Carbonate Tufa Research Articles

Emergence of wet conditions in the Mono Basin of the Western USA coincident with inception of the Last Glaciation

Abstract At present, the Basin and Range of the western USA is arid, but geologic studies show evidence of past wetness. The timing of these wetter conditions reveals a close association with glacial conditions. This association has led to the hypothesis of a causal link between glacial climate and regional wetness, but poor age control on the onset of regional wetness thwarts a test of this hypothesis. Here we determine the start of the most recent interval of persistent wetness in the Mono Basin, which is a hydrologically closed depression that sits at the west-central edge of the Basin and Range. The most recent emergence of persistent wetness in the Mono Basin is stratigraphically correlated with the depositional age of Ash 19—a rhyolitic ash bed that represents the oldest tephra of the Wilson Creek Formation and one of the earliest-known products of explosive volcanic activity from the Mono Craters. We constrain the depositional age of Ash 19 by using the U/Th disequilibrium dating method to date carbonates that are younger and older than Ash 19. Our U/Th dating results show that Ash 19 was deposited before the formation of a cross-cutting carbonate bed dated to 69.2 ± 0.3 ka but after an underlying carbonate tufa dated to 67.4 ± 3.5 ka, which suggests that the start of wetness in the Mono Basin was contemporary with the inception of the Last Glaciation—the beginning of Marine Isotope Stage 4—at ca. 70 ka. This finding corroborates the hypothesis of a link between glacial climate and regional wetness.

Potential role for microbial ureolysis in the rapid formation of carbonate tufa mounds.

Modern carbonate tufa towers in the alkaline (~pH 9.5) Big Soda Lake (BSL), Nevada, exhibit rapid precipitation rates (exceeding 3cm/year) and host diverse microbial communities. Geochemical indicators reveal that carbonate precipitation is, in part, promoted by the mixing of calcium-rich groundwater and carbonate-rich lake water, such that a microbial role for carbonate precipitation is unknown. Here, we characterize the BSL microbial communities and evaluate their potential effects on carbonate precipitation that may influence fast carbonate precipitation rates of the active tufa mounds of BSL. Small subunit rRNA gene surveys indicate a diverse microbial community living endolithically, in interior voids, and on tufa surfaces. Metagenomic DNA sequencing shows that genes associated with metabolisms that are capable of increasing carbonate saturation (e.g., photosynthesis, ureolysis, and bicarbonate transport) are abundant. Enzyme activity assays revealed that urease and carbonic anhydrase, two microbial enzymes that promote carbonate precipitation, are active in situ in BSL tufa biofilms, and urease also increased calcium carbonate precipitation rates in laboratory incubation analyses. We propose that, although BSL tufas form partially as a result of water mixing, tufa-inhabiting microbiota promote rapid carbonate authigenesis via ureolysis, and potentially via bicarbonate dehydration and CO2 outgassing by carbonic anhydrase. Microbially induced calcium carbonate precipitation in BSL tufas may generate signatures preserved in the carbonate microfabric, such as stromatolitic layers, which could serve as models for developing potential biosignatures on Earth and elsewhere.

Landscape modification due to agricultural irrigation: Carbonate tufa formation on Tenerife, Canary Islands, Spain

The use of irrigation water on Tenerife has modified the hydrogeological system resulting in the formation of an anthropogenic carbonate tufa . The processes involved in its formation are: 1) infiltration of rainwater and mixing with groundwater rich in volcanic carbon dioxide (CO 2 ), 2) weathering of volcanic rocks increasing the ion content of the water, 3) extraction of this water from subterranean galleries and channels and spilling it onto the Lomo Morin slope, 4) mechanical CO 2 degassing and photosynthetic activity driving calcite precipitation. The tufa consists of boundstones of algae and coated stems of reeds, along with laminated microbial crusts. Textures range from microspar to coarse mosaics to fibrous-radial calcite, all containing biogenic features. The presence of the green macroalga Blidingia is noticeable. Carbon stable isotope ratio ( δ 13 C) varies between -3.58 and +1.03‰ VPDB (Vienna Pee Dee Belemnite) and oxygen stable isotope ratio ( δ 18 O) between -6.77 and -5.00‰ VPDB, highlighting the largely meteoric origin of the water with some addition of deep CO 2 . A strontium isotope ratio ( 87 Sr/ 86 Sr) of 0.7030 confirms the weathering of volcanic rocks as the source of calcium. The Lomo Morin tufa provides a scale model of how water use contributes to rapid landscape change through alterations in the hydrogeological system. It also provides a good example of a CO 2 sink in a continental setting, and is comparable to the global carbon cycle, which mostly involves marine limestones. Although anthropogenic processes are commonly viewed negatively, the human modification of the hydrogeological system reported in this study has produced changes to geological and ecological conditions that have increased the geo - and biodiversity of the island.

