Where: Ecuador (1.0° N, 79.8° W: paleocoordinates 0.2° N, 76.9° W)
• coordinate based on nearby landmark
• outcrop-level geographic resolution
When: Borbon Formation, Middle Miocene (16.0 - 11.6 Ma)
• STRATIGRAPHIC RELATIONS: From the Borbon Fm, which is regionally overlain by the Esmeraldas Fm (Pliocene). AGE: Middle Miocene, on the basis of microfossil biostratigraphy; nannofossil zones N11-13; planktonic zones N13-N14. STRATIGRAPHIC POSITION: From unknown position within formation.
• bed-level stratigraphic resolution
Environment/lithology: deep-water; unlithified, tuffaceous, argillaceous mudstone
Size classes: mesofossils, microfossils
Collection methods: bulk, chemical, hydrochloric, sieve,
• COLLECTOR: Presumably the authors. REPOSITORY: Not stated, but presumably Princeton University, New Jersey. PREPARATION: Eighty-five gram samples were crushed and boiled with Calgon, then washed through 420-,m, 177-Am, 74-,m and 63- ,m screens. A cut of the fines was saved for nannofossils. The two largest fractions and half of the 74-gm fraction were dried, floated on CC14 and picked for foraminifera. The re- maining half of the 74-um fraction and the 63-,um fraction were decalcified with HC1 and washed again, then dried and floated on CClI, before mounting on slides for study of ra- diolarians. The flotation in this case was found to enrich radiolaria by a factor of about 30, and to raise the proportion of unbroken specimens. Nannofossils were concentrated from the fines that passed the 63-um mesh, in two steps: settling for 1.5 minutes in a 1-liter beaker separated a coarser fraction, to be discarded. The poured-off liquid was then settled in a similar beaker for 30 minutes, which settled out such nannofossils as could be handled by optical microscopy, while the ultra-fine ma- terial was discarded. Radiolaria and nannofossils were pre- pared for study as strewn slides mounted in balsam. Nan- nofossils were identified by optical phase contrast and polarized microscopy, at 1200 x.
Primary reference: P. F. Hasson and A. G. Fischer. 1986. Observations on the Neogene of Northwestern Ecuador. Micropaleontology 32(1):32-42 [A. Hendy/A. Hendy]more details
Purpose of describing collection: biostratigraphic analysis
PaleoDB collection 90851: authorized by Austin Hendy, entered by Austin Hendy on 19.08.2009
Creative Commons license: CC BY (attribution)