General equations for volume and surface area of a logarithmically coiled shell     

David M. Raup  Richard R. Graus 《Mathematical Geology》1972,4(4):307-316

The equations of Moseley for the volume and surface area of a coiled shell have been rewritten in their most general forms. The general volume equation has been tested with 15 gastropods and found to give satisfactory results wherever there are no significant ontogenetic changes in the shell geometry. The equations provide a means for calculating the carbonate efficiency of a coiled shell. With this parameter analyzed into its component parts, it has been possible to understand the relationships between aspects of shell calcification and environmental factors that affect calcium carbonate availability. Preliminary studies indicate that it also may be possible to discriminate morphologically between terrestrial and aquatic gastropods, the various gastropod modes of life, and higher taxonomic categories. These equations offer possibilities for other studies concerned with the ecology, paleoecology, and evolution of coiled shells.  相似文献   

滇黔桂盆地早二叠世亚丁斯克期的沉积环境分异与䗴有孔虫响应     

黄明立  田坤烜  史宇坤 《地学前缘》2020,27(6):313-328

亚丁斯克期华南滇黔桂地区沉积环境分异明显,主要发育局限或半局限海台地沉积区、开阔海台地沉积区和台地边缘沉积区,不同沉积区䗴有孔虫动物群面貌也有所区别。本文详细研究了黔南地区的猴场打望剖面和惠水竹子冲剖面阿瑟尔期—亚丁斯克期的地层,在打望剖面识别出4个䗴类化石带,由老至新为Pseudoschwagerina beedei-Sphaeroschwagerina constans共存延限带、Staffella xiushuiensis-Eoparafusulina contracta富集带、Pseudofusulina ellipsoidalis富集带和Misellina subcycloidea间隔带。竹子冲剖面识别出3个化石带,由老至新为Pseudoschwagerina uddeni-Sphaeroschwagerina sphaerica组合带、Eoparafusulina certa富集带和Staffella discoides延限带。对滇黔桂地区不同沉积相区剖面䗴类动物群以及沉积相特征的综合研究显示:开阔台地或台地边缘环境的䗴动物群以Pamirina为特征分子,同时还产出丰富的希瓦格䗴亚科(Schwagerininae)分子;局限或半局限台地环境的䗴类以史塔夫䗴亚科分子(Staffellininae)为主。沉积环境对䗴有孔虫的影响可能主要来自水动力、光照和氧气含量。个体较大、隔壁褶皱强烈的纺锤形希瓦格䗴亚科分子更适应水动力强、透光性好、氧气充足的水体;小个体、结构简单的史塔夫䗴亚科分子可在透光性差、含氧量较低的水体中生存。  相似文献   

皖南休宁地区恐龙脚印等化石的产出特征   总被引：5，自引：0，他引：5  

余心起 《安徽地质》1999,(2)

皖南休宁地区发现“三位一体”的恐龙骨骼化石、恐龙蛋化石、恐龙足迹和尾迹化石。本文着重描述这批化石的形态大小和结构特点，并从古生态学方面对化石进行了探讨分析；按化石产出层位，对应的各类恐龙活动时间总计约为40Ma。  相似文献   

华北地区早更新世生物-气候事件--以哺乳动物化石为例   总被引：1，自引：0，他引：1  

程捷 《地质科技情报》2000,19(1):5-10

讨论了华北地区几个早析世洞穴地点哺乳动物群的生态环境、气候变迁和动物迁移。龙牙洞、第１８地点、贾家山以及东洞动物群都是喜冷型动物群,反映的气候干冷或干凉,植被为稀树草原、森林－草原或干冷草原。在气候方面,它们可与黄土层堆积时气候对比。第１２地点显示炎热湿润气候,东洋界动物向北迁移,森林茂密,是我国北方一次重要的温暖事件,相当黄土剖面中的古土壤层（Ｓ２４－Ｓ２５）的气候。第９地点和西洞动物群批示气候  相似文献   

Paleoecological analysis of molluscan assemblages in two marl deposits in Waterloo Region, southwestern Ontario, Canada     

J. Yang  P.F. Karrow  G.L. Mackie 《Journal of Paleolimnology》2001,25(3):313-328

Mollusc assemblages were studied in two marl deposits at Kitchener and Cambridge, in southwestern Ontario. Lacking datable terrestrial plant material, a chronology was determined by pollen analysis. Similarities in mollusc assemblages and changes allowed five equivalent mollusc assemblage zones to be identified in the two deposits, spanning approximately 12 to 7 ka. In total, 34 mollusc taxa were identified, with 19 common to both sites. Overall, the most abundant taxa were Valvata spp., Gyraulus parvus, Pisidium casertanum, and P. ferrugineum. Terrestrial molluscs (four taxa) were rare. Overall, cool, shallow water with abundant vegetation and quiet conditions were indicated. At around 9 ka, a marked decrease in mollusc abundance and diversity, but relatively stable percentages, is noted at both sites. We speculate this was caused by an increase in sedimentation rate, perhaps caused by a brief warming.Inconsistencies in assemblages at marl sites may be partly attributable to sampling, but a chance factor in dispersal is also suggested. A minimum of two sampling sites at a given sedimentation basin, nearshore and mid-basin, are recommended to maximize assessment of assemblages. More detailed data from living molluscs are needed to enhance paleoenvironmental interpretations.  相似文献   

