View source for Eparchaean Unconformity

{{Short description|National Geo-heritage Monument in Andhra Pradesh, India}}
{{Use dmy dates|date=August 2019}}
{{Use Indian English|date=August 2019}}
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| name                  = Tirupati Eparchaean Unconformity
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| type                  = Geological monument
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| map_image             = Tirupati in Andhra Pradesh (India).svg
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| location              = Tirupati, India
| coordinates           = {{Coord|13.6833|79.35|type:landmark_region:IN-AP|display=it}}
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'''Tirupati Eparchaean Unconformity''', a notified [[National Geological Monument|National Geo-heritage Monument]]<ref name=gsi1>{{Cite web |url=http://www.portal.gsi.gov.in/portal/page?_pageid=127,529542&_dad=portal&_schema=PORTAL |title=National Geological Monument, from Geological Survey of India website |access-date=2017-05-24 |archive-url=https://web.archive.org/web/20170712055947/http://www.portal.gsi.gov.in/portal/page?_pageid=127,529542&_dad=portal&_schema=PORTAL |archive-date=2017-07-12 |url-status=dead }}</ref><ref name=gsi2>[http://pib.nic.in/newsite/PrintRelease.aspx?relid=137573 Geo-Heritage Sites, Minister of Mines Press release, 09-March-2016]</ref><ref name=gsi3>[http://naturalheritage.intach.org/wp-content/uploads/2016/09/Geoheritage-Monograph.pdf national geo-heritage of India] {{Webarchive|url=https://web.archive.org/web/20170111120428/http://naturalheritage.intach.org/wp-content/uploads/2016/09/Geoheritage-Monograph.pdf |date=11 January 2017 }}, [[Indian National Trust for Art and Cultural Heritage|INTACH]]</ref> is a major discontinuity of [[stratigraphy|stratigraphic]] significance that represents a period of remarkable serenity in the geological history of the Earth i.e. sudden changes and discontinuity in the rock layers in Earth's crust. It is seen at the steep natural slopes, road scars and ravines in the [[Tirupati (city)|Tirupati]] – [[Tirumala]] [[Ghat]] [[road]] in [[Tirupati district]] of [[Andhra Pradesh]], India.<ref name=Monument>{{Cite web|url=http://www.portal.gsi.gov.in/pls/portal/url/page/GSI_STATIC/GSI_STAT_GEO_TOURISM_MONUMENTS|title=Eparchaean Unconformity, Tirumala Ghat section|access-date=2009-09-20|publisher=Geological Survey of India|archive-url=https://archive.today/20130419091251/http://www.portal.gsi.gov.in/pls/portal/url/page/GSI_STATIC/GSI_STAT_GEO_TOURISM_MONUMENTS|archive-date=2013-04-19|url-status=dead}}</ref><ref name="GSI">{{cite book|title= Geological Monuments of India| pages=5–8, 95|work=Eparchaean Unconformity (Tirupati Tirupati Road|publisher=Geological Survey of India|year=2001}}</ref>

In 2001, the [[Geological Survey of India]] (GSI) declared the unconformity to be one of the 26 "Geological Monuments of India". GSI's commemoration document, published on the occasion of the 150 years anniversary celebration, provides an insight into the formation of the subcontinent, the [[orogeny]], the [[Paleoecology|paleoenvironment]]  and the exotic collection of paleo-[[flora]] and [[fauna]]. The details provided for the Eparchaean Unconformity monument indicate that this feature forms the boundary surface between [[Proterozoic]] Nagari Quartzites and [[Archean|Archaean]] granite. The time gap between the formation of the two units is at least 500 [[mya (unit)|Ma]].<ref name="GSI"/>

At this location, the boundary is between sedimentary rocks of the [[Cudappah]] Supergroup,  1600 million years in age, and Archaean rocks comprising [[granites]], [[gneisses]] and [[dolerite]] [[dyke (geology)|dykes]] that are more than 2100 million years old. This unconformity gives an indication of the enormous time gap in the creation of the Earth's crust.<ref name="GSI"/>

==Topography==
The geological monument is located in the Tirupati valley, which is bounded between ({{coord|13.50|N|79.375|E}}) and ({{coord|13.45|N|79.75|E}}). The basin is delimited between the [[Palakonda]]-[[Velikonda Range|Velikonda]] and Sanambatla-[[Srikalahasti]] and [[Nagari, Andhra Pradesh|Nagari]] ranges of the [[Eastern Ghats]]. [[Tirupati Temple]], the most famous pilgrimage centre in [[South India]] is in the midst of the range of hills. The hills enclose the temple town to give it a form of an amphitheatre setting.<ref name=Jivraj>{{cite web|url= https://archive.org/stream/earlyhuntergathe019426mbp/earlyhuntergathe019426mbp_djvu.txt|title= Early hunter - Gatherers adaptations in the Tirupati valley by Jacob S. Java Raj, pages 5-12, 112|publisher= Sri Venkateswara University T1rupati|access-date=2009-09-20}}</ref>

