Late Holocene in central Brazil: vegetation changes and humidity variability in a tropical wetland

The Pandeiros wetland is a high biodiversity ecosystem located within a semiarid region of the Cerrado biome, a neotropical savanna. This large wetland is of key importance for ecological and hydrological balance in central Brazil and for the conservation of the Cerrado fauna and flora. In this study, we present the first palaeoecological investigation of the Pandeiros wetland based on pollen analysis of a palm swamp sediment core encompassing the Late Holocene. Our results show that the wetland was subject to multicentennial-scale oscillations in water availability during the Late Holocene; in particular, higher local humidity was documented between 4100 and 3100 cal a bp and from 2600 to 1000 cal a bp , and two events of drier local conditions occurred at approximately 2900 and 900 cal a bp. Our results also indicate a general decreasing trend in arboreal density in the Pandeiros River Basin from the beginning of the Late Holocene to the present, with the greatest expansion of dry forest occurring between 3600 and 3100 cal a bp.     

Joint return probability analysis of wind speed and rainfall intensity in typhoon-affected sea area

Strong wind and rainfall induced by extreme meteorological processes such as typhoons have a serious impact on the safety of bridges and offshore engineering structures. A new bivariate compound extreme value distribution is proposed to describe the probability dependency structure of annual extreme wind speed and concomitant process maximum rainfall intensity in typhoon-affected area. This probability model takes full account of the case that there may be no rainfall in a typhoon process. A case study based on the observation data of typhoon maximum wind speed and maximum rainfall intensity in Shanghai is conducted to testify the efficiency of the model. Weibull distributions with two parameters are applied to fit respective probability margins, and the joint probability distribution is constructed by Gumbel–Hougaard copula. The fitting results and K–S tests show that these models describe the original data well. The joint return periods are calculated by Poisson bivariate compound extreme value distribution we have proposed. They indicate that typhoons with no rain have smaller joint return periods, and wind speed is the main factor which impacts the change of the joint return periods.     

Tracking neolithic interactions in southeast China: Evidence from stone adze geochemistry

The authors conducted a sourcing study of stone adzes recently excavated from the Damaoshan site on Dongshan Island, Fujian province, China. They used XRF, ICP‐MS, and petrographic thin‐section techniques for geochemical and petrographic analysis of six stone adzes from the site and three geological samples from Dongshan Island. The chemical data of these samples compared with other lavas in Fujian, Zhejiang, Penghu, and Taiwan suggest that the Damaoshan people imported stone raw materials either from the Penghu Archipelago in the Taiwan Strait or from the Niutoushan area on the Fujian coast. This indicates that exchange networks along the southeast coast of China, and possibly spanning the Taiwan Strait, had developed as early as 4300–5000 yr B. P. © 2005 Wiley Periodicals, Inc.     

Holocene variations of monsoon rainfall in Rajasthan

Two reconstructed histories of the monsoon rainfall in Rajasthan show that the monsoon was weak or absent in latest glacial time. With the advent of Holocene climatic patterns, fresh water lakes formed in dune fields and the pollen rain preserved in these reservoirs provides a basis for the reconstruction of the monsoon history. The two reconstructions, separated by only 150 km, have some features in common and some striking differences. Both show maximum monsoon amounts in the early Holocene, with a roughly two-thirds decrease to the present. Both show salinization in sub-Boreal time. Both show long intervals of near complete desiccation in the last four millennia. The shorter term variations, however, are not closely parallel. These shorter term variations may be explained in terms of the behavior of the present day interannual variability.     

Holocene environmental change in South Georgia: Evidence from lake sediments

The Holocene environmental history of South Georgia is important because of the island's location in the Southern Westerlies in an oceanic zone of the world devoid of high resolution terrestrial records. This is the first attempt to interpret a palaeoenvironmental record from lake sediments in South Georgia. It is based on a wide variety of analyses undertaken on cores from two lakes. Both are in the same, unglaciated, drainage basin, but one is at 80 m above sea-level and near the altitudinal limit for vegetation growth, whereas the other is at 25 m and within the zone of continuous vegetation cover. Results from both lakes indicate shifts of vegetation boundaries, which, together with evidence for changing biotic productivity within the lakes themselves, are interpreted as indicating climatic changes. Radiocarbon dates on the main changes identify a climatic optimum, beginning before 5620 ± 290 ¹⁴C yr BP, and ending at around 4815 ± 330 ¹⁴C yr BP, when conditions in the upper part of the catchment were more conducive to plant growth than they are today. The record obtained from the lower lake was shorter, but indicates two periods of harsher climate relative to the present since 4000 yr BP. This interpretation of the lake evidence agrees with other dated evidence of environmental change from peat sections, glacial stratigraphy and geomorphology in South Georgia. Together the work allows an overall reconstruction of environmental change in the Holocene.     

