Tuesday, November 30, 2010

Remotely India # 1: A New Series On Indian Geology

I'm experimenting with a new series. The idea is to put up a satellite image of an interesting geological feature from India along with a brief explanation. I'm going into this without much preparation. I have about 5 locations ready but will have to actively look for more features to put up.

Which imaging service should I use? Google Maps and Bing Maps are the easily accessible choices,  but in honor of India's Remote Sensing Program which has been a credit to the country, wherever possible I will be putting up an image from an Indian Remote Sensing Satellite as well. I'm going to be using the public domain web mapping service Bhuvan as the source of the images taken from Indian satellites. The resolution allowed for unrestricted use of imagery via services like Bhuvan is a maximum of 5.8 meters, and so I will supplement that with an embeddable Google Maps frame for higher resolution images and a more interactive experience.

The inaugural image is a sentimental choice from my first solo mapping project in the Proterozoic Cuddapah Basin of Andhra Pradesh, south India, located between the towns of Kurnool and Nandyal.

Gani Kalva Anticline

Source: Resourcesat 1

The feature is an ENE plunging asymmetric anticline with spectacular dip slopes of quartz arenites making up the southern limb of the fold and left-lateral movement along a regional fault steepening the northern limb of the fold. There is some copper mineralization along the fault. The Cuddapah basin is an intra-cratonic basin which was filled up in several depositional mega cycles. Sections of two of these mega cycles are exposed in this area. The older mega cycle comprising the Cuddapah subgroup is exposed in the core of the anticline. An angular unconformity separates the older cycle from the younger Kurnool cycle (sub group) which is exposed along the limbs.


View Larger Map

Posting will be on Tuesday but maybe not every Tuesday! Suggestions and recommendations welcome..

Thursday, November 25, 2010

USGS Primer And India Rare Earth Element Potential Host Types

via Geology.com, the USGS has released a pretty useful primer on the geology of Rare Earth elements. The types of host rocks are described along with the challenges of mineral processing for element extraction.

A table summarizes the host rock types along with examples of their occurrence. ... a bit surprised that no examples from India have been given. There is active mining in India of placer sand type deposits from the coasts of Kerala.  These sands are rich in monazite a phosphate derived from granitic rocks which has been used as a source of Thorium but is increasingly now gaining importance as a source of Rare Earths too. Inland placers have also been identified as potential sources.

There are two other potential geological sources of Rare Earths  in India. Alkali and carbonatite intrusives and volcanic flows. These broadly fall in two age groups; through the Proterozoic, developed during episodic magmatic events.  Tamil Nadu and Rajasthan carbonatites are well known but their Rare Earth potential needs to be evaluated in detail. The younger ones are late Cretaceous in age, related to the Deccan volcanic episodes and are located in the western regions around Gujarat. 

The third potential source of Rare Earths are the thick residual clay and lateritic soils developed on granitic source rocks. These types of deposits are being exploited in south China.  Such soils are present through the western parts of south India. They formed during intense weathering of Precambrian  terrains during the Cenozoic. I am not sure how well they have been characterized in terms of their Rare Earth element concentrations.

Even if they are recognized as a resource, it will be tough to exploit them. Most of these thick soils are covered with tea and coffee plantations... a mighty industry of its own.

Monday, November 22, 2010

Rocky Plateaus Of Western Ghats Need Protection

The Times of India Sunday Pune Edition (Nov 21) carried a good article (the print edition has a more detailed write up) by Dipannita Das on the ecological importance of the rocky plateau landforms of the Western Ghats. These outcrops are often termed "wastelands", a terminology that reflects classification of landscapes by their economic potential, a classification tradition that goes back to the days of the British Raj. Rocky plateaus were thought to be unproductive and were termed wastelands.

Here is a classic example of one of these rocky plateaus from Panchgani, a hill station south of Mumbai. The cap is made up of an early Cenozoic laterite. At other locations the plateaus are hard basalt flows.

And here is a view of the surface of such plateaus.

It may seem mostly barren, but as the article details, such plateau environs are teeming with plant and animal life, specialized to live in crevices and along the slopes and depressions and hollows and water seeps that have formed by the action of physical and chemical weathering.

There is a national level effort going on to map the biodiversity of the Western Ghats (see site WesternGhatsIndia.. not working at the time of writing ) and one hopes that many of these ecologically rich and interesting rocky plateaus will be afforded protection from various anthropogenic activities. These plateaus are of geological importance too. As I wrote in an earlier post, many of these "rocky" surfaces tell a story of the erosional, uplift and weathering history of the Western Ghats.

