青海湖钻孔沉积物中的羟基甘油二烷基甘油四醚类化合物及其环境意义

来源于古菌细胞膜脂的类异戊二烯甘油二烷基甘油四醚类化合物（isoGDGTs）是古环境重建的有力工具。最近的研究发现,自然环境中还存在着一类isoGDGTs烷基长链上含有羟基的OH-GDGTs,其相对含量与温度负相关,具有示踪古温度的潜力。然而,目前湖相环境中关于OH-GDGTs的研究还很少。我们通过高效液相色谱-大气压化学电离-质谱分析,在青海湖8ka以来沉积物中检测到了OH-GDGTs的存在,其含量（相对含量% OH-GDGTs及浓度）与奇古菌特征标志物crenarchaeol相对含量和奇古菌amoA基因丰度一致,表明青海湖中的OH-GDGTs可能主要来源于奇古菌。进一步与湖泊水位指标对比显示,青海湖中% OH-GDGTs的变化可能主要反映了湖水深度变化导致的古菌群落的变化。因此,认为湖泊沉积物中的OH-GDGTs可指示古水文条件变化。

     

Influence of lake water pH and alkalinity on the distribution of core and intact polar branched glycerol dialkyl glycerol tetraethers (GDGTs) in lakes

Branched glycerol dialkyl glycerol tetraethers (GDGTs) are bacterial membrane lipids, ubiquitously present in soils and peat bogs, as well as in rivers, lakes and lake sediments. Their distribution in soil is controlled mainly by pH and mean annual air temperature, but the controls on their distribution in lake sediments are less well understood. Several studies have found a relationship between the distribution of branched GDGTs in lake sediments and average lake water pH, suggesting an aquatic source for them, besides that for soil transported to the lake via erosion. We sampled the surface water suspended particulate matter (SPM) from 23 lakes in Minnesota and Iowa (USA), that vary widely in pH, alkalinity and trophic state. The SPM was analyzed for the concentration and distributions of core lipid (presumed fossil origin) and intact polar lipid (IPL, presumed to derive from living cells) branched GDGTs. The presence of substantial amounts (18–48%) of IPL-derived branched GDGTs suggests that branched GDGTs are likely of autochthonous origin. Temperature estimates based on their distribution using lake-specific calibrations agree reasonably with water temperature at time of sampling and average air temperature of the season of sampling. Importantly, a strong correlation between the distribution of branched GDGTs and lake water pH was found (r² 0.72), in agreement with a predominant in situ production. An stronger correlation was found with lake water alkalinity (r² 0.83), although the underlying mechanism that controls the relationship is not understood. Our results raise the potential for reconstructing pH/alkalinity of past lake environments, which could provide important knowledge on past developments in lake water chemistry.     

Distribution of glycerol dialkyl glycerol tetraethers in surface sediments of Lake Qinghai and surrounding soil

Glycerol dialkyl glycerol tetraethers (GDGTs) are increasingly used as proxies for paleoclimate studies of marine and lacustrine environments. While GDGT-based proxies have been applied to a number of lake environments globally, little is known about the distribution of GDGTs on the Qinghai-Tibet Plateau. We have investigated the isoprenoid GDGTs (iGDGTs) and branched GDGTs (bGDGTs) in Lake Qinghai sediments and the surrounding surface soil in order to examine their potential use as paleoclimate proxies on the Qinghai-Tibet Plateau. The results show that (i) the values of the iGDGT/bGDGT ratio for surrounding soil were at the higher end among globally distributed soils and consequently BIT values (avg. 0.71) at the lower end, (ii) the TEX₈₆ values decreased while the MBT and CBT values increased along an onshore soil–nearshore sediment–offshore sediment transect, (iii) the TEX₈₆ values for the offshore sediments were almost identical and their inferred temperatures were close to mean summer surface water temperature and (iv) the bGDGT-inferred mean annual air temperature (MAAT) and pH for soil were consistent with measured MAAT and pH. However, the CBT-inferred pH for offshore sediments seemed inconsistent with the pH of lake water or sediment. Our results suggest that (i) the higher pH may be an important factor leading to the higher iGDGT/bGDGT values (and lower BIT values) in surrounding surface soil, (ii) both iGDGTs and bGDGTs may originate from terrestrial input and in situ production for this saline lake, especially for nearshore sediments. However, for offshore sediments, terrestrial iGDGT input seems minor, and TEX₈₆ may be useful for paleoclimate studies of Lake Qinghai.     