Holocene environmental changes in the alpine zone,northern San Juan Mountains,Colorado: Evidence from bog stratigraphy and palynology

Cores from five high alpine basins in the northern San Juan Mountains show several fluctuations in lithology. Typically, peats are interbedded with coarser clastic sediments or else woody peats alternate with fibrous peat. Twenty ¹⁴C dates provide radiometric control. Sediment rates averaged about 2.5 cm/100 yr but varied at the different sites between 1.19 and 50 cm/100 yr. Rates were lower during the middle of the Holocene. Basal radiocarbon dates indicate that these high (ca. 3600 m a.s.l.) northeasterly facing cirques were icefree by 9000 BP. There is some evidence in the cores for a short climatic reversal sometime between 8000 and 7000 BP. A major change occurred in the high basins very close to 5000 BP and thereafter there are several intervals of increased clastic sedimentation which may be related to Neoglacial climatic fluctuations. Analysis of a 2.15 m core near Hurricane Basin indicates significant fluctuation of pollen and macrofossils occurred during the 9000 ± year record. The Picea/Pinus ratios are used to delimit changes in the apparent elevation of the site: the ratios indicate that a short drop of “treeline” occurred about 8000 BP and then remained near present level until about ≥1800 BP when the apparent elevation of the site rose. Macrofossils indicate that spruce was present in the Hurricane Basin (and others) at specific periods and confirms the general results of the Picea/Pinus ratios. The San Juan Mountains do not possess a glacial Neoglacial record but the stratigraphy of these high cirque basins can be used to define glacial stades (cf. Jardine, 1972). The interpreted climatic response record on vegetation and sediment flux has both similarities and differences from other records in the western mountains of North America.     

Holocene climate changes in southern Greenland: evidence from lake sediments

A Holocene lake sediment record is presented from Lake N14 situated on Angissoq Island 15 km off the main coast of southern Greenland. The palaeoclimatic development has been interpreted on the basis of flux and percentage content of biogenic silica, clastic material, organic material and sulphur as well as sedimentation rate, moss content and magnetic susceptibility. A total of 43 radiocarbon dates has ensured a reliable chronology. It is argued that varying sediment composition mainly reflects changing precipitation. By analogy with the present meteorological conditions in southern Greenland, Holocene climate development is inferred. Between 11 550 and 9300 cal. yr BP temperature and precipitation increase markedly, but this period is climatically unstable. From 9300 yr BP conditions become more stable and a Holocene climatic optimum, characterised by warm and humid conditions, is observed from 8000 to 5000 cal. yr BP. From 4700 cal. yr BP the first signs of a climatic deterioration are observed, and from 3700 cal. yr BP the climate has become more dry and cold. Superimposed on the climatic long‐term trend is climate variability on a centennial time‐scale that increases in amplitude after 3700 cal. yr BP. A climatic scenario related to the strength and position of the Greenland high‐pressure cell and the Iceland low‐pressure cell is proposed to explain the Holocene centennial climate variability. A comparison of the Lake N14 record with a terrestrial as well as a marine record from the eastern North Atlantic Ocean suggests that the centennial climate variability was uniform over large areas at certain times. Copyright © 2004 John Wiley & Sons, Ltd.     

Late Holocene high resolution palaeoclimatic reconstruction inferred from Sebkha Mhabeul, southeast Tunisia

Relations between climate change and landscape evolution during the last two millennia in southeastern coastal Tunisia have been documented using high-resolution reconstruction of flood history and fire activity in the Sebkha Mhabeul core. The age model, based on tephrochronology, indicates that the core extends from Roman to modern times and encompasses the well-defined climatic periods of the last two millennia. This record provides a first palaeoecological/palaeoclimatic high resolution reconstruction in North Africa using a cross-disciplinary approach with both physical (grey-scale intensity, quartz particles) and biological (charcoal and pollen) indicators. The flood history shows four wet/dry cycles (ca. AD 550-950, 950-1300, 1300-1570 and 1570-1870) of different duration. Major hydrological instabilities are concentrated during the Medieval Climate Anomalies and the early Little Ice Age, between AD 1000 and 1550. Direct correlation between climate and fire cannot be established suggesting that the fire history of the Sebkha environment is mainly influenced by human activity. This study demonstrates the great value of sebkhas as palaeoenvironmental archives.     