Lacustrine carbonate tufa facies of Winnemucca Dry Lake Basin, Nevada, U.S.A.

ABSTRACT Lacustrine carbonate tufa deposits are common in present-day lakes and dry pans of the western United States, and large-scale deposits (> 100 m high) are found throughout the subbasins of Pleistocene Lake Lahontan. This study presents a depositional model for very well exposed tufa in Winnemucca Dry Lake, a subbasin of Lake Lahontan, that incorporates new observations of tufa growth over length scales of 10–4–102 m. Tufa depositional facies are defined on the basis of outcrop morphology and texture. Deposits were mapped using satellite imagery and field observations. Tufa facies and volumes were quantified for seven tufa exposures across the basin using digital outcrop and elevation models from aerial images acquired from a small uncrewed aerial system (sUAS). Tufa thin sections were examined using transmitted-light petrography and scanning electron microscopy and combined with measurements of porosity and permeability to define small-scale facies characteristics. Both porosity and permeability are highly variable across textures; average values for both (ϕ = 29%, k = 5.5 D) indicate that all tufa types may exhibit excellent reservoir properties. The age and distribution of these facies across the basin are directly linked to hydroclimate and variations in lake level. The most important controls on tufa distribution at the basin scale are basin hydrology and pathways of groundwater inflow. Groundwater flow into the basin is largely concentrated along the western flexural margin along the contact between volcanic and volcaniclastic bedrock and alluvial sediments, rather than concentrated along the border fault margin, in contrast to other models which predict strong fault control of tufa occurrence. Microbially influenced tufa textures and morphologies are the most volumetrically significant tufas in the basin, composing between 77% and 100% of tufa volume at individual exposures; these are inferred to form during times when lake waters were warmer and levels higher, while physico-chemical processes dominate during early tufa formation, and generally in colder waters and under conditions of lower lake level. Deposition of tufas is a result of combined physical, chemical, and biological factors that are directly related to the basin geology and hydroclimate; however, the importance of each controlling factor is highly variable both spatially and temporally, complicating the development of effective and predictive depositional models. This case study describes tufa deposition intrinsically linked to basinal hydroclimatic histories, and understanding these relationships may assist in predicting volumes, physical properties, and stacking patterns of petroleum reservoir facies in lacustrine basins.

Influence of the petrophysical and durability properties of carbonate rocks on the deterioration of historic constructions in Tebessa (northeastern Algeria)

A thorough investigation of the weathering phenomena affecting a Byzantine Wall has been carried out. This Wall is a representative example of historic constructions in Tebessa (northeastern Algeria), in which limestone and carbonate tufa were the main materials used. Field investigations showed several weathering forms, including flaking, alveolisation, efflorescence, discolouration, fracturing, material loss and powdering. These weathering forms were mainly produced by salt action (gypsum and halite) and were related to the textural and petrophysical properties of the limestone and carbonate tufa. The quantification of the degree of deterioration using a Schmidt hammer revealed damage ranging from medium to severe. Petrophysical and durability properties were measured for both stone types extracted from ancient quarries. Pore structure, capillarity imbibition, P wave velocities and uniaxial compressive strength were used to characterise the petrophysical properties of the stones, and salt crystallisation tests were used to estimate their durability. These properties are closely linked to the stone microstructure. Carbonate tufas show excellent durability under salt crystallisation and a lower mechanical strength than limestone. Limestone, on the other hand, despite its low porosity and better mechanical strength, shows lower durability values. While micropores contribute to the relatively lower durability values of limestone, in tufa, macropores reduce the salt crystallisation effectiveness and improve the durability. According to our investigation, the Byzantine Wall requires urgent preservation measures. In the built heritage of Tebessa, limestone is expected be more prone to deterioration than carbonate tufa.