基于XRF岩芯扫描的贵州喀斯特地区晚全新世泥炭古环境研究

文章选取发育于贵州喀斯特地区的兴义泥炭为研究对象,对钻孔上部300 cm岩芯进行高分辨率XRF连续扫描,并测定了样品含水量、色度（亮度L^*、红度a^*、黄度b^*）和碳酸盐含量。通过对Rb、Ti、Zr、Al、Si、Ca、Sr、Mg等元素含量及其比值、色度和其他代用指标的综合分析,结合主成分分析方法,探讨XRF岩芯扫描在兴义泥炭研究中使用的可行性,并进一步分析兴义泥炭化学元素的来源、指示意义及所记录的古环境演化过程。基于AMS¹⁴C测年构建的年代框架,发现：1）XRF岩芯扫描的Ca元素含量与气量法测定的碳酸盐含量具有较好的一致性。XRF岩芯扫描和分光测色计获得的L^*、b^*相关性高,尽管这两种方法获得的a^*存在差异,但其数值表现上相似性仍较高;2）晚全新世以来兴义泥炭的地球化学元素主要来源于周边碳酸盐岩风化、淋溶、随流水搬运而最终沉积到湿地的物质;3）兴义泥炭Sr/Ca比值处于高值,Si/Al、Rb/Sr比值处于低值时,气候偏干,反之则指示气候偏湿润。此外,兴义泥炭Al、Si、Ca、Sr、Mg、Rb/Sr、Si/Al、Sr/Ca的变化趋势与烧失量、腐殖化度等具有较好的一致性;4）晚全新世以来兴义地区总体上呈现出由湿润向干转变的趋势,3270~2700 cal.a B.P.由湿润持续转干,2300~1670 cal.a B.P.降水持续减少,与西南季风主控区众多古环境记录能较好地对应,并揭示了2700~2300 cal.a B.P.降水稳步增加的过程。对兴义泥炭进行XRF岩芯扫描能挖掘其蕴含的物质来源、物质变化特征等多方面信息,有助于拓展XRF岩芯扫描分析方法在泥炭沉积中的应用,并能深化对西南地区古环境演化历史的认识及丰富泥炭研究档案。

     

Characteristics,genesis and classification of a basin peat soil under negative human impact in Turkey

The objective of this research was to investigate the morphology, genesis and classification of organic soils formed on depression and flat land around Lake Yenicaga, west-central Turkey. Formation of the area has been influenced by tectonic and karst processes. This peatland is important in this area due to its extensive use as a horticultural plant growth medium resulting from positive physical and chemical properties. Organic soils in the study area were formed in nutrient-rich conditions and it is classified as typical basin peat. Four representative pedons were excavated in the study area based on extensive observations performed with random grid method using an auger. Samples were taken from horizons in each profile for laboratory analyses. Organic matter contents ranged from 12.5 to 91.5% across all four pedons. Fiber contents were between 4.3 and 91.5%, and N ranged from 0.56 to 2.19%. Cation exchange capacity ranged from 37 to 222 cmol kg⁻¹, bulk density from 0.09 to 0.78 g cm⁻³, lime from 0.15 to 2.62%. The pH and EC_e values ranged from 5.38 to 7.92 and 0.50 to 3.80 dS m⁻¹, respectively. Sand, silt and clay contents of the organic soils ranged between 0.75–3.92, 40.70–74.77 and 24.15–57.30%, respectively. Differences in organic soils were found to depend on the environment, botanical origins, decomposition degrees, and groundwater composition. The organic soils of the research area were classified in the typic, hemic and hydric subgroups of Medifibrists (Soil Taxonomy 1999).     

坦桑尼亚某矿区土壤地球化学特征与找矿远景分析

坦桑尼亚姆潘达地区矿产资源丰富,但地质工作程度较低。PL5141-1矿区内岩浆活动频繁、强烈,断裂构造发育,地表发现铬铁矿(化)点、钒钛磁铁矿点、铁锰矿化点、金矿化点、铜矿化点。该地区1∶50 000土壤地球化学分析数据显示Au、Cu、Cr异常明显,经过综合研究分析,认为该区具有寻找蚀变岩型和石英脉型Au、Cu矿体和铬铁矿的潜力。     

Gold potential of the Mpanda Mineral Field, SW Tanzania: evaluation based on geological, lead isotopic and aeromagnetic data

Gold and base metals of the Mpanda Mineral Field (MMF) is the focus of this paper. Gold veins and gold-bearing base metal occurrences are structurally controlled by conjugate sets of NW–SE and E–W trending faults and/or shear zones that crosscut high-grade metamorphic rocks and post-kinematic intrusions. It was anticipated that Palaeoproterozic country rocks could have been potential host rocks for the gold mineralisation in this area. This argumentation was based on Pb model ages of various deposits from the MMF. Recent fieldwork and Pb isotopic results presented herein indicate that epigenetic gold and base metal vein-type mineralisation in the MMF is post-Palaeoproterozoic.Our Pb isotope study concentrates on constraining the sources of metals in gold-bearing quartz reefs and base metal occurrences. Pb isotopes of whole rocks and minerals indicate that mineralisation was emplaced during the Neoproterozoic, contemporaneous with the intrusion of alkaline granites and carbonatite complexes (e.g., Sangu–Ikola carbonatite complex) at 720 Ma. The source of Pb in the mineral occurrences is compatible with that characteristic of the Palaeoproterozoic host rocks. Aeromagnetic data suggest that the gold-bearing, NNW–SSE trending area continues to the north beyond Mpanda town. Pb isotope results and aeromagnetic data have significant implications for future exploration programs within the region, in that the search should potentially focus on the defined geophysical borders and trendlines, and on Neoproterozoic, rather than Palaeoproterozoic vein systems.     

大九湖泥炭柱样的木质素特征

根据大九湖泥炭柱样的木质素特征,结合C/N、δ13C和δ15N数据,分析了有机物的来源和降解特征.结果表明,陆地C3高等植物是有机物的主要来源.木质素的S/V和C/V参数指示该泥沼的主要维管植物是草本被子植物.有机碳含量(OC)的变化与这些植被参数具有良好的对应关系,说明植被变化是控制有机碳含量的重要因素.(Ad/AI)v和(Ad/A1)s参数表明泥炭中的木质素经历了中等程度的氧化降解,而棕腐菌的去甲基/去甲氧基过程是控制木质素含量的主要降解途径.木质素在埋藏后的降解很小,其降解程度更多地受对应年代的环境条件的控制,例如,在温暖湿润的全新世气候最适宜期,木质素降解程度显著高于之前的寒冷干燥时期.     

中亚阿尔泰山南坡表土和泥炭沉积物GDGTs综合研究

相对于我国季风区,西北内陆地区表土和泥炭沉积物的甘油二烷基甘油四醚化合物（GDGTs）现代过程研究结果报道较少。对中亚干旱区阿尔泰山南坡海拔梯度表土、高山泥炭地哈拉沙子和那仁夏周边坡地表土以及哈拉沙子表层泥炭沉积物进行了GDGTs分析,结果表明：1）其海拔梯度表土当中细菌来源支链结构GDGTs（brGDGTs）的分子分布特征主要响应于湿度的变化;2）同样主要由于湿度变化的影响,奇古菌的影响和贡献在相对低海拔地区更为明显,产甲烷古菌的影响和贡献在相对高海拔地区上升,导致古菌来源的类异戊二烯结构GDGTs（isoGDGTs）的TEX₈₆参数随海拔上升具有显著的降低趋势;3）哈拉沙子和那仁夏泥炭地泥炭沉积物当中的brGDGTs和isoGDGTs都并非主要来自周边坡地土壤的异源输入,而主要都是泥炭地原地自生来源。这些研究结果,一方面为在该区域利用GDGTs开展古环境、古气候重建提供基础性参考;另一方面,也对其他区域相应研究结果形成有益补充。

     

Fractal distribution of particle size in carbonate cataclastic rocks from the core of a regional strike-slip fault zone

We present particle size data from 31 samples of carbonate cataclastic rocks collected across the 26 m thick fault core of the Mattinata Fault in the foreland of the Southern Apennines, Italy. Particle size distributions of incoherent samples were determined by a sieving-and-weighting technique. The number of weight-equivalent spherical particles by size is well fitted by a power-law function on a log–log space. Fractal dimensions (D) of particle size distributions are in the 2.091–2.932 range and cluster around the value of 2.5. High D-values pertain to gouge in shear bands reworking the bulk cataclastic rocks of the fault core. Low D-values characterise immature cataclastic breccias. Intermediate D-values are typical of the bulk fault core. Analysis of the ratio between corresponding equivalent particle numbers from differently evolved cataclastic rocks indicates that the development of particle size distributions with D>2.6–2.7 occurred by a preferential relative increase of fine particles rather than a selective decrement of coarse particles. This preferentially occurred in shear bands where intense comminution enhanced by slip localisation progressed by rolling of coarse particles whose consequent smoothing produced a large number of fine particles. Our data suggest that during the progression of cataclasis, the fragmentation mode changed from the Allègre et al.'s [Nature 297 (1982) 47] “pillar of strength” mechanism in the early evolutionary stages, to the Sammis et al.'s [Pure and Applied Geophysics 125 (1987) 777] “constrained comminution” mechanism in the subsequent stages of cataclasis. Eventually, localised shear bands developed mainly by abrasion of coarse particles.     

Subsidence due to peat oxidation and impact on drainage infrastructures in a farmland catchment south of the Venice Lagoon

Large agricultural areas reclaimed in the past century, south of the Venice Lagoon, have experienced significant land subsidence due to oxidation of peat organic soils. This has exposed the region to flood hazard particularly during severe storms and has contributed to increase the marginal management cost of the infrastructures (ditches, levees, pumping stations) designed to operate the drainage system. Direct measurements and indirect evidence from the channel network suggest a land settlement between 1.5 and 2 m over the past 70 years. This paper provides an overview of the problem with important information on its most recent evolution.     

坦桑尼亚主要成矿区带的划分及成矿特征

文章综合以往有关坦桑尼亚的地质资料,结合近年来地质矿产勘查新进展和高精度同位素年代学数据,梳理了坦桑尼亚主要地质特征及其演化规律,对坦桑尼亚划分出6个成矿区带,重点论述了其中的坦桑尼亚克拉通太古宙金成矿带、乌本迪古元古代乌本迪金-铜-铁-多金属成矿带、基巴拉中元古代镍-铜-锡成矿带、莫桑比克活动带新元古代宝石成矿带及其典型矿床的地质特征。     

Holocene peat and carbon accumulation rates in the southern taiga of western Siberia

Although recent studies have recognized peatlands as a sink for atmospheric CO₂, little is known about the role of Siberian peatlands in the global carbon cycle. We have estimated the Holocene peat and carbon accumulation rate in the peatlands of the southern taiga and subtaiga zones of western Siberia. We explain the accumulation rates by calculating the average peat accumulation rate and the long-term apparent rate of carbon accumulation (LORCA) and by using the model of Clymo (1984, Philosophical Transactions of the Royal Society of London Series B 303, 605-654). At three key areas in the southern taiga and subtaiga zones we studied eight sites, at which the dry bulk density, ash content, and carbon content were measured every 10 cm. Age was established by radiocarbon dating. The average peat accumulation rate at the eight sites varied from 0.35 ± 0.03 to 1.13 ± 0.02 mm yr⁻¹ and the LORCA values of bogs and fens varied from 19.0 ± 1.1 to 69.0 ± 4.4 g C m⁻² yr⁻¹. The accumulation rates had different trends especially during the early Holocene, caused by variations in vegetation succession resulting in differences in peat and carbon accumulation rates. The indirect effects of climate change through local hydrology appeared to be more important than direct influences of changes in precipitation and temperature. River valley fens were more drained during wetter periods as a result of deeper river incision, while bogs became wetter. From our dry bulk density results and our age-depth profiles we conclude that compaction is negligible and decay was not a relevant factor for undrained peatlands. These results contribute to our understanding of the influence of peatlands on the global carbon cycle and their potential impact on global change.     

X-ray imagery and physical core logging as a proxy of the content of sediment cores in cold-water coral mound provinces: a case study from Porcupine Seabight,SW of Ireland

Three provinces, characterized by the presence of carbonate mounds interpreted as cold-water coral banks have been reported in Porcupine Seabight, SW of Ireland and were recently subjected to many detailed studies. This contribution discusses the use of X-ray imagery and physical properties in deciphering palaeoceanographic, sedimentological and biological processes. Physical property core logging and X-ray imagery are used to identify and describe sedimentation regimes and so their respective palaeoceanographic and palaeoclimatological settings in two mound provinces, respectively the Belgica mound province and the Magellan mound province. Both provinces show at present time clear differences in the hydrodynamic environment. This study confirms that also during the past the oceanographic and sedimentological environment of both provinces differ clearly. Impacts of glacial–interglacial variations and locally derived ice rafting events (IRE), comparable with the North Atlantic Heinrich events (HE) have been recognized in both provinces. Moreover, the combination of X-ray imagery, magnetic susceptibility, gamma density and P-wave velocity makes it possible to estimate the coral content and coral distribution in unopened cores localized on top of carbonate mounds. A comparison between on-mound and off-mound cores in both provinces allowed revealing some mechanisms of mound evolution and coral growth versus time.     