Development and carbon sequestration of tropical peat domes in south-east Asia: links to post-glacial sea-level changes and Holocene climate variability

Tropical peatlands of SE-Asia represent a significant terrestrial carbon reservoir of an estimated 65 Gt C. In this paper we present a comprehensive data synthesis of radiocarbon dated peat profiles and 31 basal dates of ombrogenous peat domes from the lowlands of Peninsular Malaysia, Sumatra and Borneo and integrate our peatland data with records of past sea-level and climate change in the region. Based on their developmental features three peat dome regions were distinguished: inland Central Kalimantan (Borneo), Kutai basin (Borneo) and coastal areas across the entire region. With the onset of the Holocene the first peat domes developed in Central Kalimantan as a response to rapid post-glacial sea-level rise over the Sunda Shelf and intensification of the Asian monsoon. Peat accumulation rates in Central Kalimantan strongly declined after 8500 cal BP in close relation to the lowering rate of the sea-level rise and possibly influenced by the regional impact of the 8.2 ka event. Peat growth in Central Kalimantan apparently ceased during the Late Holocene in association with amplified El Niño activity as exemplified by several truncated peat profiles. Peat domes from the Kutai basin are all younger than ～8300 cal BP. Peat formation and rates of peat accumulation were driven by accretion rates of the Mahakam River and seemingly independent of climate. Most coastal peat domes, the largest expanse of SE-Asian peatlands, initiated between 7000 and 4000 cal BP as a consequence of a Holocene maximum in regional rainfall and the stabilisation and subsequent regression of the sea-level. These boundary conditions induced the highest rates of peat accumulation of coastal peat domes. The Late Holocene sea-level regression led to extensive new land availability that allowed for continued coastal peat dome formation until the present. The time weighted mean Holocene peat accumulation rate is 0.54 mm yr^?1 for Central Kalimantan, 1.89 mm yr^?1 for Kutai and 1.77 mm yr^?1 for coastal domes of Sumatra and Borneo. The mean Holocene carbon sequestration rates amount to 31.3 g C m^?2 yr^?1 for Central Kalimantan and 77.0 g C m^?2 yr^?1 for coastal sites, which makes coastal peat domes of south-east Asia the spatially most efficient terrestrial ecosystem in terms of long term carbon sequestration.     

Magnetic susceptibility as a proxy for rainfall: Worldwide data from tropical and temperate climate

The magnetic susceptibility of soils has been linked with climate, mainly through rainfall, by numerous investigators. For this study we assembled a worldwide dataset of 272 samples, both published and new, to determine the nature of the relationship between MS and rainfall. On a worldwide basis there is a crude relationship (r² = 0.265) between MS and rainfall. MS increases with increasing rainfall from about 200 mm/yr to 1000–1200 mm/yr. Above 1200 mm/yr, MS decreases as rainfall increases up to about 2000 mm/yr. Under arid and semi-arid conditions, below about 200 mm/yr of rainfall, MS and rainfall exhibit no relationship, likely the result of limited pedogenic activity.When tropical and temperate localities are analyzed separately, the correlation between MS and rainfall exhibits a dramatic improvement, r² = 0.568 and 0.520, respectively. For similar amounts of rainfall tropical localities generally exhibit lower MS values which may be related to differences in the seasonal variation of rainfall. Because the soil environment is highly variable, it is unlikely that a global or even regional equation could accurately estimate rainfall from MS. Using data from Morocco and Mali we demonstrate that local equations using only MS to estimate rainfall produce reasonable results, r² = 0.700 for Morocco and 0.611 for Mali. However, a single independent variable is unlikely to capture the variability of the complex soil system. To the local equations described above we experimented with adding several independent variables in addition to MS including diffuse reflectance spectral data (DRS), x-ray diffraction (XRD), and x-ray fluorescence (XRF). For DRS data, % reflectance and red, yellow, and near-infrared wavelengths appear important; for XRD illite and kaolinite counts are important whereas for XRF Fe₂O₃ is important. The addition of these other independent variables dramatically improves prediction quality. In the case of the Mali transect, estimating rainfall from these variables produces an r² that exceeds 0.9. Based on these data we conclude that MS has the potential to be a reasonable proxy of rainfall for mean annual precipitation values from 200 to 2000 mm/yr, especially if local equations are used. Predictions can be improved by including other independent variables that show sensitivity to climate and are related to MS through the chemistry of the weathering process; we included DRS, XRD, and XRF data with good results.     

