Hot-spring travertine facies and sequences, Late Pleistocene, Rapolano Terme, Italy

Late Pleistocene travertines up to 40 m thick near Rapolano Terme in Tuscany, central Italy, were precipitated by hot water issuing from springs on hillsides and flowing into adjacent depressions to mix with rainwater. Proximal light-coloured slope and terrace travertines pass distally into darker reed mound and depression-fill travertines. Lithotypes include crystalline crust, shrub, pisoid, paper-thin raft, coated bubble, reed, and lithoclast-breccia. High precipitation rates resulted in rapid slope aggradation and progradation. Dilution by rainwater likely lowered precipitation rates in depressions, but deposition was augmented by allochthonous material eroded from upslope travertines. Slope Depositional Systems consist of Smooth and Terrace Slope facies characterized by white crystalline crusts, with diverse additional lithotypes in terrace pools. Depression Depositional Systems have mixed light and dark travertines with horizontal to gently concave stratification. Extensive light-coloured Shrub Flat travertine is dominant; darker Marsh-Pool Facies composed of fine lithoclast and reed travertine is localized. Reed Mounds composed of mixed light and dark travertines localized by abundant reed growth, formed where spring water emerged near the bases of low angle slopes. Distal reduction in accretion rate was the major influence on sequence development. Light-coloured slope travertines interdigitate with darker depression deposits. Vertical aggradation of slope deposits, mound progradation, and filling of topographic depressions is expressed by advance and retreat of facies. Evolution from depression to slope or mound sequences is termed ‘steepening up’. Up-sequence change from slope or mound to depression facies is termed ‘levelling up’. Exposure surfaces associated with palaeosols are common in all facies and often constitute sequence boundaries. They are more closely spaced in depression sequences, reflecting slower and possibly also more discontinuous accumulation at sites furthest from hot springs.     

Travertine deposition and faulting: the fault-related travertine fissure-ridge at Terme S. Giovanni,Rapolano Terme (Italy)

In this paper we describe an example of travertine fissure-ridge development along the trace of a normal fault with metre displacement, located in the eastern margin of the Neogene–Quaternary Siena Basin, in the Terme S. Giovanni area (Rapolano Terme, Italy). This morphotectonic feature, 250 m long, 30 m wide and 10 m high, formed from supersaturated hot waters (39.9°C) flowing from thermal springs aligned along the trace of the normal fault dissecting travertines not older than Late Pleistocene (24 ± 3 ka). A straight, continuous fissure with a maximum width of 20 cm occurs at the top of the ridge, along its crest. Hot fluids flow from cones mainly located at the extremities of the ridge, where travertine is depositing. The travertine fissure-ridge shows an asymmetrical profile since it buries the fault scarp. The difference in height of slopes corresponds to the vertical displacement of the normal fault. Fissuring of the recent travertine deposits along the strike of the crestal fissure, as well as recent hydrothermal circulation, lead us to believe that the Terme S. Giovanni normal fault may be currently active. On the whole, the Terme S. Giovanni fissure ridge can be defined as a travertine fault trace fissure-ridge, adding a helpful example for studying the relationship between faulting and travertine deposition.     

Origin and diagenesis of Quaternary travertine shrub fabrics, Rapolano Terme, central Italy

Millimetre to centimetre sized arborescent shrub-like calcite precipitates are common constituents of hot water travertine shallow pool deposits of Quaternary age at Rapolano Terme, Tuscany, Italy. In the presently forming travertines, the shrubs consist of apparently random associations of (i) micrite aggregates and (ii) subhedral to euhedral rhombic spar crystal aggregates. In thin section, the micrite aggregates appear dark and the spar-rhomb aggregates light, giving the shrubs a mottled appearance. Travertines are basically produced by CaCO₃ precipitation due to degassing and evaporation of the spring waters, although biological influence may also stimulate precipitation. The formation of masses of erect shrubs, rather than dense crystal crusts that form on slopes, is probably due to limited water flow in the pool environments. Microbes, including bacteria and diatoms, are important influences on shrub microfabric and external shape. The micrite aggregates are associated with bacteriform bodies, seen as tiny rods and spheres. The micrite precipitates around these bodies and in adjacent biofilm. Spar-rhomb precipitation appears to be external to the biofilm, and may be related to the presence of diatoms which are locally closely associated with the spar-rhombs, although an essentially inorganic origin, particularly for the more euhedral rhombs, cannot be ruled out. In the older Quaternary travertines, the original microfabric of the shrubs has been diagenetically altered. The original mottled appearance of the shrubs has become uniformly dark and micritic, and the evidence for the dual micritic and spar-rhomb origin of the shrubs is obscured or destroyed. Spar-micritization of the shrubs is probably due to abiotic, and locally biotic, dissolution. Previous studies did not recognize the diagenetic micritization and attributed shrub formation entirely to bacterial activity.     

