1) Field observations revealed an irregular elevation profile and the presence of a deep, V-shaped ravine extending from the university to the sea, despite the low gradients typical of coastal areas. 2) Layers of alternating sandstone and conglomerate were found, with conglomerate deposits atypical for coastal areas. 3) Evidence suggests neo-tectonic activity, including a syn-sedimentary uplift allowing conglomerate deposition, followed by erosion forming the ravine during a subsequent uplift. Seismic activity in the region supports the interpretation of reactivated faulting.

1. Curiosity about a
Ravine
An attempt to unlock the mystery!

2. Welcome to Pondicherry University

3. Observation 1
Elevation profile along the path shown

4. Problem Statement 1:
▪ Why such an irregularity in the elevation profile and topography?
▪ Pondicherry is in the Eastern Coast of India and there shouldn’t be much
change in elevation profile near the sea coast.
▪ What are the possible causes for such irregularity?

5. Observation 2
Presence of a huge crack as seen from
Google Earth

6. Field observation of the crack

7. Inference:
▪ On field observations suggest that this crack is a “deeply incisedV-
shaped Ravine.”
▪ This ravine seems to be extending from the central area of the
university to almost near the sea.

8. Problem Statement 2:
▪ How did the Ravine form?
▪ What are the probable causes for it’s formation?
▪ The valleys and ravines are usually a function of gradient i.e., more
the gradient, deeper is the valley or the ravine.
▪ Coastal areas are known for very low gradients.
Need for an Explanation??

9. Observation 3:

10. Observation 3:

11. Inference:
▪ Presence ofAlternate Sandstone and conglomerate layers.
▪ Lithology of Pondicherry: Cuddalore Sandstone as the supracrust
covered by marine/fluvial deposits as regolith.
▪ Conglomerates are deposited in a area where they are not usually
found.
▪ Presence of rounded angular fragments in the conglomeritic layer.

12. Problem Statement 3:
▪ Conglomerate forms where a sediment of rounded clasts at least two
millimeters in diameter accumulates. It takes a strong water current
to transport and shape particles this large.
▪ Streams are a function of gradient => Deposition along the stream is
also a function of gradient.
▪ Coastal areas are known for very low gradients => Only sand and silt
are deposited…. Conglomerate??
Need for an Explanation??

13. Thinking Board

14. Answer Statement 3:
▪ Conglomerate deposits => High gradient and high velocity.
▪ It is a well known as that the SouthWestern part of the Indian
Subcontinent is well elevated than the South Eastern Part.
▪ The conglomerates should be deposited somewhere in the central
part.
▪ There must be a “Shift in the slope” in the South Eastern Part that
led to the deposition of the Conglomerate.

15. The Grand Reconstruction

16. Answer Statement 2 & 1:
▪ There could be a syn-sedimentary upliftment in the Eastern coast.
This explains the deposition of the conglomerate in the area.
▪ After the consolidation of the rock mass, there could be another
upliftment in the area.
▪ The torrential rain or stream flow in the area eroded the weak-zones
of the rock carving a beautiful ravine.

17. Clear indication of neo-tectonic activity
▪ Evidences:
1. The ravine is the major evidence to support our theory.
2. Conglomeritic Deposits also provides an indirect evidence pointing
to a change in slope of the area.
3. Recent seismic activity indicate a re-activated thrust fault system in
Pondicherry causing a M 5.5 earthquake in 2001.

19. Pondicherry Area Remodelled using DEM:

20. Evidence of Seismicity in Pondicherry

21. References
▪ DEM Data Courtesy: Mr. Lakshmi Ramprasath, Research Scholar,
Dept. of Earth Sciences, Pondicherry University.
▪ Murthy, G P S., Subrahmanyam, AS., Murthy, K S R., Sarma, KV L N
S., 2012, Evidence of fault reactivation off Pondicherry coast from
marine geophysical data, Current Science, 1446-1449.
▪ Ravine’s Picture courtesy :
https://sruthinlal.wordpress.com/2014/10/18/a-ravine-and-an-
adventure-one-day-at-pondy/

22. THANK YOU!
A presentation by:
G N S SREE BHUVAN and
CVENKATESWAR REDDY
Integrated M.Sc. (Applied Geology) 2nd year.