The Elastoplastic Analysis of high pressure Cylinder and Autofrettage Test under 12 Kb

This paper systematically introduces the elastoplastic analysis and autofrettage method of the pressure nder .It describes in detail the 12,100kg/cm2 hydraulic autofrettage test of a cylinder with its outside diameter 240 mm ,inside diameter 40-82 mm, and the height 362 mm. A cross –hole with diameter 4 mm is drilled ,then 9，925 kg/cm2 cyclic hydraulic pressure is applied .The result of the test is an expectant success .The behavior of the cylinder is satisfactory in its later usage . Conclusions are made as follows: 1. Using the hydraulic autofrettage technique ,the ultimate fatigue strength of the triaxial chamber cylinder ,which has the changeable cross section and is made by the super strengthened steel 37SiMnCrNiMoV,can be increased . 2. The hydraulic autofrettage technique can improve stress concentration of the cross-bore of the high pressure vessels.     

高压筒体的弹-塑性分析及其一万二千大气压自增强试验

自从1911年卡门〔1〕做了第一个岩石三轴试验之后,国外很多学者相继进行这方面的工作.特别是近廿年来,随着核爆和地震等方面研究的发展,随着超高压容器和密封技术的发展,促使岩石三轴试验研究有大的发展.美国的G riggs〔2〕、Handin〔3〕和日本的Mogi〔4〕等人在这方面作了大量工作.目前,美国已采用刚性试验机和伺服控制系统〔5〕,从而达到岩石三轴试验自动化.     

Insect traces from nonmarine ephemeral puddles

Metz, Robert 1987 06 01: Insect traces from nonmarine ephemeral puddles. Boreas , Vol. 16, pp. 189–195. Oslo. ISSN 0300–9483.
Field observations of nonmarine clay-lined ephemeral puddles have revealed numerous exogenic traces formed by a variety of insects. Most of these traces are described here for the first time. A number of different insects produced similar appearing traces. Relatively rapid drying of the shallow puddles often traps the insect, so that the trace and its maker are initially well preserved. This dessication process, in contrast to many lakes, streams and ponds having deeper water conditions, offers high potential for the exogenic trace to be preserved as a trace fossil. Trace fossil forms similar to those documented for ephemeral puddles include Gordia, Cochlichnus, Lithographus, Helminthopis and Isopodichnus . Ephemeral puddles should be considered a prime candidate for the origin of many of the trace fossils found in ancient nonmarine sedimentary rocks.     

杭州湾庵东滨岸潮间带现代沉积物中的生物遗迹特征

杭州湾庵东滨岸潮间带软底质沉积中发现的造迹动物有泥螺、珠带拟蟹守螺、弹涂鱼、宁波泥蟹、沙蚕、竹蛏、虹光亮樱蛤、海葵以及鸟类和植物等,包括软体动物、节肢动物、环节动物、脊索动物、腔肠动物等5个动物门类,共计8属,营造的生物遗迹主要有运动迹（爬迹、拖迹、足辙迹）、居住迹、觅食迹（进食迹）、生殖迹、停息迹、排泄迹、逃逸迹以及鸟类足迹和植物根迹等。分析表明潮间带不同的沉积环境,造迹生物及其遗迹的主要类型、空间分布、丰度、多样性具有明显的差异。1）研究区潮间带不同的沉积环境,造迹生物种类与分布不同,其遗迹的主要类型和分布特征具有明显的差异性,高潮区沉积物主要是富含有机质的砂质泥,生物遗迹包括珠带拟蟹守螺拖迹、停息迹和生殖迹,泥螺拖迹和停息迹,宁波泥蟹的觅食迹、居住迹和足辙迹,沙蚕的拖迹、觅食迹、居住迹和排泄迹,弹涂鱼的爬行迹和居住迹,以及鸟类足迹和植物根迹,其中层面遗迹以珠带拟蟹守螺的拖迹、沙蚕拖迹和觅食迹丰度最高,层内遗迹以沙蚕居住潜穴丰度最高,分布面积最广,扰动程度强烈,宁波泥蟹居住潜穴局部密集,扰动程度强烈,植物根迹密集,深度可达50~60 cm,这些生物遗迹常与平行直脊波痕和干涉波痕共生。中潮区沉积物主要由灰色粉砂和含砂粉砂构成,含水率较高,植被较稀疏。中潮区平坦的潮坪上生物遗迹主要由虹光亮樱蛤的居住潜穴和竹蛏的居住潜穴和摄食迹组成,丰度较高,具有少量泥螺拖迹以及植物根迹和鸟足迹。在中潮区潮沟两侧,沉积物颗粒较细,常见珠带拟蟹守螺的拖迹,宁波泥蟹的居住潜穴、足辙迹,弹涂鱼的爬迹。中潮区潮坪上多发育舌型波痕,生物遗迹多与舌型波痕共生。低潮区沉积物主要是灰色粉砂和粉砂质砂,含水率高,多为汤底,无植被,常见遗迹主要是虹光亮樱蛤的居住潜穴,竹蛏的居住潜穴以及少量海葵居住潜穴。2）沉积物的粒度、含水率影响遗迹的清晰度;3）由于受潮水、波浪运动的冲刷作用,沉积物表面的遗迹易被破坏,保存率极低,底内动物的居住潜穴保存率相对较高。该研究不仅为杭州湾潮间带沉积环境研究提供了新的现代生物遗迹信息,而且也可为古代强潮河口湾潮间带沉积环境中的古遗迹学研究提供借鉴。     