Over the last couple of years I have come across increasing number of reports in newspapers on various environmental issues. Reporters are talking not just to a few well known and politically connected scientists, but also to faculty and researchers from local colleges and institutes that are on the front line ... doing field work, collecting data and conducting research on various biological and geological aspects of the surrounding landscapes.

That marks a positive change in terms of increased science outreach by the media and raising awareness of these issues in the communities that are going to be directly affected by the unplanned development of the nearby environment.

Tuesday, November 16, 2010

Geological Cross Sections And Profiles Of My Lesser Himalayan Hiking Area

 [Update October 2012: Please refer to my new post on the Lesser Himalayas -Stratigraphy and Structure of the Lesser Himalayas in Gharwal and Kumaon]

Update November 29 2012:

Interactive Geologic Map and Cross Section Of The Kumaon Lesser Himalayas In The Shama Gogina Region


 This has been pending for the last couple of weeks.

I went hiking in the Mukteshwar area of the Kumaun Himalayas and promised I would be posting some geological maps and cross sections and so here goes.

If you are a field geologist looking for some classic fold belt structures to map you are not going to be over excited if you are restricted to the  Mukteshwar area. The outcrop geology given the contorted and complex standards of portions of the Himalayas is quite sedate.

The entire region is made up of a NE steeply dipping block of phyllites, quartzites and mica garnet schists. Great exposures are few due to the lush vegetation. The one on the left are mica-garnet schists and quartzites forming an escarpment which is used for rappelling and rock climbing.

Along road cuts like the one below you do get a good view of the quartzites and schists. This one contains elongate deformed quartz veins.

These north east dipping strata are one limb of a regional synform. The cross section below depicts the internal geology of the synform made up of a sequence of medium to high grade metamorphic rocks intruded by granites. All the thrust faults shown in the cross sections are thought to sole in to the Main Central Thrust. The interpretation is that the Main Central Thrust has splayed or split into these subsidiary faults. I'll explain the role of the Main Central Thrust a little later in the post. My location was close to the label Study Area.

 Source: T. Kulkarni 2008

The larger geological context within which this quartzite-schist terrain stands is quite interesting.

As I mentioned Mukteshwar falls in what is known as the Lesser or Lower Himalayas. Below I've put up a topographic profile across the Kumaun Himalayas. SH - Sub Himalays, LH - Lower/Lesser Himalayas, HH- High Himalayas , ITS - Indus Tsangpo Suture beyond which is the Tibetan plateau.

 Source: An Yin 2005

Early mapping in some areas indicated that these physiographic divisions also corresponded with 4 different geological domains which were in tectonic contact along great thrust faults.

So, the Sub Himalayas or Siwaliks are made up of Cenozoic foreland basin sediments separated from the Gangetic alluvium by the Himalayan frontal thrust and from the Lower Himalayas by the Main Boundary Thrust.

The Lower Himalayas in turn are made up of unmetamorphosed to low grade metamorphic mid-late Proterozoic Indian basement (Lesser Himalayan sequence) separated from the High Himalayas by the Main Central Thrust.

And the High Himalayas are made up of high grade metamorphic mid late Proterozoic Indian basement (Greater Himalayan Crystalline sequence) along with unmetamorphosed Paleozoic sediments (Tethyan Himalayan sequence) and this terrain meets the Asian plate along the Indus Tsangpo suture, the zone of plate collision.

The simplified story is that as the Indian continental crust collided with the Asian crust, the Indian plate buckled, deformed and broke up perhaps along pre-existing zones of weaknesses in the Indian crust. These breakages evolved into the major thrust faults bringing into structural contact different geological terrains. The gradient of compressive forces and vertical uplift increases from SW to NE imposing a conformity between the physiographic and geological divisions.

Physiography and geology do coincide in regions like central Nepal but the correspondence between the physiography and geology does not hold up everywhere. For example the Almora /Mukteshwar area which falls in the physiographic Lower/Lesser Himalayas has exposures of very high grade rocks corresponding to the Greater Himalayan crystalline sequence normally found in the physiographic Higher Himalayas.

Below is a map of the Himalayan orogen. I was located just east of cross section C in the Almora-Dadheldura nappe. 

