Secondary Sediments Research Articles

Features of carbonate speleothems from the Belaya Cave (Zabaykalsky Krai)

The research gives the first data on mineralogical studies of carbonate speleothems in the karst cave named Belaya. Dolomite-calcite, calcite-magnesite and hydromagnesite compositions of secondary carbonate sediments in various grottoes of the cave were determined by thermal analysis (TG-DSC) and X-ray diffraction (XRD). Creating a mineralogical reserve or park with the Belaya Cave as its core is suggested.

Analysis of Temperature Influence on Precipitation of Secondary Sediments during Water Injection into an Absorptive Well

The extraction of hydrocarbons is associated with obtaining certain amounts of water, which is heavily contaminated with a wide range of chemical compounds that negatively affect the environment. At present, practically the only method of managing extracted reservoir waters is their injection into absorbing horizons. Large changes in parameters (pH, Eh, temperature, etc.) occurring during the extraction and storage of water, as well as the contact of the injected water with reservoir water and rock, may result in the precipitation of secondary sediments. The complexity of the injected water/native water/deposit rock system and the wide range of possible interactions do not always allow for correct interpretation of the processes and their impact on near-well zone permeability. One of the factors which has a decisive influence on dissolution/precipitation is temperature change. Applying analytical data of water with low (W-1) and high (W-2) mineralization, calculations were carried out with the use of PRHEEQC software. Changes in solubility index values were determined at ambient temperature (20 °C) and reservoir temperature (94 °C). The obtained results indicate that with increasing temperature, SI changes for a given chemical compound may run in different directions and take different values, depending on the composition of the injected water. The calculations indicate the possibility of a change in the direction of the reaction from dissolution to precipitation, which may lead to clogging of the near-well zone. Simulations of the injected water’s contact with minerals present in the reservoir rock were also carried out. The obtained data indicate that these minerals, in the entire studied temperature range, dissolve in the injected water, but the solubility of anhydrite and dolomite decreases with increasing temperature. If the water is saturated with minerals at low temperature, after heating in the bed, sedimentation and blockage of rock pores may occur, which means there is a reduction in the efficiency of water injection.

Rock mass and Earth’s surface movement during underground working of cryolithozone placers

The results of the researches on the processes of movement of rock mass and the Earth’s surface during underground working of alluvial mines in the cryolithozone are presented. Geologically, the area of the deposit is an alluvial placer. The productive seam is represented by pebble deposits. The cementitious composition of pebbles is clay, sand and ice. The thickness of the productive seam is on average 1.8 m. The average thickness of loose deposits is 30 m. The temperature of the rocks is minus 6-8°C. The moisture content of the rocks is 22%. Mine-field parameters: width - 50 m; length - 320 m; development depth - 30 m. Development system -pillar. Roof control - the collapse of the roof rocks onto the T-13K powered support. The first spontaneous roof caving occurred during a longwall face span 28 m from the contour of the mine-field. The beginning of the movement of Earth’s surface was noted at bottom hole deviation from the contour of the mine-field by 55 m 15 days after the first caving. During the development of the second half of the mine-field, the rates of maximum subsidence increased significantly, reaching in some cases 30 mm./day. An increase in the rate of subsidence of surface bench marks (12-18 mm/day) refers to secondary roof sediments. The following features of the rock mass movement have been established: the general deformation of the roof rocks begins at 2500 - 3000 m2, the angles of strike shift and across the strike of the mine-field are practically the same and fluctuate within 75-80° the maximum subsidence of the shift trough with full additional working is 0.75-1.0 m and is located in the middle of the mine-field.

Experimental Study on the Self-Healing Behavior of Fractured Rocks Induced by Water-CO2-Rock Interactions in the Shendong Coalfield