山东青岛和日照滨岸潮间带现代生物遗迹组成与分布特征*

在山东青岛和日照滨岸潮间带可见到现代生物营造的各种遗迹。通过分析这些生物遗迹与其沉积背景的关系,取得以下成果: (1)研究区生物遗迹中,层面遗迹以腹足类动物的拖迹为主,层内遗迹以居住迹丰度最高,且类型多样。(2)建立了2个生物遗迹组合: 一是高潮区组合,主要遗迹类型包括珠带拟蟹守螺拖迹、沙蚕的拖迹、摄食迹和居住迹、四角蛤的居住迹、弹涂鱼的爬行迹和居住迹、鸭嘴海豆芽的居住迹以及螃蟹的居住迹和摄食迹;该组合产生的沉积物底层具有含泥量较高,水、氧、有机质含量均较丰富及基底较稳固等特点。二是中低潮区组合,主要由斑玉螺的拖迹和停息迹、扁玉螺的爬行迹和停息迹、寄居蟹的爬行迹、长竹蛏的居住迹、虾蛄的爬行迹和居住迹、鸭嘴海豆芽的居住迹以及螃蟹的居住迹和摄食迹组成;该组合产生的沉积物底层具有含泥量较低、粒度较粗、间隙水不易保存、有机质含量低等特点;研究区潮间带为急剧多变的海洋环境,该遗迹组合可指示温带季风气候条件下的海洋潮间带沉积环境。(3)通过分析各种造迹生物及其遗迹的组成和空间分布特征以及其与底层沉积物和沉积环境的关系,建立了研究区潮间带沉积中的生物遗迹组合及其沉积环境分布模式。     

成都金沙遗址距今3000年的古气候探讨

成都金沙遗址位于成都西郊金沙村,可能是商代晚期至西周时期（约公元前11世纪–前770年）古蜀国的都邑所在地。本文分析了金沙遗址两个探方WT7908和IT8305的31个孢粉样品,探方IT8305孢粉组合表明：蕨类植物孢子占60.3%,草本被子植物花粉占24.8%,木本裸子和被子植物花粉占14.2%,水生植物花粉相对较少,仅占0.7%。蕨类植物主要以蹄盖蕨科、水龙骨科和凤尾蕨属为主,草本植物中野牡丹科占绝对优势,木本裸子和被子植物中主要以松属和桦木属为主,水生植物主要包括双星藻、鸭跖草科和香蒲属。成都平原在这个时期的气候分为两个阶段,前期阶段的气候属于亚热带温暖湿润气候,平原上生长着茂盛的草本植物和蕨类植物;后期阶段的气候虽然还属于亚热带气候,但较前期更加湿热,气温和降雨量都比前期要高。定量分析和重建了金沙遗址距今3000年的古气候：年均温17.7–19.8ºC、最热月均温21.7–28.6ºC、最冷月均温11.5–11.9ºC、年较差12.1–14.9ºC、年降雨量993.3–1113.3 mm、最大月降雨量224.6–268.1 mm、最小月降雨量6.9–14.1 mm。成都地区3000年前的年均温比现在要高1.7–2.8ºC,而年降雨量基本和现在一致。     

First discovery of cryptotephra in Holocene peat deposits of Estonia, eastern Baltic

