Question

Symestery and geometry of Sikkim

Answer 1

Step-by-step explanation:

In geometry, an object has symmetry if there is an operation or transformation (such as translation, scaling, rotation or reflection) that maps the figure/object onto itself (i.e., the object has an invariance under the transform). Thus, a symmetrycan be thought of as an immunity to change.

Answer 2

Answer:

In the Darjeeling – Sikkim Himalaya the Main Central thrust (MCT) system has

translated the Greater Himalayan hanging wall rocks over large distances so that

Greater Himalayan rocks are exposed within 7 km of the mountain front. The sub-MCT

Lesser Himalayan duplex is composed of two duplex systems and has a more complex

geometry than in the rest of the Himalayan fold-thrust belt. Within the duplex, a

foreland-dipping component and reactivation of the roof thrust resulted in large

southward translation of the overlying MCT sheets in this region. The growth of the

duplex resulted in a plunge culmination that manifests itself as a broad N-S trending

structural high in this region; this is not a “river anticline” as its trace lies west of the

Teesta river.

A transport parallel balanced cross section constructed across this region

suggests a total minimum shortening of ~502 km (~82%) south of the South Tibetan

Detachment system (STDS). The Lesser Himalayan duplex accommodates nearly half

of this total shortening. In this region, the average long-term shortening rate is

estimated to be ~22 mm/yr. Comparison of available shortening estimates from

different parts of the Himalayan arc makes it difficult to evaluate the primary cause for

the variation in shortening; however, shortening in the Himalayan fold - thrust belt

(FTB) is highest in the middle of the Himalayan arc (western Nepal) and progressively

decreases towards the two syntaxes. Although, the width of the Lesser Himalayan belt

decreases in the eastern Himalaya, the Lesser Himalayan shortening percentage remains

approximately similar to that in both eastern and western Nepal Himalaya, where the

belt is widest. In addition, the shortening accommodated within the Lesser Himalayan

duplex progressively increases from the western to the eastern Himalaya. Thus, the

width of the original Lesser Himalayan basin may have played an important role inpartitioning the shortening in the Himalayan FTB.

The retrodeformed cross section in the Darjeeling – Sikkim Himalaya region

provides insights into the palinspastic extent of the Gondwana basin of Peninsular India,

suggesting that this basin extended ~150 km northward of its present northernmost

exposure in this region.