Depositional system and palaeoclimatic interpretations of Middle to Late Pleistocene travertines: Kocabaş, Denizli,south‐west Turkey

Travertine deposits in western Turkey are very well‐exposed in the area of Kocaba?, in the eastern part of the Denizli Basin. The palaeoclimatic significance of these travertines is discussed using U/Th dates, stable isotope data and palynological evidence. The Kocaba? travertine occurrences are characterized by successions of depositional terraces associated with palaeosols and karstic features. The travertines have been classified into eight lithotypes and one erosional horizon, namely: laminated, coated bubble, reed, paper‐thin raft, intraclasts, micritic travertine with gastropods, extra‐formational pebbles and a palaeosol layer. The analysed travertines mostly formed between 181 ka and 80 ka (Middle to Late Pleistocene) during a series of climatic changes including glacial and interglacial intervals; their δ¹³C and δ¹⁸O values indicate that the depositional waters were mainly of basinal thermal origin, occasionally mixed with surficial meteoric water. Palynological results obtained from the palaeosols showed an abundance of non‐arboreal percentage and xerophytic plants (Oleaceae and Quercus evergreen type) indicating that a drought occurred. Marine Isotope Stage 6 is represented by grassland species but Marine Isotope Stage 5 is represented by Pinaceae–Pinus and Abies, Quercus and Oleaceae. Uranium/thorium analyses of the Kocaba? travertines show that deposition began in Marine Isotope Stage 6 (glacial) and continued to Marine Isotope Stage 4 (glacial), but mostly occurred in Marine Isotope Stage 5 (interglacial). The travertine deposition continued to ca 80 ka in the south‐west of the study area, in one particular depression depositional system. Palaeoenvironmental indicators suggest that the travertine depositional evolution was probably controlled by fault‐related movements that influenced groundwater flow. Good correlation of the stable isotope values and dates of deposition of the travertines and palynological data of palaeosols in the Kocaba? travertines serve as a starting point for further palaeoclimate studies in south‐west Turkey. Additionally, the study can be compared with other regional palaeoclimate archives.     

U/Th dating of fissure ridge travertines from the Kirsehir region (Central Anatolia Turkey): structural relations and implications for the Neotectonic development of the Anatolian block

Travertines exposed in several locations in Central Anatolia are the important lithological product for the interpretation of local neotectonics. The fissure-type travertines provide significant information about stress orientation during deposition. Two travertine masses cropping out in the Kirsehir region have been studied and dated by the U-series method to obtain new chronological constraints, determine dilation rates and contribute to studies on the recent tectonic evolution of the area. The Kusdili and Kayabasi travertine masses are located on the hanging wall of the Kirsehir Fault, similar to numerous fissure ridge banded travertine deposits which are inactive today in the region. While individual fissures of the Kusdili travertine mass (Late Pleistocene-Holocene) have been dilated at rates of between 0.303 and 0.386 mm yr–1 during deposition, the Kayabasi travertine mass (Late Pleistocene) produced measured dilation rates of between 0.136 and 0.187 mm yr–1. The central fissures, filled by banded travertine, roughly follow the ridge crests. While the ridge crest has a NNE-SSW trend in the Kayabasi travertine mass, the ridge crest of the Kusdili travertine mass shows a NE-SW trend. This difference may be related to the clockwise rotation of the stress tensors from Late Pleistocene to Late Pleistocene-Holocene in the region.     

