Tuesday, September 24, 2013

Quote: Robert Folk On Microbiota and Carbonate Petrology

JSR Paper Clips in a look back 20 years ago features an important paper by Robert Folk, carbonate sedimentologist par excellence, on SEM imaging of bacteria and nanobacteria in carbonate sediments and rocks.

..he says: “the minute interface between bacteria and carbonate petrology may be lilliputian in scale but are conceivably gargantuan in importance….”

Folk was probably moved in to making this utterance by a scene like the one below


These are layered dolomite strata of Triassic age from the Alps.  Folk argued that bacteria and nanobacteria have catalyzed the precipitation of such enormous thicknesses of carbonate minerals on the sea floor right through geologic history.

Many carbonate sedimentologists today do acknowledge that microbes play an important role in carbonate mineral precipitation but the details of the geomicrobiology i.e. exactly what physiological and chemical reactions enhance this precipitation is still being worked out. My recent post on this topic explores the role of microbes in dolomite formation.

It's not often you get to witness seminal breakthroughs in science. I now count myself lucky that I was present at the talk at the 1993 GSA meeting in Boston when Robert Folk described this hypothesis of bacterial influence on dolomite precipitation... 20 years on his argument is withstanding the test of time.

References: Folk, R. L., 1993b, Dolomite and dwarf bacteria (nannobacteria): Geological Society of America Abstracts with Programs, v. 25, p. A-397.

Thursday, September 19, 2013

Flood Risk Assessment Of River Kosi And Disaster Management

From Geology  Pre-Issue Publication

Exploring the channel connectivity structure of the August 2008 avulsion belt of the Kosi River, India: Application to flood risk assessment- R. Sinha, K. Gaurav, S. Chandra and S.K. Tandon

The August 2008 avulsion of the Kosi River, northern India, resulted in a maximum eastward shift of >100 km and created an avulsion belt of 2722 km2. Based on A.D. 2000 Shuttle Radar Topography Mission data and on 2005 Landsat Thematic Mapper satellite image–derived channel network (pre-avulsion), we use a topography-driven connectivity model to simulate the avulsion pathway, which corresponds, to a large extent, to that observed in the post-avulsion period. We then use this model to postulate the avulsive course of the river from another upstream point based on avulsion threshold analysis. Our results demonstrate that this model has the potential for postulating the path of an avulsive channel, and can provide a priori information on the areas likely to be flooded following an embankment breach. 

The Kosi flood and channel shifting in 2008 absolutely devastated large extents of Bihar, so this kind of research is urgently needed. The problem is that it may sit within the confines of a small number of geomorphology experts and not make its way to people who draw up disaster management plans. As geologist K.S. Valdiya not so far back lamented, geology and geologists have not found their way or have not been invited to sit in position that can influence policy.

Sometime despite explicit warnings from geologists, government apathy is to blame. Take the recent flash floods and destruction of Kedarnath town in the High Himalayas. Its not that geologists were unaware of the danger. A recent documentary on National Geographic interviewed many geologists who expressed little surprise at the extent of damage done by the floods. The combination of steep Himalayan slopes made up of foliated fractured rocks, glacial debris, moraine blocked lakes that could breach and overflow and narrow valleys where precipitation and stream waters get focused and funneled into raging torrents makes for an elevated risk of landslides, debris flows and floods during heavy rains.

Ignoring all advice government authorities turned a blind eye as the town of Kedarnath made up of often flimsy substandard construction mushroomed unplanned unregulated in the narrow river bed and floodplain of the Mandakini river. That is inviting catastrophe and nature at some point will oblige.


Monday, September 16, 2013

Field Photos: A Trek To Tikona Fort

Come September I am heading out again in the Deccan Basalt landscapes. Last Saturday I went for a day trek to Tikona Fort, about an hour and half drive from Pune on the backwaters on the Pavana dam.

