Fissure Ridge Travertines Research Articles

Neotectonics and Geothermal potential of the East Anatolian Tectonic Block: A case study in Diyadin (Ağrı) geothermal field, NE Turkiye

The study area is Diyadin, which is situated 71 km ESE of Ağrı very close to the Turkish-Iranian State border. It is one of several type localities of promising geothermal fields in the Eastern Anatolia. The neotectonic regime and related structures are dominated by a strike-slip tectonic regime governed by a stress field in the Eastern Anatolia where the greatest principal stress (σ1) is operating in NNW direction (N22°W) while the least principal stress (σ3) is N68°E. This stress field state was proved once more by the tensor solution of the 12 June 2022 Akçift (Muradiye-Van) earthquake of Mw = 5.1. The strike-slip neotectonic regime started at the time of latest Pliocene-early Quaternary and then triggered the first occurrence of the fissure eruption along the NNW trending Kaletepe open fracture. This event was followed by the development of both the two-peaked Tendürek strato-shild volcano and the Diyadin geothermal field (DGF). The geothermal potential of the DGF is high and its most common manifestations are the active tectonic regime and related faults (extensional horse tail strucure), active volcanoes (Tendürek and Ağrı volcanoes), fumeroles, numerous hot water springs to artesian wells, widespread iron-rich alteration zones, actively 
 growing fissure-ridge travertines and the probable presence of the unroofed hypabyssal felsic to intermediate intrusions of Quaternary age at the roots and their near environs of the isolated Quaternary volcanoes in the Eastern Anatolia. In addition, some significant similarities and contrasts are seen between the DGF and the IGF when they are compared.

Multiple geochemical, mineralogical and isotopic approaches to constrain the deposition conditions of Gazlıgöl travertines, western Turkey

Owing to the complex tectono-magmatic evolution within the Alpine-Mediterranean belt, Turkey hosts numerous geothermal springs, which actively precipitate travertine deposits. In this study, we investigate geochemistry, stable and isotopic, mineralogical features, and depositional conditions of fissure-ridge travertines in the Gazlıgöl area, western Anatolia. U/Th age data of the studied travertines, which are precipitated by CO2-rich waters depressurized during episodic seismic events, vary from 279 ± 82 to 110 ± 61 ka revealing a prolonged seismic activity from middle to late Pleistocene. Gazlıgöl travertines composing chiefly of calcite have δ18O values in the range of −18.5 to −16.4‰ (VPDB) and δ13C values between 1.8 and 2.4‰ (VPDB). Δ47 values of samples vary from 0.584 to 0.638‰ and crystallization temperatures are estimated in a wide range between 36 ± 6 and 68 ± 4 °C. Considering the oxygen isotope fractionation between calcite and water (Δ18OCc-water), δ18O of paleofluids which precipitated the Gazlıgöl travertines was computed in the range of −14.9 to −10.6‰ (VSMOW), which is similar to the isotope composition of modern thermal waters (−13.1 to −10.9‰, VSMOW) of meteoric derivation in the study area. 87Sr/86Sr values of Gazlıgöl travertines fall in a narrow range from 0.720667 to 0.720837, suggesting that bedrocks in the Gazlıgöl area are the source of Sr in calcite bands. Like other travertines in western Anatolia, REE compositions of Gazlıgöl fissure samples are significantly lower than basement lithologies, which might be attributed to insufficient time for the interaction of CO2-bearing waters with the host rock because of their rapid ascent.

High geogenic arsenic concentrations in travertines and their spring waters: Assessment of the leachability and estimation of ecological and health risks

Travertines and their springs are rarely investigated as a source of toxicity. Remarkably high contents of As (up to 10 g/kg) have been found in travertine deposits and associated spring waters, nearby Ghorveh city (western Iran). Two types of travertines were distinguished: (i) Fissure ridge travertines, in areas with a carbonate-dominated basement, are characterized by a relatively low content and leaching of As. Their spring waters contain > 150 µg/L of As; (ii) Mound travertines, rich in non-carbonate impurities, occur in areas with volcanic substrates and contain high As concentrations (on average ~1,500 mg/kg) with high leachability. Their spring waters have lower As concentrations than equivalent fissure ridge waters. Principal Component Analyses of the elemental and mineralogical composition show the unstable association of As over a wide range of pH values to non-carbonate related elements, in particular iron, related to clay minerals. The high potential release of As may result in adverse ecotoxicological effects in surrounding agricultural soils and crops. An ecological risk assessment confirms the enrichment and very high potential ecological risk of As around mound carbonates. The human health risk assessment based on calculation via exposure factors suggests adverse non-carcinogenic and high carcinogenic risk with regard to As, both for adults and children.