温泉钙华沉积的影响因素

钙华是在泉水、河水、湖水、洞穴周围沉积的非海相碳酸钙沉积物。钙华是陆地水循环过程中物质迁移的一种表现形式,研究钙华的形成有助于了解局部水文循环中的物质迁移规律并间接了解古气候与古水文地质条件。部分温泉的泉口附近沉积有形态多样的钙华。本文综述温泉钙华的形成过程、钙华沉积的主要影响因素和它们之间的相互影响关系。水化学条件是钙华沉积的物质基础和必要条件,水动力条件是钙华沉积的充分条件,生物效应对钙华沉积起到加强的作用,沉积环境通过影响水化学条件或水动力条件间接控制钙华的沉积。     

Geotechnical handicap of travertine with different lithotype levels as foundation material

Two major earthquakes occurred on October 23rd, 2011 (M=7.1) and November 9th, 2011 (M=5.6) in Tabanli and Edremit districts of Van province in Turkey, respectively. New settlement areas for Van city were determined after these destructive earthquakes. One of the most important areas for new settlements to be built was Edremit region, consisting travertine where nearly 80% of new housing units (12.384) were built by TOKI (Housing Development Administration of Turkey). Travertines have different lithotypes depending on their depositional process such as crystalline crust, shrub, reed which can affect mechanical and engineering properties of travertine and each level has different handicaps. The purpose of this study is to investigate the relationship between lithotype and physico-mechanical properties of travertines. According to the results, lithotype has an effect on physical, mechanical and rock mass properties of travertine. It is ascertained by several research methods that various handicaps may occur on such areas when the active tectonic structure of the area is evaluated along with the karstic cavities within the travertine and different lithotype qualities.     

Aragonite laminae in hot water travertine crusts, Rapolano Terme, Italy

Small (5–30 μm) aggregates of aragonite needles occur in calcite crystal crusts of present day hot water slope travertines at Rapolano Terme in Tuscany, Italy. The aggregates are mainly concentrated in irregular, wispy and dark laminae which cross-cut calcite crystal feathers to create a pervasive millimetre scale banded appearance in the deposit; they also occur less commonly scattered irregularly through the calcite layers. The aragonite needle aggregates are in the form of crosses, fascicles (sheaf shaped bundles, or dumbbell shaped), rosettes and spherulites. Locally, irregular masses of needles also occur. The fascicles, rosettes and spherulites have hollow centres which resemble microbial components (?fungal spores, bacterial colonies and pollen), suggesting that the aragonite crystals are biotically nucleated. The lamination is interpreted to reflect diurnal control. Stimulation of microbial activity during daylight concentrates cells in laminae and promotes aragonite calcification. Calcite feather crystals, although traversed by the aragonite aggregate laminae, have a clear appearance under the light microscope. They form more or less continuously through the diurnal cycle by abiotic precipitation. The constant association of aragonite with organic nuclei, irrespective of whether the latter are in laminae or scattered through the calcite layers, supports a biotic control on aragonite formation. Lamination in Pleistocene travertines is superficially similar to that in the present day deposits, but is diagenetically altered. In the Pleistocene deposits, the calcite feathers appear dark under the light microscope and the aragonite aggregates, where they are not altered to dark calcite, are dissolved, together with parts of the adjacent spar calcite, and therefore appear light coloured.     

U/Th dating of the travertine deposited at transfer zone between two normal faults and their neotectonic significance: Cambazli fissure ridge travertines (the Gediz Graben-Turkey)

Abstract

The neotectonic characteristics of the travertines that outcrop near Cambazli Village to the west of the Gediz Graben in the Western Anatolia and the age determination of the travertine were carried out using the ²³⁰Th/^234,238U disequilibrium method. The Cambazli fissure ridge travertines represent the travertine depositions that develop at a transfer zone. The extent of these travertines is at NW-SE and NE-SW orientations and the ridge crest-trend of these travertines range between approximately 55° and 82° and they are located at an intersecting position. The evaluation of the fissure ridge travertine directions indicated that the compression stress that was responsible for the deposition of the Cambazli travertine was determined to be in the N-S orientation and the extensional stress was determined to be in the E-W orientation. The orientation of the dominant extension in Western Anatolia during the neotectonic period was N-S and this orientation is not in accordance with the directions of stress for the travertines. This situation indicates that the travertines were deposited along a transfer zone in N10W orientation between two normal faults. The travertines were determined to be active since the Upper Pleistocene as indicated by the age determination conducted using the ²³⁰Th/^234,238U disequilibrium method. The dilation rate of the travertines during dilation and the post-dilation period and the average dilation rate of the Cambazli travertines to the north of the Gediz Graben were calculated as 0.01–0.02 mm yr^?1 during deposition and as 0.05 mm yr^?1 during the post-dilation period. These dilation rates indicate lower tectonic activity along the northern ridge of the Gediz Graben than along the southern ridge.

