On New Ammonites from the English Chalk
On New Ammonites from the English Chalk
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论英国粉笔中的新菊石
DOI：
10.1017/s0016756800083710
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发表时间：
1926
影响因子：
2.3
通讯作者：
L. Spath
中科院分区：
文献类型：
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作者：
L. Spath
菊石在塞诺曼阶或下白垩期相对常见，在土伦阶或中白垩期则较为稀有，而在上白垩期则非常稀有。在前一次场合，当作者指出虽然英国的 Micraster cor-testudinarium Chalk 中没有菊石，但它们却出现在法国北部的同一个 Chalk 中时，作者倾向于将这种缺失或稀缺归因于菊石水平分布的有限。然而，白垩层序中存在间隙的可能性是不可否认的，例如在Actinocamax plena的地平线处、在白垩岩处、在cor-anguum区域内和上方等。 Micraster cor-anguinum 区域并不像下面的区域那么贫瘠，但迄今为止从该区域已知的唯一菊石是可疑的例子，可能与 Parapuzosia 有关。迪布利先生在肯特郡诺斯弗利特的伦敦-波特兰坑中收集了一个大型牡蛎腹侧部分的印痕，该标本可能是 P. corbarica Grossouvre sp.，罗博士记录了来自多塞特郡和约克郡的可能类似的 Parapuzosia（“leptophyllus 组的菊石”）。
Ammonites are comparatively common in the Cenomanian or Lower Chalk, become rarer in the Turonian or Middle Chalk, and are very scarce in the Upper Chalk. On a former occasion, when pointing out that while ammonites were unknown from the Micraster cor-testudinarium Chalk of England, they occurred in the same Chalk in the north of France, the writer was inclined to attribute this absence or scarcity to limited horizontal distribution of the ammonites. The possibility, however, of there being gaps in the Chalk succession, for example at the horizon of Actinocamax plena, at the Chalk-Rock, in and above the cor-anguinum zone, etc., cannot be denied. The zone of Micraster cor-anguinum is not quite so barren as the zone below, but the only ammonites hitherto known from it are doubtful examples, probably referable to Parapuzosia. One impression, on an oyster, of part of the ventral area of a large specimen, possibly of P. corbarica Grossouvre sp., was collected by Mr. Dibley in the London-Portland Pit at Northfleet, Kent, and Dr. Rowe recorded probably comparable Parapuzosia (“ammonites of the leptophyllus group”) from Dorset and Yorkshire.