PLANKTONIC FORAMINIFERA RECORD OF THE MID ALBIAN SEA LEVEL RISE, UPPER MAGDALENA VALLEY, COLOMBIA

Micropaleontological descriptions and analysis of three sections from a lower Cretaceous unit in southern Colombia named “Tetuán Limestone”, has allowed the comparison between the stratigraphic distribution (range) of the planktic foraminifera and the ammonites collected from the same samples. This appraisal presents for the first time in Colombia the recognition and calibration with other fossil groups of two planktic foraminifera interval zones: Ticinella primula and Biticinella breggiensis, with late mid Albian and early late Albian ages respectively.

The “Tetuán Limestone” belongs to a great sedimentary succession that extends along the Upper Magdalena Valley (Huila Department), and is described as intercalations of micritic limestones and micritic concretions of thin to middle size, tabular and cuneiform beds with interbedded dark gray, laminated, calcareous claystones with common imprints of ammonites, bivalves and fish.

Presence of marine planktic microfauna within the claystones of the “Tetuán Limestone”, immediately above the mainly arenaceous and barren of planktic microfauna Caballos Limestone, is understood as a marine transgression marker at the end of mid Albian.

Slow increase of planktic foraminifera like Ticinella primula, T. aff. albiana, T. caronae, T. madecassiana, T. roberti, Biticinella breggiensis, Hedbergella delrioensis, H. gorbachikae, H. simplex, Favusella washitensis, etc. is in contrast to those ones of benthic life trough the studied interval, the former showing a constant sea level rise, at least up to the late Albian to early Cenomanian. At the same time, planktic foraminifera change from initial trocospiral forms of ticinellids and hedbergellids to predominant subconic, planispiral and robust trocospiral forms of heterohelicids, globigerinelloids and whiteinellids.

The residing water masses that occupied the accumulation enclosure were mostly warm; nevertheless, abundant and punctual presence of species like Whiteinella baltica indicate temporal incursions of cold currents.

Planktic foraminifera associations exhibit greater geographic affinities with those from Mexico and Texas and in minor proportion with the Tethys realm. On the other hand, benthonic foraminifera are very similar to those reported for the Albian in Trinidad.