吐鲁番拗陷中侏罗世孢粉植物群及古环境   总被引：2，自引：0，他引：2  

王永栋  江德昕 《沉积学报》1997,15(3):133-140

根据吐鲁番拗陷葡１井和草南１井中侏罗世的孢子花粉化石及其组合特征，研究孢粉植物群、古植被面貌及古生态环境，探讨中侏罗世的古气候性质、演变及其对聚煤作用和油气生成的影响。  相似文献   

生态地层学的研究现状与进展   总被引：1，自引：0，他引：1  

童金南 《地质科技情报》1992,11(4):46-50

本文简要介绍了近阶段在生态地层学的基本概念,生态地层学的基础——群落结构和群落生态,以及生态地层学在地层学和盆地分析中的应用等方面的研究中所取得的进展、成果和研究现状。  相似文献   

Bioerosion on Late Pleistocene Marine Mollusks: A Paleoclimatological and Paleoecological Comparison of MIS 7 and MIS 5e with Modern Beaches (Río Negro, Argentina)     

Melisa P. CHARó  Gisela D. CHARó  Guillermo ACE?OLAZA  Jose L. CAVALLOTTO 《《地质学报》英文版》2022,96(4):1181-1198

The Late Pleistocene littoral ridges of southern South America, especially those of the north of Argentinean Patagonia, contain remains of mollusk shells with bioerosion traces. Eleven sites from marine isotope stages (2 from MIS 7, 4 from MIS 5e) and five sites from modern beaches from northern Río Negro Province, with 40 taxa (17 bivalves and 23 gastropods) were analyzed, in the area between west of Baliza San Matías and Las Grutas (41°S). Three ichnogenera were identified in deposits of MIS 7: Entobia, Gastrochaenolites (Domichnia) and Oichnus (Praedichnia) with one ichnospecies (G. torpedo). Six ichnogenera were identified in deposits of MIS 5e: Entobia, Meandropolydora, Pinaceocladichnus, Iramena, Caulostrepsis and Oichnus with one ichnospecies (O. simplex). Seven ichnogenera were identified from modern beaches: Entobia, Meandropolydora, Iramena, Caulostrepsis, Pinaceocladichnus, Gastrochaenolites (Domichnia) and Oichnus (Praedicnia), with two ichnospecies (O. simplex and O. paraboloides). On this basis, it is inferred that Pleistocene benthic communities were constituted from cheilostome bryzoans and polychaete annelids, together with drilling bivalves, predatory gastropods and overall warm-water species of mollusks. Of these, Chama iudicai was found on Plicatula gibbosa from MIS 7 and MIS 5e. The record of warm temperature species suggests a higher sea surface temperature (SST) than the present one and/or the influence of the warm southward Brazilian Current affecting the waters of Golfo San Matías. On the modern beaches surveyed, there is an increase in polychaete annelids, cheilostome bryzoans, temperate-cold species and drilling bivalves, as well as sandy substrate species, which together with an increase of Gastrochaenolites and Caulostrepsis, suggest a colder climate due to the greater influence of the Malvinas Current during the Holocene.  相似文献   

甘肃宝积山盆地中侏罗世植物群特征及古生态、古气候研究     

刘松欣  辛存林  王晶菁  狄国芸  焦志鹏  赵涵  王志韬 《地质学报》2021,95(12):3592-3605

本文对甘肃宝积山盆地窑街组植物大化石进行了系统研究,经鉴定共有19属50种,结合已有的宝积山盆地中侏罗世植物化石资料,发现甘肃宝积山盆地中侏罗世植物群由27属73种组成.其中,银杏类植物10属30种,真蕨类植物5属26种,松柏类植物5属6种,楔叶类植物3属5种,苏铁类植物2属4种,裸子植物球果和种子化石2属2种.基于当前植物群组成特征,对植物化石埋藏学特性进行分析,确定植物化石主要为原地埋藏或亚原地埋藏,少数属种为异地埋藏,并通过对化石类群古生态特征进行分析,结合现生植物的生存环境,初步重建了宝积山盆地中侏罗世植物群落,划分为四个植物群落:岸边湿地楔叶类植物群落、低地蕨类苏铁类植物群落、坡地银杏类植物群落和高地松柏类植物群落.通过对植物群组成特征和植物化石叶相特征的统计分析,并与其他气候带植物群特征进行对比,推断中侏罗世时期甘肃宝积山盆地为温暖潮湿的暖温带气候.  相似文献   

塔中Ⅰ号坡折带上奥陶统成礁背景分析   总被引：6，自引：1，他引：5  

王振宇  孙崇浩  张云峰  韩剑发  李新生  吉云刚 《沉积学报》2010,28(3):525-533

自塔中Ⅰ号坡折带上奥陶统良里塔格组发现生物礁滩作为重要储集层后,有关礁的形态和规模一直存在较大的争议。本研究解析该地区礁的古生物组合、古生态结构和沉积环境,以此为基础系统论证生物礁的沉积序列。礁的建造方式可归属于珊瑚骨架礁丘、层孔虫—海绵骨架礁丘、海绵—层孔虫骨架礁丘以及管孔藻—层孔虫骨架礁丘几种生态类型,这些骨架礁丘无论从造礁生物多样性、生态组合特征以及造礁规模,皆不同于前时代的前寒武纪叠层石礁、寒武纪古杯礁、早奥陶世的灰泥丘和托盘海绵礁,而呈现出单个礁体厚度大、发育旋回多之特点,多期礁体的垂向叠加、横向迁移造成礁体叠置连片, 形成了呈条带状展布的大型生物礁群。  相似文献