Links: Volcanic Underworld, First Americans, Billion Year Old 3D Microfossils

Readings over the past few weeks.

1) Taking the First Steps Into a Newly Formed Volcanic Underworld: Maya Wei- Haas describes a fascinating landscape on the Canary Islands in the Atlantic Ocean. Volcanic eruptions and the transport of lava via underground tubes has formed a subterranean world of stacked lava tunnels and caves. Their mapping is ongoing and scientists hope to understand not just the details of volcanism and the hazards it poses, but also how life can colonize such nascent surfaces, powered by nutrients from minerals. As one of the scientists remarks- "lava tubes is a rare chance to watch an evolving ecosystem from time zero".

2) It looks like the 23ky old human footprints at White Sands are solid: What is the earliest securely dated evidence of people in the America's? In 2021, there was a report of human footprints from an ancient lake in New Mexico. Since the footprints themselves could not be dated, seeds of an aquatic plant that were found in the same layer were carbon dated to about 23 thousand  years ago. That result was greeted with caution. The main concern was that the seeds may have taken up much older lake water containing less of the radioactive isotope C14. This may have made the dated material look older than it actually was. 

Now, there has been more work on the geochronology of the site using two more independent lines of dating. The results agree with the previously estimated date of 23 thousand  years. ArcheoThoughts summarizes the dating methodologies. 

3) Discovery of oldest 3D-preserved microorganisms: Before organisms evolved the ability to build hard skeletons, their remains have been preserved as impressions on soft sediment or as chemical degradation products recognizable by a light carbon isotope signal. Stefanie Terp reports on a discovery of 3D preservation of microorganisms from a mine in Ukraine. They are 1.5 billion years old! 

Scanning Electron Microscopy reveals the filamentous structure of these creatures. They are most likely a variety of fungi. Groundwater in the granite environment in which they lived was saturated with aluminum and silica. The microorganisms were covered and entombed in micrometer thin layers of aluminum silicate, perfectly preserving their delicate structure.

Iron Pisolites From Western Ghats

A reader sent me this photograph of a pebble he had collected from a stream bed near Belgaum, Karnataka.

 Photo credit: Gopisundar

These look to me like iron rich pisolites. These spheroidal grains form by the accretion of iron, manganese, and aluminum hydroxides around a nucleus. The core may be an aggregate of soil particles, a rock fragment, or even wood debris. 

You will notice that the core is quite massive and structureless but in a few grains a crude concentric layering is seen at the margins. The pisolites are bound together into a firm mass by mixture of clay and iron aluminum hydroxide. Pisolites form during prolonged episodes of chemical weathering of  rocks like basalt or shale or iron aluminum rich metamorphic rocks. They are present in thick laterite and bauxite profiles. 

The picture below is a representative example of pisolite from a location in Brazil. It shows the occurrence of pisolite layers in a weathered soil profile, along with a hand sample and a cross section under high magnification.

 

Source: K Marques et.al. 2022: Geochronology (preprint).

Here is a map of the landscape just south of Belgaum that I am describing in this post. 

 

 Source: Amanda Jean et.al 2020: Journal of Geological Society

It shows the distribution of three distinct horizons of chemically weathered soil, named as the S1, S2 and S3 surfaces. Each of these horizons consist of tens of meters of laterite or bauxite and manganese rich ore. There has been some recent success in dating these weathered layers using the mineral crytomelane, a potassium rich manganese oxide. Three distinct weathering periods are documented. As India broke away from Gondwanaland it eventually drifted northwards into tropical climatic belts. Throughout the Eocene to Miocene, long phases of hot humid climate resulted in intense chemical alteration of the Western Ghat landscape. 

The oldest soil, surface S1 in the map, formed between 53-44 million years ago. Surface S2 formed later in the Oligocene-Miocene between 39-22 million years ago. And surface S3 developed in the mid Miocene, between 14-10 million years ago. 

The graphic below tells a story of landscape evolution recorded in the formation of these three weathering profiles. 

 

 Source: Amanda Jean et.al 2020: Journal of Geological Society

Episodic dissection of a plateau through the Cenozoic kept stripping away rock layers, and younger bauxite and manganese rich soils formed at lower altitudes on freshly exposed rock and debris flows. The youngest surface S3 has developed on a pediment. These are layers of debris eroded from surrounding hills that accumulate in low lying areas. Surface S3 indicates a very active phase of weathering and erosion of the surrounding mountains ranges that took place between 22 and 14 million years ago. As a once contiguous plateau was fragmented, older surfaces S1 and S2 remain preserved on isolated mesas and table lands.