Impact of salt and frost weathering on the physical and durability properties of travertines and carbonate tufas used as building material

This study was financed by the Spanish Ministry of Education and Science (MEC) through the Research Project CGL2006-05027/BTE and Community of Madrid (S2023/MIT 2914). A pre-doctoral research fellowship was awarded to N. Cueto by the MEC.

Paleospring tufa deposition in the Kurkur Oasis region and implications for tributary integration with the River Nile in southern Egypt

Though southern Egypt is currently hyperarid, relict freshwater carbonate deposits called tufas near Kurkur (region centered at 23° 54′ N, 32° 19′ E) indicate that ambient rainwater-fed alkaline springs formerly sourced drainages in the Sinn El-Kaddab or Eocene scarp, and precipitated carbonate tufa deposits at waterfall cascades, pools, and streams. Petrographic analysis enables the reconstruction of a variety of vegetated microenvironments during Quaternary time. The Kurkur tufas are very porous rocks with an abundance of fossil plant casts and molds making up the petrofabrics at the macroscale. The tufas also preserve laminations of successive generations of calcified remains of microbes visible at the microscopic scale. Original carbonate framework architectures are massive carbonate structures to the decameter scale, with characteristic highly porous and permeable rock fabrics, including vegetation-rich phytoherms and stromatolite forms. The tufas are relatively pristine, preserving their original rock textures with minimal post-depositional alteration. Structural controls affecting the development of tufa deposits near Kurkur include fissure, cracks and fault planes that would have enhanced groundwater recharge and emergence of carbonate-saturated springs from perched aquifers above the Nubian Aquifer System during periods of greater effective rainfall in the past when the water table was significantly higher. The Kurkur tufas are relict archives from phases when groundwater discharge supported comparatively more vegetation than the modern day, and spring flows sustained baseflow in the Wadi Kurkur tributary of the Upper Nile. Episodes of tufa deposition along now-defunct tributaries therefore reflect phases of a more integrated Nile drainage system.

Archeological deposits at Abric Romaní extend to 110 ka: U-series dating of a newly cored, 30 meter-thick section

Recent exploratory drilling at Abric Romaní reveals that carbonate tufas similar to the archeologically rich levels excavated to date extend at least 30m beneath the current base of excavation. The present project focused on sampling and measuring a suite of new U-series dates on core samples to determine whether reliable dates could be obtained from the older tufas and, if so, their temporal extent.Using relatively small (~100mg), carefully selected samples analyzed by inductively coupled plasma mass spectrometry, we obtained a total of 20 dates for 10 core samples and one sample near the base of the current excavation. Corrections for thorium from contaminating detritus were generally negligible, as indicated by a median 230Th/232Th activity ratio of 360. At selected levels in the sequence, two or three coeval samples were prepared and analyzed in order to determine the reproducibility of their dates. Reproducibility at most levels was similar to analytical errors, consistent with rapid carbonate deposition followed by evolution of closed U–Th systems. In contrast in the sample nearest the base of the core, scatter of dates beyond analytical errors was observed among sub-samples, probably indicating failure of the U–Th system to remain closed.The dates, which preserve stratigraphic order in all cases, range from ~55ka for a sample from level N of the existing excavation to ~110ka at the base of the core. The new dates show that tufas at Abric Romaní extend at least to early Marine Isotope Stage (MIS) 5. Mean accumulation rates in the core varied widely, from a minimum of 17cm/ka during the later parts of MIS 5 to a maximum of 130cm/ka during the Last Interglacial in early MIS 5, suggesting that a wetter hydroclimate prevailed in the region during periods of low global ice volume. The new dates show that burned travertine and sand intersected by the drill-core, which are likely indicators of human presence, are as old as ~100ka. Thus, evidence for human presence at Abric Romaní now extends over ~60thousandyears.