This study experimentally investigated the self-healing behavior, referring to the naturally occurring water permeability decrease, of fractured rocks exposed to water-CO2-rock interaction (WCRI). The experiment was conducted on prefractured specimens of three rock types typical of the Shendong coalfield: coarse-grained sandrock, fine-grained sandrock, and sandy mudrock. During the experiment, which ran for nearly 15 months, all three specimens exhibited decreasing permeabilities. The coarse- and fine-grained sandrock specimens exhibited smooth decreases in permeability, with approximately parallel permeability time curves, whereas that of the sandy mudrock specimen decreased rapidly during the initial stage and slowly during later stages. The sandrock specimens were rich in feldspars, which were dissolved and/or corroded and involved in ionic exchange reactions with CO2 and groundwater, thereby generating secondary minerals (such as kaolinite, quartz, and sericite) or CaSO4 sediments. These derivative matters adhered to the fracture surface, thereby gradually repairing fractures and decreasing the water permeability of the fractured rocks. In comparison, the sandy mudrock had a high content of clay minerals, and the water-rock interaction caused rapid expansions of illite, mixed illite-smectite, and other clay minerals, thereby narrowing the fractures and causing the rapid permeability decrease during the initial stage. In later stages, the derivative matters generated by the dissolution and/or corrosion of feldspars and other aluminum silicate minerals in the mudrock filled and sealed the fractures, causing the slow permeability decreases during the later stages, as in the sandrock specimens. Neutral and basic groundwater conditions facilitated better self-healing of fractured mudrocks rich in clay minerals, whereas acidic groundwater conditions and the presence of CO2 facilitated better self-healing of fractured sandrocks. Thus, this study’s results are of significant value to aquifer restoration efforts in the Shendong coalfield and other ecologically vulnerable mining areas.

Analysis of shale property changes after geochemical interaction under CO2 sequestration conditions

This study implements a supercritical CO2 (scCO2) sequestration environment in a laboratory and investigates the geochemical effects of scCO2 on the properties of rock specimens. Shale specimens constituting caprock were kept in a laboratory reactor chamber with scCO2 for 63 days. Chemical interaction between rock surface and the scCO2 was then induced, and the changes in the properties were inspected before and after the reaction through various tests. The non-destructive tests comprised measurement of elastic wave velocity, shore hardness followed by investigation using the inductively coupled plasma mass spectrometer, and scanning probe microscope. The destructive tests include uniaxial compressive strength, Brazilian tensile strength, and X-ray fluorescence tests. Results show that mechanical properties are significantly weakened when shale specimens are exposed to both scCO2 and brine. The specimens reacting with only scCO2 induced a self-healing effect by precipitation of secondary sediments, becoming a more intact rock with increased strength and elastic modulus. The results denote that the geochemical alteration of shale occurs in a short time and are highly dependent on the reaction conditions. These results provide fundamental information for the stability of CO2 storage sites regarding the physical and chemical reactions between rocks under geological sequestration conditions.

The Geochemistry of Rare Earth Elements in Natural Waters and Secondary Mineral Sediments of Thermal Fields of Kamchatka

The distribution of rare-earth elements in surface and underground waters, water-bearing rocks, and secondary mineral neoformations of thermal waters of the Paratunka and Vilyuchinsk hydrothermal systems of Kamchatka has been studied. It is revealed that their content, distribution, and fractionation differ with respect to the geochemical type of water and the pH–Eh of the aquifer. All waters are characterized by the domination of the transportation of dissolved rare earth elements, which exceeds their transportation with colloids by 1000 times. It has been shown that neoformations of carbonates, sulfates, and silicates, including calcite, gypsum, and amorphous opal, are widespread in the discharge areas of the studied thermal waters. The redistribution intensity of rare earth elements in the rock–water–secondary deposits system is very low in waters of the sulfate type, where the elements are bonded to sulfates. At the same time, the precipitation of rare earth elements as newly formed mineral phases is most intensive in water with carbonate complexes.

ЭЛЕМЕНТНЫЙ АНАЛИЗ БИОМАССЫ АКТИВНОГО ИЛА В ПРОЦЕССАХ СОВМЕСТНОЙ БИОЛОГИЧЕСКОЙ И РЕАГЕНТНОЙ ОЧИСТКИ СТОЧНЫХ ВОД И ОЦЕНКА ВОЗМОЖНОСТИ ЕЕ УТИЛИЗАЦИИ

The aim of this work was to study the elemental composition of bioactive sewage sludge produced by wastewater treatment facilities located in various cities during the biological and chemical treatment of wastewater. In addition, the possibility of recycling and re-using such sediments was assessed. The elemental composition was characterized using X-ray fluorescence analysis, whereas the presence of heavy metals was determined by the method of inductively coupled plasma mass spectrometry with a preliminary wet ashing of the samples in a microwave oven. The experimental results showed significant amounts of Ca, P, Si and S in the bioactive sludge samples under study. The content of heavy metals in the secondary sediments of biological wastewater treatment plants was studied, with the possibility of using these sediments as an unconventional fertilizer being assessed. The increased content of heavy metals is shown to be characteristic of samples obtained from a wastewater treatment plant in Usti nad Labem, Czech Republic. The secondary precipitates from the cities of Kazan and Zelenodolsk did not exceed the norms established for the 1st group sediments by GOST R 17.4.3.07-2001, 2008 in terms of the heavy metal content. An increase in the concentration of some heavy metals after a combined biological treatment with reagent preparations was established.

