Fractal dimensions and geometries of caves

Lengths of all caves in a region have been observed previously to be distributed hyperbolically, like self-similar geomorphic phenomena identified by Mandelbrot as exhibiting fractal geometry. Proper cave lengths exhibit a fractal dimension of about 1.4. These concepts are extended to other self-similar geometric properties of caves with the following consequences.Lengths of a cave is defined as the sum of sizes of passage-filling, linked modular elements larger than the cave-defining modulus. If total length of all caves in a region is a self-similar fractal, it has a fractal dimension between 2 and 3; and the total number of linked modular elements in a region is a self-similar fractal of the same dimension. Cave volume in any modular element size range may be calculated from the distribution.The expected conditional distribution of modular element sizes in a cave, given length and modulus, also is distributed hyperbolically. Data from Little Brush Creek Cave (Utah) agree and yield a fractal dimension of about 2.8 (like the Menger Sponge). The expected number of modular elements in a cave equals approximately the 0.9 power of length of the cave divided by modulus. This result yields an intriguing parlor trick. An algorithm for estimating modular element sizes from survey data provides a means for further analysis of cave surveys.     

From subsurface to surface: a multidisciplinary approach to decoding uplift histories in tectonically-active karst landscapes

We present an integrated study of subsurface and surficial karst landforms to unravel the uplift history of karst landscape in a tectonically-active area. To this end, we apply a multidisciplinary approach by combining cave geomorphology and Th/U dating of speleothems with remote sensing plus geophysical imaging of surface landforms. We use as an example Mt. Menikio in northern Greece where four caves share well-defined epiphreatic/shallow phreatic characteristics that are related to the distribution of surface and buried doline fields and provide evidence for three distinct water table stillstands (e.g. expressed as cave levels) now lying at ~130 m, ~800 m and ~1600 m a.m.s.l. Our dating constraints delimit the age of the lower water table stillstand prior to 77 ka ago and imply a maximum rate of relative base level drop of 0.45 mma^-1, which is consistent with relative tectonic uplift rate estimates along currently active normal faults. We interpret the elevation of the higher water table stillstands to reflect earlier phases of uplift related to the regional tectonic events associated with the development of the North Anatolian Fault and the Northern Aegean area. Our analysis shows that the combined study of epiphreatic/shallow phreatic caves and surficial karst landforms together, is a robust way to investigate the uplift history of a karst landscape in a tectonically-active setting. © 2019 John Wiley & Sons, Ltd.     

Occurrence and distribution pattern of Palaemon spp. shrimps in a shallow submarine cave environment: a study case in South‐eastern Italy

The common shrimps of the genus Palaemon are often reported as living in Mediterranean submarine caves. The present study quantifies the distribution pattern of a Palaemon spp. populations throughout 1 year of observations in a shallow submarine cave in South‐eastern Italy, Ionian Sea. The cave was subdivided into six sectors from the entrance towards the inner portion of the ‘blind cave’ and 16 dives (four per season, during both day and night) were performed with SCUBA equipment. The population was estimated in situ using visual census. Four different species of Palaemon were identified. This study has shown that Palaemon spp. assemblages live throughout the year in submarine caves. Moreover, the results suggest submarine caves play an important role in the biology of Palaemon spp. populations, by providing refuge, juvenile recruitment and food resources.     

Geological risk assessment of the area surrounding Altamira Cave: A proposed Natural Risk Index and Safety Factor for protection of prehistoric caves

Altamira Cave occurs in a carbonate sequence-dated as middle to upper Cenomanian, being characterized by tabular bedding. This sequence has been studied in detail and mapped in an attempt to delimit the beds in which the cave was formed. The cave forms part of a karstic complex developed in the Altamira Formation, which consists of eight stratigraphic units characterized by karstic forms and landslides as the main geomorphologic elements. The strong relationship between sinkholes and faults within the area was also revealed, with sinkholes of oval morphology aligned along the faults. Inside the cave, the subhorizontal bedding is intersected by subvertical joints, generating geometrical blocks prone to falling down. This is the main process of the present evolution of the cave in addition to the dissolution and precipitation of carbonates in local zones. We used this geological characterization as the basis for the definition of protection areas around prehistoric caves, applied in this article to the Altamira Cave. Landslides, water flow towards the cave, rock falls within cave and karstic features are the main geological risks affecting the karstic complex. Two semi-quantitative indexes were proposed, the Natural Risk Index (NRI) and Safety Factor (SF), with the main aim of determining the risk level in different zones of the study area. The information provided by geological studies as well as the results obtained using the proposed indexes allowed definition suitable protection areas around the cave.     

