A section you can walk through
Stratigraphy is built on a simple idea: in an undisturbed pile of layers, the oldest lie at the bottom and each higher bed is younger. The Salt Range is where that principle — superposition — is easiest to see in Pakistan, because so much of the record is stacked in one accessible place and tilted gently to the south, so a short traverse crosses hundreds of millions of years.
What makes it exceptional is not any single rock but the completeness. Few sections anywhere carry Precambrian, Cambrian, Permian, Mesozoic and Cenozoic strata in one continuous hillside, with the gaps between them just as instructive as the layers themselves.
The salt at the bottom
At the base lies the Salt Range Formation — a thick body of rock salt, gypsum and red marl that gives the range its name. It is mined at Khewra, one of the oldest and largest salt mines in the world, worked for many centuries. The salt is generally regarded as Precambrian to earliest Cambrian, laid down when this land lay in an arid basin near the edge of Gondwana; its exact age has been debated for over a century precisely because salt carries so few fossils.
That salt matters for more than mining. Because it is weak and mobile, it acts as a lubricating layer — a décollement — on which the whole overlying pile has slid and crumpled as the Himalaya pushed south. The Salt Range is, in effect, the leading edge of that moving sheet.
Cambrian shelf and a long gap
Above the salt come Cambrian shelf deposits: the purple Khewra Sandstone, then the Kussak, Jutana and Baghanwala formations — sandstones, dolomites and shales laid down in shallow seas. Then the record simply stops. Across most of the range, rocks of the Ordovician, Silurian, Devonian and most of the Carboniferous are missing entirely, a hiatus of well over a hundred million years. This surface is one of Pakistan’s great unconformities, and the missing time is itself a record — of a land standing above the sea, neither collecting sediment nor being deeply buried.
Ice, then a Permian sea
Deposition resumes dramatically in the Permian with the Tobra Formation, a glacial tillite that records the Indian plate sitting near the South Pole during the great Late Palaeozoic ice age. Above it, cold-water marine beds (the Dandot Formation, with its distinctive Eurydesma fauna) give way to the Warchha Sandstone and then a thick Permian marine succession — the Amb, Wargal and Chhidru formations — whose upper beds reach close to the greatest mass extinction in Earth history, at the Permian–Triassic boundary.
Mesozoic and Cenozoic, to the present
The Mesozoic follows in orderly fashion: Triassic units (Mianwali, Tredian, Kingriali), Jurassic sandstones and limestones (Datta, Shinawari, Samana Suk), and Cretaceous beds (Chichali, Lumshiwal). Then come the Paleocene and Eocene marine limestones and shales — Hangu, Lockhart, Patala, Nammal, Sakesar, Chorgali — the same units that host oil and gas elsewhere in the region. Capping everything is the Siwalik molasse, the young river-laid sandstone and mudstone dumped by rivers draining the rising mountains.
Why it became the teaching ground
Because a near-complete slice of Earth history is exposed in one walkable place, the Salt Range is where generations of Pakistani geologists first applied the principles of the science in the field — superposition, original horizontality, faunal succession — and where its unconformities are textbook examples in their own right. It remains the natural first stop for anyone learning to read the country’s rock record.
To place these units in time, see the time scale; to browse the formations named here, start with the formations index.