Tensile strength of peat: laboratory measurement and role in Irish blanket bog failures

The morphological characteristics of bogflows, bog bursts and other types of peat failures suggest that the tensile strength of peat may have had a significant influence on their occurrence and development. This paper describes a method for the determination of peat tensile strength utilising small block samples (100 mm × 100 mm, up to 60 mm thick) in a newly developed laboratory apparatus. The results, demonstrating good reproducibility and being consistent with published data, were applied to a case example. The stability of a recent 35,000-m³ bogflow on Maghera Mountain, Co. Clare, Ireland, was analysed using a standard limit equilibrium technique. The breaking stress (i.e. maximum tensile strength) of the acrotelm peat at the Maghera bogflow was 5.35 kPa (range 2.9–7.6 kPa). Using this value to represent the overall strength of the acrotelm in the model, analyses showed that even above the crest of an escarpment, the acrotelm was strong enough to contain a large volume of low or zero-strength lower catotelm peat within the blanket bog upslope from the escarpment. Furthermore, simple analysis of single blocks of peat at the upslope edge of a retrogressively developing failure established the size of blocks that should develop, i.e. 3–4 m. The floating acrotelm rafts observed in the Maghera bogflow, typically up to around 3 m, were broadly consistent with this analysis. This paper therefore presents for the first time quantitative evidence of the importance of the acrotelm tensile strength in bogflows and a new method for routinely obtaining tensile strength data.     

Lipid geochemistry in a sediment core from Ruoergai Marsh deposit (Eastern Qinghai-Tibet plateau, China)

Peats in a sediment core from Ruoergai bog, which has a cold and moist plateau climate with major source input from herbaceous plants, have been studied by GC–MS in order to understand the composition and diagenetic processes of lipids in this depositional environment. Long chain components (C₂₁–C₃₅) predominate in the n-alkanes, n-alk-1-enes, n-fatty acids, n-alkan-2-ones and n-alkanols with a maximum of C₃₁, C_27, C₂₂ or C_24, C₂₃ or C₂₅ and C₂₂, respectively. A herbaceous origin for these long chain compounds is suggested, and this is supported by their stable carbon isotopic compositions. Diterpenoid hydrocarbons with abietane, pimarane and kaurane skeletons, some of which have not been reported often in modern sediments, are prominent and are derived from higher plants. Several triterpenoid ketones and alcohols with oleanane or lupane skeletons, and a series of des-A-triterpenoid hydrocarbons which have not been reported often in modern sediments are also present, and are assigned to a higher plant source. Hopanoids, including their alkanes, alkenes, ketones, alcohols and esters, are abundant and of bacterial origin. Steroid ketones and alkanols are dominated by C₂₉ homologues. C₂₈ and C₂₉ steroids are derived mainly from higher plants, whereas the C₂₇ component is assigned to a microbial source. The presence of short-chain n-alkanes with no odd-even carbon predominance, bacterially derived fatty acids (C₁₄, C₁₅, iso- and unsaturated acids), n-alkan-2-ones, des-A-triterpenoid hydrocarbons, hopanoids and some steroid ketones indicate that intense microbial reworking of the organic matter has taken place in this depositional environment. The chemical and biochemical conversions of some cyclic alkenes to alkanes, such as tricyclic diterpenoids, tetracyclic terpenoids and steroid ketones, are also evident with depth. The dominance of C₂₀ components in the diterpenoid hydrocarbons may reflect an oxidizing or reducing depositional condition.     

Aspects of Rift Valley faulting and volcanicity in North Tanzania: report of a Geologists’ Association Field Meeting in 2008

The African Rift Valleys results from Neogene-Recent breakup up the African Plate due to continental extension. Compared with the western sector, in the eastern or Gregory Rift Valley the fracturing is accompanied by a large amount of volcanic activity and, in northern Tanzania, the volcanic rocks are relatively young compared with those in Ethiopia and Kenya where the products of the earliest stages of mantle melting are buried beneath older, more-extensive volcanic formations. The volcanic rocks vary from Pliocene and early Pleistocene intraplate basalts and trachytes to late Pleistocene/Holocene nephelinites and carbonatites.     

