This document summarizes the stratigraphy of the Cretaceous sediments in the Trichinopoly district of Tamil Nadu, India. It divides the sediments into four groups from oldest to youngest: Uttatur Group, Trichinopoly Group, Ariyalur Group, and Niniyur Formation. Each group contains multiple formations characterized by their lithology, thickness, fossil content, and age. The sediments were deposited in marine environments from the Aptian to early Paleocene stages and include limestones, sandstones, shales, and shell beds. Fossils found include ammonites, bivalves, wood, and dinosaur remains, providing insights into the paleoenvironment and basin evolution.

1. STRATIGRAPHY OF
TRICHINOPOLY
PRESENTED BY;
ABHISHEK KUMAR
414ER2018
M.SC.(APPLIED GEOLOGY)
abhi.gly@gmail.com

2. INTRODUCTION
o The great Cenomanian (98 Ma) transgression covered
considerable area in the southestern part of Tamil Nadu between
the covery river and Pondicherry.
o The outcrops near Trichinopoly are the largest with an areal
extent of about 400 sq. km ranging in age from Aptian/Albian to
Early Paleocene nearly 120-61 Ma.
o The sedimentation is often interrupted by low angle
unconformities.
o Activity of hydrocarbon exploration in these areas has brought
out a wealth of information on biostratigraphy,
Paleoenvironmental analysis and basin evolution.
o The cretaceous succession in the Trichinopoly area is broadly
divided into four widely known group-
i) Uttatur
ii) Trichinopoly
iii) Ariyalur
iv) Niniyur (Early Paleocene Sediments) Geological map showing Cretaceous outcrops,
Trichinopoly

3. STRATIGRAPHY
o Trichinopoly district, Cretaceous sediments overlain
granitic gneisses and charnockites.
o Western margin, a thin fringe of upper gondwana
sediments, 1.5 km ENE of uttatur and 1.5 km NE of
Terani.
o The boulder conglomerate is classic example for
fanglomerate, derived from tectonically active source
due to faulting.
o The Terani plant Beds, a unit of kaolinitic clay and
ferrugineous sand interbeds.
o The Cretaceous sediments dip at very low angle,
higher dips have been recorded to the contact zone
of the sediments with the crystalline rock.
o The sediments of the uttatur and Trichinopoly Groups
show evidence of folding.
o The faults traced at the western boundry of the
cretaceous sediments.

4. TRICHINOPOLY(GROUP, FORMATION, LITHOLOGY & FAUNA)

5. UTTATUR GROUP
Stratigraphy:
o The lower stage named after the village Uttatur, lying at thr western margin of
Cretaceous basin
o A thin ferrugineous bed seprates Gondwana from the overlying Cretaceous strata.
o The Uttatur sediments range in thickness from 300 to 600 m.
o Albian to Turonian have been recognised in the in the Uttatur Formation.
o The topography is charecterised by trellis drainage and exhibits badland
topography.
Kallakkuddi limestone
Karai Shale
Lithology:
o Basal conglomerates, grey shale, sponge-coaral-algal limestone and shale/clay .
o Buff-coloured clays are charecterised by gypsum veins.
o The presence of gypsum is suggestive of the prevalence of warm and moist
climate.
Fossils:
o Gastropods, lamellibranchs, cephalopods, corals.
o Ammonites, including some uncoiled forms abound and coiled ones with a
diameter of about a meter have been traced.

6. UTTATUR GROUP
Kallakudi/(Dalmiapuram) Limestone:
o The age of this unit is Middle Aptian-Middle Albian.
o Actively mined for cement
o Its composed essentially of different siliceous and calcareous sponges, layered coral,
algae, bivalves, cidarids, belemnites, bryozones, forminifera and coral fragments.
o The limestone is presumably in an intertidal zone in protected still-water bay.
Karai Shale/Clay:
o This unit is assigned to late Albian to Middle Turonian age.
o Shale/Clay is Dark grey, chocolate brown to yellow with occasional ferruginous sand and
limestones.
o Trellis type drainage and badland topography.
o The fossil present includes ammonites, serpulid worms, bivales (Pecten, Alectryonia,
Exogyra), foraminiferides, nanofossils, and ostracodes.

