The late Jurassic to early Cretaceous Purbeck Limestone Group of Dorset has been a focus for media and academic attention for the last 150 years. For example, The Illustrated London News in 1857 carried an article by the Revd Charles Kingsley, (of The Water Babies fame), titled ‘Geological Discoveries at Swanage’. describing fossil‐hunting endeavours of Samuel Husband Beckles (1814–1890; Fig. 1 ). Beckles had been encouraged by Richard Owen (1804–1892) to go in search of the tiny fossilized mammalian remains in these strata. Beckles rose to the challenge and at his own expense employed a team of workmen to carry out the excavations; in the process they uncovered a thin layer containing the numerous remains of diminutive mammals along with the remains of other vertebrates, including turtles, crocodiles and ornithischian dinosaurs. Since then, dinosaur tracks and related discoveries from these same strata have often caught the imagination of the press, inspiring sensational headlines such as ‘Builder digs up giant lizard fight’ and ‘Dinosaur graveyard in Swanage Bay’! Figure 1 Open in figure viewer PowerPoint Contemporary illustration of Samuel Beckles’ excavation on the cliffs of Durlston Bay, from Charles Kingsley's account of the discoveries at Swanage which appeared in The Illustrated London News in 1857. 相似文献
Given a marine basin of near homogeneous lithology, a known sea level curve, and known submarine abrasion rates, a model is developed to estimate the volume of material eroded by marine action. Assumptions of the model are that erosion is effected solely by submarine abrasion, which is assumed known and uniform through time, and that the volume eroded is small relative to the total volume of the basin. The basis of the model is that the volume eroded V, between time limits t1 andt2,is essentially a function of the perimeter length l of the basin, which in turn is time-dependent on the sea level curve, so that $$V = k\int_{t1}^{t2} {l(t)dt} $$ where k is an abrasion rate constant. The model was tested on Kiel Bay, Western Baltic, a shallow semienclosed, essentially nontidal sea, for which considerable data is available. Critical for numerical integration of the model is the k value, representing the volume eroded from the shore normal profile per unit length of shoreline per year. A number of possible k values were utilized, the most likely realizing a total volume eroded over the past 9000 y, since the sea first entered Kiel Bay, of 2.60×109m3. From this model, long-term average vertical submarine abrasion rates for Kiel Bay can be deduced as being between 0.001 and 0.0004 m/y. An extension to the model analyzes the effect of sea level transgression rate on whether cliffs develop and predicts the theoretical form of the submarine profile based on varying abrasion rates summarized as $$y_B (x) = \left\{ {\begin{array}{*{20}c} {h({x \mathord{\left/ {\vphantom {x {V_c }}} \right. \kern-\nulldelimiterspace} {V_c }}) - a_T (x) for x > 0;} \\ {x\tan \theta - a_T (x) for x > 0.} \\ \end{array} } \right.$$ Here the origin x=0, yB=0 is chosen horizontally at the position where cliff formation first occurs, and vertically at the sea level at that time. The coordinate x measures distance inshore from the origin, yB(x) is the vertical position of the sea floor, aT(x) is the total depth abraded, tanθ is the original land surface slope, Vc the rate of cliff retreat, and h(t) the sea-level at time t. The synthetic profiles are compared to actual erosional profiles from representative sectors of Kiel Bay. The model predicts cliff development began at about 5800 yB.P., resulting in submarine abrasion profile lengths of about 1740 m and cliff heights of about 17.4 m for original land surface slopes of 0.01. This agrees to within about 10% of mean values obtained from bathymetric and topographic maps. 相似文献
The tragic scenes of human suffering in the wake of the Asian tsunami in late December 2004 have thrown into sharp relief the Earth's destructive power (Fig. 1 ). Caused by a tectonic event off the coast of Sumatra, it could be described as a very large earthquake, an unusual tsunami and a massive disaster. Or, with a longer view, it could be considered a normal feature of a convergent plate boundary. Both views are correct. Figure 1 Open in figure viewer PowerPoint Mass destruction after the tsunami hit the village on the sand bar at Phi Phi Island, Thailand, with unscathed limestone hills behind (Rex Features). 相似文献