Anomalous gold contents in brown coals and peat in the south-eastern region of the Western-Siberian platform

One hundred twenty-two samples of Jurassic and Paleogene brown coals and 1254 peat samples from the south-eastern region of the Western-Siberian platform were analyzed for gold by the neutron-activation method. Mean content of Au in Jurassic coals is 30 ± 8 ppb, in Paleogene coals is 10.6 ± 4.8 ppb, and in peat is 6 ± 1.4 ppb. Concentrations of gold as high as 4.4 ppm were found in coal ash and 0.48 ppm in the peat ash. Coal beds with anomalous gold contents were found at Western-Siberian platform for the first time.Negative correlation between gold and ash yield in coals and peat and highest gold concentrations were found in low-ash and ultra-low-ash coals and peat. Primarily this is due to gold's association with organic matter.For the investigation of mode of occurrence of Au in peat the bitumen, water-soluble and high-hydrolyzed substances, humic acids, cellulose and lignin were extracted from it. It was determined that in peat about 95% of gold is combined with organic matter. Forty to sixty percent of Au is contained in humic acids and the same content is in lignin. Bitumens, water-soluble and high-hydrolyzed substances contain no more than 1% of general gold quantity in peat.The conditions of accumulation of high gold concentrations were considered. The authors suggest that Au accumulation in peat and brown coals and the connection between anomalous gold concentrations and organic matter in low-ash coals and peat can explain a biogenic–sorption mechanism of Au accumulation. The sources of formation of Au high concentration were various Au–Sb, Au–Ag Au–As–Sb deposits that are abundant in the Southern and South-Eastern peripheries of the coal basin.     

Apatite fission track and (U-Th)/He thermochronology from the Archean Tanzania Craton: Contributions to cooling histories of Tanzanian basement rocks

Borehole and surface samples from the Archean Tanzania Craton were analysed for apatite fission track(AFT) and(U-Th)/He data with the aim of deciphering cooling histories of the basement rocks. Fission track dates from borehole and outcrop samples are Carboniferous-Permian(345± 33.3 Ma to271±31.7 Ma) whereas(U-Th)/He dates are Carboniferous-Triassic(336±45.8 Ma to 213±29 Ma) for outcrop grains and are consistently younger than corresponding AFT dates. Single grain(U-Th)/He dates from the borehole are likely to be flawed by excessive helium implantation due to their very low effective uranium contents, radiation damage and grain sizes. All AFT and(U-Th)/He dates are significantly younger than the stratigraphic ages of their host rocks, implying that the samples have experienced Phanerozoic elevated paleo-temperatures. Considerations of the data indicate removal of up to 9 km overburden since the Palaeozoic.Thermal modelling reveals a protracted rapid cooling event commencing during the early Carboniferous(ca. 350 Ma) at rates of 46 m/Ma ending in the Triassic(ca. 220 Ma). The model also suggests minor cooling during the Cretaceous of the samples to surface temperatures. The suggested later cooling event remains to be tested. The major cooling phase during the Carboniferous is interpreted to be associated with compressional tectonics during the Variscan Orogeny sensu far field induced stresses. Coeval sedimentation in the Karoo basins in the region suggests that most of the cooling of cratonic rocks during the Carboniferous was associated with denudation.     

Sedimentary evolution of a late Pleistocene wetland indicating extreme coastal uplift in southern Tanzania

Facies analyses of Pleistocene deposits from southern coastal Tanzania (Lindi District) document that sediments formed in a wetland evolving on a coastal terrace in the Lindi Fracture Zone foreland. The exposed succession shows a marked sedimentary change from tidal to terrestrial facies. ¹⁴C analyses on gastropod shells indicate the emergence of the Lindi coast at ∼ 44 ¹⁴C ka BP. Emergence and subsequent elevation of terraces to 21 m above present-day sea level was linked to the falling eustatic sea level prior to the last glacial maximum, and to a periodic elevation due to extensional tectonic episodes in the eastern branch of the East African Rift System (EARS). Since ∼ 44 ¹⁴C ka BP tectonic uplift at the coast was 80-110 m, comparable to that in the extreme uplift areas of the EARS.