Taphonomic and sedimentologic implications of crinoid intraskeletal porosity
Taphonomic and sedimentologic implications of crinoid intraskeletal porosity
复制标题
海百合骨骼内孔隙度的埋藏学和沉积学意义
DOI：
10.1111/j.1502-3931.1996.tb01870.x
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
N. Lane
中科院分区：
文献类型：
--
作者：
M. Savarese;J. Dodd;N. Lane
海百合柱状体的多孔结构有以下几点含义：(1)软组织腐烂后，海百合原本铰接的骨架分崩离析。(2)多孔小骨成为沉积物的一部分，但它们在流体动力学上的行为像小得多的固体矿物颗粒。(3)由于海百合板块的水动力特性，它们应该相对容易地从它们的生活栖息地转移出去。(4)多孔骨架在成岩作用中起到“海绵”的作用，是成岩矿物沉积的场所。通过电子探针的后向散射图像或单个柱状体（仅适用于现存物种）的体积和质量，测定了5种现代深海海百合和多达7种石炭纪海百合柱状体的孔隙度和比重。这些方法给出了现代海百合的孔隙度值为52-72%，化石海百合的孔隙度值为3949%。这相当于现代柱状石的净比重为1.47-1.83，化石的净比重为1.54-2.10（固体方解石的比重为2.72）。为了比较矿物颗粒更密集的海百合板的水动力行为，测定了5种现代物种柱状体的沉降速率和水槽夹带阈值。柱状体的沉降速率和夹带阈值相当于直径小于柱状体直径十分之一的石英球（以最大尺寸测量）。柱的单位浸入质量（UIM：有效质量，是比重的函数，除以柱的投影面积）与沉降速度和夹带速度有很好的相关性；然而，柱状形状显著影响行为。交叉层状、含海百合颗粒岩和石英砂岩的粒度数据显示了海百合与其他颗粒之间的差异。如果骨内胶结早于埋葬，则柱的比重会增加，从而影响其流体动力学行为。因此，有机质腐烂的时间和孔隙的成岩充填相对于最终埋藏的时间都应该影响岩柱的运移历史。潜流学，生物生态学，流体动力学行为，m 'noid柱状体。
The porous texture of crinoid columnals has a number of implications:(1) After soft tissue decays, the originally articulated skeleton of the crinoid falls apart.(2) The porous ossicles become part of the sediment, but they will behave hydrodynamically like much smaller solid mineral grains.(3) Because of their hydrodynamic behavior, crinoid plates should be transported away from their life habitat with relative ease.(4) The porous skeleton should act as a ‘sponge’during diagenesis and serve as the site of deposition of diagenetic minerals. Porosity and specific gravity of columnals from five species of modern, deep-sea crinoids and from as many as seven form-species of Carboniferous crinoids were determined from either back-scatter images from an electron probe or from the volume and mass of individual columnals (extant species only). These approaches give porosity values of 52-72% for modern crinoids and 3949% for fossil crinoids. This corresponds to net specific gravities of 1.47-1.83 for modern columnals and 1.54-2.10 for fossils (solid calcite has a specific gravity of 2.72). In order to compare hydrodynamic behavior of crinoid plates with more dense mineral grains, settling rates and flume entrainment thresholds were determined for columnals of the five modern species. Columnals have settling rates and entrainment thresholds equivalent to quartz spheres with diameters less than a tenth of the diameter of the columnal (measured as largest dimension). A columnal’s unit immersed mass (UIM: effective mass, a function of specific gravity, divided by the projected area of the columnal) correlates fairly well with settling and entrainment velocities; however, columnal shape significantly influences behavior. Grain-size data from cross-bedded, crinoid-bearing grainstones and quartz arenites show this differential behavior between crinoid and other grains. If intraskeletal cementation predates burial, a columnal’s specific gravity would be increased, affecting its hydrodynamic behavior. Therefore, both the timing of organic decay and diagenetic filling of porosity relative to final burial should influence the transport history of a columnal. OTaphonomy, paheoecology, hydrodynamic behavior, m’noid columnals.