31 research outputs found
Cenomanian-Turonian and Neogene sediments from northeast of Kerguelen Ridge, Indian Ocean
Pithonella paratabulata n. sp., a lower cretaceous calcisphere with external paratabulation
Biostratigraphy, Depositional Environments, and Diagenesis of the Tamana Formation, Trinidad: a Tectonic Marker Horizon
The Tamana Formation of the Central Range of Trinidad was studied in order to determine its importance in the stratigraphical and structural development of northâeastern South America. Biostratigraphical, petrological and mineralogical data, combined with field mapping show that the Tamana sediments are composed of five distinct lithofacies: inner to outer shelf, burrowed shaley mudstone; outer shelf, Feârich sandy limestone; submarine channel, conglomeratic mudstone; middle shelf to nearshore, algalâforam packstone/grainstone; and intertidal to nearshore, algalâstromatoliteâcoral boundstone with coral bioherms. Maximum thickness of the Tamana Formation is 244 m.
Deposition of the Tamana limestones occurred between the Praeorbulina glomerosa (latest early Miocene) and Globorotalia fohsi robusta (middle part of the middle Miocene) planktonic foraminiferal zones, and in a more continuous trend than is seen in the current outcrop belt. Detailed biostratigraphy shows that the Tamana Formation is a facies equivalent of the shallowâ and deepâwater shales of the Brasso Formation, and the deep water turbidites of the Herrera Member of the Cipero Formation.
The early diagenetic history of the Tamana limestones was dominated by the precipitation of authigenic glauconitic smectite, and the dissolution of skeletal grains and carbonate matrix. Late burial diagenesis was dominated by the precipitation of illite and illite/smectite. Comparative mineralogy and textural analyses indicate a minimum range of burial depth for the Tamana Formation at 800â1500m, with a maximum of 2400 m. Alteration of Feâbearing minerals to geothite and late fracturing occurred during postâPliocene tectonic uplift and unroofing of the Central Range.
The Tamana Formation sediments can be used as a structural and stratigraphical event marker within the Late Tertiary geological history of Trinidad. These units record a phase of the tectonic interaction between the Caribbean and South American plates in the southâeastern Caribbean, and reflect the onset of contractile deformation in the Central Range