Genesis and diagenesis of travertine, Futamata hot spring, Japan

Genetic and diagenetic processes of travertine were examined at Futamata hot spring, where both active and inactive (subfossil and fossil) travertines are present. Geochemical and geomicrobiological analyses of active travertines reveal that abiotic process of CaCO3 precipitation is predominant. Photosynthetic inhibition of CaCO3 precipitation occurs at the upstream, while the cyanobacterial population is low in the downstream, resulting in photosynthesis-induced CaCO3 precipitation only in the midstream. Nonetheless, microorganisms have an effect upon depositional fabrics, and filamentous cyanobacteria possessing non-acidic sheaths contribute to the particle trapping/binding and the generation of pore space. Both active and inactive travertines are mainly composed of calcite; however, active travertine in the up-/midstream also contains some aragonite due to high rates of CO2 degassing. Active and subfossil travertines are characterized by domal topography, and relatively high flow rates are assumed due to the dominance of slope facies. On the other hand, fossil travertines are characterized by fissure-ridge topography and relatively low flow rates are assumed due to the dominance of crest and marsh facies. The elemental composition of travertines primarily reflects their constituent minerals, and the active travertines consisting of both aragonite and calcite show higher Sr, Ba, Na, and K contents, whereas travertines consisting solely of calcite show higher Mg and Mn contents. Due to elevated Mn content, bright cathode luminescence is exhibited by the primary calcite of active travertines. Most fossil travertines have experienced prominent diagenetic alteration in the vadose zone and are commonly cemented and recrystallized. In addition to meteoric water, percolating hot spring water was also involved in the diagenetic process. Combined with the results of U–Th dating, our results suggest that the formation of fissure-ridge travertines at Futamata hot spring began approximately 20 thousand years ago (ka) via fault activity, which terminated at around 7 ka and the domal travertines were formed by hot spring water discharging from several vents.

Temporal changes in geochemical-isotopic systematics of the late Pleistocene Akkaya travertines (Turkey) – Implications for fluid flow circulation and seismicity

We investigate the temporal variations in stable carbon and oxygen and radiogenic Sr isotope as well as rare earth element contents of Akkaya travertine deposits in the Eskipazar region, northwest Turkey. U-Th age data indicate that studied travertines in the periphery of the 1944-earthquake rupture of the North Anatolian Fault Zone formed in a time span of 93 to 1.8 ka BP. The younger group is represented by fissure-filling carbonates whereas the older sequence is composed of veins with varying crystallization ages that are injected to bedded travertines. The age data on vein injections and fissure-ridge travertines in the Akkaya site indicate the seismic reactivation along the west-central part of the North Anatolian Fault Zone to be intensified at least 4 periods (1.8, 20, 47 and 88 ka BP) during the last 90 ka.δ18O and δ13C systematics of Akkaya travertines, which are precipitated by CO2–rich fluids depressurized during episodic seismic unrest, are in the range from −15.86 to −7.67‰ (VPDB) and 4.66–8.68‰ (VPDB), respectively. δ18O of the fluid equilibrating with the studied travertines is estimated in the range of −11.2 to −10.2‰ which is quite consistent with the average value (−12.3‰) reported for the Akkaya thermal spring. Stable isotope values of travertines indicate modification by rapid CO2 degassing associated with seismic events. Helium isotope compositions of gas phase and dissolved gas of thermal fluids in the area refer to mantle contribution up to 12 %. Sr isotope values of Akkaya travertines are probably originated from Upper Cretaceous marine limestones or mafic basement rocks. REY contents are about 3 orders of magnitude lower than those of basement lithologies.

Kuzey Anadolu Fay Zonu’nda Traverten Çökeliminde Sıcak Su Kaynağı Olarak Görev Yapan Bir Açılma çatlağı: Reşadiye Çatlak Sırtı

