叠锥构造的特征及其成因机制: 进展与实例*

叠锥构造是纤维状矿物呈锥状嵌套分布的一类特殊沉积构造,自20世纪90年代以来一直是国际研究的热点,但中国对于叠锥构造的研究起步较晚,研究程度较低。文中详细总结了叠锥构造研究进展,并简要介绍了笔者于新疆托克逊凹陷、准噶尔盆地东部以及哈密盆地3处新发现的叠锥构造。叠锥构造的发育层系广泛,二叠纪末—三叠纪初以及三叠纪末—侏罗纪初发现的叠锥占绝大多数,揭示其可能与生物大灭绝有关;叠锥构造的形成环境较广,不能简单地将叠锥构造作为湖泊相或海相等的相标志。对新发现的叠锥构造初步分析后认为,叠锥构造为与生物(化学)作用有关的原生沉积构造,但对叠锥构造成因机制的深层次研究还需建立在叠锥构造纤维状矿物生长习性及其与形成环境和发育层系的耦合关系研究之上。

Features and genetic mechanism of cone-in-cone structures: Progress and examples

As a special kind of sedimentary structures,cone-in-cone,laminated cones consist of fiber-shaped minerals encased in a cone outlook, and has been the focus of intense study since 1990s. However,the research on the cone-in-cone in China started later,while the concomitant understanding is relatively poor. This paper aims to summarize and analyze in detail the morphology,strata occurrence,formation environment,composition of previously documented-laminated cones,combined with three undocumented outcrop examples in the Tuokexun sag,the east of Junggar Basin,and Hami Basin. The unique cone-in-cone structures were well developed in sedimentary sequences from the Paleoproterozoic to the Neogene,especially concentrated on late Paleozoic to Mesozoic practically. It is worth mentioning that cone-in-cone structures indeed developed particularly in Early Jurassic and Late Triassic or Triassic-Jurassic(T-J)boundary. Therefore, cone-in-cone structures may be related to mass extinctions. Moreover,cone-in-cone structures are seen to occur in both marine and non-marine settings, suggesting that ocean processes are not mandatory for the formation. Original biochemical action would be an explanation for cone-in-cone structures. However,the growth habits of fibrous minerals and the relationship between cone-in-cone structures and their environment and sequence need to be further documented.