The pisolite my friend sent me could have broken off from one of these surfaces. Its hard to say which one. The overall light color suggests that it is aluminum rich, and may have been sourced from the bauxitic S1 or S2. But this is just a guess. 

Pebbles from a stream can hold many secrets. Don't just chuck them away :)

Readings: Earth's Ice, Neanderthal Women, Indian Monsoons

Some good stuff from the past few weeks.

1) How much of the Earth's Ice is Melting? Sid Perkins writes about the variety of methods of estimating ice loss from the high latitudes. These methods are showing where and how much melting is taking place, in turn, helping scientists make predictions of future sea level rise. The overall scenario is rather gloomy. 

2) The Lives of Neanderthal Women. "Archaeology is no exception to biases against women’s interests across science and the humanities". Archaeologist Rebecca Wragg Skykes expertly constructs a picture of what the lives of Neanderthal women might have been like.

3) Indian Monsoon Across Millennia. Stalagmites from a cave in Meghalaya, NE India are giving paleoclimatologists information about monsoon variability over a thousand years. Their geochemistry points to periodic deadly droughts that coincide with phases of major social and political turmoil in India. Paper authors Gayatri Kathayat and Ashish Sinha describe their research. 

 

Links: Tonga Volcano, Old Carbon, Indian Palaeontology

 Sharing these readings.

1) My first impression of the massive Volcanic eruption in Tonga was the mushrooming ash plume seen in a satellite imagery. Over the days more sensors have captured additional information about this event. When it is safe, geologists will travel to the site to sample the volcanic debris and subject it to detailed textural and geochemical analysis to piece together the journey of magma from its source to its explosive entry on the surface.

Scientific American has a good summary - Why the Tonga Eruption Was So Violent, And What to expect next. 

2) Debate is an integral part of scientific progress. One common platform to engage in a critique and discussion with your colleagues is the Comment and Reply section in scientific journals. You can submit a note explaining the issues you have about a paper, and it is published along with the author’s response. I am across a good example of this in the journal Science. The topic was the recent announcement of roughly 22,000 year old human footprints from Lake Otero, New Mexico. These dates suggest that humans  were present in North America during the Last Glacial Maximum, a few thousand years earlier than what other data has indicated.

The debate revolves around the accuracy of dating these footprints. Of particular interest here is the problems one can encounter with carbon dating a sample. Living beings have amounts of the radioactive isotope carbon 14 in them in equilibrium with the atmosphere. After death, the amount of this isotope in organic tissue starts decreasing due to natural radioactive decay of carbon 14. Knowing the decay rate and measuring its proportion in the organic material gives us estimates of how old the sample is. But what if the source of carbon is old? For example,  it is from very old groundwater or from the bottom of a lake which is not exchanging gases with the atmosphere? The carbon 14 values in such a réservoir will be very low due to ongoing decay and no replenishment of newly formed carbon 14 from the atmosphere. If organisms consume carbon from such a reservoir (which contains carbon 12 and carbon 13 too) and then are sampled , they will be estimated to be older than they really are. 

The Comment and Reply focuses on this problematic aspect of recognising and correcting for the ‘reservoir age’ of carbon 14. Of pointed importance too is the context and location of collected samples. 

A very informative debate on the nuances of sampling and assigning ages. 

Comment- Évidence of humans in North America during the last glacial maximum. 

Reply- Evidence of humans in North America during the last glacial maximum. 

3) I have posted about this topic before. Thé challenges and triumphs of Indian palaeontology very well described by Kamala Thiagarajan in this recent article. 

Why India’s Fossil Wealth Has Remained Hidden. 

Previously, Sreelatha Menon had written about the lack of importance palaeontology is accorded in the earth sciences and the devastation this neglect is inflicting to palaeontology education, awareness, and research. Her essay is worth reading too; What do you do when palaeontology is itself endangered in India?