==Geology==
[[File:Plaque at Tirumal hills on Eparchean Unconformity.jpg|thumb|left|250px|Plaque gives brief details of Eparchaen Unconformity]]
The Tirupati hills are situated at the foot of a range of hills known by several names, including 'Seshachala', 'Venkatachala' and 'Balaji'. There are four geological units:
:(1) Archaean rocks of the eastern Dharwar Craton (the granites and gneisses)
:(2) the Eparchean unconformity (Quartzose sandstones overlying the granite with a distinct unconformity)
:(3) Puranas (a general name for Proterozoic sedimentary sequences found in a series of basins deposited on the Indian Shield; including the Cuddapah Basin)<ref>[https://books.google.com/books?id=Z9Ziw7-SG2UC&dq=%22cuddapah+basin%22+nagari+quartzite&pg=PA99  Balasubrahmanyan, M.N. 2006. Geology and tectonics of India: an overview, Memoir No.9, International Association for Gondwana Research]</ref>
:(4) Quaternary deposits
The Tirumala hills essentially of [[precambrian]] period are composed of [[sedimentary rocks]] &ndash; [[quartzites]] and intercalated [[shales]], which are referred to as the Nagari quartzites, which forms part of the Cuddapah Supergroup. It is  a subset of the Purana rock succession that rests above the archaean rocks.<ref name="GSI"/><ref name=Jivraj/><ref>{{cite book|url= https://books.google.com/books?id=aKEcAAAAMAAJ&q=Eparchaean+Unconformity,+Tirumala+hills|title= The Tirumala Temple by N. Ramesan|year= 1981|publisher=Tirumala Tirupati Davasthanams, 1981|access-date= 2009-09-20}}</ref>

The hill ranges of the Tirumala rise to a height of {{convert|900|m|ft}} (at Tirumala) from the average height of {{convert|150|m|ft}} in the plains at Tirupati. The steep scarp of the ranges shows the Eparchian Unconformity's topographic, structural and denudational features.<ref name="GSI"/><ref>{{cite web|url= http://www.ias.ac.in/jarch/currsci/45/00000149.pdf |title=Eparchian Unconformity at Tirumalai – A Study by K.V.Suraynarayana|publisher=Venkateshwara University, Tirupati|access-date=2009-09-20}}</ref>
The sedimentary thickness of the Cudappah basin is of the order of {{convert|12|km|mi}}, and includes [[volcanic]] sequences in the form of [[Sill (geology)|sills]] and [[Dike (geology)|dykes]]. A prominent Eparchaean Unconformity of the formation resting on the archaean [[peninsular]] gneissic complex is noted. Rocks of the Cuddapah Supergroup, and the overlying [[Kurnool]] Group, comprise the stratigraphic sequence of the basin. This feature is contiguous all along the defined Archaean-Cuddapah contact zone even though its age may vary along its traced path.<ref name="GSI"/><ref>{{cite web|url=http://www.dae.gov.in/amd/regions/sr.htm |title=General information, Southern Region, Broad Geological features |publisher=Department of Atomic energy Atomic Minerals directorate for exploration and research GOI |access-date=2009-09-20 |url-status=dead |archive-url=https://web.archive.org/web/20081204130800/http://www.dae.gov.in/amd/regions/sr.htm |archive-date=4 December 2008 }}</ref>

==Access==
The location of the Geological Monument is well connected by road, rail and air routes.
The nearest railhead to Tirumala hills is [[Tirupati (city)|Tirupati]]. The geological monument is located  {{convert|10|km|mi}} northwest of Tirupati town, at the {{convert|12|km|mi}} point on the Tirupati – Tirumala Ghat road. From Tirupati railway station the approach to the Tirumala temple is only by road, a distance of {{convert|10|km|mi}}.<ref name="GSI"/><ref>{{cite web|url= http://www.indiainfoweb.com/andhra-pradesh/excavations/silathoranam.html|title= Silathoranam|access-date= 2009-09-20|archive-url= https://web.archive.org/web/20090106031143/http://www.indiainfoweb.com/andhra-pradesh/excavations/silathoranam.html|archive-date= 2009-01-06|url-status= dead}}</ref>
The nearest airport is located at [[Renigunta]], in [[Tirupati (city)|Tirupati]] city, which connects to [[Chennai]], [[Hyderabad, Andhra Pradesh|Hyderabad]] and [[Bangalore]] airports. Regular bus services (both private and government) are operated by all the states bordering Andhra Pradesh.<ref name=Monument/><ref name="GSI"/><ref>{{cite web|url=http://www.mustseeindia.com/Tirupati/how-to-reach|title=must see India|access-date=2009-09-20|archive-url=https://web.archive.org/web/20090202132247/http://www.mustseeindia.com/Tirupati/how-to-reach|archive-date=2009-02-02|url-status=dead}}</ref>

==Gallery==
<gallery widths=160px heights=160px perrow=4>
File:Detrital rocks of Tirumala Hills Ghatroad Tirupati.JPG
File:Sandstone of detrital quartz rocks at Kapilatheertham Tirupati.JPG
File:Garuda cliff in Tirumala.jpg
</gallery>

==References==
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[[Category:National Geological Monuments in India]]
[[Category:Geology of Andhra Pradesh]]
[[Category:Tirupati]]
[[Category:Tirupati district]]
[[Category:Geography of Tirupati district]]