Abstract
The age of the Uscari Formation in the Victoria Area, located a few kilometers southwestern Limon City, is Medium to Upper Miocene, the samples were recolected in the central part of that area, in the Uscari creek (type locality) and in the mouth of the Watsi river.
Twenty five species of Planktonic Foraminifera founded in forty two samples, recovered in the main rivers, were studied because of their biostratigraphic importance.
The Coincident Extension Zones of Globorotalia siakensis Le Roy- G. menardii (Parker, Jones & Brady)- Orbulina spp. and Sphaeroidinellosis seminulina (Shwager) S. subdehiscens (Blow)- Globigerinoides extremus Bolli & Fermúdez, and data of Praeorbulina glomerosa (blow), Orbulina Globorotalia siakensis Le Roy and Globigerina nepenthes Todd, allow to assign a Middle to Upper Miocene age.
Catapsydrax dissimilis (Cushman & Bermúdez), C. cf. unicavus (Bolli, Loeblich & Tappan) and Globigerina tripartita Koch are reworked material belonging to Lower Miocene rocks