This article reports the first discovery of middle Holocene cryptotephra from a peat sequence in Estonia, eastern Baltic. Two sequences, Mustjärve and Parika (located 110 km apart), were chosen for a pilot study aimed at finding traces of tephra fallout during the middle Holocene. Peat accumulation at both sites started in the early Holocene (c. 9500–9000 ¹⁴C yr BP; c . 11 000–10000 cal. yr BP) and continued throughout the whole Holocene. The radiocarbon-dated intervals between c. 2000 and 5000 ¹⁴C yr BP (c. 2000–5500 cal. yr BP) were chosen from both sites for the study. Colourless tephra shards were identified at 312–316 cm below the peat surface in the Mustjärve peat sequence, while no tephra was found in peat of the same age at Parika. Electron microprobe analyses suggest a correlation with the initial phase of the Hekla-4 eruption (c. 4260 cal. yr BP), although the age-depth model indicated an age around 4900 cal. yr BP. Small concentrations of colourless to light brown tephra shards at 266–270 cm in the Mustjärve sequence indicate that the Kebister tephra (c. 3750 cal. yr BP) might also be present, but geochemical analyses were not possible. The low concentration and small size of the tephra particles indicate that Estonian bogs are probably on the verge of where tephrochronology is possible in northwestern Europe. Further studies of full Holocene sequences are required in order to discover traces of other ash plumes reaching as far east as the eastern Baltic area.     

Shallow-level metamorphic fluids in a high uplift rat metamorphic belt; Alpine Schist, New Zealand

Abstract Fluids, some of which are CO₂-rich (up to 40 mol.% CO₂) and some of which are highly saline (up to 18 wt% NaCl equivalent), are trapped as fluid inclusions in quartz-calcite (∼ metallic minerals) veins which cross-cut the pumpellyite-actinolite to amphibolite facies rocks of the Alpine Schist. Fluids were commonly trapped as immiscible liquid-vapour mixes in quartz and calcite showing open-space growth textures. Fluid entrapment occurred at fluid pressures near 500 bars (possibly as low as 150 bars) at temperatures ranging from 260 to 330° C. Saline fluids may have formed by partitioning of dissolved salts into an aqueous phase on segregation of immiscible fluids from a low-density CO₂-rich fluid. Calcite deposited by these fluids has δ¹³C ranging from – 8.4 to – 11.5 and δ¹⁸O from + 4 to + 13. Isotopic data, fluid compositions and mode of occurrence suggest that the fluids are derived from high-grade metamorphic rocks. Fluid interaction with wall-rock has caused biotite crystallization and/or recrystallization in some rocks and retrogression of biotite to chlorite in other rocks.
Fluid penetration through the rock is almost pervasive in many areas where permeability, probably related to Alpine Fault activity, has focussed fluids on a regional scale into fractured rocks. The fluid flow process is made possible by high uplift-rates (in excess of 10 mm/year) bringing hot rocks near to the surface.     

Holocene peat growth and decay dynamics in sub-arctic peat plateaus, west-central Canada

Peat and net carbon accumulation rates in two sub-arctic peat plateaus of west-central Canada have been studied through geochemical analyses and accelerator mass spectrometry (AMS) radiocarbon dating. The peatland sites started to develop around 6600–5900 cal. yr BP and the peat plateau stages are characterized by Sphagnum fuscum peat alternating with rootlet layers. The long-term peat and net carbon accumulation rates for both profiles are 0.30–0.31 mm/yr and 12.5–12.7 gC/m²yr, respectively. These values reflect very slow peat accumulation (0.04–0.09 mm/yr) and net carbon accumulation (3.7–5.2 gC/m²yr) in the top rootlet layers. Extensive AMS radiocarbon dating of one profile shows that accumulation rates are variable depending on peat plateau stage. Peat accumulation rates are up to six times higher and net carbon accumulation rates up to four times higher in S. fuscum than in rootlet stages. Local fires represented by charcoal remains in some of the rootlet layers result in very low accumulation rates. High C/N ratios throughout most of the peat profiles suggest low degrees of decomposition due to stable permafrost conditions. Hence, original peat accretion has remained largely unaltered, except in the initial stages of peatland development when permafrost was not yet present.     