The Resadiye (Tokat) geothermal field is located in the northern part of the right-lateral North Anatolian Fault Zone. Geothermal waters at temperatures between 48-52°C from this geothermal field are currently used mostly in hotels, pools and bathrooms and provide significant tourism potential for the region. The area where the geothermal sites are located includes a ~NW-SE trending fissure-ridge type travertine with a length of about 600 meters. Approximately 500 meters south of the geothermal field and parallel to the Kelkit River, the active segment of the North Anatolian Fault Zone comprises the Kelkit Valley fault segment extending N72°W. The average strike direction of Resadiye fissure-ridge type travertine is around N33°W. There is an angle of 39° between the master trend of NAFZ and the direction of the Resadiye fissure-ridge travertine. This 39° angle between the extensional cracks in the fissure-ridge travertine and the NAFZ is compatible with extensional fractures developing in well-formed strike-slip faults at an angle of ~45° with the master fault. U/Th determination of two samples from banded travertines from the travertine deposits yielded ages of 7,563 and 12,529 years. Combined with other evidence, the samples indicate an opening rate of 0.093 mm/year for the Resadiye geothermal travertine field.

U-series dating and origin of Yaprakhisar (Güzelyurt-Aksaray) travertines in Central Anatolian Volcanic Province, Turkey

This study reveals the age, setting, and geochemistry of fissure ridge travertines outcropping in Yaprakhisar (Guzelyurt-Aksaray) that is located in the Central Anatolian Volcanic Province (CAVP) and investigates their relationship with main tectonic structures. Dating studies with the U-series analysis method identified that travertine formations were deposited from 3 to 147 ka BP. The travertines in the study area were divided into two groups based on the age and extension direction. The first group consists of fissure ridge travertines with 70° NE and deposited in the range of 126–147 ka BP. The second group has 10° NW strike and are fissure ridge travertines dated to 3–47 ka BP. The association between the travertine groups and the significant fault zones in the region was investigated, and three different formation models are presented. The relationship between the fissure ridge travertines and faults deforming the CAVP was determined using paleo-discontinuities. The Yaprakhisar travertines were determined to have Ce and Eu anomalies, along with low Ba and relatively low Sr values. When the trace element and REE content of the Yaprakhisar travertines are considered together, the travertines are concluded to have been deposited under oxic conditions from limestone-evaporite-dolomite-sourced hypogene water with low acidity and relatively low temperature.

U/Th Dating of the Akhüyük Fissure Ridge Travertines in Ereğli, Konya (Central Anatolia, Turkey): Their Relationship to Active Tectonics

Fissure ridge travertines that form the Akhuyuk travertine mass are located in Central Anatolia and are exposed in an area of 1.5 km $$^{2}$$ with N30 $$^{\circ }$$ W direction. These fissure ridge travertines have ages determined between 3345 ± 105 yr and 47850 ± 980 yr by U-series dating methods. Development of the travertines can be correlated with faults that have been active since the late Pleistocene. The dilation rate in the Eregli (Konya) basin was determined using age data and the widths of the banded travertines at the opening center of the fissure ridge travertines. The dilation rate for the formation of Akhuyuk travertines yields 0.025–0.05 mm yr $$^{-1}$$ on average. When considering positions and extension directions of fissure ridge travertines, they are consistent with the Tuz Golu Fault Zone which is one of the most important structures in the region. The maximum earthquake intensity potential in this region is estimated to be $$M_\mathrm{s}$$ 6.3, when the dilation rate of the fissure ridge travertines is taken to be 0.05 mm yr $$^{-1}$$ and with a 10,000-year earthquake recurrence interval.

Fossil findings from the Sıcak Çermik fissure ridge-type travertines and possible hominid tracks, Sivas, Central Turkey

Sıcak Çermik (Sivas) is an important geothermal and recent travertine formation area in Central Anatolia. The majority of travertines found in the region comprise fissure-ridge type travertines according to morphological classification. At the location called Tepe Çermik within the travertine area, fill containing fossil bone fragments of Equus sp., Bovidae and other abundant animals formed within the fracture axis of a N–S striking fissure-ridge travertine developed under control of tectonic forces. The finds of these fossils in fissure-ridge travertines linked to tectonic forces indicates formation of a unique fossil environment created under the control of these forces. The Accelerator Mass Spectrometry Radiocarbon Dating analyses of fossils from the study area determined the fills were older than 43,000 years. The U/Th age of a sample from the most recently-formed banded travertine in the axis of the fracture was identified as 278,540 ± 18,436 years. As a result, the ages of fossils found within this fill are thought to be between 43,000 and 278,540 ± 18,436 years old. The high amount of perissodactyla and artiodactyla fossils found within fill in the axis of the fissure-ridge travertine probably indicates the presence of hominids who chose the region for hunting or settlement. The Equus sp. and Bovidae fossil samples found in the axis of the fracture indicate that in the dry and cold glacial period the paleogeography in a large portion of Anatolia comprised desert-like steppe.