Analysis of Temporal and Spatial Variations in Trace Element Migration in Karst Critical Zone:An Example of Jiguan Cave, Henan

To explore the temporal and spatial variations and the process of trace element migration in the karst critical zone, continuous fixed-point monitoring and sampling analysis was applied to measure each cave system component, which includes rainfall, soils, bedrock, drip waters, and their aerial sediment. Approximately 650 experimental data were obtained from October 2009 to May 2015 in a typical karst critical zone in north China-an interactive zone of the Jiguan Cave in the west Henan Province. The variations in and the migration rules of Ca, Mg, Ba, Sr, and δ13C as well as their ratios to different components were studied. The results show that:① Soil and bedrock are the main sources of drip water. The values of Mg, Ba, and Sr are consistent with the "soil-bedrock" two end-members model and their respective proportions are 43.6:56.4, 1.01:98.09, and 47.2:52.8. ② From the spatial perspective, element migration of each component in the cave system interactive zone is interrelated. Drip water inherits the signals of the soil and bedrock and the modern sediment can continue the element information of the drip water. Elements in the soil profile cause the leaching and deposition effect and the subsoil better inherits the information of trace elements in the bedrock. ③ From the temporal perspective, the migration of elements in the cave system interactive zone is complex. Because of the leaching effect, soil and drip water show obvious seasonal discrepancies. However, under the influence of karst water migration path, the prior calcite precipitation (PCP), and extreme arid and annual precipitation type, the seasonal discrepancy in the element concentrations in drip water is smaller than in soil. The PCP effect, selective leaching, and other factors change the continuity of elements released from sediment to drip water. ④ In order to systematically and comprehensively ascertain the trace element migration in the karst critical zone and energy transformation rules, the study of cave system should be based on the research of the cave's critical zone and should consider comprehensive information ranging from the atmospheric origins to secondary sediments.

Water-rock-ore Interaction (on Example: Major Bakchar Iron-ore Deposit – Western Siberia, Russia)

The paper includes data of the enclosing sediment, iron ore and groundwater composition within Bakchar iron ore cluster. Based on the water chemical composition analysis the thermodynamic equilibrium was calculated for enclosing sediment–groundwater–secondary sediments system, and being correlated to existing geological data. According to thermodynamic calculations, water is non-equilibrium to primary enclosing rock aluminosilicate minerals in which they dissolve and, consequently, are enriched by these chemical elements: Fe, Ca, Mg, K, Na, Si, Al, Mn and others. These accumulated elements in the solution provide clay-water equilibrium, carbonate-water equilibrium, Fe oxides and hydrooxides-water equilibrium.

Early pottery from the Lingjing site and the emergence of pottery in northern China

In the Chinese context, pottery that predates ca. 9000 14C BP is referred to as “early pottery”. Research on the early pottery of China had been conducted mostly in central and southern China; in contrast, research in northern China has been restricted, and only 5 sites had been discovered to date. Therefore, additional data is needed to foster the progress of research on early pottery in northern China. Given this situation, there is great value in the investigation of the many potsherds associated with microblade industry that have been found in secondary sediments of Layer 5 of the Lingjing site in Henan Province, on the Huang-Huai Plain at the southern end of the North China Plain.Based on AMS 14C dates (ca. 9.8 cal ka), typological features of the pottery, and features of the other artifacts found at Lingjing, these potsherds are argued by this paper to be examples of early pottery, meaning that Lingjing constitutes a new site yielding early pottery in northern China. Other than these archaeological results, our research on Lingjing pottery has also yielded primary data on stable carbon/nitrogen isotope analysis and starch residue analysis.On the basis of archaeological research on early pottery, including examples from Lingjing, it appears that pottery in northern China generally emerged at the beginning of the Holocene (11.7 cal ka). Therefore, this emergence of pottery was likely related to the rapid warming just after the end of the last glacial period, after the Younger Dryas. The archaeological evidence also indicates increasing utilization of plant resources and diversification of food resources beginning prior to that time, suggesting that early pottery may have played a major role in this change in subsistence strategy in northern China.Archaeological comparisons between the early pottery of northern and central/southern China show substantial differences. Based on its association with microblade technology and on characteristic features such as vessels with a flat base, this early pottery from northern China may be related to that from regions further north, such as the Russian Far East.

