Qaurtenary formation of Saurashtra and mainland Gujarath

1. Quaternary formation of Mainland and
Saurashtra Gujarat
Shankar Lamani
223104024
MSc Geology
MIT

2. Qautenary
• Quaternary is divided into Pleistocene and Holocene epochs and is known for climatic changes.
• Quaternary covers a period 1.81 million years and is very important as it provides a link between the
geological, archaeological and human history.
• The Pleistocene, the lower division of the Quaternary, is known for the glaciations interrupted by periods of
ice melting, referred to as the interglacial periods.
• The glacial and interglacial periods varied in duration and intensity and resulted in the advance and retreat
of glaciers.

4. Source: Assessment of phytomass carbon pools in forest ecosystems in india by Dhadwal et al.

5. Mainland
• Quaternary sediments in mainland Gujarat are of fluvial, aeolian, and marine origin.
• Narmada, Mahi, Sabarmati, and Luni rivers have had varied histories of development/evolution, controlled
by tectonics, climate, and changes in sea level.
• Total exposed thickness of sediments in Narmada, Mahi, and Sabarmati rivers is around 35 to 40 m, which
date back to Late Pleistocene (-125 Ka).
• Total continental Quaternary sediment thickness varies from 300-800 m in Mainland Gujarat.
• Invariably the base of the exposed sequences is made up of marine bluish clay, overlain by alluvial fan and
alluvial plain sediments.
• Occur a 7-15 cm thick deeply pedogenesid brownish red to reddish brown buried soil, which is laterally
consistent and has been considered as a marker horizon for stratigraphic correlation.

6. • A series of alluvial fans were deposited along the Narmada-Son fault during Early Holocene.
• The Middle-Late Holocene sediments (-6 to 2 Ka) occur as valley fill terraces which are estuarine tidal in the
lower reaches and fluvial in the upper reaches of the rivers of Mainland Gujarat.
• Along the coast are Middle to Late Holocene deposits comprising raised mud flats, stabilised (inland) coastal
ridges and shelly beach rocks.
• The foraminiferal assemblage includes species of Rotalia, Ammonia, Quinqueloculina, Spiroloculina,
Triloculino, Elphidium, Nonionella, Nodosaria etc.
• and constitutes the youngest marine sediments and these indicate shallow warm water conditions.

8. Source:Late Pleistocene Relative Sea-Level Changes from Saurashtra, West Coast of India by Prizomwala et al.

9. Saurashtra
• The Quaternary sediments of Saurashtra are of both marine and continental origin.
• Rocks of "Miliolite Formation' referred to in literature as 'Miliolite' or "Porbandar Stone, are the most striking
Pleistocene deposits of Saurashtra.
• These are "granular deposits composed of oolitic particles of calcareous sand and united together into a firm
compact rock on the Arabian Sea coast having predominance of the form belonging to the genus Miliolina.“

10. • Miliolidae on an average is about 2 to 5% of the total rock volume.
• The miliolites occur all along the southern coast of Saurashtra from Gopinath in the east to Porbandar in the
west.
• The highest miliolite occurrence is at Chota hill, which is about 165 km inland from the open sea. This hill is a
358 in high dome of Deccan Trap basalt.
• Outcrops of miliolites in the interior area occur along the gorges and slopes of hills of the Cirnar ranges
between Chotila and Rajkot and on the flanks of Chamardi hills of Sihor and of Osham hills.

11. Source: Gir forest

12. • Besides Miliolina the other foraminiferal forms found in the malolites are-Streblus beccari, Cibicides
lobatulus, Elphidium cf. advena, Globigerina trilobata, G bulloides. Quinquiloculina seminulum, Spiroloculina,
Nonian scapha, Textularia of conica, Bolivina, Loxostromum of. limbatum etc.
• Ostracodes are also found associated with these assemblages.
• The forms are mainly of benthonic nature. Most of them are much rolled and difficult to identify and belong
to Rotalidae, Elphididae, Nubeculariidae and Milioliidae families.
• Broken shell fragments of mollusca, bryozoa, echinoderm, ostracods, corals and algae are among the chief
allochems.

13. • Miliolites are assigned both marine and aeolian origin.
• The inland miliolites have a meteoric-vadose cementation of magnesian blocky sper, No feature of marine
origin is indicated. They are of aeolian origin.
• In the coastal belt, however, marine macrofossils are found in the basal part of miholite quarries. They are all
well preserved and do not show any evidence of transport.
• Based on geomorphologic and pedologic criteria, the base of the 10-20 km wide miliolite belt may be of
marine origin.
• The miliolite beds rest unconformably on the Pliocene strata, north of Porbandar Summing up, the lower
parts maybe of marine lagoonal origin, whereas the upper parts of the beach ridges represent former
coastal dunes.
• Fluctuations in sea level, and neotectonics have played some part, beside wind action, in the present day
geographical distribution of these deposits.

14. • The problem of dating the miliolites is complicated because of faunal components and the cementing
calcium carbonate undergoing recrystallization during diagenesis.
• The ages in general are considered to be too young.
• However, different age ranges (Th230/U234 and C14) are noted from samples collected from different areas.
• For instance in Kutch, which is applicable to Saurashtra as well, three age groups were arrived at, spanning
50-70, 75-115 and >140 kyr ages.
• Ages above 200 kyr and around 30 kyr have also been obtained.

15. • Holocene sediments of Saurashtra named Chaya Formation are made up of semi-consolidated to
consolidated shell limestone (calc-rudites), coral reefs and oyster beds, mainly along the coast.
• Recently miliulites have been recognised and mapped beneath the Chaya Formation along some parts of
southeastern Saurashtra.
• The coral growth started in late Holocene and a few islands still support coralline forms. The fauna consists
of lamellibranchs. gastropods, harnacles, corals, echinoderms and calcareous algae.
• These rocks seem to be the products of Holocene transgression.
• The sand of the present day beaches, alluvium of the rivers and the coastal plains constitute the youngest
Holocene sediments.
• Radiometric dates available indicate only two age groups of corals in Saurashtra spanning 6000-7000 and
1,18,000-1,76,000 years.

17. Reference
• Assessment of phytomass carbon pools in forest ecosystems in india by Dhadwal et al
• Late Pleistocene Relative Sea-Level Changes from Saurashtra, West Coast of India by Prizomwala
et al.
• Geology of India, Volume 2 by M. Ramakrishnan, R. Vaidyanadhan