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Nam Duk Formation

Nam Duk Fm

Period:

Permian

Age Interval:

Early and Middle Permian (15)

Province:
Indochina Block: Khorat Plateau,

Type Locality and Naming

Nam Duk Fm is the open marine lateral equivalents of the Pha Nok Khao Fm platform carbonates. Named after the reservoir in the Nam Phong gas field. Middle formation of the Saraburi Gr in this region.

Synonym:

[Figure: Distribution of Carboniferous and Permian in NE Thailand. Data mainly based on 1:1 million scale geological map of Thailand (DMR 1999) with minor modiﬁcations (Ueno K. & Charoentitirat T., 2011. Page 88).]

Lithology and Thickness

Open marine carbonates.

Lithology Pattern:

Limestone

Relationships and Distribution

Lower contact

Overlies (along with the coeval lower part of the Pha Nok Khao Fm) the mixed siliciclastics and carbonates of the Late Carboniferous Si That Fm.

Upper contact

Coeval and transitional into the Pha Nuk Kaho Fm platform carbonates, which is indicated as the more prevalent facies in the middle Permian.

Regional extent

Khorat Plateau subsurface

GeoJSON

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Fossils

Age

Spans the entire Early through Middle Permian (transitional laterally to the Pha Nuk Khao Fm platform carbonates); but Booth, J. & Sattayarak N. (2011, Chapter 9 Subsurface Carboniferous-Cretaceous geology of NE Thailand) schematically indicate that this Nam Duk Fm carbonate facies is most developed in the lower part of that interval.

Age Span:

Beginning stage:

Asselian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

298.88

Ending stage:

Artinskian

Fraction up in the ending stage:

0.0

Ending date (Ma):

290.06

Depositional setting

"By the late Early Permian and through the Middle Permian a series of large carbonate platforms (the Pha Nok Khao Fm) became established in all of these basins, located on isolated fault-bounded highs or as ramps attached to basin margins (Fig). Interpretation of seismic lines indicates that the lateral equivalents of these carbonate platforms (the Nam Duk Fm) were deposited in moderately deep water and unobstructed seaways, but well control of this interpretation is lacking. The fact that carbonate deposition dominated the edges of the basins (Fig) suggests that the supply of coarser clastic material to the central parts of these basins was probably severely restricted. On this basis it is thought that the Nam Duk Formation probably consists of carbonate debris aprons around the platforms and carbonate turbidites and micritic mudstones in more distal settings." [Booth, J. & Sattayarak N., 2011, Chapter 9 Subsurface Carboniferous-Cretaceous geology of NE Thailand].

[Figure: Known and interpreted distribution of carbonate platforms of the Pha Nok Khao Formation equivalents within the Isan Basin Complex. Where not proven by drilling, the presence and extent of these carbonate platforms is based on their distinctive seismic reﬂection facies (Booth, J. & Sattayarak N., 2011, Chapter 9 Subsurface Carboniferous-Cretaceous geology of NE Thailand. Page 196)]

Depositional pattern:

Additional Information

Compiler:

Wen Du -modified from Ueno K. & Charoentitirat T., 2011, Chapter 5 Carboniferous and Permian, and Booth, J. & Sattayarak N., 2011, Chapter 9 Subsurface Carboniferous-Cretaceous geology of NE Thailand in Ridd, M.F., Barber, A.J., and Grow, M.J., editors, The Geology of Thailand, Geol. Soc. of London.;.