STRATIGRAPHY OF TRICHINOPOLY

PRESENTED BY;ABHISHEK KUMAR

414ER2018M.SC.(APPLIED GEOLOGY)

abhi.gly@gmail.com

INTRODUCTIONo 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

STRATIGRAPHYo 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.

TRICHINOPOLY(GROUP, FORMATION, LITHOLOGY & FAUNA)

UTTATUR GROUP

Stratigraphy: o The lower stage named after the village Uttatur, lying at thr western margin of

Cretaceous basino 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 limestoneKarai 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.

UTTATUR GROUPKallakudi/(Dalmiapuram) Limestone:o The age of this unit is Middle Aptian-Middle Albian.o Actively mined for cemento 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.

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).KulakkalnattamAnaipadio 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.

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.

ARIYALUR GROUPStratigrphy: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 sedimentoutcrops and subcrop, Ariyalur area

ARIYALUR GROUPSillakudi 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 sedimentoutcrops and subcrop, Ariyalur area

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

ARIYALUR-KALLANKURICHIA. 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

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 sedimentoutcrops and subcrop, Ariyalur area

ARIYALUR-KALLAMEDUa) 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.

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.

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