Chitinoidellids from the Early Tithonian-Early Valanginian Vaca Muerta Formation in the Northern Neuquén Basin, Argentina

KIETZMANN, D.A.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017 vol. 76 p. 152 - 164

0895-9811

As part of microfacies studies carried out on the Tithonian - Valanginian carbonate ramp of the Neuquén Basin, two stratigraphic sections of the Vaca Muerta Formation were chosen in order to analyze the chitinoidellid content and distribution. Calpionellidsin the studied sections are relatively poorly preserved; hyaline calcite walls are often recrystallized making the systematic determination difficult. However,microgranular calcite walls seem to have resisted better the incipientneomorphism presented by the limestones of the Vaca Muerta Formation. Seven known species of Chitinoidellidae and four known species of Calpionellidae are recognized. The distribution of calpionellid species allows recognizing the Chitinoidella and Crassicollaria Zones in the Neuquén Basin.The Chitinoidella Zone can be divided into two subzones. The lower one is poorly defined, while the upper one can be assigned to the Boneti Subzone. The Crassicollaria Zone in the Neuquén basin needs a detailed revision. Similar associations were reported in Mexico and Cuba, showing good consistency between these regions. However,in the Neuquén Basin unlike the Tethys, chitinoidellids persist until the lower Berriasian.