Fossil Dickinsonia in Bhimbetka Sandstones: Nature India Article

 My short piece published in Nature India on the surprising report of Ediacaran age fossil Dickinsonia in the Bhimbetka caves near Bhopal, Central India, and its geological and biological significance.

an excerpt:

"The biological affinity of Dickinsonia is controversial. Most scientists tend to accept it as an early animal. Some like Gregory Retallack, co-discoverer of this fossil, think of it to be a large algae or lichen. He argues that the mainstream view that Dickinsonia was a marine animal is based on weak evidence, while his own detailed work shows that Dickinsonia was a land creature, forming biogenic crusts on soils. Interestingly, the Bhimbetka rocks were deposited in a mostly terrestrial setting, more in alignment with Retallack's interpretation. Importantly for geology, its restricted time span, being found only in rocks between 555-550 million years old, makes it a diagnostic age indicator. So far, no animal fossils have been found in the Vindhyan rocks. This finding may inspire geologists to start searching contemporaneous Indian basins afresh for such subtle clues".

Fossil from dawn of animal life found in India’s famous caves.

Glacial Saraswati?: New Data On An Old Question

Did a perennial glacial fed river flow through the Indus Civilization region of what is now Haryana and Rajasthan? Previous work on the fluvial history of this region had indicated that a distributary of the glacially sourced Sutlej was flowing through a network of paleo-channels buried under the river now known as the Ghaggar until around 8,000 years ago. The Sutlej distributary system then died out, turning that river course into a smaller monsoon fed channel system.

For a more detailed history of research on this topic you can follow this link - Ghaggar /Saraswati Posts.

Recently, in November 2019, Anirban Chatterjee and colleagues published new data on deposits of grey sand in the subsurface of the Ghaggar channel and adjacent floodplains. The youngest of these deposits are 4, 500 years old. Geochemical fingerprinting points to High Himalayan granites and gneisses as their source. This likely extends the glacial phase of the Ghaggar to more recent times, until about the beginning of the urbanization of the Indus Valley Civilization (IVC).

Here is the abstract:

The legendary river Saraswati of Indian mythology has often been hypothesized to be an ancient perennial channel of the seasonal river Ghaggar that flowed through the heartland of the Bronze Age Harappan civilization in north-western India. Despite the discovery of abundant settlements along a major paleo-channel of the Ghaggar, many believed that the Harappans depended solely on monsoonal rains, because no proof existed for the river’s uninterrupted flow during the zenith of the civilization. Here, we present unequivocal evidence for the Ghaggar’s perennial past by studying temporal changes of sediment provenance along a 300 km stretch of the river basin. This is achieved using 40Ar/39Ar ages of detrital muscovite and Sr-Nd isotopic ratios of siliciclastic sediment in fluvial sequences, dated by radiocarbon and luminescence methods. We establish that during 80-20 ka and 9-4.5 ka the river was perennial and was receiving sediments from the Higher and Lesser Himalayas. The latter phase can be attributed to the reactivation of the river by the distributaries of the Sutlej. This revived perennial condition of the Ghaggar, which can be correlated with the Saraswati, likely facilitated development of the early Harappan settlements along its banks. The timing of the eventual decline of the river, which led to the collapse of the civilization, approximately coincides with the commencement of the Meghalayan Stage.

The geological work looks to be sound. The data on sediment fingerprinting overlaps with what we know about High Himalayan geochemical signatures and present day Sutlej sand composition.

I do want to comment on another sentence from the abstract (emphasis mine)-

"This revived perennial condition of the Ghaggar, which can be correlated with the Saraswati, likely facilitated development of the early Harappan settlements along its banks"

Saraswati is the name given to this river by the Vedic people. Correlation of the river's perennial phase between 9,000-4,500 years ago with Saraswati is valid only if  you can demonstrate that the Vedic people were inhabitants of this region from before 4,500 yrs ago. Geological studies cannot establish this. A combination of archeology, linguistics (cracking the Indus script would be nice!) and genetics will eventually answer that. The other scenario is that the Vedic people could have migrated into this region much later and began venerating a smaller monsoonal Ghaggar as Saraswati. Work by Liviu Giosan and colleagues suggests that stronger monsoons over the Siwaliks sustained sufficient flow in the old channels of the Ghaggar until the late IVC period (~1800-1600 B.C).

When did this river come to be called the Saraswati is still an open question.

Two recent genetics papers using ancient DNA recovered from the IVC site of Rakhigarhi and from Central Asia argue that people from the Pontic-Caspian steppes migrated into South Asia between 2000 -1500 B.C. bringing with them the Indo-Iranian branch of the Indo-European language family. These would presumably be the Vedic people.

Read these papers. They are interesting.