渭河平原全新世气候与季风强度变化

为探讨渭河平原全新世黄土沉积时期的气候、土壤与季风变化,本研究以2.15 m厚度的宝鸡宝陵剖面为研究对象,选取了化学元素、碳酸钙以及土壤微结构作为研究指标,对全新世气候特征、土壤类型以及季风降水与强度变化进行探讨。实验结果表明,S₀发育时期表现为中等化学风化,CaCO₃含量在S₀中下部小于1%,在全新世黄土层中的平均含量为12.14%。S₀以发育新生红色粘土胶膜的致密块状微结构为主要特征,L₀以孔隙发育的团块结构为主要特征。主要结论如下：1)晚全新世L₀黄土堆积时气候相对冷干,年均降水量为500~600 mm,冬季风增强,冬季风与夏季风强度相近,并非冬季风占主导地位;2)晚全新世L₀发育时夏季风带来的降水量占当时年降水量的50%左右,与其他来源的降水量基本相同;3)晚全新世发育的L₀黄土受成壤作用较弱,具有碱性褐色土的特征。中全新世的成壤作用较强,发育的S₀古土壤为湿润条件下的亚热带黄棕壤;4)中全新世气候温暖湿润,当时年均降水量为800 mm左右,夏季风带来的降水量明显多于其他来源的降水量,表明中全新世时期,夏季风确实占主导地位。

     

Changing rainfall inputs in the Volta basin: implications for water sharing in Ghana

We present evidence from the analysis of gridded annual rainfall data that, increased variability and declining rainfall totals are the main cause of declining lake levels in the Volta basin above the Akosombo Dam. West Africa has undergone a period of diminished rainfall, punctuated by a series of severe droughts and marked by a shift in rainfall regime. As a result, lake levels behind the hydro-electric impoundment have fluctuated so widely at times that, power has had to be rationed. The trends in the spatial and temporal variability of annual rainfall in the riparian nations explain the low impoundment levels frequent in recent decades. The drying of Burkina Faso and Mali is particularly marked and synchronous to an apparent shift in the rainfall regime in Ghana towards a longer dry season and vanishing short dry spell, the effects which tend to negate each other. The various regional and temporal associations between El Niño-Southern Oscillation phenomenon (ENSO) are investigated as a possible cause of variation across the basin. The strengths of these associations and low frequency shifts suggest an unfortunate correspondence between national and climatological boundaries which may serve to heighten regional political tensions resulting from ENSO effects. Lack of re-investment in the Akosombo Dam as a result of management policies, political and pre-construction contractual agreements have all conspired in recent decades to make these hydro-climatological changes more devastating.     

Vertisols (cracking clay soils) in a climosequence of Peninsular India: Evidence for Holocene climate changes

Smectitic parent material from the weathering Deccan basalt has been deposited in the lower piedmont plains, valleys and microdepressions during a previous wetter climate. The cracking clay soils (Vertisols) were developed in such alluvium during drier climate of the Holocene period. In India they occur in humid tropical (HT), sub-humid moist (SHM), sub-humid dry (SHD), semi-arid moist (SAM), semi-arid dry (SAD) and arid dry (AD) climatic environments and thus indicate an array of soils in a climosequence.The soils show a change in their morphological, physical, chemical and micromorphological properties in the climosequence. Soils of HT climate are dominated by Ca⁺⁺ ions in their exchange complex throughout depth. However, in the sub-humid climates Mg⁺⁺ ions tend to dominate in the lower horizons. The sub-humid moist to aridic climatic environments caused a progressive formation of pedogenic calcium carbonates (PC) with the concomitant increase in Na⁺ ions in soil solution. This facilitated the translocation of Na-clay in the soil profile. This is responsible for the increase in pH, decrease in Ca/Mg ratio of exchange sites with depth and finally in the development of subsoil sodicity. The reduction in mean annual rainfall (MAR) from sub-humid moist to arid climates accelerated the formation of PC and thus the soils of semi-arid and arid climates (SAM, SAD and AD) are more calcareous and sodic than soils of other climates (SHM and SHD).Formation of PC, illuviation of clay and the development of subsoil sodicity are concurrent, contemporary and active pedogenetic processes operating during the climate change of the Holocene period. These processes impaired the hydraulic properties of soils in general, and in soils of drier climates in particular. As a result, cracking pattern, chemical composition and plasmic fabric were more modified in soils of the drier climates. Such modifications in soil properties have a place in the rationale of Vertisol order of the US Soil Taxonomy. The soils of wetter climates (HT, SHM and SHD) are grouped in Typic Haplusterts whereas the soils of drier climates (SAM, SAD and AD) are classified as Aridic Haplusterts, Sodic Haplusterts and Sodic Calciusterts. The present study demonstrates how the intrinsic soil properties of the cracking clay soils in a climosequence may help in inferring the change in climate in a geologic period.     