Cпелеокомплекси природних карстових печер

The paper is devoted to the definition of “speleocomplex” and its interpretation and place in natural karst caves. The limits of the territories on the earth’s surface and deep in the bowels of the earth are substantiated. A proposed name for such spatial units is speleotopes. Taking into consideration that a lot of caves have a long length within one layer of karst rocks, complicated genesis, different morphology, and unique secondary sediments the author identified next types of speleotopes: morphological speleotopes – elementary surfaces of the topography of caves; litospeleotopes – areas homogeneous in secondary sediments; climatological speleotopes – galleries or their parts with homogeneous microclimate; phitospeleotopes – areas homogeneous in phitocenosis; zoospeleotopes – areas with regular concentration of troglophiles or with signs of their activities. The complex of the speleotopes can form speleochore. Author focus attention on the self-restoration of the underground spatial subsystems and its speed. Karst landscapes on the surface have a quicker energy exchange in comparison to underground landscapes. Therefore, the author argues that caves landscapes should have the higher level of protection and reservation. Main types of the use of the caves landscapes are described in the paper, among them mining, recreational, speleological and scientific. According to the level of changes author identified such types of speleological complexes: unchanged (natural) – speleological complexes of the underground cavities that are unknown or untouched by human beings; slightly changed – anthropogenic activity is present but natural processes are unchanged; changed speleocomplexes (highly changed) – with a long-lasting anthropogenic footprint; transformed (cultural) – with a regular anthropogenic load and steadily degrading. The necessity of the allotment of elementary spatial units in underground speleological karst subsystem is highlighted. Concepts and terminology for speleological complexes of natural karst cavities that experienced anthropogenic transformations are defined – anthropogenic penetration and changes due to engineering. The paper also presents examples of anthropogenic speleological landscapes in Ukrainian caves. The author shows main directions for the optimization works (revitalization) of the transformed speleological complexes. Causes of the degradation of speleological complexes and ways of rational speleological management are also described.

Condor seamount (Azores, NE Atlantic): A morpho-tectonic interpretation

High-resolution datasets collected by multibeam and acoustic backscatter surveys were used to produce fine-scale seafloor nature and morpho-tectonic interpretations of the Condor seamount. Condor constitutes an elongated volcanic ridge that extends for 39km and rises more than 1800m from the surrounding seafloor. Constructive morphologies include (i) linear eruptive centres, (ii) volcanic cones with or without summit depressions, (iii) lava flows and (iv) hummocky sectors. Eruptive type is interpreted to vary with depth. On the deeper seamount extremities, the predominance of highly acoustically backscattering volcanic cones and hummocky terrain is interpreted to result from effusive eruptions not yet covered by sediment deposits. In contrast, the smoother relief of the central seamount flanks is interpreted as draping and infilling of the underlying effusive relief by (i) primary volcaniclastic deposits produced by explosive eruptions on the shallowest parts of the ridge, together with (ii) secondary volcanigenic sediments resulting from truncation of the seamount top by swell erosion and (iii) sediments resulting from biogenic production.A set of WNW–ESE to NW–SE trending volcano-tectonic structures are shown to control most of the fissural volcanism that formed the ridge. A network of NNW–SSE trending faults is identified on the sea-floor around Condor but they show little relation with the distribution of volcanic edifices or with post-emplacement dismantling of the seamount. These fault sets are related to the transtensional regime acting on the Azorean segment of the Eurasia–Nubia plate boundary.Erosional features include (i) palaeo wave-cut platforms on the seamount summit, (ii) landslide scars produced by lateral collapses of the NE and SW-facing flanks, (iii) gullies and turbidity current channels and (iv) mass-wasting deposits. Iceberg drag and bump marks are also identified on the seamount upper flanks, representing the first reference to such features in the Azores and an additional low latitude record.Given the lack of major erosional and tectonic dismantling, Condor is suggested to be a relatively young seamount. A revised factoring of eustatic, erosional and isostatic processes does not exclude that the summit may have been eroded as late as the Last Glacial Maximum.

