1. Deccan Trap Volcanic Province
Stratigraphy of Dike Swarms and Deccan Formations
Joshua Vance
GEO 310 Stratigraphy

2. Deccan Trap Mantle Plume Theory
Tholeiitic magma from deep within the mantle rose to the surface
Dike swarms created broad shield-volcano like structures
Episodic volcanism erupting large volumes of magma rapidly
Main episodes were tholeiitic with alkalic and carbonatitic episodes before and after
Magma erupted between 65 – 62 Ma (Cretaceous – Paleocene)
90% of magma erupted within 0.5 million years (K-T Boundary)

3. Deccan Trap Volcanic Province
Chemostratigraphy
Formations are the fundamental units
Members are sub-divisions of Formations
Sub-groups are sets of mineralogical and geochemical similar formations
Formations determined by mineralogy and geochemistry
Formations have relatively homogenous mineralogy and geochemistry
Formations are distinct from adjacent rock units
Formations boundaries are based on mineralogical or geochemical changes
Formations must have a sufficient thickness to be mappable
Formations must be traceable from outcrop to outcrop

4. Deccan Trap Volcanic Province
Formations and Sub-groups
Sub-groups
Formations
Shallower
Desur
Panhala
Mahabaleshwar
Ambenali
Poladpur
Bushe
Khandala
Bhimashankar
Thakurvadi
Neral
Igatpuri-Jawhar
Younger
Mai
Depth
Age
Lonavala
Kalsubai
Deeper
Older

5. Deccan Trap Dike Swarms
Three Main Dike Swarms
Nasik Mumbai Pune

6. Sangamner Dikes in the Western Ghats
Geology
Positive relief features (humps or spines) due to resistance to erosion
Thickness ranging from 1 – 18 meters
Approximate dip ranging between 70˚ and 80˚
Occurrence in pairs
Chilled margins
Strong preferred orientation NE - SW

7. Sangamner Dikes in the Western Ghats
Comparison Between Dikes and Deccan Formations
Physical Stratigraphy
- Sangamner dikes intrude formations of the Mai and Lonavala sub-groups therefore they could not have been the source for the Kalsubai formations
Mineralogy and Geochemistry
- Tholeiitic Composition
- Plagioclase Phenocrysts
- Major, minor, and trace elements
Isotope Ratios
- 87Sr/86Sr ratios

8. Sangamner Dikes in the Western Ghats
Comparison of Multi-element Patterns
This harker diagram compares multi-element patterns of some Sangamner dikes samples with some Deccan formations samples. Notice how they follow very similar trends.

9. Sangamner Dikes in the Western Ghats
Conclusions
Positive relief features (humps or spines) due to resistance to erosion
Thickness ranging from 1 – 18 meters
Approximate dip ranging between 70˚ and 80˚
Occurrence in pairs
Chilled margins
Strong preferred orientation NE - SW

10. Acknowledgments
Bondre N.R. et al. “Geology and Geochemistry of the Sangamner Mafic Dike Swarm, Western Deccan Volcanic Province, India: Implications for Regional Stratigraphy.” Journal of Geology. vol pp 155 – 170.
Gore, Pamela. “Stratigraphy and Lithologic Correlation.” < >
Pande, Kanchan et al. “40Ar – 39Ar Age of a Lava Flow from the Bhimashankar Formation, Giravali Ghat, Deccan Traps.” Proc. Indian Acad. Sci no 4. December pp 755 – 758.
Sen, Gautam. “Generation of Deccan Trap Magmas.” Proc. Indian Acad. Sci. 110.no 4.
December pp 409 – 431.
Sheth, Hetu. “The Deccan Beyond the Plume Hypothesis.” 29 August 2006.
< >
Sheth, Hetu. “Building a Continental Flood Basalt Province: Key Significance of the Deccan Trap Dyke Swarms.” < >