Temperature–time path for the low-pressure Ryoke metamorphism, Japan, based on chemical zoning in garnet

Garnet crystals from low-pressure/high-temperature (LPHT) Ryoke metamorphic rocks in the Yanai district, south-western Japan, show several kinds of chemical zoning patterns that systematically vary with grain radius between c . 0.1 and 0.5  mm. Large grains (> c . 0.4  mm) show normal zoning and small grains (< c . 0.4  mm) show unzoned or reversely zoned cores. Observations of the chemical zoning and of the spatial and size distributions of the garnet grains between c . 0.1 and 0.5  mm in radius suggest that they were formed by continuous nucleation and diffusion-controlled growth.
A previously estimated temperature–time path ( T  – t path) for the Ryoke metamorphism, using 1-D numerical simulation, is characterized by a rapid increase in temperature, 0.0017  °C yr⁻¹ on average, and a period of high temperature (>600  °C) shorter than 0.5 Myr, which was presumably caused by the intrusion of a granodiorite sheet. Chemical zoning of garnet grains with different radii simulated for the T  – t path using a numerical model of continuous nucleation and diffusion-controlled growth, in combination with intracrystalline diffusion, compares well with the observed zoning patterns in garnet grains with different radii. This is in spite of the fact that the simulated zoning patterns vary greatly, depending on subtle differences in the T–t history. Therefore, they suggest that the T–t path gives a good explanation for the LPHT Ryoke metamorphism. Although this study only refers to the Ryoke metamorphism, the technique may be applicable to thermal modelling of other metamorphic terranes.     

A standard profile for Littorina transgressions in western Skåne, South Sweden

The investigation is based on diatem- and pollen analyses of a main profile from the ancient lagoon Barsebäcksmossen. The chronology is bared on C¹⁴-^-dating.
Seven transgressions are indicated, viz. 5200–4800 B.C., 4600–4400 R.C., 4150–3900 B.C., 3800–3700 B.C., 3600–3500 B.C., 3100–2950 H.C. and 2050–1850 B.C. Thc trangressions 4150–3900 B.C., 3800–3700 B.C. and 3600–3500 B.C. may only represent fluctuations during a 'complex' transgresssion. The transgresssion in Barsebäcksmtrssen are correlated with the transgresssion established by Berglund in the Baltic Sea and by Mörner in the Kattegatt sea.
A change in the date of the pollen-zone boundary AT 1/AT 2 from 4500–4600 B.C. to 5200 B.C. is proposed.     

P–T–t paths and tectonic history of an early Precambrian granulite facies terrane, Jining district, south-east Inner Mongolia, China

Abstract The widespread khondalite series of south-east Inner Mongolia consists largely of biotite–sillimanite–garnet gneiss and quartzo-feldspathic gneiss with some marble and mafic granulite layers. It has experienced two metamorphic events at c. 2500 and 1900–2000 Ma.
A pre-peak stage of the first metamorphism at T = 600–700°C and P > 6–7 kbar is recognized by the relict amphibolite facies assemblage Ky–Grt–Bt–Pl–Qtz and 'protected'inclusions of biotite, hornblende, sodic plagioclase and quartz in garnet or orthopyroxene. The peak stage, with T = c. 800 ± 50°C and P 8–10 kbar, is characterized by the widespread granulite facies assemblages Sil–Grt–Bt–Kfs–Pl–Qtz in gneiss and Opx–Cpx–Pl ± Hbl ± Grt in granulite. The P–T–t path suggests that the supracrustal sequence was buried in the lower crust by tectonic thickening during D1–D2.
The beginning of the second metamorphism is characterized by further temperature rise to 700°C or more at lower pressure. This stage is manifested by the appearance of cordierite after garnet, fibrolite (Sil2) after biotite in gneiss and transformation of Hbl1 into Opx2 and Cpx2 in granulite. Coronas of symplectitic Opx2 + Pl2 surrounding Grt1 and Cpx1 in mafic granulite are interpreted as products of near-isothermal decompression. The P–T–t path may be related tectonically to waning extension of the crust by the end of the early Proterozoic.     