Controlling factors on changes of gold mineralization in Saqqez (Kurdistan) shear zones and reagent ratios of the mineralized section

Investigating the secondary geochemical environments, river, and stream sediments are considered as one of the geochemical exploratory methods on a primary scale, which is justifiable regarding the expenses and time of execution. Evaluating the factors related to mineralization of gold shear zones based on stream and river sediment sampling, located in the southwest of Saqqez (Kurdistan), is the main purpose of this research. Using multivariable analyses and investigating the cluster graph of the elements, controlling factors of mineralization have been investigated and effective factors are divided into two groups, one is probably related to the mineralization of gold in the region which contains the elements (Pb, Zn, Mo, Ag, Cu, Bi, etc.), and other is related to typical petrogenetic processes which contains the elements (Co, V, Cr, Ti, Ni, Mn, etc.). Based on factor analysis, seven main factors, which justify about 80% of the changes of the region, were introduced; factors 3, 1, 5, and 6 were related to mineralization and factors 2, 4, and 7 were related to the lithology of the region. For a more precise separation of the processes related to mineralization, various ratios were investigated and reagent ratios (Au/Bi and Au/Mo) were identified. It is found that the ranges of [23–100] for Au/Bi and [8–80] for Au/Mo are related to gold mineralization. Using the modeling of the reagent ratios probability graph and determining the exploratory threshold, significant parameters in gold mineralization were separated from insignificants.

Responses of Secondary Currents and Sediments to Submerged Groynes

Recent studies have shown that submerged groynes can provide an extremely valuable habitat for fish and macroinvertebrates in addition to the function to establish a more desirable channel for flood, navigation and bank erosion.In this paper, we investigated experimentally the effect of submerged groins, which are positioned downstream, upstream and normal to a straight channel flow, on secondary currents and sediments. Experimental results showed that groynes facing upstream lead to the minimum scouring around the head of groins and deflected most effectively the main flow away from the bank.

Problems of Stratigraphic Correlation and New K-Ar Data for Ignimbrites from Cappadocia, Central Turkey

Extensive calc-alkaline ignimbrite volcanism occurred in Central Anatolia since the late Miocene. At least eight major and two minor rhyolitic nonwelded and welded deposits can be identified within the Urg¨p Basin and on the adjacent Nevsehir Plateau in the Central volcanic province. They are separated from one another by Plinian pumice, surge deposits of individual eruptions, and extensive secondary volcaniclastic sediments. Although exposures in the study area between Nevsehir and the Sultansazligi depression are excellent, disconnected outcrops resulting from recent and paleotopographic as well as young volcanic and sedimentary cover have led to controversial interpretations of the stratigraphic succession, especially in the upper part. The stratigraphic succession presented here modifies previous views, also based on the ignimbrites. Furthermore, an attempt is made to further subdivide the Kavak stratigraphic unit. The ignimbrites of the Urg¨p Basin/Nevsehir Plateau are, from bottom to top, Lower Gore...

Secondary Currents and Sediments Control by Delta Vanes in Open Channels

The streamwise development of pairs of longitudinal vortices and their effects on the sediments were investigated experimentally for different vortex pair configuraions. Three-components velocity measurements have been made in an open channel flow with a vortex pair artificially generated by two delta vanes protruding from the flatbed. The experimental results showed that delta vanes produced sand ribbons and controlled the longitudinal vortices, the mean motion of the vortex centers qualitatively followed a vortex filament model and the vortices with the flow depth spacing indicated a significant interaction between them.

Secondary Currents Structure and Sediments Characteristics in River Confluence

In this paper, experiments were conducted in the confluence with a training dike to investigate the interaction between vertical and longitudinalvortices, sediment discharge and the three-dimensional characteristics of the turbulence produced from the merging of two parallel streams with different flow discharge. The distribution of primary flow velocity, secondary currents and bed load were examined in detail by comparing with the two-dimensional turbulent mixing layer behind the thin flat plate.The experimental results showed that the secondary currents with a vortex diameter of about a flow depth existed in the confluence and they developed due to the interaction of corner secondary currents during the merging process and received effects of vertical vortices within the mixing layer. In addition, the sand ridges, which are defined as sand wave with elongate ridges parallel to the main stream, were formed at even number multiple of a flow depth distant from the plate and downstream position behind it.