兖州煤田采煤沉陷土地利用分区研究

从采煤沉陷土地持续利用角度,依据沉陷土地利用的自然和社会特性,提出采煤沉陷土地的分区方案;以兖州煤田为例,进行实用分区,并依据各分区的特点提出持续利用方向和方案;最后,根据分区实例,就采煤沉陷土地的持续利用提出几点建议。     

柳州市静兰防洪堤工程岩溶发育特征及渗漏评价

本文论述了柳州市静兰防洪堤工程区岩溶发育特征、规律,阐明了西江船厂区地下河系、溶洞、落水洞、漏斗、洼地等的发育规模、连通性,并进行岩溶渗漏评价。结果表明采取围井、填埋等措施后,渗漏量只有0 55×104m3 d,能有效地防止岩溶水的倒灌。     

Distribution of trace metals in anchialine caves of Adriatic Sea,Croatia

This study presents results of the first comprehensive research on ecotoxic trace metals (Cd, Pb, Cu and Zn) in aquatic anchialine ecosystems. Data show the influence of hydrological and geological characteristics on trace metals in highly stratified anchialine water columns.     

塔里木盆地塔河油田TH12402井区中下奥陶统古岩溶洞穴发育模式*

塔里木盆地塔河油田TH12402井区位于志留系覆盖区,发育典型的古岩溶缝洞型储集层,是塔河油田西北部奥陶系主要的产建阵地之一。基于三维地震数据、测井和钻井资料,并结合地震属性提取技术,对该区下奥陶统岩溶发育条件和储集层发育特征进行了研究,探讨了岩溶洞穴的控制因素和发育模式。结果表明: TH12402井区处于北西向次级鼻状构造的南翼,该区发育加里东中期Ⅲ幕古岩溶作用,岩溶地形以低幅度的溶丘和洼地为主,地表水系呈南北向汇流且分支水系相对欠发育;岩溶储集空间以大型迷宫状岩溶管道和分散的孤立状洞穴为主,主要分布在不整合面以下40~100m,且以未充填为主;近东西向的走向断层、次级鼻状构造以及上奥陶统地层尖灭线联合控制了古岩溶洞穴的发育,形成了平缓岩溶地貌区走向断裂汇流型岩溶洞穴模式。上述成果为相似井区的古岩溶储集层预测和井位部署提供了理论依据。     

Speleogenesis of an exhumed hydrothermal sulphuric acid karst in Cambrian carbonates (Mount San Giovanni,Sardinia)

In the past few years the systematic study of caves intercepted by mine workings in southwest Sardinia has permitted us to observe morphologies due to rare speleogenetic and minerogenetic processes related to ancient hydrothermal activity. These relic morphologies are slowly being overprinted by recent speleogenetic processes that tend to obscure the hypogene origin of these caves. A combined geomorphological and mineralogical investigation has permitted a fairly detailed reconstruction of the various phases of evolution of these caves. Cave formation had already started in Cambrian times, but culminated in the Carboniferous, when most of the large voids still accessible today were formed. A key role in carbonate dissolution was played by sulphuric acid formed by the oxidation of the polymetallic ores present in the rocks since the Cambrian. During the Quaternary a variety of minerals formed inside the caves: calcite and aragonite, that yielded sequences of palaeo‐environmental interest, and also barite, phosgenite, hydrozincite, hemimorphite and many others. These minerals are in part due to a phreatic thermal hypogenic cave forming phase, and in part to later epigene overprinting in an oxidizing environment rich in polymetallic ores. Massive gypsum deposits, elsewhere typical of this kind of caves, are entirely absent due to dissolution during both the phreatic cave formation and the later epigenic stage. Copyright © 2013 John Wiley & Sons, Ltd.     

Electron spin resonance dating of Quaternary bone material from Tasmanian caves—A comparison with ages determined by aspartic acid racemization and C14

Abstract

Fourteen bone samples are analysed to test the usefulness of equivalent dose (ED) determinations by electron spin resonance (ESR) as a rapid method of determining relative age and making an estimate of absolute age. ED values are compared with eight aspartic acid dates and two C¹⁴ dates. The latter are dates on charcoal found in close association with bone at archaeological sites. For samples less than 25 000 years old an excellent correlation is obtained when ED values are compared with dates obtained by the other two methods. The relationship suggests that ED values can be converted to estimates of bone age by assuming a mean annual dose rate of 0.1 rad/yr. Age determinations provide little evidence to support earlier suggestions that elements of the Late Pleistocene megafauna survived until the end of the Pleistocene. Bone material at some sites in the‐Florentine Valley and near Montagu appears to be much older than had previously been believed. Only one site (Main Cave, Montagu) containing megafaunal elements appears to be terminal Pleistocene in age but the possibility of reworking of megafauna material from nearby older sites cannot be excluded. ESR dating has considerable potential as an exploratory dating tool but can only be applied to dense, unaltered bone samples. Attempts to analyse five samples from Kutikina Cave in Western Tasmania were unsuccessful because of post‐depositional contamination of the bone.