the facility from surface to groundwater in response to contamination by whirling disease, which is caused by a trout parasite. The unconfined aquifer system that provided the hatchery water became infected through the recharge of infected irrigation water obtained from the Provo River. Whirling disease was first discovered in Utah in 1991 at a private fish farm. Infected fish from the farm quickly infected many of Utah’s waterways and infected the hatchery in 2000. Because the parasite completes its life cycle in multiple organisms and can survive for decades in a variety of harsh environments, a comprehensive study of the hydrostratigraphy and hydrodynamics at the hatchery was critical in order to understand the hazard and avoid further contamination. Drilling revealed the presence of a shallow unconfined (surface to 10 m) and two deeper confined aquifer systems (~20–35 m and >40 m bgs). Confinement is related to tufa layers, detected both by drilling and reflection seismology. The tufa layers are associated with past discharge of the thermal system. Vertical leakage is apparent from upward hydraulic head gradients and incrementally increasing unconfined aquifer discharge into downstream on-site drainage canals. High-resolution seismic profiles reveal small-offset faults that provide pathways for upward flow. Analysis of water quality data demonstrates an inverted geochemical gradient in that apparent 14C ages, solute concentrations, and temperatures decrease with depth. The origin of the inverted geochemical gradient is related to mixing of upwelling thermal, high-TDS waters with cold, low-TDS systems several kilometers up-gradient from the hatchery. Thermal upwelling appears to be fault controlled. Up-gradient of the hatchery, near-surface groundwater mixes with a larger proportion of thermal groundwater than does deeper groundwater. As these mixed systems flow toward the hatchery, a major locus of groundwater discharge, they are segregated into confined and unconfined compartments. Our study requires integration of hydrological, geochemical, and geophysical strategies in order to understand a complex natural hazard and thus may serve as a model for other similarly complex hydrological environments.

Geologic and hydrogeologic factors affecting sinkhole (obruk) development in Central Turkey

Konya region is located near Tuzgolu (salt lake) in the center of Turkey. The surface of the study area which is between Cumra-Karapinar and Aksaray-Sultanhani-Obruk plains in the Konya region is 2,100 km2. Obruk landforms are concentrated in a 100 km2 section of the study area which contains approximately 50 obruks. The climate is typically continental and annual average precipitation varies between 314.2 mm/year in Sultanhani, 298.4 mm/year in Karapinar, and 333 mm/year in Besagil. Evaporation value is 1,444 mm/year. In the study area, agricultural activities are carried out on 5,115 ha of land, which is irrigated from the 109 wells drilled and operated by several soil-water cooperatives. The static water levels in the wells vary between 75–91 m. Even though Karapinar and Sultanhani plains are closed basins, there is groundwater connection between them. Since the groundwater flow in this area is canalized between some lithological and tectonic barriers, the underground formations are eroded by groundwater flow moving between the limestone. Over time, dissolution occurs within the limestone formations and they eventually collapse. Generally speaking, circular obruks are formed in horizontal layers and oval ones are observed in layers with inclination. Some obruks reach the groundwater table. The main composition in the study area is, from the oldest to the youngest, Paleozoic schist–fillit–quartzite–crystallized limestone and Mesozoic ophiolites, Cenozoic limestone with pebble, marl, clay, calcite, silica, dolomites and tufa, marl layers with gypsum and salt, lacustrine limestone with tufa layers and andesite near the volcanites, sediments of clay, sand, pebble, and silt of Plioquaternary and basalt flows. Samples collected from all of the sampling stations were analyzed and hydrochemical graphs were prepared. According to hydrochemical evaluations, pH is between 7.1 and 8.2, EC is between 840 and 1,965 μmho/cm, and hardness varies between 40 and 81 FS°, and the water is classified as C3 S1 category according to US Salinity Laboratory interpretations. With respect to irrigation water criteria, the water is of good quality, but not good as drinking water. In the study, the effects of dissolved CO2 in groundwater on karstification were also investigated. Water from wells drilled at Yarimca, Acikkuyu, and Badirik plains contains large amounts of CO2. As is commonly known, those waters which contain CO2 more than 50 mg/l are considered to be corrosive and can cause dissolution of limestone. Through the preparation of topographical elevation maps of the groundwater, water level maps were drawn and the flow direction of groundwater, recharge area of groundwater, groundwater hydraulic balance and level fluctuations of the groundwater, as well as the locations of possible exploitation sites were determined.