Evolution of Çamlık fissure-ridge travertines in the Başkale basin (Van, Eastern Anatolia)

Fissure-ridge travertines (FRTs) are of great importance for the determination and comparison of tectonic deformation in a region. The coeval development of these travertines with active fault zones supplies significant information about regional dynamics in terms of deformation pattern and evolution. In this paper, the characteristics of FRTs of the Başkale basin (eastern Turkey) and responsible regional tectonism are discussed for the first time. The Başkale basin is located between the Başkale Fault Zone (BFZ) characterised by Çamlık fault and Işıklı–Ziraniş fault. It is located between dextral Yüksekova Fault Zone and southern end of dextral Guilato–Siahcheshmeh–Khoy Fault system (Iran). Various morphological features indicating recent activity are exposed along the BFZ, including offsetting rivers, fissure-ridge travertine and fault scarps. The Çamlık fissure-ridge travertine composing of three different depositions is observed along the eastern edge of the BFZ with approximately parallel orientations. The Çamlık fissure-ridge travertine has been formed and developed on fault zone related to strike-slip or oblique movements. We explain how kinematic changes of faults can influence the fissure-ridge development.

Hydrothermal fluids circulation and travertine deposition in an active tectonic setting: Insights from the Kamara geothermal area (western Anatolia, Turkey)

Coexistence of thermal springs, travertine deposits and tectonic activity is a recurring feature for most geothermal areas. Although such a certainty, their relationships are debated mainly addressing on the role of the tectonic activity in triggering and controlling fluids flow and travertine deposition. In this paper, we present the results of an integrated study carried out in a geothermal area located in western Anatolia (Turkey), nearby the well-known Pamukkale area (Denizli Basin). Our study focused on the relationships among hydrothermal fluids circulation, travertine deposition and tectonic activity, with particular emphasis on the role of faults in controlling fluids upwelling, thermal springs location and deposition of travertine masses. New field mapping and structural/kinematics analyses allowed us to recognize two main faults systems (NW- and NE-trending), framed in the Neogene–Quaternary extensional tectonic evolution of western Anatolia. A geo-radar (GPR) prospection was also provided in a key-area, permitting us to reconstruct a buried fault zone and its relationships with the development of a fissure-ridge travertine deposit (Kamara fissure-ridge). The integration among structural and geophysical studies, fluids inclusion, geochemical, isotopic data and 230Th/238U radiometric age determination on travertine deposits, depict the characteristics of the geothermal fluids and their pathway, up to the surface. Hydrological and seismological data have been also taken in account to investigate the relation between local seismicity and fluid upwelling. As a main conclusion we found strict relationships among tectonic activity, earthquakes occurrence, and variation of the physical/chemical features of the hydrothermal fluids, presently exploited at depth, or flowing out in thermal springs. In the same way, we underline the tectonic role in controlling the travertine deposition, making travertine (mainly banded travertine) a useful proxy to reconstruct the seismological history of an area, as well as the characteristics of the parent geothermal fluids, adding an effective tool for geothermal exploration tasks.

Growth of a Pleistocene giant carbonate vein and nearby thermogene travertine deposits at Semproniano, southern Tuscany, Italy: Estimate of CO2 leakage

A giant carbonate vein (≥50m thick; fissure ridge travertines) and nearby travertine plateaus in the Semproniano area (Mt. Amiata geothermal field, southern Tuscany, Italy) are investigated through a multidisciplinary approach, including field and laboratory geochemical analyses (U/Th geochronology, C, Nd, O and Sr isotope systematics, REE abundances, and fluid inclusion microthermometry). The main aim of this work is to understand: (1) modes and rates for the growth of the giant vein and nearby travertine deposits within a Quaternary volcano-tectonic domain; (2) implications in terms of the CO2 leakage; and (3) possible relationships with Quaternary paleoclimate and hydrological oscillations. Results show that the giant vein was the inner portion of a large fissure ridge travertine and grew asymmetrically and ataxially through repeated shallow fluid injections between >650 and 85ka, with growth rates in the 10−2–10−3mm/a order. The giant vein developed mainly during warm humid (interglacial) periods, partially overlapping with the growth of nearby travertine plateaus. Estimated values of CO2 leakage connected with the vein precipitation are between about 5×106 and 3×107mola−1km−2, approximately representing one millionth of the present global CO2 leakage from volcanic areas. Temperature estimates obtained from O-isotopes and fluid inclusion microthermometry indicate epithermal conditions (90–50°C) for the circulating fluid during the giant vein growth, with only slight evidence of cooling with time. Geochemical and isotope data document that the travertine deposits formed mainly during Pleistocene warm humid periods, within a tectonically-controlled convective fluid circuit fed by meteoric infiltration and maintained by the regional geothermal anomaly hosted by the carbonate reservoir of the Mt. Amiata field.