Recent and subrecent sedimentary conditions in the southern part of the North Sea–Baltic Sea transition

The recent rate of net sedimentation (0–5mm/yr) in the southern Kattegat is to a high degree governed by resuspension. In shallow areas (10–25 m) there is no or very little sedimentation. Sediments here are sandy lag sediments with a low content of organic matter (0.5–3.0%), nitrogen (0–0.1%) and phosphorus (0.01–0.05%). In deep water (30–60 m) the sediments are clays or fine silts and generally have high contents of organic matter (3.0–10.8%), nitrogen (0.1–0.34%) and phosphorus (0.05–0.10%). Shallow water sediments are relatively well sorted because of resuspension of fine material, which is transported to deeper water. Here the sorting becomes poor because relatively coarser material is supplied during exceptional storm events. Discrimination on erosion/transport bottoms and on depositional bottoms was based on resuspension calculations, grain-size parameters and Passegas (1964) CM diagrams. The IG/N ratio was an useful additional tool. From the sediment content of CaCO₃ it is suggested that recent sedimentation in the deeper parts of southern Kattegat is less influenced by contributions from the North Sea than it was during the early Holocene.     

庐山冰川现象之观察

庐山第四纪冰川遗迹,首由著名地质学家李四光教授于1931年发现,并以专著“冰期之庐山”于1947年公布于世。此文发表后,赞称与反对者均有人在。1983年8月,作者在庐山疗养期间,从庐山地貌及其演化观点,对此问题进行了观察,草成本文以示支持李师的冰川观点。文成之后,未遑发表,现值李师百年诞辰之际,特以此文纪念恩师培养之情。     

Coronas and high-P veins in metagabbros of the Kohistan island arc, northern Pakistan: evidence for crustal thickening during cooling

Abstract The E-W-trending Kohistan terrane in the NW Himalaya is a sandwich of a magmatic arc between the collided Karakoram (Asian) and Indian plates. The southern part of the Kohistan arc is principally made up of amphibolites derived from volcanic and plutonic rocks of Early Cretaceous age. Gabbroic relics in the amphibolites display calc-alkaline character, and their mineralogy is similar to low-P plutonic rocks reported from modern and ancient island arcs. The largest of these relics, occurring along the southern margin of the amphibolite belt near Khwaza Khela, is subcircular in outline and is about 1 km across. It consists of cumulate gabbros and related rocks displaying a record of cooling and crustal thickening. Primary olivine and anorthite reacted to produce coronas consisting of two pyroxenes +Mg-Fe²⁺-Al spinel ± tschermakitic hornblende at about 800° C, 5.5–7.5 kbar. This thermotectonic event is of regional extent and may be related to the overthrusting of the Karakoram plate onto the Kohistan arc some 85 Ma ago, or even earlier. Later the gabbros were locally traversed by veins containing high-P assemblages: garnet, kyanite, zoisite, paragonite, oligoclase, calcite, scapolite and quartz ° Chlorite ° Corundum ± diopside. Formed in the range 510–600° C, and 10–12 kbar, these suggest further thickening and cooling of the crust before its uplift during the Tertiary. This paper presents microprobe data on the minerals, and discusses the tectonic implications of the coronitic and vein assemblages in the gabbros.     

The aging of gypsum in underground mines

The aging properties of gypsum extracted from two underground mines in France (Livry–Gargan and Grozon) have been highlighted by means of observation performed using scanning electron microscopy on samples taken along horizontal boreholes drilled through to the middle of several pillars. The aging process is exhibited by the presence of traces of dissolution (edges of the dissolved crystals, corroded crystalline surfaces, important intra- and intercrystalline space). These dissolution figures decrease in number and in intensity from the wall heading towards the middle of the pillar. The “older” pillars display a greater number of dissolution traces than the “more recent” pillars. Then, the role of the aging has been assessed by determining various physical and mechanical parameters on cylindrical samples of 38 mm in diameter and 76 mm in height, machined from the set of drilled boreholes. The following parameters have been quantified: density, grains density, total porosity, porosity accessible to water, intrinsic permeability to nitrogen, velocity of ultrasonic compression and shear waves, dynamic Young's modulus, dynamic Poisson's ratio, uniaxial compressive strength and static Young's modulus. Significant variations in parameter values between the wall and the middle of the pillar were recorded and recognized as being strongly correlated with the intensity of dissolution traces, and hence with gypsum aging.     