Evidence for Holocene environmental changes in the northern Fertile Crescent provided by pedogenic carbonate coatings

Holocene environmental changes in the northern Fertile Crescent remain poorly understood because of the scarcity of local proxy records in the region. In this study we investigated pedogenic (soil-formed) carbonate coatings on stones at the Pre-Pottery Neolithic site Göbekli Tepe as an indicator of local early-mid Holocene environmental changes. The ¹⁴C ages and stable isotopic composition of carbon and oxygen in thin (0.2–0.3 mm thick) pedogenic carbonate lamina indicate two main periods of coating formation: the early-Holocene (ca. 10000–6000 cal yr BP) and the mid-Holocene (ca. 6000–4000 cal yr BP). During the first period, there was an inverse relationship between δ¹³C and δ¹⁸O curves: a decrease in δ¹³C values coincide with an increase in δ¹⁸O values. For this period a trend towards higher temperatures is suggested. In the mid-Holocene, the mean rate of coating growth was 2–3 times higher than in the early Holocene. Both δ¹³C and δ¹⁸O reached their maximum values during this time and the direction of changes of the δ¹³C and δ¹⁸O curves became similar. The combination of data suggests that this period was the most humid in the Holocene and on average warmer than the early Holocene. At ca. 4000 cal yr BP secondary accumulation of carbonate ceased, presumably reflecting a shift to a more arid climate.     

Mid- to late Holocene environmental and climatic changes in New Caledonia, southwest tropical Pacific, inferred from the littoral plain Gouaro-Déva

Multiproxy analysis of three littoral cores from western New Caledonia supports the hypothesis that the main controlling factors of environmental changes are sea-level change, ENSO variability and extra-tropical phenomena, such as the Medieval Warm Period (MWP) marked by a tendency for La Niña-like conditions in the tropical Pacific. The record starts during the late Holocene sea-level rise when the terrestrial vegetation indicated wet and cool conditions. The site was a coastal bay definitely transformed into a freshwater swamp at around 3400 cal yr BP, after the rapid drawdown of sea level to its current level. Sediments and foraminiferal assemblages indicated subsequent episodes of freshwater infillings, emersion or very high-energy conditions, likely related to climatic changes and mostly controlled by ENSO variability. Between 2750 and 2000 cal yr BP, relatively dry and cool climate prevailed, while wetter conditions predominated between ca. 1800 and 900 cal yr BP. The Rhizophoraceae peak between ca. 1080 and 750 cal yr BP, coeval with the MWP, may indicate a global phenomenon. Microcharcoal particles present throughout the record increased after 1500 cal yr BP, suggesting an anthropogenic source. From ca. 750 cal yr BP the appearance of current type of vegetation marks the human impact.     

考虑降雨敏感度的泥石流危险性评价——以藏东南地区为例

藏东南是泥石流发生的高频地区,也是G318国道铁路的途径之地,泥石流对当地社会发展和重大工程建设构成严重的威胁。文中针对藏东南区域的条件选取了距公路距离、距河流距离、距断层距离、高程、坡度、降雨、NDVI等11个致灾因子来研究该地区的泥石流发生规律。在ArcGIS中导出并分析泥石流点各因子数据,进行相关性检验和建立因子敏感度等级。利用层次分析法计算权重后,结合因子敏感图层制作2015年藏东南地区泥石流危险分布图来检验模型的正确性。针对不同降雨敏感度制作不同的危险分布图来预测未来的泥石流易发区。当全区降雨敏感度为3时,藏东南近一半地区都是泥石流的极高易发区,G318国道沿线都处于高危险地区中。降雨敏感度为2时,藏东南没有极高易发区,全区危险指数大大降低,G318国道沿线高危险部分占84.56%。结果表明降雨量对研究地区泥石流的危险性分布影响较大,该研究成果可为藏东南的社会发展及重大工程基础建设提供理论支撑。     

