Nam Can Fm

The type section is established at 165 to 255 m in borehole LK.216, drilled in Nam Can Townlet, Ngoc Hien District, Ca Mau Province (N = 8°45’; E = 105°).

Synonym: Hệ tầng Năm Can: Nguyễn Ngọc Hoa et al. 1996; Trjnh Dánh (in Vũ Khúc et al. 2000).

Type section: (1). (Depth 255 - 243.5 m): sand (70-80 %), grit-gravel (5-7 %), silt (5-10 %), clay (4-5 %), containing a few marine mollusc shells, 11.5 m thick. Sand is well sorted (So = 1-2), with mean grain diameter Md = 0.1 - 0.3 mm, good roundness (about 2.5). (2). (Depth 243.5 - 232.5 m): clay (70-80 %), silt (20-30 %) with some sand, 11 m thick. These sediments are usually yellowish-grey, containing salt-water algae. (3). (Depth 232.5 - 190 m): yellowish-grey, fine-grained sand, interbeds of brown-grey, pinkish silt, 42.5 m thick. The lower layer contains many remains of carbonized herbaceous plants and some mollusc shells. The sand is composed mainly of quartz (70-80 %), some clay fragments. The heavy minerals consist of ilmenite, in the upper part - tourmaline and laterite fragments. (4). (Depth 190-165 m): mainly of fine-grained sediments with clay (50-60 %), silt (10-20 %), sand (10 %), 25 m thick. They are usually greenish-grey colored, thin-bedded (1-2 mm), and containing fine sand on the bedding surface. The total thickness of the formation in this section is 90 m.

Fossils collected in the formation include: foraminifera, scattered throughout the entire section in large quantity, such as in borehole LK.215A with Globoquadrina dutertrei, Globogerina bulloides, Gl. nepenthes, Cl. parabuỉỉoides, Globigerinoides trilocularis, Eponides urnbonatus, Elphidium crispum, Ammonia annectens, etc. determined by Mai Van Lac as of Pliocene age; diatoms conccntrated in the upper part of the section (at 165-190 m). Among diatoms the Chrysophyta group comprises a large quantity, with species of the Discoaster broweri Zone, that, according to Dang Due Nga, has an epibole at the end of the Late Pliocene and then became rapidly extinct.