開析谷の遺跡とそれをとりまく古環境復元 関東平野中央部の川口市赤山陣屋跡遺跡における完新世の古環境

Paleoenvironmental reconstruction of the Holocene since 8, 000 years ago, based on detailed archaeological excavation and geological and paleobotanical studies, including fossil pollen assemblage, plant macrofossil assemblage, and fossil wood assemblage, has been performed on the sediments in the dissected valley at the Akayama Site (35°50′55″N, 139°45′10″E), about 15km north of Tokyo, in the southeastern part of the Ohmiya Upland, central Kanto Plain. From the results, 5 epoch-making events (E-1 to E-5) and 6 paleoenvironmental stages (I to VI, divided based on their events) were identified. An event is characterized by an erosion and a subsequent drastic change of the sedimentary environment in the valley.Both Stage I(ca 8, 000-6, 500y.B.P.) and Stage II (ca 6, 500-5, 300y.B.P.), corresponding to the Earliest and Early Jomon Ages in archaeology, are characterized by a landslide or collapse of the precipice along the marginal upland ridge, and the reclamation by them or their secondary sediments in a valley under a marine or brackish environment. The sea reached a level 3m above its present level in late Stage I. During both stages, a warm-temperate deciduous broad-leaved forest composed of mainly Quercus subgen. Lepidobalanus stood on the upland to scarp, and Polygonum thunbergii, Chrisoplenium, and Carex communities covered the ridge at the edge of the water, in the valley.Stage III(ca 5, 300-4, 000y.B.P.) corresponds to the Middle Jomon Age, and is distinguished by a standing of Alnus japonica forest in the valley and an invasion of Aphananthe and Celtis in the upland to scarp forest. The deposition of clayey soil containing many Castanea-Castanoposis and Mallotus plant fossils is evidence of the destruction of the forest and the cultivation or semicultivation of Castanea on the scarp to upland.Stage IV (ca 4, 000-2, 200y.B.P.) corresponding to the Late and Later Jomon Ages is defined as an invasion of Fraxinus mandshurica, Aesculus turbinata and Acer to the Alnus forest in the valley, and the beginning of a wide expansion of Cryptomeria, Chamaecyparis group and Quercus subgen. Cyclobalanopsis on the upland. These facts testify to a cooler and wetter climate than that in previous stages. During this stage, part of the bottom forest was destroyed by man, and then manufacturing of Aesculus products was begun.Stage V (ca 2, 200-500y.B.P.) and Stage VI (since 500y.B.P.), later than the Yayoi Age in terms of archaeology, were characterized by a strong impact of man on vegetation and by a swampy valley bottom in which Cyperaceae and Gramineae communities stand. Almost all of the scarp and bottom forests have disappeared mainly as a result of human activities.

Seismic refraction survey in the Western Approaches to the English Channel: preliminary results

A seismic refraction survey of the Western Approaches was completed in the autumn of 1973, totalling 28 stations. In addition to a few sonobuoys, an improved method of detection was used, consisting of geophones or hydrophones positioned on the sea floor. The seismic signal was transmitted by radio to a shipboard receiving and recording apparatus. This new technique considerably improved the signal noise ratio. The major structural trend in the Western Approaches to the Channel is NE—SW. Two large northeast—southwest fault systems border a large, downfaulted, elongated basin, floored by depressions and ridges. The seismic refraction data lead to the recognition of two distinct geological sequences. The first is associated with the tectonized, metamorphic floor with igneous intrusions and conformably layered Palaeozoic series. The second sequence is made up of nearly horizontal layers, consisting mainly of secondary and younger sediments. The two sequences seem to be separated by an unconformity. The relatively light sediments filling depressions of the Palaeozoic floor may partially cause the observed low free-air gravity anomalies. The basement has a block-faulted aspect, the blocks being tilted in a southeast and possibly also in a southwest direction.

Ein speläochronologischer Beitrag zur postglazialen Klimageschichte

Abstract. Secondary calcium carbonate sediments in caves offer good presuppositions for the application of radio carbon dating. Some results of measurements on stalagmites are reported; they were received by the C14-Laboratory of the 2. Physikalisches Institut, University Heidelberg. If for secondary calcium carbonate a recent standard of 85% is assumed, the growth periods of the examined stalagmites lie within the postglazial climatic optimum. That strengthens the opinion that growth limits of sediment generations are time marks for phases of climatic changes. The situation will be examined in a planned series of measurements which should result in C14-dates for the postglacial history of climate.