© 2011 Lavoisier SAS. All rights reserved     

Travitonics: using travertines in active fault studies

Late Quaternary travertines deposited from hot springs can reveal much about the neotectonic attributes and histories of structures. On the basis of field studies in the Aegean region (Turkey and Greece), the northern Apennines (Italy) and the Basin and Range province (USA) we conclude that the following relationships are of predictive value: (i) travertine deposits are preferentially located along fracture traces, either immediately above extensional fissures or in the hanging walls of normal faults; (ii) the locations of many travertine fissure-ridge deposits coincide with step-over zones (relay ramps) between fault segments; networks of intersecting tensional fissures reflecting the complex strains experienced in such settings are probably responsible for enhancing hydrothermal flow; (iii) the morphology of travertine deposits overlying extensional fissures is controlled by the rheology of the underlying materials; tufa cones (towers, pinnacles) form on former and present lake floors where fissures underlie unconsolidated sediments, whereas fissure-ridges develop where fissures cut bedrocks at the surface; (iv) fissure-ridges comprise outwardly dipping bedded travertine flanking a central tensional fissure filled by vertically banded travertines; fissures can be used to infer local stretching directions; (v) where there are travertines datable by the U-series method it is possible to calculate time-averaged dilation and lateral propagation rates for individual fissures; (vi) most fissures cutting fissure-ridges comprise self-similar angular segments with fractal dimensions in the range 1.00–1.12, the properties of bedded travertine combined with stress perturbations at fissure tips probably being responsible for such similar fractal dimensions being inferred from such a wide range of locations. Fissures gradually increasing in width with depth are products of continuous fracture dilation in contrast to those that form during episodic dilation which display stepped increases of width with depth; (vii) travertine deposited from springs along fault zones accumulate in terraced-mounds sited down slope of the spring line; (viii) many post-depositional fractures cutting travertine deposits are locally oriented at right angles to deposit margins; and (ix) systematic joints in travertines are restricted to those parts of eroded sheet deposits that have been exhumed.     

钙华的形成环境与特征及在油气储集方向的探讨

钙华是一种特殊的化学或生物化学沉积,它们在大陆内部广泛地分布且含有重要的地质信息,是一种特殊的油气储集体。影响钙华沉积的因素复杂多样,在调研钙华的形成过程及分类的基础上,从气候环境、水文地质条件、水体物理化学条件、生物活动及构造活动五个方面讨论钙华形成的控制因素;并从沉积环境与模式、沉积速率等方面将新疆塔北地区的钙华与国外钙华沉积体进行类比,发现塔北钙华沉积体在温暖湿润的环境下表现出良好的季节性分层,五道班地区钙华在沉积时汇入了大量的陆源碎屑,受生物活动影响较大;硫磺沟地区的钙华沉积则是伴随断裂活动所形成热液上涌的产物。通过对比发现,塔北露头缝洞内充填的钙华内部孔隙发达、连通性较好,并有良好的含油显示,故钙华具备一定的储集能力。     

Determination of horizontal extension from fissure-ridge travertines: a case study from the Denizli Basin,southwestern Turkey

Travertine deposits reflect some aspects of the regional tectonics because of the close association between travertine deposits and active fractures, that later of which provide conduits along which travertine-depositing waters may rise. Fissure-ridge travertines form above extensional fissures which are located in the hanging walls of normal faults, in step-over zones between fault segments, or in active or recently active) volcanic provinces. Numerous active and inactive fissure-ridge travertines are located in the hanging walls of normal faults in the Denizli Basin. A typical fissure-ridge comprises a central fissure along its long axis and flanking bedded travertines dipping away from the fissure. Central fissures of travertine ridges have been dilating since the initiation of the fissures. Samples from both the margins and centres of banded travertine deposits were dated by Th/U methods in order to determine dilation rates. Individual fissures have been dilating at average rates of between 0.008 and 0.1 mm yr^–1 during travertine deposition, and ~ 0.001 and 0.007 mm yr^–1 after cessation of travertine deposition. There is a noticable decrease in dilation rate from west to east in the Denizli Basin, and this decrease in dilation rate may be related to decrease in overall extension in southwest Turkey, which decreases eastward.     

