359.2

542.0

2,500.0

4,000.0

Arch

ean

299.0

251.0

199.6

145.5

65.5

99.6

161.2

175.6

228.7

245.0

260.4

270.6

318.1

55.8

23.0

5.3

2.6

0.012

33.9

*coal-bearing formationsPeriods of nondeposition or erosion are shown by absence of stratigraphic names

Boka Bil Fm.* and Bhuban Fm. of Surma Gp.

Barail Group

Dupi Tila FormationGirujan Clay Formation of Tipam Group

Tipam Sandstone Formation of Tipam Group

Dihing FormationMadhupur Clay

Alluvium

Rajmahal Trap

Kuchma Formation*

basement complex basement complex

Parharpur Formation*

Sibganj Trapwash Formation

Kopili Formation of Jaintia GroupSylhet Limestone Formation of Jaintia Group

Tura Formation/Sandstone* of Jaintia Group

Bogra Formation

Dupi Tila Formation

Jamalganj Formation

Madhupur Clay

Alluvium

Central and Eastern BangladeshNorthwest Bangladesh

542.0

System Subsystem

Cam

bria

nto

Devo

nian

Prot

eroz

oic

AGE (Ma) EraEon

Perm

ian

Tria

ssic

Jura

ssic

Cret

aceo

usQu

ater

nary

Terti

ary

Pale

ogen

eN

eoge

ne

Carb

on-

ifero

us Upper

Upper

Lower

Middle

Upper

Lower

Middle

Upper

Lower

Middle

Upper

Holocene

Pleisto-cene

Paleo-cene

Pliocene

Miocene

Oligocene

Eocene

Lower

Pale

ozoi

cM

esoz

oic

Ceno

zoic

Phan

eroz

oic

Figure 4. Correlation chart of stratigraphic units in coalfields of BangladeshAbbreviations used: Fm. - Formation; Gp. - Group; Ma - Megaannums (millions of years).Source of stratigraphic data: Khan and Muminullah (1988), Rahman and others (1985).Geological ages from USGS Fact Sheet 2010-3059; colors from International Commission on Stratigraphy (2009), except Tertiary from USGS Fact Sheet 2010-3059.