Spatial Bacterial Diversity in a Recent Freshwater Tufa Deposit

16S ribosomal RNA gene clone libraries were generated to assess the prokaryotic diversity within a laminated tufa stromatolite core, obtained from the hardwater rivulet Westerhöfer Bach, Lower Saxony, Germany. Libraries were obtained from the biofilm and six tufa layers, each about 4 to 8 mm thick and 2,351 partial sequences were analyzed. Cyanobacteria and other aerobic organisms dominated the 500 μ m thick biofilm and the first layer, represented by 112 and 154 phylotypes, respectively. DGGE and UniFrac analyses revealed that these two layers were clearly separated from the deeper layers which showed a higher diversity than the tufa surface with less than 350 phylotypes. The species richness of deeper layers was dominated by a broad range of phyla, predominantly of acidobacterial, bacteroidetes and alpha-, beta- and gammaproteobacterial phylotypes. In total, sequences belonging to 26 phyla were detected. Sequences related to anaerobes, including photosynthetic Proteobacteria, are present in low numbers in the deeper layers but their metabolic activities in the dark and water-aerated core remain unclear.

Late Holocene water level fluctuations of Lake Afourgagh (Middle-Atlas Mountains, Morocco) inferred from charophyte remains

Water level fluctuations of Lake Afourgagh (Middle-Atlas Mountains, Morocco) over the last 2500 years (Late Holocene) have been reconstructed using charophyte remains in the lake sediment archives. The study involved 22 pits (1–3 m deep) dug along a transect across the lake shore terrace. Biogenic activity appears to be a dominant contributor to the accumulation of the lake sediments, as the thickest deposits are tufas composed of charophyte-encrusted stems with numerous gyrogonites (termed “charophyte tufas”). The gyrogonites were identified as Chara aspera and Chara hispida remains. The spatial distribution of these two species, measured vertically within a single core and horizontally along the shore terrace, varies according to bathymetry. Shallow proximal environments are characterized by the development of C. aspera, whereas C. hispida remains are mostly observed in distal sediments. Moreover, according to their ecological characteristics, the C. hispida belt migrated proximally when the water level rose, whereas the C. aspera belt migrated distally when the water level fell. These trends were observed successively in a single charophyte tufa layer which records the rise, highstand, and fall of lake level in a single depositional sequence. The late Holocene palaeobathymetry of Lake Afourgagh was inferred by comparing data on charophyte remains and deposit geometry. Data provide evidence for four major low lake level phases (estimated in terms of amplitude) which induced the development of palaeosols in proximal settings at 2191 cal. BP, 1769 BP, 1515 cal. BP and 1062 cal. BP. These results confirm the accuracy of charophyte-based palaeobathymetry studies.

Oxygen isotope fractionation in three freshwater ostracod species from early Holocene lacustrine tufa in northern Estonia

