Rimkhim-Sumna- Geologists’ Delight

By- Colonel Satish Singh Lalotra

A combination of toughness and fascinating beauty with captivating surroundings, full of peace and tranquillity all over, the mighty Himalayas attains a unique and significant status amongst the mountain chains in the world. Besides attaining the moniker ---‘Roof of the world ‘or the proverbial ‘Third pole’ these mountains are choc-a-bloc with exotic beauty, unparalleled varied wealth of natural resources to include minerals and crystal-clear water and multitude of flora and fauna.

The quintessential Himalayas thus have been the cynosure of people from all fields due to its singular capability of providing something or the other to all the above mentioned in whatever quantity. Quite naturally, the vast treasure of varied rocks and minerals occurring in the Himalayas had been attracting the attention of geologists too for over a century. Geologists from all over the world in all fields of specialization have contributed immensely on a large variety of themes in different parts of the Himalayas.

Now the geologists are focusing on a particular region of Garhwal Himalayas. During one of my visits surprisingly on reaching Sumna after a straight climb from ‘Girthi Dobala’ I found encampment of doctoral students from the ‘Department of earth sciences’ university of  Roorke who had come there for their geological field investigations in this ‘Sumna- Rimkhim’ section. The first thing which I noticed on reaching Sumna is the changed texture of the terrain that is visible on its mountain sides giving a look of pre-historic times. Certain portions of the mountains carried a view as if they wore the imprints of sea waves.

That is quite queer in such a wind-swept high-altitude region of Garhwal Mountains. One curiosity led to another when I was informed that the area where we were interacting with the research fellows formed part of ‘Tethyan Garhwal’ or ‘Tethys Himalayas’, which was supposed to be under the prehistoric ‘Tethys Sea’ also called as the ‘Tethys Ocean’. This was a prehistoric ocean during much of the Mesozoic era and early ‘Cenozoic’ era located between the ancient continents of ‘Gondwana’ and ‘Laurasia, before the opening of the Indian and Atlantic oceans during the Cretaceous period.

The term ‘Tethys Himalayas’ was introduced for the first time in 1935 for the fossiliferous occurrence in this part of Garhwal Mountains. Apparently, the team  of  doctoral level students were busy in carrying out  a  series of palynological tests for processing rock samples. Palynological tests are primarily conducted on dust particles or other remnants of ‘particulate matter’ that come to settle down on the rock surfaces or the mountain sides which a geologist carries out to study in order to ascertain the life, environment and energetic conditions that produced  them. It is a science that studies contemporary and fossil remains including pollen, spores, orbicular together with particulate organic matter (POM) in sedimentary rocks, which ‘Sumna ‘was abundant with. 

On my query if this area of Sumna was submerged under sea, these students were quick to reply that way back in  1974  Geological field surveys had confirmed the presence of remains of trilobite and some minute languid brachiopods in general area Sumna and Rimkhim. Now for a layman a ‘trilobite’ and a ‘Brachiopod’ are a kind of early animals of which our knowledge of them has been gained from  the study of their fossils, usually the hard impressions left of their shells after burial in sediment that subsequently hardened into a rock. That was proof enough of this area of Garhwal mountains once submerged in the prehistoric ‘Tethys Ocean millions of years ago.

Like many early invertebrate animals (born without a spinal cord) living today, including crustaceans, spiders, and insects, trilobites were Arthropods, belonging to the phylum Arthropoda. In addition to the above, the first fossil floral occurrence was recorded in the year 1974 of Branched algae in this general area of Sumna –Rikhim.    

The Litho-strategraphic units (group of rocks identified as per their formation, age and type of formation) erected and designated by earlier workers put the age of these rocks at Sumna –Rimkhim in the category of Cambrian to Silurian  age.  As per Geological studies Cambrian age and Silurian age corresponds to approximately 538.8 million years ago and ending at 485.4 million years ago respectively. As per certain doctoral research  papers  as late as late 90s twenty genera and sixty-seven species of acritarchs have been identified in the general area of Sumna-Rimkhim.

Acritarchs are what is known as a polyphyletic group, meaning  that they probably include some  organisms  that are similar but not closely related to each other.   In  addition  to the above there have been a  preponderance of traces of Boron (Ba) elements  in  many  of the rock fossils found in the Sumna –Rimkhim section of this Tethys Himalayan region of eastern Garhwal. Traces of Boron lend credence to the fact that here thrived a very active marine life. I  was  reminded of this area having a geological importance way back in 1991 while still in service and was prompted to go once again along the Girthi Ganga axis. It is true that the Himalayas never ceases to surprise even the most disinterested of a traveller. For every traveller of diverse tastes this range has got something in its innermost recesses to keep you occupied.