1) On the existence of a perennial river in the Harappan heartland.
2) The formation of human populations in South and Central Asia.
3) An Ancient Harappan Genome Lacks Ancestry from Steppe Pastoralists or Iranian Farmers.

Dating Rock Art

I love it when science is explained with a well thought out and cleanly drawn illustration.

A commentary in Nature News and Views by David G. Pearce and Adelphine Bonneau presents this diagram on dating rock art.

Two recent studies on dating cave paintings from Spain are discussed.

Who were the artists?

The oldest minimum age for the paintings is 66 ka (thousand  years) leading to speculation that they might have been drawn by Neanderthals. The earliest presence of modern humans in Spain is from  40 ka. This would imply independent evolution of symbolic behavior in Neanderthals.  However, the same painting throws up a range of minimum dates from ~ 60 ka to ~ 3 ka making an exclusive link  to Neanderthals problematic.

Field Photos: Glacial Deposits Of The Darma Valley, Kumaon Himalaya

During my recent trek to the Panchachuli Glacier in the Kumaon Himalaya, I obsessed about observing changes in metamorphic grade of the Greater Himalayan Sequence on the trek route and also about finding the South Tibetan Detachment fault system. I wrote about this in an earlier post.

But there were other interesting geological observations too. The Panchachuli Glacier has left a thick record of glacial deposits. The river Dhauliganga originates from this glacier. Along this river valley, glacial deposits can be observed to a distance of at least 5 kilometers downstream of the present location of the snout of the glacier, indicating that the glacier was much more extensive in the past. Tributary glaciers flowing out of the ranges east of the Dhauliganga have also left an extensive record in the form of thick fluvio-glacial deposits. These can be observed as far south as the village of Baaling.

We heard anecdotes in village Dugtu about how this glacier was much bigger in living memory and how it has been receding rapidly in the past few decades. On one level such stories are believable because studies of Himalayan glaciers have shown that many of them have been shrinking over the past few decades (ref). This is partly due to anthropogenic global warming, but glacial response to warming may be varied due to local variations in topography, precipitation and wind conditions. Some glaciers don't show retreat while some are actually seen to be expanding. Overall though, there a substantial ice loss observed across the Himalaya. Exactly how much of that is due to recent global warming and how much, as some scientists caution, due to natural factors is still being studied. Sustained warming though will cause these glacier to shrink further over the next century.

There is also a longer geological story of glacial advance and retreat written in these deposits.

I've embedded below an annotated interactive map of the glacial deposits of the Dhauliganga river valley in the Panchachuli Glacier area. This will enable readers to zoom in and recognize the various glacial landforms present in the valley. You can also access it via this Permanent Link.



The annotations depict:

a) The dark blue lines are the snout of the glacier.
b) The light blue lines are the recent terminal moriane fields.
c) The pink lines are older lateral moraines.
d) The yellow lines are outlines of older fluvio-glacial deposits
e) Numbers 1 -12 mark the locations of glacial deposits.

I have mapped only a few representative examples of each of the feature types. Readers can use these to explore similar features scattered throughout the valley. 

Location 1: This is the snout of the glacier. It is a mass of ice and frozen mud. The river Dhauliganga emerges out of an ice cave.

Location 2: Taken from near the snout of the glacier looking downstream. Ridges of the terminal moraine can be seen in the foreground. The arrows in the background outline a ridge of an older lateral moraine. Notice how the ridge decreases in elevation downstream suggesting that the terminus of this older glacial phase in somewhere nearby downstream.

Location 3: The older lateral moraine can be clearly seen as a sharp ridge line (arrow) separated from the valley wall by a depression. 

This moraine top is a few hundred meters above the valley floor implying that the glacier was thicker in the past. When was this lateral moraine deposited? It may be at least a few hundred years old. In the Garhwal Himalaya, similar older lateral moraines close to the glacier has been dated to be several hundred years old. They have been interpreted to be a result of glacial growth and deposition during the Little Ice Age, a period of earth cooling and climate instability that lasted from around the 1300's to the mid 1800's (for more on this climatic episode, I recommend Brian Fagan's book The Little Ice Age: How Climate Made History 1300-1850).

Location 4: A view of the glacier and an older lateral moraine (arrow) on the other side of the valley.