7. TRICHINOPOLY GROUP
Stratigraphy:
o Turonian to lower Senonian age.
o The group unconformably rest over the uttatur.
o Its divisible into lower Kulakkalnattam (=Paravay) and Upper Anaipedi (=Garudamangalam).
Kulakkalnattam
Anaipadi
o Formation spareated from each other by a conglomerate bed.
Lithology:
o Sandstones, grits, shale, and shell limestone.
o The shell limestone, when polished forms a beautiful ornamental stone.
o The occurrence of of fossil wood in sediments, deposited in marine environment is interesting.
o Thickness of sediments 300 m to 600m.
Fossils:
Lamellibranchs and gastropods, but uncoiled ammonites charecterestics of the uttatur stage is rare.
Trichinopoly formation into three biostratigraphy zones:-
i. Lewasiceras vaju ii. Kossamaticeras theobladianum iii. Placenticeras tamulicum.

8. TRICHINOPOLY GROUP
Kullakkalanttam:
o The thickness of this unit is about 60m.
o Kullakkalanttam formation is a calcareous sandstones unit.
o Ferruginous concrtionary bodies extensively bioturbated by feeding
burrows like Thalassinoids.
o Its intercalated with dark grey limestone.
o Thick shelled bivalves (Oysters), ammonites, rhynconellids, brachiopods
and silicified wood.
Anaipadi:
o The thickness of this group is about 100 m. its of Coniacian-Santonian age.
o Formation is essentially made of sandtone, siltstone with concretionary
layers rich in fossils.
o Fossils includes inoceramids, gastropods, and ammonites besides large
fossil tree trunks bored by wood-boring teridinids.
o An 18 m long conifer fossil tree preserved as a geological monument at
sattatntur.
o A Stegosauras dinosaur with partial skull, tooth, pelevic elements, armour
plates were picked up near Siranattam.

9. ARIYALUR GROUP
Stratigrphy:
o The member of ariyalur stage occur around Ariyalur town,
Vriddachalam and Pondicherry.
o The lower zone has been assigned a Campenian age.
o Thickness is 1200 m.
Sillakudi(500 m)
Kallankurichi(40 m)
Ottakovil(60 m)
Kallamedu(100)
Lithology:
o Sandstones, grey, light brown and white colour have been traced to a
total thickness of 1000 m.
o The depositional environment appears to be high-energy transgressive
tidal bars or shoals.
Fossils:
Faunal remains in the sediments includes those of reptiles, fishes,
cephalopods, lamellibranchs, gastropods, echinoderms and corals.
Reptilian fossils include bones of Megalosauras and Titanosauras. Location map of Campanian-Maastrichtian sediment
outcrops and subcrop, Ariyalur area

10. ARIYALUR GROUP
Sillakudi formation:
o Formation comprises ferruginised arkosic sandstone and
limestone bands.
o The fossil records include large sized Nautilus, Inoceramus,
rhynconellides, echinoids, ammonites and forameniferids.
Kallankurichi Formation:
o The age of this unit is Upper Campanian-Early Maastrichtian.
o Resting unconfromably over the Sillakudi formation.
o Massive rudist bivalve carbonate shell-bank of about 40 m
thickness.
o It is mined for cement industry.
o Lithologically it is mainly made of bioclastic packstone,
grainstone facies.
o Bivalves brachiopods, echinoids, ammonites, foraminiferids
and ostracodes.
Location map of Campanian-Maastrichtian sediment
outcrops and subcrop, Ariyalur area

11. ARIYALUR-
KALLANKURICHI
A. Alternate barren and
shell rich thin beds of
the Grey Sandstone
Member;
B. Subrounded
lithoclastic boulder
C. Thalassinoid burrow;
D. Gravel sized feldspar
clast

12. ARIYALUR-
KALLANKURICHI
A. Carbonate sand beds (a) overlain by a
fragmented shell limestone bed (b) with a
sharp erosional surface in between;
B. Thick population of insitu gryphean shells
Tancem mines, south of Srinivasapuram village;
C. Conformable, but erosional surface contact
between the Kallankurichchi Formation (a) and
the Kallamedu Formation (b) as exposed in a
mine located southeast of the Kallankurichchi
Formation. the scour structure, (indicated by
an arrow) presumable representing a cross
section of a fluvial channel;
C

13. ARIYALUR GROUP
Ottakovil Formation:
o The overlying calcareous sandstones of about 60 m thickness.
o The age is Maastrichtian.
o Ottakovil formation is overlain by white to grey, cross bedded thick
sandstones intercalated with greenish grey to red clay.
o Which delimit the cretaceous succession.
o Echinoids, Alectryonia, Euboculites, turritellids, bryozones and
echanofossils.
Kallamedu Formation:
o The Kallamedu sedimentary sequence, one of the least investigated
sedimentary formations in South India (Ariyalur District, Tamil Nadu
State).
o well known for the occurrence of dinosaur remains.
o It has been observed in the field that dominant lithologies comprise of
fine grained siltstones and fine laminated clays with rare occurrence of
coarser sandstones and polished pebbles in the fine sandstone units.
Location map of Campanian-Maastrichtian sediment
outcrops and subcrop, Ariyalur area

14. ARIYALUR-KALLAMEDU
a) Photograph showing upward fining sequence –
sandstone, siltstone and clays towards top;
b) Trough cross bedded sandstone section;
c) Plane bedded sandstone sequence at the bottom and
fine siltstone and clays towards top;
d) Photograph showing fine laminated whitish siltstone
sequence towards top;
e) Field photo exhibiting few polished quartz/quartzite
pebbles in the sandstone unit;
f) Photograph showing coarse gritty sandstone overlying
the fine sandstone/siltstone unit – suggesting cyclic
sedimentation;
g) greenish and red clays at the bottom and fine laminated
sandstone/siltstone towards top;
h) Mud crack features on the surface.

15. NINIYUR FORMATION
o The cretaceous succession is unconformably overlain by a thick
carbonate sequence.
o The carbonate sequence is of about 60 m in thickness.
o Lithologically this unit is divisible in lower fossiliferous
limestone, middle crystalline shelly limestone.
o Upper argillaceous gritty nodular limestone collectively known
as Niniyur Formation.
o The fossils present include algae, cephalopods, gastropods,
foraminiferids, and ostracodes suggesting an early Paleocene
age.
o Beds equivalent to Niniyur formation are seen in vridhachalam
and Pondicherry areas.

16. REFERENCE’S
 SEDIMENTOLOGICAL STUDIES OF KALLAMEDU FORMATION IN ARIYALUR AREA, TAMIL NADU,
INDIA
S. Ramasamy, *A. Ramachandran, K. Velmurugan, David Lalhmingliana Chawngthu,
S.Bhuvaneswari and M.Suresh Gandhi
 Lithostratigraphy, depositional history and sea level changes of the Cauvery Basin, southern India
MUTHUVAIRVASAMY RAMKUMAR1, DORIS STÜBEN2 & ZSOLT BERNER
 DOLOMITIC LIMESTOE I THE KALLAKURICHCHI FORMATIO,(LOWER MAASTRICHTIA), ARIYALUR
GROUP, TAMIL ADU
Mu.RAMKUMAR
 Stratigraphy and Paleobathymetric Interpretation of the Cretaceous Karai Shale Formation of
Uttatur Group, TamilNadu, India1
R. Nagendraa, P. Sathiyamoorthya, S. Pattanayaka, A. Nallapa Reddyb, and B. C. Jaiprakashc