Methane‐related microbial gypsum calcitization in stromatolites of a marine evaporative setting (Münder Formation,Upper Jurassic,Hils Syncline,north Germany)

Fossil stromatolites may reveal information about their hydrochemical palaeoenvironment, provided that assignment to a specific microbial community and a corresponding biogeochemical mechanism of formation can be made. Tithonian stromatolites of the Münder Formation at Thüste, north Germany, have traditionally been considered as formed by intertidal cyanobacterial communities. However, thin sections of the stromatolites show elongated angular traces of former gypsum crystals in a dense arrangement, but no algal or cyanobacterial filament traces. Moreover, high Fe²⁺ and Mn²⁺ contents, oxygen‐isotope and sulphur‐isotope ratios of carbonate‐bound sulphates, and sulphurized hydrocarbon biomarkers of the stromatolitic carbonate indicate that CaCO₃ precipitation occurred near the oxic–anoxic interface as a result of intensive bacterial sulphur cycling rather than photosynthetic activity. Furthermore, anaerobic oxidation of methane by Archaea may have driven CaCO₃ precipitation in deeper parts of the biofilm community, as reflected by high concentrations of squalane with a strongly negative δ¹³C in conjunction with evaporite pseudomorphs showing extremely low δ¹³C_Carb ratios. Consequently, the Thüste stromatolites are now interpreted as having initially formed by gypsum impregnation of biofilms. Subsequently, early Mg‐calcitic calcitization within the biofilms occurred because of combined bacterial iron, manganese and sulphate reduction, with an increasing contribution of anaerobic oxidation of methane with depth. This model plausibly explains the prominent preservation of signals derived from oxygen‐independent metabolic pathways, whereas virtually no geochemical record exists for an aerobic community that may, nevertheless, have prevailed at the stromatolite surface. Photic‐zone stromatolites with a prominent signal of anaerobic oxidation of methane may be common in, and indicative of, oxygen‐depleted sulphate‐bearing environments with high rates of methane production, conditions that possibly were fulfilled at the Archaean to Proterozoic transition.     

Monochromatic infra-sound waves recorded offshore Ecuador: possible evidence of methane release

ABSTRACT Methane is known to be a greenhouse gas but it is difficult to estimate its significance. We have identified a new approach for monitoring fluxes of methane from large areas of sea floor. During spring 1998, we conducted an offshore passive seismic experiment using 13 three-component digital Ocean Bottom Seismometers. During this 3-week experiment, we recorded unusual sustained and intense monochromatic infrasound waves (6–7 Hz). The origin of the noise is tentatively interpreted as pressure-waves resulting from oscillating clouds of bubbles. Such clouds must have a characteristic size of ∼ 10 m, at depths of 5–15 m, and must contain more than 10¹⁰ bubbles of 1 mm radius to produce the observed frequency. The presence of a Bottom Simulating Reflector in the study area suggests that gas seepage may occur at the seafloor, near 500 m depth. Then, bubbles of gas, namely methane, could form in the water column. Although highly speculative, Ocean Bottom Seismometer records could potentially be useful for monitoring gas seeps and/or related unusual behaviour of the seabed.     

Analysis of the relationship between displacements and dimensions of faults

Displacement gradients on single fault surfaces are a function of the maximum displacement on a fault and the dimensions of the fault surface. Data on the maximum lateral dimensions (widths) and maximum displacements on normal faults and thrusts, with maximum displacements from 4 mm to 40 km, are used to derive an expression relating width, displacement and material properties. The basis of this expression is a fault growth model in which width is proportional to the square root of displacement. Width/displacement ratios vary systematically with the size of a fault from values of ca 30,000, which are characteristic of a single slip event, to about 10 in the case of thrusts with displacements of 40 km. Rocks from which the fault data are derived have a likely range of shear moduli from ca 0.1 to ca 30 GPa, which is sufficient to account for the range of data.Data on widths and maximum displacements of 308 fault traces recorded on British coalmine plans are shown to be consistent with variation of shear modulus of about half an order of magnitude. Data on 58 further fault traces are shown to be consistent with the fault growth model. Synsedimentary faults may have growth curves characteristically different from those of other faults.It is suggested that the increase in dimensions of a fault is a postseismic process of subcritical crack propagation for which the significant material property is fracture toughness.     

Trilobite trace fossils and their stratigraphical significance in the Cambrian sequence of the Holy Cross Mountains,Poland

Abundant and varied trilobite trace fossils are recognized and described in the Cambrian sequence of the Holy Cross Mountains. Cruziana and Rusophycus are stratigraphically significant and some of the described traces may be used as local index fossils. The first recognition of the Cruziana barbata ichnozone in Poland is made and it occurs in the uppermost Middle Cambrian. A new position for the Middle/Upper Cambrian boundary is established. Three new ichnospecies are described: Cruziana magna, C. regularis and Rusophycus crebus.