An interactive map of the Tikona Fort area


View Larger Map

Monsoon clouds hover over the summit

Tuesday, September 10, 2013

Geopathic Stresses Behind Indian Expressway Mishaps

Ok..something lighthearted.. but this really was published as a serious article in the newspaper DNA:

Geopathic stress or simply “bad energies” are harmful radiation arising from the depths of our planet. According to geophysicists, there is a natural magnetic field on the earth’s surface to which all beings are acclimatised. Geopathic stress arises when this natural magnetic field of the earth is distorted by weak radiations generated by underground streams of water, sewers, drains, certain mineral concentrations, fault lines and underground cavities. This stress impact on the physiological condition of drivers leading to critical errors while driving. However, awareness about the existence of this factor can help drivers, experts say.

... Tyres bursting at this spot are the cause of a major number of accidents. The stretch has numerous cracks in the road, which are affecting vehicles. These cracks are due to hollow spots, which are generated due to tectonic movements and cannot be repaired by re-tarring, the earth at these high geopathic stress spots shifts periodically in intervals.

An explanation by people who dabble in Vastu.. which studies among other things the "energy" being emitted by the earth. This "energy" is manifest only to a select few.. alas the world's physicists have been unable to measure it and understand its nature.

Geopathic stress levels were determined by a rigorous survey and using sophisticated measurements along all the accident spots on the highway. Apparently the high "geopathic stresses" are indicated by vigorous movement of a dowsing rod like equipment. Geopathic stresses are ranked on a scale known as the Lecher scale from 1 to 15. Spots on this highway go up to 11. 2 on the Lecher.  The greater the movement of the dowsing rod - which a person holds in their hand while surveying- the higher the "geopathic stress". The scale was established after assiduously applying a correction for the "hand tremble syndrome" that seems to afflict practitioners of this art (I made up the last bit).

I am learning a lot!

As a geologist I am not really aware of the earth's magnetic field being distorted by underground sewers and such and that "distortions" will suddenly affect human physiology to the point of being disoriented. Claims that there are cracks in the road due to tectonic movements are also false... "Uhh.. we would have noticed the earthquake?" Movements large enough to generate cracks in the road will have registered on seismometers.. no such largish earthquake damage has been reported by geologists in this part of the country..

After all this hooey.. the Vastuworld team does give admirable advice:

...one major help in reducing the accident rate on the expressway would be that the drivers would still have to drive safely and without breaking the rules.

 Now..the day that happens in India.. the earth will rumble mightily.. right up to 15 on the Lecher scale !

Wednesday, September 4, 2013

Geochemical Data Supports Yamuna Became Tributary Of Ganga In The Pleistocene

How long has the Yamuna been flowing along its present course in the Indian plains i.e. flowing eastwards as a tributary of the Ganga?

Exploring the temporal change in provenance encoded in the late Quaternary deposits of the Ganga Plain - Shailesh Agrawala, Prasanta Sanyal, Srinivasan Balakrishnan, Jitendra K. Dash - Sedimentary Geology April 2013

Temporal analysis of Sr isotopes in soil carbonates and Sr and Nd isotopes in silicate fractions has been carried out in a sedimentary core (Kalpi core; 50 m long) raised from the southern bank of the Yamuna river, Ganga Plain, India. The aim of the study is to constrain sediment provenance through comparison with the modern Himalayan and peninsular river systems' water and bank sediments. Sr isotopic data in soil carbonates (0.71874 to 0.71410) and Sr\Nd isotopic data in silicate (0.72865 to 0.74544 and−13.9 to−17.2, respectively) vary significantly with depth and are indicative of both Himalayan and peninsular sources for sediments in the southern Ganga Plain. The positive correlation between 87Sr/86Sr ratio and 1/Sr in soil carbonate and the negative correlation between 87Sr/86Sr and ╬ÁNd in silicate confirm mixing of sediments from these sources. Variations of 87Sr/86Sr ratios in soil carbonates show that at ~80 and 45 ka the Himalaya acted as the major source of sediments in the southern part of the Ganga Plain. The gradual decrease in 87Sr/86Sr ratios after 80 and 45 ka indicates change in source to peninsular India which is also supported by limited Sr and Nd isotope data in silicates. The change in sediment provenance corresponds well with the available climatic record and is suggestive of strong climatic control in sediment supply with high supply from the Himalaya during the interglacial period and peninsular sediments during glacial period.

Background: