Extinction pattern and process of siliceous sponge spicules in deep-water during the latest Permian

来源 :Science in China(Series D:Earth Sciences) | 被引量 : 0次 | 上传用户:CBN_cntjlz
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
Diverse and abundant siliceous sponge spicules were found in the latest Permian beds, Dongpan and Ma’anying sections, South China, including 52 types and 85 forms. Further investigation on these spicules allows us to understand extinction patterns and processes of deep-water sponges. These sponge spicules rapidly decreased below the Permian/Triassic boundary (PTB), and the extinction rates reach up to 88%-90% for types and 88%-92% for forms. Their extinction pattern is a gradual one that consists of two stages: the first is characterized by a gentle and slow extinction speed and low extinction rate, and the second by sharp and fast extinction speed and high extinction rate. The morphological extinction process is involved in the disappearance first of the triaxons and tetraxons, then of the polyaxons and demas, and last of monaxons. In exterior structure extinction, the complex spicules with branches and spines became extinct more easily than did smooth spicules. After the end-Permian mass extinction, only five common and smooth forms survived: Oxeas A, Oxeas B, Strongles B, Oxy-orthpentactines and Oxy-orthohexactines A. Diverse and abundant siliceous sponge spicules were found in the latest Permian beds, Dongpan and Ma’anying sections, South China, including 52 types and 85 forms. Further investigation on these spicules allows us to understand extinction patterns and processes of deep-water sponges. These sponge spicules rapidly rapidly below the permian / Triassic boundary (PTB), and the extinction rates reach up to 88% -90% for types and 88% -92% for forms. Their extinction pattern is a gradual one that consists of two stages : the first is characterized by a gentle and slow extinction speed and low extinction rate, and the second by sharp and fast extinction speed and high extinction rate. The morphological extinction process is involved in the disappearance first of the triaxons and tetraxons, then of the polyaxons and demas, and last of monaxons. In exterior structure extinction, the complex spicules with branches and spines became extinct more easily than did smooth spicules. After the end-Permian mass extinction, only five common and smooth forms survived: Oxeas A, Oxeas B, Strongles B, Oxy-orthpentactines and Oxy-orthohexactines A.
其他文献
近年来,各级财政部门认真贯彻落实党中央、国务院关于“三农”工作的各项决策部署,不断加大财政支农投入力度,完善支农政策措施,让公共财政的阳光越来越多地照耀农村,有力地
赵云旗是个颇有艺术家气质的中年学者,眉目间有着神似腾格尔的不羁。办公室座位身后几乎与人同高的财政年鉴显示了他对财政史史料的珍惜。有意思的是书虽然多,但从窗外阳光照
在工业设计的教学模式中,由造型基础、设计基础、专业设计三大块组成的“三段式”的教学方法是至今仍被高校普遍采用的教学模式。而这种按部就班的教学方法显然已经不适应当
加强和规范财政资金专户管理,是深化国库集中收付制度改革、强化财政资金监管的关键环节,也是从源头上预防和治理腐败的重要措施。财政部对财政资金专户管理工作十分重视,多
Based on Taylor series expansion and strain components expressions of elastic mechanics, we derive formulae of strain and rotation tensor for small arrays in sp
本文认为,依据我国当前的经济发展水平、特殊的经济制度背景以及供给对需求的内在制约,要使我国经济走出低谷,必须适时地实行需求管理政策向供给管理政策的转换。具体的途径是:1.继
西沙必利是一种不具有抗多巴胺能特征的苯甲酰胺类衍生物 ,是第二代胃肠动力药。临床应用广泛 ,但该药属于管制药品 ,必须在医生指导下使用。1 新生儿呕吐新生儿 92例 ,在原
湖北省国库集中收付改革从2003年开始试点,经过2004年扩大范围、2005年整体推进、2006年以后深化完善,目前已将各类财政性资金纳入改革范围,并将改革延伸到乡镇一级和绝大部分
北京市怀柔区自2001年推行部门预算改革以来,预算的规范化程度得到了很大的提高,预算约束力和公开透明程度进一步增强,财政资金使用效益明显提高,初步建立起与部门预算紧密结
针对现役空心板桥单板受力病害极为普遍的现象,分析了单板受力病害产生原因,通过工程实践总结出了顶板植筋加强桥面铺装加固、顶板植筋+竖向拉杆加固、П形钢板加固等3种单板