 Source: An Yin 2005

Nappes are terrains which have moved some distance along thrust faults. In this case the Main Central Thrust has moved the Greater Himalayan crystalline terrain over the Lesser Himalayan sequence along a nearly flat or low angle thrust. During continued orogenic forces the continental crust kept buckling, resulting in the Greater Himalayan crystalline terrain along with the Main Central Thrust in this region becoming folded into a broad synform and antiform. Erosion has removed the antiform leaving exposures of the Greater Himalayan crystalline sequence stranded on top of the Lesser Himalayan sequence- cut off from its root in the Higher Himalayas.
This is how high grade metamorphic rocks of the Great Himalayan crystalline sequence and sediments of the Paleozoic Tethyan sequence which make up the High Himalayas are in many regions exposed in the Lower Himalayas.

They are erosional remnants of thrust sheets.

Cross section C below is a depiction of this scenario. The pink is the Greater Himalayan crystalline sequence, the pale brown is the Lesser Himalayan sequence and the blue is the Tethyan Himalayan sequence. MCT is the Main Central Thrust. The red arrow indicates my approximate location within this synform.

 Source: An Yin 2005

Such blocks of the nappe isolated from its root terrain are called klippen. The Almora /Mukteshwar area high grade crystalline rocks are part of a klippen surrounded by unmetamorphosed to low grade Lesser Himalayan sequence.

This is the consensus view.... put forward after decades of mapping and dating rocks in this region. The movement of the thrust sheets and the erosional formation of klippen according to this view took place in the mid Miocene, synchronous with a major uplift and deformation phase of the Himalayas. Another view is that the rocks of the Almora-Mukteshwar area are not allocthonous or transported from elsewhere but are authocthonous i.e. they are a rooted part of the Lesser Himalayan sequence, the different grades of metamorphism reflecting local metamorphic gradients.

You don't really get a feel for this larger picture if you are hiking within a small area as I was. Still it was pretty awesome thought, that I was standing on a klippen whose root lay in the High Himalayas some 75 km away in front of me.

Saturday, November 13, 2010

Planting Trees Will Provide Clean Air To Pune?

Pune has several hills scattered throughout its extents. About 1600 odd hectares of them going by the various sources. Some of the hill land is owned by government and is managed by the forest department, some is government owned and is covered by slums and some is under private ownership.

There is a grand plan to convert all or most of this 1600 odd hectares into bio-diversity parks. While the idea of setting aside large swaths of hills as open spaces is creditable, reporting by the media on the supposed benefits of these parks verges on the side of being silly.

Here are a couple of examples I see again and again in media reports on this issue, most recently in yesterday's Times of India (Nov 12 2010, Pune edition):

Air pollution in Pune is a threat to health and well being. The United Nations recommends at least 12 sq m of green area per person for adequate environment for physical and mental health.

An average family of five will require 60 sq m of green area to survive and breathe. Once it comes up, the BDP's will provide clean air for approximately 35 lakh people.

BDP's are the bio-diversity parks and 35 lakhs equals 3.5 million.

Reading this strange environmental calculus makes me wonder how people in Tokyo, Hong Kong, Dubai and Las Vegas, cities with either hyper dense populations or ones bereft of any greenery manage to live healthy lives.

Going by the U.N criteria as presented in the Times of India (TOI) all the people in these cities should be diseased wrecks by now.

The fact is that the greening of the hills will not make a dent in either offsetting carbon dioxide emissions or preventing other types of air pollutants. Pune by a rough estimation of the number of vehicles (approaching 2 million) likely emits more than a million tons of carbon dioxide a year from vehicles alone (here is another estimate). There are other sources that add to this.

1600 hectares of the Utopian forest that may or may not come up on these hills will sequester at most a few thousand tons of carbon dioxide per year. That is the best case scenario. Most likely the number will be disappointingly smaller. Currently the forest on these hills sequester a few tens of tons per year according to this study on carbon sequestration in Pune.

Besides trees don't suck in particulate matter and sulfur and nitrous compounds which have ill effects on health. More than CO2, these pollutants pose an immediate threat to our health. These continue to be emitted in large quantities mostly as vehicular emissions and tree plantations won't reduce their presence in the air above Pune.

I would like to see at least parts of these hills being left as open spaces..there are clear benefits in terms of providing cool recreational spaces for citizens and as a refuge for the urban bird and animal populations. But whether those hills are left barren or are built upon or are completely covered by trees won't make a difference in terms of providing clean air to the city.

That will happen only through cleaner and more efficient use of energy sources particularly a move towards cleaner vehicular fuels.

