A Gatun ostracode fauna from Cativa, Panama. American Museum novitates ; no. 956

Abstract

The material from which this fauna is described was collected by Captain John Embich during September, 1934, from a marl formation in the town of Cativa, located five miles east of Colon, on a small inlet of the Caribbean sea.The beds dip gently to the north at an angle of 10O- 12.They are very fossiliferous.The fauna consists of gastropods, cephalopods, pelecypods and bryozoa as the macrofossils with many for- aminifera and ostracoda as the microfossils.The determination of the age of this marl as Lower Gatun is on the basis of specimens identified as Clementia dariena (Conrad), which, in the opinion of Woodring, is con- fined to the Lower Zone of the Gatun formation.The fauna, itself, is noteworthy because of the occurrence in it of many new specimens with very definite recent affinities.The less ornamented and smooth shelled forms are much like living ostracodes, both in hinge structure and in the features of the inner lamella.Specializa- tion is evidenced by the extremely ornate specimens, and the presence of similar ornamentation in unlike forms such as Cativella naves and Navecythere delicata.The definite appearance of modernistic trends and the occurrence of such a high degree of ornamentation indicate that in the Caribbean region rapidly changing environmental conditions accom- panied the diastrophic movements which were in progress at that time.The following table shows the position of the Cativa marl formation in the geological classification.MIOCENE Upper Middle Lower Toro limestone Gatun formation Emperador limestone Upper Upper Culebra formation Middle Lower-Cativa marls Vamos-a-vamos Map of Panama Canal Zone showing the location of the Cativa collecting locality.