Stratigraphic correlation of Cambrian–Ordovician deposits along the Himalaya: Implications for the age and nature of rocks in the Mount Everest region

Abstract

The depositional age and stratigraphic correlations of metamorphosed and variably deformed rocks of Mount Everest are poorly known because of limited recovery of diagnostic fossils. Detailed study of Cambrian and Ordovician strata from along the length of the Himalaya has produced a coherent stratigraphy that stretches from northern India to Tibet. Our work also demonstrates that the North Col Formation rocks (= Everest series), between the Qomolangma and Lhotse detachments of the South Tibetan detachment system, still locally preserve sedimentary textures and primary stratigraphy that match those within Cambrian strata ~1100 km to the west in northern India. This demonstrates a coherency of depositional systems and stratigraphic architecture for Cambrian deposits along much of the Himalaya Tethyan margin. It also allows, for the fi rst time, identifi cation of precise depositional ages of several units in the Everest region, in particular, the Yellow Band carbonate and directly underlying siliciclastic strata, which are both shown to be late Middle Cambrian in age. Detrital zircon data presented herein for a sample from these siliciclastic strata contain a similar age spectrum to those from Middle Cambrian strata in northern India, as well as grains as young as ca. 526 Ma, both of which support the depositional age and continuity of depositional systems along the length of the Himalaya. Highly fractured rocks of the Ordovician lower Chiatsun Group in the hanging wall of the South Tibetan detachment system in Nyalam, 75 km to the west of Everest, correlate with Ordovician strata of the Mount Qomolangma Formation on Mount Everest. Our correlations indicate that the base of the summit pyramid of Everest, the foot of the "Third Step," is composed of a 60-m-thick, white-weathering thrombolite bed. The top of this ancient microbial deposit crops out only 70 m below the summit of Mount Everest.

Proceedings of the 25th Himalaya-Karakoram-Tibet Workshop

“…These very high p values strongly support the assertion of Myrow and others (2009) concerning the detailed correlation of Cambrian strata across the Himalaya to unfossiliferous, relatively high-grade rocks on the slopes of Mt. Everest and adjacent regions.…”

Geochronological, geochemical and Nd–Hf–Os isotopic fingerprinting of an early Neoproterozoic arc–back-arc system in South China and its accretionary assembly along the margin of Rodinia

“…At ∼0.98-0.90 Ga (Fig. 18a), Eastern Cathaysia of the eastern SCB received orogenic detritus from the latest Mesoproterozoic mountain belt that lay in the Prince Charles mountains region of Antarctica (e.g., Myrow et al, 2006Myrow et al, , 2009Boger et al, 2000;Jayananda et al, 2000). At the same time, the Wuyi-Yunkai arc-back-arc system was developed and the Shuangxiwu system continued until ∼880 Ma.…”

“…The final amalgamation along the Wuyi-Yunkai domain is roughly synchronous with the deformation of the East Ghats of India (∼960 Ma) and the northern Prince Charles Mountains of East Antarctica (∼990-960 Ma; e.g., Boger et al, 2000;Jayananda et al, 2000). These relationships, combined with the biogeographic consistency of the eastern SCB with Australia and the late Neoproterozoic tectonic relationship with India (e.g., Wang and Li, 2003;Yang et al, 2004;Myrow et al, 2006Myrow et al, , 2009Wang et al, 2010b), suggest to us that the SCB was situated along the margin of Rodinia between Australia and East Antarctica (e.g., Hoffman, 1991;Yang et al, 2004), as shown in Fig. 17.…”

Cambrian rocks and faunas of the Wachi La, Black Mountains, Bhutan

“…1). The absence of intervening fossil-bearing Cambrian rocks in the Tethyan Himalaya of Nepal and Tibet is likely to be due to metamorphism, as rocks of this depositional age are present in these regions (Brookfield, 1993;Myrow et al 2009). …”

“…The Cambrian System is of special importance in this regard because of its widespread distribution along and across the Himalaya (Hughes & Jell, 1999), and recent work provides the outline of a stratigraphic correlation for Neoproterozoic and Cambrian rocks that stretches from Pakistan to the Everest region of Nepal, and across strike onto the Indian craton (Bhargava, 1998;DiPietro & Pogue, 2004;Hughes et al 2005;Myrow et al 2009Myrow et al , 2010. These correlations have allowed for precise age determination of strata even in the absence of diagnostic fossils , †Author for correspondence: nigel.hughes@ucr.edu and have permitted reinterpretation of the structural relationships across major Himalayan fault systems.…”