Strike-slip neotectonic regime and related structures in the Cappadocia region: a case study in the Salanda basin, Central Anatolia, Turkey

The study area is a strike-slip basin of approximately 1-9 km wide, 66 km long and N65°W trending, located between the historical Kesikköprü in the west and the Sarıhıdır settlement in the east along the northern side of the Central Anatolian Volcanic Province. It was evolved on a regional erosional surface of a pre-Quaternary volcanosedimentary sequence during Quaternary. This is evidenced by the stratigraphical, structural, and seismic data. The total amounts of throw and dextral strike-slip displacement accumulated on the basin-boundary faults during the evolutionary history of the basin are 178 m and 5 km, respectively. The average slip rate on the Salanda master fault is approximately 4 mm/year since the late early Pleistocene based on the total dextral strike-slip offset accumulated on it. The throw amount is small compared with the dextral strike-slip offset, which implies a strike-slip regime rather than a tensional tectonic regime in the basin. This is also supported by the combination of both the contractional and extensional structures such as reverse faults, fissure-ridge travertines, and a series of stepped terraces of late Quaternary age. Finally, it would be useful to take this paper into account in new works to be carried out in other sections of the Cappadocia region, because a new neotectonic regime (strike-slip tectonic regime) is first introduced here for this region.

Relationship between Akhüyük fissure ridge travertines and active tectonics: their neotecteonic significance (Ereğli-Konya, Central Anatolia)

The Akhuyuk travertine mass crops out approximately 10 km to the north of Eregli (Konya, Central Anatolia). Its morphology and relationship with the main controlling fault zones are investigated. The morhpological properties of six different fissure ridge travertines which make up the travertine mass are classified into four groups based on their geometrical properties and orientation. The fissure ridge travertines having a banded travertine thickness of 120 and 170 cm are considered as the oldest travertines in the study area. Sill-like structures and dilation are observed, indicative of the ongoing deformation after travertine precipitation. The height-to-width ratio of the fissure ridge travertines vary between 0.08 and 0.5. The morhological structures and parameters observed in the fissure ridge travertines are interpreted to stem from the low deformation rate in the study area. The relationship of the formation of the Akhuyuk Fissure Ridge travertine with the Tuz Golu (TGFZ) and Nigde fault zones (NFZ) is investigated. The TGFZ is determined to be the most significant structure that controls the Akhuyuk fissure ridge travertines based on the extension direction determined, the location of the travertines, and the fact that the faults on the central and southeastern end of the TGFZ display the active normal fault zone with a right-lateral strike-slip component.

Investigation of the subsurface geometry of fissure-ridge travertine with GPR, Pamukkale, western Turkey

Cracks in the upper crust are the result of either local or regional tectonic stress. Such structural elements are conduits for fluids in the crust. In Pamukkale, hot water which is rich in calcium carbonate emerges from fissures. The hot water issuing from the fissures precipitates travertine both in the fissures and on the surface. As a result, a ridge, which is called fissure-ridge travertine, forms along the central fissure. Fissure-ridge travertines are lens-shaped at the surface. Since fissure-ridge travertines are of great tectonic significance, their surface characteristics have been studied in detail. However, the subsurface geometry of travertine ridges is not well known. GPR was used to examine the subsurface geometry of fissure-ridge travertine and the central fissure. GPR profiles were combined across the ridge to produce a three-dimensional (3D) subsurface image of the travertine mass. The 3D image showed that the thickness and width of the travertine mass are at a maximum near the centre of the ridge and they both decrease asymmetrically towards the ends. Perpendicular GPR slices across the central fissure showed that the thickness of the vertically banded fissure-travertine increases with depth. 3D modelling suggests that the lateral propagation of the central fissure is asymmetric.