Monday, November 8, 2010

Religious Selection In Mexican Fish Populations

This one I could not pass on and it gives me a chance to nitpick about reporting on evolution :)

The Zoque people of southern Mexico pray to the rain gods every year by releasing a leaf-bound paste made of lime and the ground-up root of the barbasco plant in to cave waters. This mixture is a natural fish toxin.

Researchers from Oklahoma State Univ. and Texas A and M found out that fish populations exposed to this poison have evolved a resistance to it over centuries.

From the Science Daily press release:

However, a team of researchers led by Dr. Michael Tobler, an evolutionary ecologist at Oklahoma State University, and Dr. Gil Rosenthal, a biology professor at Texas A&M, has discovered that some of these fish have managed not only to develop a resistance to the plant's powerful toxin, but also to pass on their tolerant genes to their offspring, enabling them to survive in the face of otherwise certain death for their non-evolved brethren.

The use of the phrase ....these fish have managed not only to develop a resistance.. may be read by many who are not familiar how evolution works to mean that some individual fish over their lifetimes develop a physiological resistance to the poison and then pass on that trait to their offspring.

That is inheritance of acquired characteristics and that is not how evolution by natural selection works. Rather some fish within a population will by chance happen to have genes that confer some resistance to the poison. These individuals will leave behind more descendants than individuals who don't possess that version of the gene. Over time the poison tolerant gene will become more common in the population.

The press release does better later in the article:

Mollies able to tolerate the poisonous conditions survived and passed those traits to their offspring, resigning those that perished to their fate of serving as a ceremonial feast for the Zoque.

The two came out meaning different things to me in terms of how evolution works... the second paragraph sounds more accurate.

Link to paper: An indigenous religious ritual selects for resistance to a toxicant in a livebearing fish. Biology Letters, 2010; DOI: 10.1098/rsbl.2010.0663

Sunday, November 7, 2010

Indian Public Pick Out Future Energy Winner

One hopes green energy will increasingly contribute to India's energy pie.. but there is no denying which energy source the Indian public and industry place their confidence in..

Coal India IPO oversubscribed 15 times

Carbon sequestration I realize is expensive and not demonstrated on a large scale but maybe we should be giving some space to this technology in our conversations about reducing our carbon footprint.

Wednesday, November 3, 2010

Thinking About Early Land Bridges Between India and Asia

As the Indian continental block ploughed northwards and approached Asia starting earliest Cenozoic, when did the sea between the two continents disappear. When did the two continents become one, when did the first "land bridges" between the two continents develop.

Last week's post about early Eocene insect fossils preserved in amber from the Cambay shale in western India prompted these questions. The insects show similarities to Cenozoic insect fauna from Europe, Asia and Australiasia.

Although similarities between insect fauna imply faunal exchanges between continents they may not necessarily indicate that the two continents were connected by land bridges. Insects can survive on rafts for long periods and favorable ocean currents and island chains in the ocean between the two continents may have provided sufficient stepping stones for insect trans-continental migration.

Two types of evidence speak more directly to the presence of land bridges. One is the first appearance of distinctly Indian mammals on the Asia plate and vice versa. Mammals would have needed a solid connection between the two continents to migrate.

Another type of direct evidence is the presence of terrestrial sediments in the zone of collision. As the two continents collided, there would have been the development of complex topographic in the zone of collision.  High thrust mountains but also regions which sagged and became basins. Of interest are basins which were filled with lakes or became courses for rivers.

The presence of lacustrine or fluvial sediments resting on rocks of the Indian plate but containing grains which show the provenance or source to be rocks of the Asian plate is strong evidence that the two continents had sutured into one and rivers originating on one plate were transporting sediments and depositing them on the other, i.e. land bridges had formed between the two.

There are at least two other indirect ways of inferring land bridges. One is the reduction in plate velocity. The moving Indian plate had set a Cretaceous record for speed but abruptly slowed in the earlier Cenozoic. That implies that continental crust was meeting resistance from another continental block and the two continents were suturing.

The other indirect way is to look at the metamorphism of continental crust. As the continents collided, continental crust was transported to depth and transformed into a suite of metamorphic minerals at high temperatures and pressures. The timing of these metamorphic events speak to the coming together of continents.... so do the presence of intrusive granites which formed by melting of the continental crust during the collision.

We know from all these above types of evidence that the collisions began in early Eocene and it was not uniform and simultaneous across the present length of the Himalayas. The western edge of the Indian plate met first and the continents sutured eastwards through the Cenozoic.