Geologia e litogeoquímica de migmatitos, charnockitos e granulitos do Complexo Guaxupé na região de São João da Boa Vista (SP)

Nesse trabalho são apresentados os procedimentos metodológicos envolvidos no imageamento digital de paleocavernas colapsadas com ground penetrating radar (GPR), que ocorrem em tufas carbonáticas, situadas na borda oeste da Bacia Potiguar. Foi mapeada uma área em Quixeré (CE) e selecionado um afloramento na rodovia CE-377, denominado de Afloramento Quixeré. Em uma porção desta área foi confeccionado um fotomosaico e levantada uma seção-teste, com o GPR, para a comparação e parametrização das geometrias cársticas (aflorantes e as imageadas na linha geofísica). Os resultados foram satisfatórios e permitiram a adoção de critérios para a interpretação das paleocavernas colapsadas nas outras seções GPR, levantadas na região do afloramento. Foram adquiridas duas malhas de linhas GPR, a primeira mais ampla e espaçada norteou a locação da segunda, mais adensada, na porção sul do Afloramento Quixeré. Nos radargramas foram interpretadas e parametrizadas as geometrias das principais paleocavernas colapsadas. Para cada malha foi elaborado um modelo de sólido digital do Afloramento Quixeré, sendo que o primeiro modelo permitiu o reconhecimento da distribuição geral das tufas e a localização das paleocavernas colapsadas, enquanto o segundo modelo digital, por ser mais detalhado, possibilitou não apenas a individualização 3D das principais paleocavernas mas também o cálculo dos seus respectivos volumes. Os modelos de sólidos digitais são aqui apresentados como uma nova fronteira no estudo de afloramentos análogos a reservatórios (hídricos ou petrolíferos), na qual a parametrização e a caracterização volumétrica dos corpos geológicos passam a ser fundamental para compor bancos de dados, que conjuntamente com informações de propriedades petrofísicas serão utilizados em simulações computacionais mais realísticas de reservatórios.

UNUSUAL HOLOCENE SERPULID-TUFA BIOHERMS, ENRIQUILLO VALLEY, DOMINICAN REPUBLIC: MORPHOLOGIES AND PALEOENVIRONMENTAL IMPLICATIONS

During the early Holocene, rising waters of the Caribbean Sea flooded the Enriquillo Valley of southwestern Dominican Republic. A fringing coral reef developed and flourished along the margins of the Enriquillo Seaway for several millennia, until the seaway became restricted due to a combination of slowed sea-level rise, tectonic uplift, and increased sedimentation. Following changes in salinity and death of the coral reef by about 5 ka, meter-scale bioherms composed of the tubes of opportunistic, aggregating serpulid worms and associated with carbonate tufa that precipitated from the ancient lake or declining seaway waters formed along the steep walls of the valley over a period of 1,000 years or more. Paleoenvironmental conditions likely conducive to formation of these unusual bioherms include: non-normal marine salinity, warm and restricted waters, periods of stable water level, high Ca 2+ and CO3 22 influx, and moderate wave action. Although apparently rare elsewhere in the rock record, occurrences of serpulid-tufa bioherms provide useful constraints on paleoenvironmental settings. In previous literature, variations in terminology used to describe both tufa and serpulid-tufa bioherms have hindered intersite comparisons. Herein, serpulid-tufa bioherm structures are described at macro-, meso-, and microscales, and the varied bioherm macromorphologies are classified as individual, clustered, terraced, and patch types. These form descriptions are compared with previously published classifications of similar structures; the goal is to facilitate development of a comprehensive and universal classification of serpulid-tufa bioherms to further understand their formation and paleoenvironmental significance.