The origin and growth of a recently-active fissure ridge travertine over a seismic fault, Tivoli, Italy

An enigmatic, c. 2km-long and 15m-high travertine ridge, the Colle Fiorito ridge, occurs in the northwestern sector of the Tivoli travertine plateau, central Italy. The main questions addressed in this paper concern the origin and mode of growth of this prominent ridge. The presence of active structures beneath the studied ridge is inferred by recent and past earthquakes located at shallow depths immediately beneath Colle Fiorito. To understand the surficial structure of the Colle Fiorito ridge and the travertine depositional environment, we constructed a 10m-resolution DEM, analyzed recent and past aerial photographs, and conducted field surveys and meso- to micro-scale sedimentological analyses. To understand the ridge subsurface structure, we studied a set of 32 stratigraphic well logs available from previous works and from the local decorative stone industry, and realized a 2D electrical resistivity tomography (ERT) across the ridge. Results show a gentle antiformal structure affected by subvertical zones of strata discontinuity. The Colle Fiorito structure is interpreted as a previously-unknown fissure ridge travertine grown at the edge of the Tivoli travertine plateau, perhaps when the volumetric deposition rate reached its climax in the plateau for the abundance of fluid discharge and the rise of the water table. Such a fluid pressure may have activated the faults and fractures beneath Colle Fiorito, thus opening new pathways for the ascension of geothermal fluids toward the surface.

Growth of fissure ridge travertines from geothermal springs of Denizli Basin, western Turkey

Fissure ridge travertines grown from geothermal springs of Denizli Basin, southwestern Turkey, are investigated through stratigraphic, structural, geochemical, and geochronological methods, with the aim of understanding the growth of these elongate mound-shaped structures. Two main types of travertine deposits are recognized: (1) bedded travertines, which grew as flowstone on sloping surfaces and form the bulk of fissure ridges, and (2) banded travertines, which grew as veins within the bedded travertine chiefly along its central feeding conduit. Stratigraphic and structural observations shed light on the bedded-banded travertine relationships, where the banded features grew through successive accretion phases, crosscutting the bedded travertine or forming sill-like structures. The bedded and banded travertines alternated their growth, as demonstrated by complicated crosscutting relationships and by the upward suture, in places, of banded travertine by bedded travertine that was, in turn, crosscut by younger banded travertine. The bedded travertine is often tilted away from the central axis of the fissure ridge, thus leaving more room for the central banded travertine to form. U-series ages confirm the bedded-banded travertine temporal relationships and show that the growth of the studied fissure ridges lasted up to several tens of thousands of years during Quaternary time. The banded travertine was deposited mainly during cold events, possibly in coincidence with seismic events that might have triggered the outflow of deep geothermal fluids. C and O stable isotope and rare earth element data indicate a shallow feeding circuit for the studied structures with a fluid component deriving from a deeper geothermal circuit. A crack-and-seal mechanism of fissure ridge growth is proposed, modulated by the interplay of local and regional influencing factors and mechanisms such as geothermal fluid discharge, paleoclimate, tectonics, and the progressive tilting of bedded travertine limbs over a soft substratum creating the necessary space for the central veins to grow.

Morphotectonics of fissure ridge travertines from geothermal areas of Mammoth Hot Springs (Wyoming) and Bridgeport (California)

Eleven Quaternary fissure ridge travertines from Mammoth Hot Springs (Wyoming) and seventeen ones from Bridgeport (California) were mapped and studied with a morphotectonic approach to understand possible relationships between travertines and active versus passive tectonics. Results are compared with other known geothermal fissure ridges on the Earth. The studied fissure ridges are all located in the hangingwall of normal faults, but the fissure ridges appear as non-dislocated by faults, rather by axial fissures. Both in the two principal study areas and elsewhere, azimuthal analyses of faults and fissure ridges show that the distribution of fissure ridge long axis is rather dispersed around the strike of the local normal faults. No correlation occurs between the fissure ridge length and the angle between the strike of the normal fault and the strike of fissure ridges. The studied fissure ridges are 2 to 360m long (mean length: 72.1m), 1 to 15m wide (mean width: 6.7m), and 0.5 to 8m high (mean height: 3.9m). Fissure ridge aspect ratios show a moderate correlation between the length and both the width and the height of fissure ridges, whereas the correlation between width and height is less marked. The growth in height and width of ridges appears as much more inhibited than in length. A model is proposed in which fissure ridge travertines grow with enhanced elongation along one sub-horizontal direction, which seems moderately controlled by the associated normal fault and the regional extension. Other factors, such as the inherited fracture network and the geothermal and artesian pressure of fluids (fluid discharge) may be important in the development of the studied fissure ridges. Results from this study may contribute to the knowledge of factors that control the long-term geothermal circulation and also the long-term hermetic durability of CO2 subsurface repositories.

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)

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

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.