Carbonate concretions are common features of sedimentary rocks of all geological ages. They are most obvious in sandstones and mudstones as ovoid bodies of rock that protrude from natural outcrops: clearly harder or better cemented than their host rocks. Many people are excited by finding fossils in the centre of mudstone‐hosted concretions ( Fig. 1 ) but spend little time wondering why the fossils are so well preserved. While the study of concretions has benefitted from the use of advanced analytical equipment, simple observations in the field can also help to answer many questions. For example, in cliff sections, original sedimentary beds and sedimentary structures can be traced right through concretions ( Fig. 2 ): so it can be deduced that the concretion clearly formed after these depositional structures were laid down. In this article we explain how and where concretions form and discuss the evidence, ranging from outcrop data to sophisticated laboratory analyses, which can be used to determine their origins. The roles of microbes, decaying carcasses, compaction and groundwaters are highlighted. Concretions not only preserve fossils but can also subdivide oil, gas and water reservoirs into separate compartments. Figure 1 Open in figure viewer PowerPoint An early diagenetic carbonate concretion split in half to reveal an ammonite retaining its original aragonite shell, from the Maastrichtian of Antarctica. Image courtesy of Alistair Crame (British Antarctic Survey, NERC). Lens cap is 6 cm. 相似文献
The microfacies analysis and diagenetic fabric of the Lockhart Limestone are studied in an outcrop section exposed in the Margalla Hill ranges. The Lockhart Limestone is predominantly composed of medium to thick bedded, nodular and occasionally brecciated, highly fossiliferous limestone with thin interbeds of marl and shale. On the basis of detailed petrographic investigations, four microfacies have been identified including bioclastic packstone, wackestone (siliciclastic bioclastic rich sub-microfacies), wackestone-packstone, and mud-wackestone. Based on the microfacies analysis, the Lockhart Limestone is interpreted to have been deposited in the fore-shoal mid-ramp, mid-ramp, and outer ramp depositional environments. The Paleocene age has been assigned to the Lockhart Limestone based on age diagnostic foraminifera, i.e., Miscellanea, Lockhartia, and Ranikothalia. The diagenetic fabric of the Lockhart Limestone is characterized by several diagenetic features such as micritization, neomorphism (aragonite to calcite transformation and development of microspar), compaction, pressure dissolution (microstylolites), and cementation (calcite-filled microfractures). Such diagenetic features are developed in marine, meteoric, and burial diagenetic settings. The Paleocene Lockhart Limestone of Pakistan shows analogous features to that of the Paleocene Zongpu Formation (Member-3) of the Gamba-Tingri Basin of southern Tibet based on the outcrop features, microscopic fabric, and depositional environment. 相似文献
The Verkhnyaya Kardailovka section is one of the best candidates for the GSSP (Global Stratotype Section and Point) at the base of the Stage (Mississippian). For boundary definition, the first appearance of the conodont Lochriea ziegleri Nemirovskaya, Perret et Meischner, 1994 in the lineage Lochriea nodosa (Bischoff, 1957)?L. ziegleri is used. L. ziegleri appears in the Venevian Substage somewhat below the base of the Serpukhovian in the Moscow Basin. The position of the FAD of L. ziegleri within the Hypergoniatites?Ferganoceras Genozone is confirmed and lies between 19.53 and 19.63 m above the section’s base. Before 2010, deep-water stylonodular limestone containing the boundary in unnamed formation C at Kardailovka was well exposed but only 3 m of Viséan strata cropped out immediately below. Recent trenching exposed another 10 m of underlying Viséan carbonates in formation C and older Viséan siliciclastics and volcanics in unnamed formation B. The contact between formation B and underlying crinoidal limestones in unnamed formation A representing the middle Viséan Zhukovian (Tulian) regional Substage was excavated. The boundary succession, situated in the Magnitogorsk tectonic zone above the Devonian Magnitogorsk arc and Mississippian magmatic and sedimentary rift succession, was deposited west of the Kazakhstanian continent during closure of the Ural Ocean. In the lower part of the section, Viséan tuffaceous siliciclastics and volcanics of formation B record rapid deepening after deposition of neritic middle Viséan crinoid lime grainstone of formation A and subsequent subaerial exposure. The overlying condensed upper Viséan to Serpukhovian succession in formation C comprises deep-water limestone deposited in a sediment-starved basin recording minor turbidite influx and carbonate-mound development. The δ13Ccarb plot shows a positive shift of 1‰ V-PDB (from +2 to +3‰) between 17.0 and 17.75 m (3.05 and 1.97 m below FAD L. ziegleri). The δ18Oapatite graph displays a prominent upward shift from 19.9 to 21.1‰ V-SMOW (at 19.15 to 19.51 m) in the nodosa Zone below FAD of Lochriea ziegleri. 相似文献