Location 5: Further downstream are thick glacial deposits. The river has incised or cut through these sediments. As a result the deposits form flattish plateaus or terraces that hug the mountain slopes. Village Dugtu, where we stayed, has been built on top of one such glacial terrace. The arrow in the top picture points to an exposure of these glacial deposits. A close up of this deposit is seen in the bottom picture. Notice the extremely ill sorted texture. Such ill sorted sediment deposited by glaciers is called Till. Large boulders are mixed in with  gravel, pebbles and much finer sized rock flour (the light to brown colored matrix).

Location 6: Another exposure of a glacial deposit near Dugtu. Again, notice the ill sorted deposit. However, at the top is a well sorted pebbly layer. This suggests deposition in more vigorous flowing water. Glacial retreat from time to time would have resulted in the establishment of a fluvial regime and deposition in these streams. These deposits may be a few hundred to several thousand years old.

Location 7: The glacial terrace on which village Dugtu is built is seen in the lower right corner. Farther away is village Philam built on the thick fluvio-glacial deposits of a tributary glacier originating in the range east of Dugtu. At village Dugtu, the east flowing river Dhauliganga makes a sharp southerly turn. The river has cut through these deposits and the slopes of the valley are thickly forested suggesting the great antiquity of these deposits.

Location 8: A nice view of glacial deposits south of village Baun along a smaller tributary of the  Dhauliganga. Notice the waterfall!

Location 9: A walk right through these thick fluvio-glacial deposits along a forested section of the valley slope. Again, notice the ill sorted nature of the deposits. Glacier are viscous and cannot sort sedimentary particles like water or air can. The result is a jumble of boulder, gravel and rock flour.

Location 10: Another cliff made up of fluvio-glacial deposits. I'm calling the deposits east of Dugtu as fluvio-glacial, since I observed intervals which show layering. This suggest deposition in water, either in streams or in melt water lakes and ponds that form in front of glaciers.

Location 11: A thick sequence of fluvio-glacial deposits along the Dhauliganga river. If you zoom and pan the satellite image you can recognize these terraces  southwards almost up to the village of Baaling.

I did not observe such deposits south of Baaling. However, there are smaller glaciers, such as the Naagling glacier, originating in the ranges on either side of the Dhauliganga. There would be smaller deposits scattered in these tributary valleys.

I have been vague about how old these deposits could be. If we assume that the Panchachuli glacier would have attained its maximum extent in the Pleistocene during the Last Glacial Maximum about 20,000 years ago, then the deposits furthest away from the present location of the glacier would be the oldest. As the glacier recedes one should find younger and younger deposits closer to the active glacier.

A study by Dirk Scherler and colleagues in the Garhwal Himalaya found such a pattern. They studied deposits of the prominent Jaundhar Glacier and the Bandarpunch Glacier in the Tons Valley. I've posted below a map showing the interpreted ages of deposition of glacial sediments.

 Source: Scherler et. al. 2010

Notice how the oldest deposits are further away from the present location of the glaciers (eastern most extremity of the map). These oldest deposits point to the maximum extent of the glacier that was reached in the Pleistocene during the Last Glacial Maximum.  However, the decreasing ages of the deposits upstream aren't the result of a uniform recession of the glacier. Instead, they point to several glacial episodes during which the glacier advanced, then receded, and then advanced again during the Holocene. Their data shows five such episodes of glacial growth dated to approximately 16 ka (ka = thousand years ago), 11-12 ka, 8-9 ka, 5 ka and less than 1 ka.


It turns out that the climate history of the Holocene is not one of uniform warming since the end of the last glacial period. The earth has gone through several minor cooling phases during the Holocene. The well known Younger Dryas Event around 12.9 -11.7 ka is one example.  Some studies suggest cooling episodes around 8.2 ka  and around 4.2 ka . And there is the Little Ice Age during the last millennium.

Another climate dynamic is fluctuating monsoon strength through the Holocene. The authors don't favor the explanation that these periods of glacial growth were triggered by global cooling events.  They argue that glacial growth corresponds to small phases of increased monsoon strength interrupting a longer trend of decreasing monsoon strength. More moisture means more snow and glacial growth. Since the long term trend in this part of the world is one of decreasing monsoon strength, every successive phase of glacial growth was smaller than the previous, resulting in younger and younger deposits upstream. The Little Ice Age deposits (which were likely driven by global cooling and not necessarily increased precipitation) mark the last major phase of glacial growth.