钙华生物沉积作用研究进展与展望

弄清钙华生物沉积作用有助于更好地理解钙华微岩相结构和地球化学特征的气候环境指示意义。总结和综述了与钙华沉积相关的生物群落、生物成因钙华微岩相结构、钙华生物沉积作用过程及其对钙华地球化学特征影响的研究进展,并展望了未来的研究重点。细菌、藻类和苔藓等广泛参与到钙华沉积中,形成了许多不同类型的孔隙结构、晶体结构和纹层结构。生物沉积过程主要包括:①生物生长扰动水流使得CO2逸出;②代谢作用(如光合作用)过程诱导碳酸钙沉积;③"表面控制"过程影响晶体成核及生长。生物沉积作用驱动了元素的迁移转化,对沉积水体和钙华地球化学特征具有重要影响。钙华在地球生物学研究中具有重要潜力,未来需要加强现代钙华沉积中的物理化学和生物过程相互作用机制及其各自贡献的量化研究,以便准确地解译钙华沉积记录。     

Impact of lake‐level changes on the formation of thermogene travertine in continental rifts: Evidence from Lake Bogoria,Kenya Rift Valley

Travertine is present at 20% of the ca 60 hot springs that discharge on Loburu delta plain on the western margin of saline, alkaline Lake Bogoria in the Kenya Rift. Much of the travertine, which forms mounds, low terraces and pool‐rim dams, is sub‐fossil (relict) and undergoing erosion, but calcite‐encrusted artefacts show that carbonate is actively precipitating at several springs. Most of the springs discharge alkaline (pH: 8·3 to 8·9), Na‐HCO₃ waters containing little Ca (<2 mg l^?1) at temperatures of 94 to 97·5°C. These travertines are unusual because most probably precipitated at temperatures of >80°C. The travertines are composed mainly of dendritic and platy calcite, with minor Mg‐silicates, aragonite, fluorite and opaline silica. Calcite precipitation is attributed mainly to rapid CO₂ degassing, which led to high‐disequilibrium crystal morphologies. Stratigraphic evidence shows that the travertine formed during several stages separated by intervals of non‐deposition. Radiometric ages imply that the main phase of travertine formation occurred during the late Pleistocene (ca 32 to 35 ka). Periods of precipitation were influenced strongly by fluctuations in lake level, mostly under climate control, and by related changes in the depth of boiling. During relatively arid phases, meteoric recharge of ground water declines, the lake is low and becomes hypersaline, and the reduced hydrostatic pressure lowers the level of boiling in the plumbing system of the hot springs. Any carbonate precipitation then occurs below the land surface. During humid phases, the dilute meteoric recharge increases, enhancing geothermal circulation, but the rising lake waters, which become relatively dilute, flood most spring vents. Much of the aqueous Ca²⁺ then precipitates as lacustrine stromatolites on shallow firm substrates, including submerged older travertines. Optimal conditions for subaerial travertine precipitation at Loburu occur when the lake is at intermediate levels, and may be favoured during transitions from humid to drier conditions.     

Relative influence of biotic and abiotic processes on travertine fabrics,Satono‐yu hot spring,Japan

The relative influences of biotic and abiotic processes on travertine fabrics are still not well understood, despite increasing interest in the last decade to better understand the record of ancient microbial life and sedimentary fabrics in microbial hydrocarbon reservoirs. This study examines travertines at Satono‐yu hot spring in Japan (the temperature of water flowing over the travertine was ca 35°C), to better understand the interaction between depositional, hydrochemical and microbial parameters at different flow settings. Characteristics of the bulk hydrochemistry, mineralogy (exclusively aragonite) and the driving force for precipitation (primarily abiotic CO₂ degassing with some photosynthetic microbial contribution) were similar among all of the flow settings. Conversely, the increase in flow velocity suppressed the influence of photosynthesis and enhanced the abiotic precipitation due to the thinner diffusive boundary layer at the travertine surface–water interface. Additionally, the increase in flow velocity changed the microbial composition and decreased the bacterial diversity by reflecting their adhesion efficiency on the travertine substrate. The acidity of the cyanobacterial sheaths controls the aragonite nucleation rate and the resulting calcification, even at significantly high equilibrium CO₂ partial pressure (ca 22 to 28 matm), high dissolved inorganic carbon concentration (ca 35 to 38 mmol l^?1), and elevated aragonite saturation state (ca 20‐fold to 34‐fold). Therefore, the increase in flow velocity suppresses the microbial influence with respect to the increase in the saturation state, the nucleation site supply and pore space generation. Overall, this results in the predominance of abiotic precipitation under high flow velocities. Consequently, a sparse‐micritic fabric with abundant interlamina porosity forms under lower flow velocity where the microbial influence is effective, while a dense‐sparitic fabric with little inter‐crystalline porosity forms under higher flow velocity where abiotic precipitation prevails. These findings provide an essential base for assessing the formation processes of ancient travertines and comparable deposits from petrological fabrics.     