Sedimentary structures and physical properties of travertine and carbonate tufa building stone

This paper establishes relationships between the structures of travertine and calcium carbonate tufa used as building stones and their physical properties. The most characteristic features of these kinds of rocks are the macropores in both stone types and the bedding planes and laminations in travertines. Large vuggy macropores have little influence on capillary water absorption, strength, elastic modulus or ultrasonic wave propagation, whereas microporosity is a much more determining factor. With travertines, the bedding planes and laminations give petrophysical anisotropy to rocks, where the highest capillary transport is reached parallel to the structure. However, rock strength and elasticity depend on both structure orientation and the predominant rock facies. The strongest and stiffest behaviour is found perpendicular to structure in low-porous banded samples, but in a parallel direction when the rock is highly porous.

The Fate of the Submarine Ikaite Tufa Columns in Southwest Greenland Under Changing Climate Conditions

Abstract Ikaite is considered a metastable mineral forming and stable only at low temperatures and therefore an indicator of low-temperature carbonate precipitation often associated with cold marine seeps. It is found world-wide but most spectacularly in Ikka Fjord in southwest Greenland as submarine carbonate tufa columns. Here, ikaite is formed as a result of submarine spring water mixing with cold seawater. As ikaite disintegrates at temperatures above 6–7°C, it has been speculated that global warming could endanger this unique habitat as well as other sites. In Ikka Fjord in situ water chemistry in and around an ikaite column measured continuously over two years showed that the column water is alkaline (pH > 9–10) throughout the year with temperatures of −1.3–6.0 °C and conductivities of 5.7–7.9 mS cm−1, favoring year-round growth of columns at 4–5 cm per month. Short-term in situ measurements with needle micro sensors from both older dehydrated and calcified parts and more recently formed solid parts of an ikaite tufa column showed similar pH and temperature values, including a temperature variation over the tidal cycle. In the uppermost, recently deposited ikaite matrix, spring water escaping at the top causes passive drag of seawater into the porous ikaite matrix, leading to a mixing layer several centimeters thick that has pH values intermediate to the spring water in the column and the surrounding seawater. We conclude that the main part of the columns, consisting of fossilized ikaite (inverted to calcite) partly sealed by calcifying coralline algae and with year-round flow of alkaline freshwater through distinct channels, are resistant to warming. In the more diffuse top part of the columns, the formation of ikaite, and thus column growth, will be limited in the future due to increased fjord water temperature during the

The lithium isotopic composition of waters of the Mono Basin, California

Mono Lake, a major closed-basin alkaline salt lake in eastern California, derives its water from a mixture of creeks and springs, with the former providing in excess of 75% of the total. The Li isotopic composition of lake water has not varied significantly over a 4 year meromictic period (δ 7Li ∼ +19.5). Springs are isotopically distinct: groundwater springs and seeps carry water enriched in isotopically heavy Li whereas thermal springs supply isotopically light (δ 7Li < lake), but 10 times more Li-rich, water. Isotopic fractionation during crystallization of carbonate tufa and evaporitic salt appears to be insignificant, and thus cannot be called on as a principal control of the isotopic balance of Li of the lake. Isotopic differences between the end-member source components permit a water budget to be calculated, suggesting (1) springs provide > 50% of the Li to the lake; (2) the Li budget is sensitively balanced on small thermal spring contributions, < 3% of the total spring inflow; and (3) the residence time of Li in the lake is 28 ka. Other Great Basin closed lakes have variable Li isotopic compositions (δ 7Li from +16.7 to +23.7), all of which differ significantly from those of several major lakes and seawater (homogeneously ∼ +32).

Characteristics and origins of the freshwater carbonate tufa : A review

Characteristics and origins of the freshwater carbonate tufa : A review

Did changes in late Last Glacial and early Holocene atmospheric CO2 concentrations control rates of tufa precipitation?

Gases trapped within Arctic, Antarctic and Greenland ice-cores document a dramatic increase in atmospheric CO2 levels (by almost 100%) in the period between the last glacial maximum and the late Holocene. The authors note an apparent correlation between increases in levels of atmospheric CO2 during this period and an episode of mass deposition of freshwater carbonate tufas and travertines. As changes in atmospheric CO2 levels are likely to affect carbonate deposition (Tucker and Wright, 1990), we propose the hypothesis that a relationship exists between increasing atmospheric CO2 levels and tufa deposition.