Type section: Caparo River valley, south of Brasso Station, Central Range.
Thickness: Maximum 8 000 feet.
New Type Section : Montserrat 1
Thickness: 3,800 feet
Another well exposed section exists between the 10 ¼ mile mark and the base of the Tamana Limestone at Mt. Tamana.
The Brasso formation unconformably overlies the Nariva Formation and is also unconformably overlain by the Manzanilla and/or Tamana.
It outcrops along most of the northern flank of the central Range and extends westward into the subsurface of the Gulf of Paria to Venezuela and to the north of the Los Bajos Fault. The thickness is greatest in the Brasso area and thins rapidly to the west where it was probably removed by the 10.5 my unconformity. It represents the neritic facies of the Cipero formation with which it interdigitates. It consists essentially of poor bedded, bluish black silts, highly calcareous shales and occasional thin sands and limestones. The lower Brasso beds of the Western Central Range are characterised by the common occurrence of pteropods. It usually contains mollusks typical of a shallow water neritic environment.
The different members of the Brasso formation are found to overstep various older beds down to the Paleocene. MAURY (l925a, p. 16) mentions Brasso Miocene without giv¬ing a stratigraphic definition. She lists Arca inaequilateralis and A. pittieri var. narivana Mansfield (1925) who mentions 70 different molluscs 2 bryozoans and 1 crustacean,
1. Biche Quarry
2. Brasso Gorge
3. Brasso between Nestor and Mamon