We quantified differences in oxygen isotope fractionation among three biostratigraphically important subfossil ostracod species (Metacypris cordata, Pseudocandona rostrata and Candonopsis kingsleii) from an early Holocene freshwater tufa layer in northern Estonia. Estimated mean δ18O values are −10.05‰ for M. cordata, −9.34‰ for C. kingsleii and −8.75‰ for P. rostrata. All three species exhibit positive offset from the weighted mean annual δ18O of contemporary precipitation (−10.7‰ in δ18OV-PDB) and from the mean δ18O value of authigenic tufa carbonate (−10.64‰) in the ostracod-bearing layer. Assuming that the known oxygen isotope fractionation in P. rostrata (+2.5‰) and M. cordata (+1.5‰) has remained constant over time, the theoretical δ18OV-SMOW of the early Holocene lake water was calculated to have been between −11.52 and −11.92‰, slightly less negative than the local Ordovician groundwater (−11.7 to −12.2‰). δ18O values of the tufa carbonate differ by +0.6 to +1.0‰ from the calculated theoretical isotope composition (δ18OV-PDB) of lake water, indicating that the tufa also did not precipitate in isotopic equilibrium with ambient waters. Results show that the greater the δ18O offset from the calculated, theoretical isotope composition of lake water for an ostracod species, the lower is its preferred mean July temperature. Both our data and earlier published results on δ18O values in Holocene lacustrine carbonates and ostracods from north-eastern Europe, display pronounced decreases in δ18O with an increase in latitude of the study site. This suggests that temperature-dependent, and therefore latitude-dependent isotopic composition of meteoric waters controlled the δ18O values in lacustrine tufa and ostracods throughout the Holocene.

Interaction between Calcite and Phosphorus in Biomineralization Processes in Tufa Carbonates

Using electron microscopy techniques (SEM, LTSEM) coupled with analytical methods (XRD and EDS) the role of phosphorus has been assessed in the formation of freshwater calcite deposits (tufa) in a small pond of the Ruidera Lakes (Spain). Differences between the cell walls and sheaths of bacteria and eukaryotic algae as well as the existence of additional layers of extracellular polymeric substances (EPS) were features that lead to differences in the process of induced calcite biomineralization. Phosphorus has influence in the biomineralization of the EPS, sheaths and cell walls of cyanobacteria allowing for fossil preservation whereas does not participate in the calcite precipitation around algae and mosses. This variability may explain the different positive or negative roles played by natural or artificial inputs of phosphorus in hard water lakes and the different morphological features of calcite precipitates associated with eukaryotic and cyanobacteria picoplankton found in natural environments. The biomineralization observed is in agreement with the isotopic composition of the tufa layers that reflect the variations in environmental conditions around biological communities. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Tufa deposition and periphyton overgrowth as factors affecting the ciliate community on travertine barriers in different current velocity conditions

A characteristic of aquatic systems in karstic region is the formation of tufa – the product of calcium carbonate precipitation. Artificial substrata (glass slides) were used to investigate the influence of tufa deposits at two different current velocities (5 cm s−1 and 50 cm s−1) on the ciliate assemblages in periphyton. After two-month exposure periods, periphyton biomass and tufa deposit were c. three times greater at 50 cm s−1 than at 5 cm s−1. Ciliate population density was also higher on artificial substrata exposed in a lotic than in a lentic microhabitat (the overall mean number of ciliates at 5 cm s−1 was 122 ind. cm−2, and at 50 cm s−1 497 ind. cm−2). At each of the two observed current velocities, a Principal Components (PCA) ordination of the colonized ciliate associations showed a spatial separation of the associations that developed under two different conditions of tufa deposition. During the period of greater tufa deposit, associated with greater periphyton overgrowth rate, the ciliate communities had higher species diversity (a higher number of species and a lower number of individuals). Species diversity of ciliates had a positive nonlinear relation to tufa deposition rate. These results suggest that artificial surfaces covered by a rough tufa layer associated with greater periphyton biomass offer diverse conditions for colonization by ciliates.

14C Dating of Calcareous Tufa from Different Environments

14C dates of carbonate and organic matter fractions are compared with a series of calcareous tufa samples from selected sites representing different geochemical environments and associated with different bedrocks. Results obtained in this study indicate values of apparent age ranging from 940 ± 110 yr for calcareous tufas associated with Pleistocene sediments to 2000 ± 110 yr and even ca 4000 yr for tufas from sites associated with Jurassic or Cretaceous limestone. It was found also that within each of the investigated sites the value of apparent age does not change significantly with the age of the tufa layer.