How are these deposits dated? Scherler and colleagues use a technique known as cosmogenic nuclide dating. This technique is one way to date the timing of surface exposure. Glaciers carry rock debris. These form a layer below the moving ice. When the glacier recedes the rock debris is deposited as a moraine or as an erratic boulder. It is exposed to the atmosphere and starts getting bombarded by cosmic rays. Energetic cosmic ray neutrons falling on atoms of minerals like quartz results in spallation reactions. This means that the collision of neutrons is energetic enough to fragment the nucleus. Oxygen bound up with silicon in the mineral quartz gets converted to an isotope of Beryllium (10Be). The amount of nuclides generated this way is proportional to the length of exposure. By measuring the amount of 10Be and comparing it with other isotopes, an 'exposure age' is estimated. This is essentially the age of glacial recession and the deposition of glacial sediment.

Samples have to been selected carefully for this method to give a true estimate of surface exposure and deposition. Care must be taken to avoid sampling rocks that have been repeatedly buried and exposed. Rocks which show signs of being subjected to prolonged glacial erosion are selected since  erosion will remove outer shells of material that may have accumulated nuclides during an earlier period of exposure.  Debris with a polished surface or with striations and grooves generally suggest subglacial transport and prolonged glacial erosion and are preferred samples.

 The figure below taken from the same study shows the reconstructed glacial extents using exposure dates of the moraine sequences in the upper Tons Valley.

Source: Scherler et. al. 2010

Such dating of glacial deposits at other locations in the Garhwal Himalaya (ref) tell a similar story of glacial growth and decay over the Holocene. And what about the Pleistocene? Is there evidence of older glacial cycles in the Himalaya? There are many studies that have identified glacial phases during the Pleistocene as well. For example, in northwest Garhwal, the Bhagirathi Glacial Stage has been dated to 63 ka (ref). And in the Ladakh Himalaya the oldest glacial stage has been dated to 430 ka (ref). Pleistocene ice ages have impacted glacial dynamics in the Himalaya too although more work needs to be done to understand the specific mechanisms of glaciation.

Location 12: Its back to the Dhauliganga valley floor. This moraine ridge (arrows) may be the remnant of an older terminal moraine. It is located about 2 kilometers downstream of the glacier.

The Panchachuli and other glaciers in the Kumaon region to the east of the Garhwal will also have their own history of past glory and recession. How much of the retreat of the Panchachuli and other Kumaon glaciers due to recent global warming?  And what is its fate? Hopefully, someone will study them with more precision in the future.

Papers- Precambrian Crustal Evolution Of Peninsular India

Over the last year or so I've collected quite a few papers on the subject of Precambrian crustal evolution and sedimentary basins of Peninsular India. I'm sharing the list with links. Many of them are available open access from various outlets.

I got my teeth cut in field geology and carbonate sedimentology during my M.S. thesis research. This involved mapping a small area of the Mesoproterozic Cuddapah basin in South India.  Peninsular India is a vast repository of these Precambrian rocks. These papers provide very interesting perspectives on various aspects of their geology. Perhaps the big leap in the past decade or so has been -finally!- the increased availability of accurate geochronology that has made it possible for geologists to start piecing together their complex polyphase history.

1) Precambrian Crustal Evolution of Peninsular India: A 3 billion year odyssey ;  Joseph G. Meert,, Manoj K. Pandit, Vimal R. Pradhan, Jonathan Banks, Robert Sirianni, Misty Stroud,Brittany Newstead, Jennifer Gifford

2) Proterozoic orogenic belts and rifting of Indian cratons: Geophysical constraints ; D.C. Mishraa, M. Ravi Kumar

3) The Archean and Proterozoic History of Peninsular India: Tectonic Framework for Precambrian Sedimentary Basins in India; Joseph G. Meert and Manoj K. Pandit

4) Precambrian Basins of India: Stratigraphic and Tectonic Context: Rajat Majumdar and Patrick G. Eriksson eds.- Collection of Paper from the Lyell Collection Geological Society of London Memoirs : Behind Paywall

5) An overview of the Palaeoproterozoic geology of Peninsular India,and key stratigraphic and tectonic issues: Dilip Saha and Rajat Mazumdar

6) Morphodiversity, complexity and macroevolution: Revealed by the megascopic life of the Palaeo-Neoproterozoic Vindhyan Supergroup, India: Poornima Srivastava

7) Stratigraphy and correlation of the Neoproterozoic deposits of central and western India: An overview: S. Kumar

8) The Central India Tectonic Zone: Geophysical perspective on continental amalgamation along a Mesoproterozoic suture:  K. Naganjaneyulu and M. Santosh

Happy reading!