Most of the Cu (± Mo,Au) porphyry and porphyry-related deposits of the Urals are located in the Tagil-Magnitogorsk, East-Uralian Volcanic and Trans-Uralian volcanic arc megaterranes. They are related to subduction zones of different ages:
(1)Silurian westward subduction: Cu-porphyry deposits of the Birgilda-Tomino ore cluster (Birgilda, Tomino, and Kalinovskoe) and the Zeleny Dol Cu-porphyry deposit;
(2)Devonian Magnitogorsk eastward subduction and the subsequent collision with the East European plate: deposits and occurrences are located in the Tagil (skarn-porphyry Gumeshevskoe etc.) and Magnitogorsk terranes (Cu-porphyry Salavat and Voznesenskoe, Mo-porphyry Verkhne-Uralskoe, Au-porphyry Yubileinoe etc.), and probably in the Alapaevsk-Techa terrane (occurrences of the Alapayevsk-Sukhoy Log cluster);
(3)Late-Devonian to Carboniferous subduction: deposits located in the Trans-Uralian megaterrane. This includes Late-Devonian to Early Carboniferous Mikheevskoe Cu-porphyry and Tarutino Cu skarn-porphyry, Carboniferous deposits of the Alexandrov volcanic arc terrane (Bataly, Varvarinskoe) and Early Carboniferous deposits formed dew to eastward subduction under the Kazakh continent (Benkala, etc.).
(4)Continent-continent collision in Late Carboniferous produced the Talitsa Mo-porphyry deposit located in the East Uralian megaterrane.
Porphyry mineralization of the Magnitogorsk megaterrane shows an evolving relationship from gabbro-diorite and quartz diorite in the Middle Devonian (Gumeshevskoe, Salavat, Voznesenskoe) to granodiorite-plagiogranodiorite in the Late Devonian (Yubileinoe Au-porphyry) and finally to granodiorite in the Carboniferous (Talitsa Mo-porphyry) with a progressive increase in total REE, Rb and Sr contents. This corresponds to the evolution of the Magnitogorsk terrane from a volcanic arc which gave place to an arc-continent collision in the Famennian. 相似文献
Plesiosaurs are an unusual and intriguing group of extinct aquatic reptiles ( Fig. 1 ). They are sauropterygians, a group known from an array of semi‐aquatic forms during the Triassic period: placodonts, pachypleurosaurs and nothosaurs. The first plesiosaurs are known from the very latest Triassic, but by the Early Jurassic plesiosaurs were cosmopolitan in distribution and lasted successfully to the latest Cretaceous, when they became victims of the K‐T extinction event. Plesiosaurs were predominantly marine organisms, although their fossils are not uncommon in brackish or even fresh water deposits. We know that all plesiosaurs were carnivorous; many of them were top predators in their respective ecosystems. But with no living descendants (or analogues) plesiosaurs are mysterious fossil organisms—as we will see, many questions regarding their biology remain unanswered or contentious. However, plesiosaurs are currently undergoing renewed scientific attention. Figure 1 Open in figure viewer PowerPoint The beautifully preserved skeleton of the plesiosaur Rhomaleosaurus victor seen in ventral view, from the Lower Jurassic (Toarcian) of Holzmaden, Germany (total length 3.44 m). Redrawn from Fraas (1910). 相似文献
A new stratigraphic nomenclature is proposed for the approximately 600 m thick, mainly clastic transitional sequence between the underlying Mempelam Limestone and overlying Kubang Pasu/Singa Formation in northwest Peninsular Malaysia. This sequence represents shallow marine deposits of the continental margin of the Sibumasu Terrane during the Middle Palaeozoic (Devonian–Carboniferous). It is separated into several formations. The Timah Tasoh Formation is an approximately 76 m sequence consisting of 40 m of laminated tentaculitid shales at the base, containing Monograptus yukonensis Jackson and Lenz and Nowakia (Turkestanella) acuaria Alberti, giving an Early Devonian (Pragian–Emsian) age, and about 36 m of rhythmically interbedded, light coloured argillo-arenites. The Chepor Formation is about 90 m thick and consists mainly of thick red mudstone interbedded with sandstone beds, of Middle to Late Devonian age. A new limestone unit is recognized and named the Sanai Limestone, which contains conodonts of Famennian age. The Binjal Formation consists of red and white mudstone interbedded with sandstone beds showing Bouma sequences. The Telaga Jatoh Formation is 9 m thick and consists mainly of radiolarian chert. The Wang Kelian Formation is composed of thick red mudstone beds interbedded with silty sandstone, and contain fossils indicative of an Early Carboniferous (Visean) age. The succession was deposited on the outer shelf, with depositional environments vertically fluctuating from prodelta to basinal marine. The Devonian–Carboniferous boundary is exposed at Hutan Aji and Kampung Guar Jentik, and indicates a major regressive event during the latest Devonian. 相似文献
Devonian and Carboniferous (Yarrol terrane) rocks, Early Permian strata, and Permian‐(?)Triassic plutons outcrop in the Stanage Bay region of the northern New England Fold Belt. The Early‐(?)Middle Devonian Mt Holly Formation consists mainly of coarse volcaniclastic rocks of intermediate‐silicic provenance, and mafic, intermediate and silicic volcanics. Limestone is abundant in the Duke Island, along with a significant component of quartz sandstone on Hunter Island. Most Carboniferous rocks can be placed in two units, the late Tournaisian‐Namurian Campwyn Volcanics, composed of coarse volcaniclastic sedimentary rocks, silicic ash flow tuff and widespread oolitic limestone, and the conformably overlying Neerkol Formation dominated by volcaniclastic sandstone and siltstone with uncommon pebble conglomerate and scattered silicic ash fall tuff. Strata of uncertain stratigraphic affinity are mapped as ‘undifferentiated Carboniferous’. The Early Permian Youlambie Conglomerate unconformably overlies Carboniferous rocks. It consists of mudstone, sandstone and conglomerate, the last containing clasts of Carboniferous sedimentary rocks, diverse volcanics and rare granitic rocks. Intrusive bodies include the altered and variably strained Tynemouth Diorite of possible Devonian age, and a quartz monzonite mass of likely Late Permian or Triassic age. The rocks of the Yarrol terrane accumulated in shallow (Mt Holly, Campwyn) and deeper (Neerkol) marine conditions proximal to an active magmatic arc which was probably of continental margin type. The Youlambie Conglomerate was deposited unconformably above the Yarrol terrane in a rift basin. Late Permian regional deformation, which involved east‐west horizontal shortening achieved by folding, cleavage formation and east‐over‐west thrusting, increases in intensity towards the east. 相似文献
The paper presents results of a detailed petrologic study of metasomatites and their host metagabbroids in the northwestern part of Kiy Island, Onega Bay, White Sea. The first evidence is acquired that coronitization and amphibolization of the host rocks took place at the peak of Svecofennian metamorphism at Т = 700–640°C, Р = 9–10 kbar, and \({a_{{H_2}O}}\) = 0.2–0.3. Accompanying metasomatism has formed a number of long (up to several meters long) melanocratic hornblendite and garnet–amphibole veins 0.3–2 m thick. In this area, metasomatites of another type make up single relatively thin amphibole–zoisite lenses that sometimes host ruby-like corundum. The fluid phase that induced metasomatism was poor in salts (Na,K)Cl, and hence, the rocks do not contain sodic plagioclase, and their amphibole is tschermakite but not pargasite. The compositions of the metasomatites of the two types are proved to be complementary, and this indicates that they were most likely produced by high-temperature metasomatism but not via the removal of components by fluid from migmatization zones. 相似文献
The magnitude 9.0 Tohoku or Sendai Earthquake ( Fig. 1 ) struck just off the northeast coast of Honshu, Japan on 11 March 2011 making it the fourth largest earthquake to be recorded since 1900, and the largest Japanese earthquake since modern seismometers were developed 130 years ago. Despite the earthquake being much more powerful than had been expected from the subduction zone east of Honshu, the earthquake preparedness of Japan resulted in relatively little earthquake damage—despite the protracted shaking with ground accelerations up to three times that of gravity. However, it was the resulting 10–15 metre high tsunami waves that wreaked havoc along the coastal plain, resulting in a death toll in the tens of thousands and an on‐going drama at the Fukushima I nuclear power plant. Modern seismology has its origins in the analyses of the 1906 San Francisco and 1923 Great Kanto earthquakes. The 2011 Tohoku (or ‘northeast’) earthquake looks set to similarly significantly advance our understanding of earthquakes and tsunamis due to the unprecedented volume of seismic, GPS, tide gauge and video data available. There is much information to be gained on how large earthquakes rupture, how buildings behave under prolonged severe shaking and how tsunamis propagate. Figure 1 Open in figure viewer PowerPoint Tohoku earthquake global displacement wavefield from IRIS. http://www.iris.edu/hq/files/iris_news/images/Sendai_RS.jpg 相似文献
According to the International Society of Rock Mechanics, squeezing is a time dependent large deformation occurring during tunnel construction around the tunnel associated with creep caused by exceeding a limiting shear stress (Barla in ISRM News J 2:44–49, 1995). This research is conducted using a case study on the Nowsoud Tunnel, Iran. Being 14 km in length and 4.5 m in diameter, the tunnel is located in the western part of Iran near the Iraq border. Nowsoud tunnel, which was excavated using a double shield TBM, exhibited severe squeezing (with 8919 m) in its critical zone which resulted in excavation termination. In this research, the best approach for predicting squeezing among the recommended methods for reducing the damages caused by squeezing on TBM was determined. In this regard, approaches commonly used to predict squeezing are empirical, semi-empirical, and theoretical–analytical methods. Besides, these methods, numerical modeling is used to estimate convergence generated along the tunnel pathways, which is ultimately used to categorize squeezing. This paper compares squeezing prediction methods in 68 section of Nowsoud Tunnel. These 68 sections indicate that the empirical methods propose a general estimation/overview of squeezing. Among the semi-analytical approaches, the one proposed by Hoek and Marinos (Rock engineering in difficult rock conditions—soft rocks and karst, Taylor & Francis Group, London, pp 49–60, 2000) are compatible with the occurrence of squeezing in the critical zone. However, the degree of predicted squeezing is less than the real degree of squeezing in this zone. Based on the result of Aydan approach, 75 % of the tunnel sections are under squeezing condition. Theoretical–analytical approaches underestimate the possibility of squeezing in the critical zone. Barla?s approach (1995) demonstrated the possibility of squeezing in the critical zone with low intensity. The numerical computations in this paper were performed using Plaxis (version 8.5), a two-dimensional numerical program based on the finite element method. Plaxis results, classified by Hoek and Marinos (2000) method, show that 8800 m of the tunnel length is under the non-squeezing condition. According to all prediction methods, the squeezing zones depend on faulted zones, argillaceous limestone and shale formations such as J1Kh, J4Kh, J5Kh, and Kgr. These formations were identified with a high quantity of shale and argillaceous limestone. Bedding of these geological formations is thin and their geotechnical properties are weaker than those of limestone formations. On the other hand, non-squeezing zones depend on limestone formations such as J2Kh, J3Kh, J6Kh, Kabg, and Kbg. Moreover, all approaches predicted squeezing potential for the critical zone where TBM is jammed. 相似文献
Early Eocene carbonate sediments of the Umlatdoh Limestone (Meghalaya, N-E India) represent a shallow marine shelf environment. The major biotic components characterizing these carbonates are calcareous green algae and small to larger benthic foraminifera. Based on the biogenic associations and general sedimentological features, five major facies types (MFTs) are distinguished. They are dominated by poor to moderately sorted grainstones followed by packstones, rudstones and wackestones. Considerable abundance of Halimeda, scarcity of z-corals and poor to moderate occurrence of filter-feeding organisms imply mesotrophic to a slightly oligotrophic nutrient regime. Rare occurrence of geniculate coralline algae is probably due to the lack of suitable substrate and environmental conditions. High incidence of grainstones and packstones, fairly preserved microfossils and few reworked specimens indicate a parautochthonous mode of deposition. Preponderance of Alveolina and Nummulites indicate the possible advent of larger foraminiferal turnover (LFT) in the east Tethys during or even before early Eocene. A conceptual palaeoenvironmental model for the studied succession is provided to showcase various facies gradients, bathymetry levels and shelf zones pertinent to the Umlatdoh Limestone. 相似文献
