The geography and timing of genetic divergence in the lizard Phrynocephalus theobaldi on the Qinghai-Tibetan plateau.

The Qinghai-Tibetan Plateau (QTP) represents one of the earth's most significant physical features and there is increasing interest in the historical generation of biodiversity within this region. We hypothesized that there should be clear geographically coherent genetic structuring within one of the world's highest altitude lizards, Phrynocephalus theobaldi, due to considerable historical population fragmentation in this environment. This was tested using a major mitochondrial DNA (mtDNA) survey and sequencing of two nuclear markers (AME and RAG-1) from P. theobaldi, from across the southern QTP. A Bayesian method (BPEC) was used to detect four geographically structured mtDNA clusters. A Bayesian phylogenetic tree, together with associated dating analyses, supported four corresponding evolutionary lineages with a timing of 3.74-7.03 Ma for the most basal P. theobaldi split and Pliocene splits of 2.97-5.79 Ma and 2.40-5.39 Ma in the two daughter lineages. Himalayan uplift and changes in the Jilong basin may have contributed to these divergences, but uplift of the Gangdese mountains is rejected due to its timing. The nuclear markers appeared to be sorted between the four mtDNA groups, and species delimitation analyses supported the four phylogeographical groups as candidate species. The study contributes to our understanding of biodiversity on the QTP

Tonian deltaic and storm-influenced marine sedimentation on the edge of Laurentia: the Veteranen Group of northeastern Spitsbergen, Svalbard

The Hecla Hoek succession of northeastern Svalbard, Norway, is an ~7 km thick Tonian– Ordovician sedimentary succession that overlies Stenian–Tonian felsic igneous and metasedimentary rocks. The carbonate-dominated upper Tonian–Ediacaran (ca. 820–600 Ma) Akademikerbreen and Polarisbreen groups have yielded important insights into Earth’s Neoproterozoic climate, environment, and biological evolution. However, the underlying siliciclastic-dominated lower Tonian (ca. 950–820 Ma) Veteranen Group has garnered little attention despite the fact that it is remarkably well-preserved and hosts diverse microfossil assemblages. Here, we present the first detailed sedimentological analysis of the Veteranen Group from a continuous ~4.4 km thick stratigraphic section at Faksevågen, Ny Friesland, Spitsbergen. Integrated facies analysis, sequence stratigraphy, and carbonate δ13Ccarb and δ18 Ocarb chemostratigraphy elucidate the early depositional history of the Hecla Hoek basin and provide fundamental paleoenvironmental constraints for future investigations of this succession as an archive of Tonian Earth History. The Veteranen Group records a long-lived deltaic and storm influenced marine sedimentary system that reveals dynamics of Precambrian clastic sedimentation prior to the evolution of land plants. Five asymmetric transgressive-regressive (T-R) sequences within the Veteranen Group thin upwards, providing support for the hypothesis that the contact with the Akademikerbreen Group represents a rift-to-drift transition. This complex record of Tonian deltaic and storm-influenced marine sedimentation along the Laurentian margin strengthens correlation between the Veteranen Group and coeval strata from East Greenland and sets the stage to better understand the Proterozoic tectonic evolution of the North Atlantic–Circum34 Arctic region following the Grenville orogeny

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

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 first time, identification 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. © 2008 Geological Society of America