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Pattani Sequence I Formation

Pattani Sequence I Fm

Period:

Paleogene

Age Interval:

Latest Eocene-Oligocene (7)

Province:
Gulf of Thailand

Type Locality and Naming

Pattani Basin (central Gulf of Thailand). Lowest of the 5 sequences.

Synonym:

[Figure: Map showing the Tertiary basins of Thailand. The solid black lines onshore are the principal rivers draining Northern and Central Thailand and the Khorat Plateau (Morley C. K. &Racey A., 2011, page 224).]

Lithology and Thickness

Depending on location, the lower units (unit I-a) comprised very coarse- to fine-grained argillaceous sandstones, while the Upper Oligocene is composed of lacustrine shales (unit I-b). The deep and hot nature of the basin has resulted in considerable diagenetic alteration of the sediments.

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

Not available

Upper contact

Underlies Pattani Sequence II Fm.

Regional extent

Pattani Basin (central Gulf of Thailand); but the succession is similar to adjacent basins (Fig. 10.16 in Morley and Racey, 2011). " In the Northern Pattani Basin this sequence is seen on seismic reflection data as a poorly reflective, ‘transparent’ sequence below a pair of strong reflections (marking lacustrine shales) dated as Late Oligocene. In the central Pattani Basin it is buried too deeply to be imaged along the basin axis while in the southern Pattani Basin the lower part of Sequence I is not present. To the SE , Sequence I is present in the North Malay Basin." (Morley and Racey, 2011).

GeoJSON

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Fossils

Age

Latest Eocene-Oligocene (Fig. 10.16 of Morley and Racey, 2011). This lacustrine sequence is of Late Oligocene to possibly Early Miocene age.

Age Span:

Beginning stage:

Priabonian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

37.99

Ending stage:

Aquitanian

Fraction up in the ending stage:

0.2

Ending date (Ma):

22.52

Depositional setting

Sequence I is interpreted as mostly syn-rift but also comprises early post-rift lacustrine shales in the uppermost part. "Sequence I is the poorly known section of inferred ?Late Eocene–Oligocene syn-rift section (alluvial fans, fluvio-deltaic sequences and lacustrine deposits), plus the Late Oligocene to Early Miocene post-rift lacustrine shale unit that is transitional to the influx of fluvio-deltaic and paralic sediments that dominate the Miocene section." (Morley & Racey, 2011)

Depositional pattern:

Additional Information

Compiler:

Wen Du - modified from Christopher K. Morley & Andrew Racey, 2011, Chapter 10 Tertiary stratigraphy in: Ridd, M.F., Barber, A.J., and Grow, M.J., editors, The Geology of Thailand, Geol. Soc. of London.; and Lexicon of Stratigraphic Names of Thailand of 2013.