A devastating earthquake of magnitude 7 struck very close and almost beneath Port au Prince the capital of Haiti, the western half of the island of Hispaniola, early in the morning of Tuesday, 12 January 2010 ( Fig. 1 ). While in absolute terms this was by no means the largest earthquake recorded this year globally, the death toll is around 230 000, making it one of the world's worst earthquakes in terms of casualties in recorded history, with almost uncountable economic loss to one of the poorest countries in the world. Figure 1 Open in figure viewer PowerPoint Intensity map of 2010 Haiti earthquake (Image: USGS). 相似文献
The age of the marine Nodular Limestone Formation of the Bagh Group is refined at Substage level through ammonoid and inoceramid index taxa. The study is based on the fresh collections from three well-defined successive intervals (Lower Karondia, Upper Karondia and Chirakhan members) of this formation having excellent exposures in different localities of the Narmada Basin, central India. The first record of the widely distributed Turonian ammonoid genera Spathites Kummel and Decker and Collignoniceras Breistroffer from the Nodular Limestone Formation constrained its age exclusively to Turonian. The Early Turonian species Spathites (Jeanrogericeras) aff. revelieranus (Courtiller) and Mytiloides labiatus (Sclotheim) occur in the lower part, while the Middle Turonian marker Collignoniceras cf. carolinum (d’Obrbigny) and Inoceramus hobetsensis (Nagao and Matsumoto) occurs in the upper part of the Karondia Member. The record of the index species Inoceramus teshioensis (Nagao and Matsumoto) in association with Placenticeras mintoi Vredenburg from Chirakhan Member allows a definite Late Turonian age. The present contribution is an attempt to resolve the controversies in the age of the Nodular Limestone Formation and also demarcation of the three divisions (Early, Middle and Late) of the Turonian Stage in the Narmada Basin, central India. 相似文献
The effects of pore water on the mechanical behaviour of Solnhofen Limestone and Carrara Marble at various temperatures and confining pressures at constant strain-rate have been experimentally investigated. It is shown that water affects the strength and ductility of calcite rocks through
1.
(1) physico-chemical action at grain boundaries, and 相似文献
Armoring of limestone is a common cause of failure in limestone-based acid-mine drainage (AMD) treatment systems. Limestone is the least expensive material available for acid neutralization, but is not typically recommended for highly acidic, Fe-rich waters due to armoring with Fe(III) oxyhydroxide coatings. A new AMD treatment technology that uses CO2 in a pulsed limestone bed reactor minimizes armor formation and enhances limestone reaction with AMD. Limestone was characterized before and after treatment with constant flow and with the new pulsed limestone bed process using AMD from an inactive coal mine in Pennsylvania (pH=2.9, Fe =150 mg/l, acidity =1000 mg/l CaCO3). In constant flow experiments, limestone is completely armored with reddish-colored ochre within 48 h of contact in a fluidized bed reactor. Effluent pH initially increased from the inflow pH of 2.9 to over 7, but then decreased to <4 during the 48 h of contact. Limestone grains developed a rind of gypsum encapsulated by a 10- to 30-μm thick, Fe-Al hydroxysulfate coating. Armoring slowed the reaction and prevented the limestone from generating any additional alkalinity in the system. With the pulsed flow limestone bed process, armor formation is largely suppressed and most limestone grains completely dissolve resulting in an effluent pH of >6 during operation. Limestone removed from a pulsed bed pilot plant is a mixture of unarmored, rounded and etched limestone grains and partially armored limestone and refractory mineral grains (dolomite, pyrite). The ∼30% of the residual grains in the pulsed flow reactor that are armored have thicker (50- to 100-μm), more aluminous coatings and lack the gypsum rind that develops in the constant flow experiment. Aluminium-rich zones developed in the interior parts of armor rims in both the constant flow and pulsed limestone bed experiments in response to pH changes at the solid/solution interface. 相似文献
Varied, well-developed limestone pavements are well exposed over an extensive area of the Carboniferous limestone outcrop
of the Orton-Asby escarpment, Cumbria. This area is the largest expanse of limestone pavements outside the well-known Ingleborough
karst of Yorkshire, and the National Nature Reserve at Great Asby Scar includes the best developed and least damaged landforms
of the whole area, most of which is now protected by Limestone Pavement Orders.
Received: 1 June 1995 · Accepted: 4 December 1995 相似文献