Travertines in the northern Hula Valley, Israel

This study describes the field and petrographic relationships of a widespread deposit of Pleistocene travertines in the northern Hula Valley, northern Israel. The travertines interfinger with conglomerate deposits and basaltic lava flows. Field relationships and radiometric dating indicate that the travertines accumulated intermittently over the past million years, and their formation virtually stopped 25 000 years ago. The travertines are characteristically highly porous. Some of the pores, as well as some spar-filled voids, preserve the shapes of stalks and leaves. The abundance of plant material suggests that photosynthesis, rather than bacterial or abiogenic processes, was the main mechanism which induced carbonate precipitation. The reasons for travertine accumulation in the past and for the cessation of its formation today are ascribed to differences in the palaeogeographic setting. In the past, water flow is viewed as having been mostly sluggish, and a widespread and shallow sheet of water was formed. The lush vegetation, combined with the relatively long residence time of the water in the area, led to increased efficiency of the calcium carbonate precipitation. Today, by contrast, water flows rapidly in gorges, precipitating only a small fraction of its load of dissolved calcium carbonate. The conjectured change in hydrological conditions is ascribed to rejuvenation of faulting activity in the Late Quaternary.     

基于微岩相分析的藻类在钙华沉积中的作用研究——以四川黄龙为例

在地表环境下,钙华沉积常常是物理化学和生物沉积过程共同作用的结果。藻类因其在钙华沉积环境中具有较大的生物量及其自身拥有多样的代谢方式,对钙华沉积过程和形态具有重要影响。本研究以四川黄龙钙华为例,通过对典型沉积点的水化学、藻类群落组成和现代钙华微岩相结构进行综合分析,来揭示藻类在钙华沉积中的作用。研究发现,黄龙钙华沉积环境中分布的藻类主要包括蓝藻、绿藻和硅藻等。这些藻类代谢活动会在一定程度上改变沉积水体水化学环境,但在快速流动的水体中,其影响有限。不同藻类群落常常形成几百微米至1~2 mm厚的微生物席或生物膜层,作为碳酸钙沉积发生的重要场所,即钙华沉积活动层。在该活动层内,藻体及其分泌的胞外聚合物（EPS）能够为碳酸钙晶体生长提供大量成核位点和生长模板,从而极大地促进钙华沉积。同时,EPS可以控制或影响碳酸钙结晶形态及钙华微岩相结构。准确认识和量化藻类在钙华沉积中的作用还需要继续开展更多微观尺度方面的研究,以便更好地理解钙华沉积机制,并为准确解译古老钙华岩相结构和地球化学特征奠定基础,同时为预测钙华景观演化和保育提供更多科学依据。      

Distribution, lithotypes and mineralogical study of newly formed thermogenic travertines in Northern Euboea and Eastern Central Greece

In the northwestern part of Euboea Island and the neighbouring part of the mainland in eastern central Greece, many hot springs exist. We collected and analysed the newly formed material around the hot springs. The samples were studied at the lab with X-Ray Diffraction, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). In all cases the studied materials were thermogenic travertine presenting many different lithotypes. The studied travertine deposits consist mainly of aragonite and calcite, but in some cases, as the main mineral phase, an amorphous hydrous ferric oxyhydroxide, probably ferrihydrite (creating a laminated iron-rich travertine deposit), was identified. The lithotypes that were identified were of great variety (spicular, shrubs, etc). Some of them (pisoliths, rafts and foam rock types) are quite rare and one of them (framework type) is described for the first time. Morphological data and field observations suggest possible inorganic and organic controls on carbonate precipitation. Similar lithotypes have been recorded at Mammoth hot springs, Yellowstone National Park in USA and at Rapolano Terme, Italy.