里下河地区全新世自然环境变迁

在区域地质调查项目进行过程中,以几个典型地质剖面和钻孔为基础,讨论了里下河区域全新世地层的分布规律,研究了地貌分布特征;探讨了全新世古植被、古气候与古环境变迁以及历史时期自然环境变化特征。里下河地区全新世自然环境变迁经历了4个重要的阶段:(1)10～7.5 kaBP,以湖沼发育为主,海水曾经影响到本区;(2)7.5～4.0kaBP,海水入侵本区,自然环境以潮滩、滨浅海、潟湖等为主,最大海侵甚至可到达运河以西地区,但里下河仍然有部分地区未被海水淹没;(3)4.0 kaBP～1128 AD,海水全面后退,岸线在范公堤一线曾做长时间停留,形成西冈贝壳砂堤,断续分布,海水时常影响西部地区;(4)1128 AD以来,由于黄河南泛夺淮入海,改变了里下河地区的地表水系,苏北滨海平原迅速向海推进,此后里下河地区远离海水的影响。     

渤海湾西侧泥质海岸带全新世岸线的变化与海洋的影响(英文)

以渤海湾泥质海岸带为例,从形态和地层证据2个方面总结了全新世岸线变化与海洋作用对该地区海岸带发育的影响。中全新世以来千年级别的岸线变迁至少以6次停顿(形成贝壳堤和泥质岭地)和岸进的交替为特征。过去130年间10年级别的岸线变化分为4个阶段,显示了"小冰期"结束后随气温上升而发生的岸线自然蚀退是如何逐渐被人类活动(特别是2000年以来的围海造陆)所取代的。全新世海相沉积中发现的9个峰值期和晚全新世的7次风暴驱动事件,表明了研究区泥质海岸带增强的海洋影响。这些结果提供了一条经由地质背景认识现代泥质海岸带过程的途径。     

Evolution of gold mineralization in the Ashanti Gold Belt,Ghana: Evidence from carbonate compositions and parageneses

Summary Ankerite, siderite, calcite and magnesite occur in variable proportions within all host and mineralized rocks of the Bogosu and Prestea mining districts of the Ashanti Gold Belt, Ghana. The compositions of coexisting ankerite-siderite grains establish that complex rhythmically zoned growth banding and replacement textures are present. This compositional variation is attributed to episodic fluctuation in the temperature and composition of fluids in the Bogosu-Prestea mesothermal gold system. Temperatures derived from the ankerite-siderite composition geothermometer are generally consistent with those from calcite-dolomite, arsenopyrite, carbon and oxygen stable isotope, and fluid inclusion geothermometers, and are about 360°C for the metamorphic peak, 400 to 350°C for carbonate alteration of mafic dikes, and 340 to 140°C for gold deposition. The latter range occurs on a thin-section scale and represents separate pulses of fluid in the ore conduit.

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Entstehung der Goldvererzung im Ashanti Gold Belt, Ghana: Rückschlüsse aus Karbonat zusammensetzungen und Paragenesen

Zusammenfassung In allen Wirtsgesteinen und mineralisierten Gesteinen der Bergbaureviere von Bogosu und Prestea im Ashanti Gold Belt, Ghana treten Ankerit, Siderit, Calcit und Magnesit in unterschiedlichen Verhältnissen auf. Die Zusammensetzung von koexistierenden Ankerit-Siderit-Körnern zeigt eine komplexe, rhythmisch zonierte Wachstumsstreifung und Verärdngungsstrukturen. Diese Änderungen in der Zusammensetzung sind auf episodische Fluktuationen der Temperatur und der Zusammensetzung der Fluide im mesothermalen Goldsystem von Bogosu-Prestea zurückzuführen. Temperaturen nach dem Ankerit-Siderit-Geothermometer stimmen im allgerneinen mit jenen aus Geothermometern, die auf Calcit-Dolomit, Arsenopyrit, den stabilen Isotopen von Kohlenstoff and Sauerstoff und auf Flüssigkeitseinschlüssen beruhen, überein. Sie liegen bei rund 360°C für den Höhepunkt der Metamorphose, bei 400 bis 350°C für die Karbonat Alteration der matischen Gänge and bei 340 bis 140°C für die Gold-Fällung. Der letztgenannte Bereich tritt in Dünnschlif Maßstab auf and repräsentiert einzelne Schübe von Fluid in den Erzgängen.