Salkhan Fossil Park, India

Khursheed Dinshaw (India)

The Salkhan Fossil Park is located in the state of Uttar Pradesh in India. Spread over 25 hectares, it is an important geoheritage site for stromatolites. These stromatolites were identified by Professor RC Misra and Professor S Kumar of the University of Lucknow.

Fig. 1. Salkhan stromatolites formed during Mesoproterozoic.

Fig. 2. Stromatolites identified by Professor RC Misra and Professor S Kumar.

Stromatolites are layered sedimentary formations created largely by photosynthetic microorganisms, such as cyanobacteria and sulfate-reducing bacteria. These produce sticky compounds that cement sand and other rocky materials to form mineral “microbial mats”, which slowly build up, layer by layer, over time, such that a stromatolite may grow to a meter or more in size. They are extremely rare today, but famous examples can be seen at in Shark Bay in Western Australia, where the hyper-saline conditions prevent predators from consuming them, as they would in more normal marine conditions.

Fig. 3. Stromatolites at the Salkhan Fossil Park.

Fig. 4. Stromatolites at the geoheritage site in Uttar Pradesh.

The stromatolites at Salkhan Fossil Park were formed during Mesoproterozoic, which is a geological era lasting from 1,600 to 1,000 million years ago (Figs. 1, 2, 3 and 4) and are remnants of cyanobacterial life cycle.

Fig. 5. Stromatolites made of calcium carbonate and silicates.

Fig. 6. Remnants of cyanobacterial life cycle.

The stromatolites of the fossil park are made of silicates and calcium carbonate (Figs. 5, 6, 7, 8 and 9).They are preserved in fawn-coloured limestone, and both big and small types can be observed.

Fig. 7. Both big and small types of Stromatolites can be observed.

Fig. 8. Stromatolites are spread over 25 hectares.

While the big limestone formations rise to almost a metre, the small columns at Salkhan are only a few centimetres in height. The stromatolites have a coniform shape and are approximately about 1.8 billion years old. At this time, the Vidhyan basin in the eastern part of Uttar Pradesh and also the western part of the states of Bihar, Jharkhand and some parts of Madhya Pradesh was under a sea. As sedimentation started and then continued for millions of years, stromatolites were formed in the region (Figs. 10, 11, 12, 13 and 14).

Fig. 9. Stromatolites in fawn limestone.

Fig. 10. Stromatolites formed almost one and a half billion years ago.

The limestone at the Fossil Park is well-developed, fine grained, dolomitic and cherty in places. The three main types of chert in the field include:

bedded chert;
stromatolitic chert; and
cherty stromatolites.

The bedded chert, which lies below the stromatolites, is dense. It is black in colour. The stromatolitic chert either underlies or overlies the stromatolites themselves. The alternate dark and light chert bands have varying thickness. Fossils can be seen in the dark bands.

Fig. 11. Microfossils are confined to dark stromatolites.

The black colour of the dark chert bands indicates the presence of organic matter. Microfossils are confined to the dark stromatolites. There are 14 genera, 21 species and six unnamed forms in the Salkhan microbiota. The Salkhan microfossils were studied by optical microscopy using transmitted as well as polarized light. Their sizes were measured using an eyepiece micrometer.

Fig. 13. Stromatolites formed during sedimentation of millions of years.

All photographs are by Khursheed Dinshaw

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