Concave-up pelecypod (Psephidia) shells in shallow marine sand, Elk River beds, southwestern Oregon
Concave-up pelecypod (Psephidia) shells in shallow marine sand, Elk River beds, southwestern Oregon
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俄勒冈州西南部麋鹿河床浅海沙中的凹形贝壳动物（Psephidia）贝壳
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发表时间：
1970
期刊：
影响因子：
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通讯作者：
S. Boggs
中科院分区：
文献类型：
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作者：
H. Clifton;S. Boggs
摘要俄勒冈州西南部上新世或更新世的埃尔克河河床中，有许多不分节的杯足类动物的瓣，特别是小型杯足类Psephidia的瓣，主要是凹向上的。由于这一特征似乎是由波浪冲刷的浅海环境中的沉积作用造成的，因此，这种贝壳形态在这里不能归因于浊流、沉积物圈闭、最上部的海滩冲流或静水中的沉积作用等机制，而这些机制以前曾被用来解释其他地方的上凹贝壳。在碎波区进行的Psephidia贝壳实验表明，上凹贝壳层是由海底小沙波纹的迁移形成的。这样的波纹可能会产生在埃尔克河B ds和其他浅海沉积物中发现的大部分层压。
ABSTRACT The Elk River Beds of Pliocene or Pleistocene age in southwestern Oregon contain numerous beds in which disarticulated pelecypod valves, particularly of the small pelecypod Psephidia, lie predominantly concave-up. Inasmuch as the trait seems to result from deposition in a wave-swept shallow marine environment, this shell configuration cannot here be attributed to mechanisms such as turbidity currents, sediment traps, uppermost beach swash, or deposition in quiet water that have been previously cited to account for concave-up shells at other places. Experiments with Psephidia shells in the surf zone indicate that layers of concave-up shells are formed by migrating small sand ripples on the sea floor. Such ripples may produce much of the lamination found in the Elk River B ds and in other shallow marine deposits.