Depth
−0 m
Composite section · not to scale
Before present
today
Dept. clock 1975
The world at this depth · schematic
Unit 1 of 7 · Holocene · today
Ganges–Padma floodplain
The river outside the department's window. Silt laid down within living memory — the youngest page of the record, still being written every monsoon.
Unit 2 of 7 · Pleistocene · ~125 ka
Barind Tract · Madhupur Clay
The oxidised red terrace Rajshahi itself stands on. A student here can walk out of the seminar room and onto this surface.
Unit 3 of 7 · Neogene · ~12 Ma
Bengal Basin fill
Sand and mud in monotonous rhythm, kilometres of it — the deepest sedimentary basin on Earth, filled by rivers tearing down the Himalaya that rose when India met Asia (~50 Ma).
Unit 4 of 7 · Eocene · ~45 Ma
Palaeogene limestone
Pale nummulitic limestone of a warm shallow sea — the Sylhet Limestone, the country's cement resource.
Unit 5 of 7 · Early Cretaceous · ~117 Ma
Rajmahal Trap basalt
Flood basalt in columns — lava that ran as Gondwana tore. At Maddhapara it is mined as the country's only hard rock.
Unit 6 of 7 · Permian · ~275 Ma
Gondwana coal measures
Black seams and pale sandstone, pressed Glossopteris forests — Barapukuria, Bangladesh's only working coal mine. The rift valleys that hold them opened as the supercontinent split (~180 Ma).
Unit 7 of 7 · Palaeoproterozoic · ~1,700 Ma
Precambrian basement
Granite and gneiss of the Indian Shield — the crystalline floor beneath everything, reached at depth below the Barind. Older than complex life.
The Golden Jubilee
Fifty years of reading five hundred million.
1975
The department
1,700 Ma
Its subject