Loc. 9-04 [Borbon Fm] (Miocene of Ecuador)

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

• ENVIRONMENT: Siliceous organisms (diatoms, radiolar- ians) are well preserved in the Miocene rocks, but the cal- careous fauna has been modified. The nannoflora and the globigerinacean assemblage are impoverished. This may re- flect dissolution of the more delicate forms before burial and suggests that these sediments were deposited at bathyal depths.
• SPECIFIC LITHOLOGY: Tuffaceous clays and mudstones. LITHIFICATION: Unlithified, as stated in text.

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)

Taxonomic list

• COVERAGE: Exhaustive for foraminifera, nannofossils, and radiolarians. NOMENCLATURE: Not an authoritative publication, but with modern nomenclature and species-resolution identifications.
 Nassellaria - Triospyrididae
 Nassellaria - Pterocorythidae
 Nassellaria - Artostrobiidae
"Botryostrobus miralstensis" = Artostobium, "Botryostrobus bramlettei" = Artostobium, "Botryostrobus cf. auritus" = Artostobium, Siphocampe cf. arachnea, Siphocampe cf. lineata
"Botryostrobus miralstensis" = Artostobium radiolarian
"Botryostrobus bramlettei" = Artostobium radiolarian
"Botryostrobus cf. auritus" = Artostobium radiolarian
 Nassellaria - Acropyramididae
 Nassellaria - Eucyrtidiidae
Eucyrtidium sp. Ehrenberg 1847 radiolarian
 Nassellaria - Eucyrtiidae
 Nassellaria -
 Spumellaria - Actinommidae
Prunopyle titan radiolarian
 Spumellaria - Coccodiscidae
  - Chilostomellidae
 Chilostomellacea - Gavelinellidae
 Rotaliina - Stilostomellidae
 Rotaliina - Cassidulinidae
 Planorbulinacea - Cibicididae
 Buliminacea - Uvigerinidae
Uvigerina gallowayi Cushman 1929
Uvigerina auberiana d'Orbigny 1839
 Buliminacea - Buliminidae
 Discorbacea - Bagginidae
 Discorbacea - Discorbidae
 Rotaliacea - Rotaliidae
 Rotaliina - Pleurostomellidae
 Nonionacea - Nonionidae
 Globigerinaceae - Globigerinidae
 Globigerinaceae - Globorotaliidae
Nodogenerina advena Cushman and Laiming 1931
 Textulariacea - Valvulinidae
 Textulariacea - Textulariidae
 Nodosariacea - Nodosariidae
 Prymnesiophycidae - Prymnesiophycidae
Discoaster variabilis Martini and Bramlette 1963
Sphenolithus abies Deflandre 1954
 Miliolida - Miliolidae