Geochronology and Geochemistry of the Late Cretaceous to Paleocene Intrusions in East Gangdese,Lhasa,Tibet and Their Tectonic Significances

In this study, we determined the granite ages in the middle to east Gangdese batholith. Zircon ages from these granites are 57.6-68.7 Ma, indicating that intrusions were formed in the Late Cretaceous to early Paleocene. The large-ion lithophile elements are highly enriched, whereas some high-field-strength elements are depleted. The Sr-Nd-Pb isotopic characteristics are similar to those of the Dianzhong volcanics in the Linzhou Basin, indicating the same origin and tectonic environment. The samples show positive εHf（t） values that are slightly lower than the values for the Linzizong volcanics, the Quxu intrusion, and other intrusions in middle Gangdese. We conclude that our samples, the Linzizong volcanics, and most main-collisional intrusions are derived from the same source with different ratios of crust and mantle input. On the basis of geological, geochemical, geochronological, and isotopic information, we conclude that the Late Cretaceous to Paleogene evolution of Gangdese can be divided into three stages. First, the collision began at 70-60 Ma, the same time as rollback of the Tethys Ocean slab. Second, during 60-50 Ma, slab breakoff triggered upwelling of the asthenosphere. Third, after 50 Ma, the Tethys Ocean slab＇s effect disappeared and the interaction between Indian and Asian crusts began influencing magmatism in Gangdese.

Genetic Contribution of Paleopolyploidy to Adaptive Evolution in Angiosperms

Ancient whole-genome duplications (WGDs or polyploidy) are prevalent in plants, and some WGDs occurred during the timing of severe global environmental changes. It has been suggested that WGDs may have contributed to plant adaptation. However, this still lacks empirical evidence at the genetic level to support the hypothesis. Here, we investigated the survivors of gene duplicates from multiple ancient WGD events on the major branches of angiosperm phylogeny, and aimed to explore genetic evidence supporting the significance of polyploidy. Duplicated genes co-retained from three waves of independent WGDs (～120 million years ago [Ma], ～66, and <20 Ma) were investigated in 25 selected species. Gene families functioning in low temperature and darkness were commonly retained gene duplicates after the eight independently occurring WGDs in many lineages around the Cretaceous-Paleocene boundary, when the global cooling and darkness were the two main stresses. Moreover, the commonly retained duplicates could be key factors which may have contributed to the robustness of the critical stress-related pathways. In addition, genome-wide transcription factors (TFs) functioning in stresses tend to retain duplicates after waves of WGDs, and the coselected gene duplicates in many lineages may play critical roles during severe environmental stresses. Collectively, these results shed new light on the significant contribution of paleopolyploidy to plant adaptation during global environmental changes in the evolutionary history of angiosperms.

A Transcriptional Network Promotes Anthocyanin Biosynthesis in Tomato Flesh

Dietary anthocyanins are important health-promoting antioxidants that make a major contribution to the quality of fruits. It is intriguing that most tomato cultivars do not produce anthocyanins in fruit. However, the purple tomato variety Indigo Rose, which has the dominant Aft locus combined with the recessive atv locus from wild tomato species, exhibits light-dependent anthocyanin accumulation in the fruit skin. Here, we report that Aft encodes a functional anthocyanin activator named SlAN2-like, while atv encodes a nonfunctional version of the anthocyanin repressor SlMYBATV. The expression of SlAN2-like is responsive to light, and the functional SlAN2-like can activate the expression of both anthocyanin biosynthetic genes and their regulatory genes, suggesting that SlAN2-like acts as a master regulator in the activation of anthocyanin biosynthesis. We further showed that cultivated tomatoes contain nonfunctional alleles of SlAN2-like and therefore fail to produce anthocyanins. Consistently, expression of a functional SlAN2-like gene driven by the fruit-specific promoter in a tomato cultivar led to the activation of the entire anthocyanin biosynthesis pathway and high-level accumulation of anthocyanins in both the peel and flesh. Taken together, our study exemplifies that efficient engineering of complex metabolic pathways could be achieved through tissue-specific expression of master transcriptional regulators.

Recognition of trench basins in collisional orogens:Insights from the Yarlung Zangbo suture zone in southern Tibet

Trench basin,as an important sedimentary repository in oceanic subduction zones,documents faithfully the evolution of paleodrainage and paleogeographic information.Because of the frequent intense deformation during and after deposition,the recognition of trench-basin strata in orogenic belts is quite challenging.Several trench-fill deposits have been identified from the Yarlung Zangbo suture in southern Tibet,which can be classified into two types based on major differences in formation timing and tectonic setting.The first type developed during subduction of the Neotethyan oceanic slab in the Cretaceous(e.g.,the Jiachala,Rongmawa,and Luogangcuo formations),and the second type developed during the initial stage of the India-Asia collision in the Palaeogene(e.g.,the Sangdanlin-Zheya formations).The former was originally deposited on the subducting oceanic crust and then accreted as tectonic slices into the subduction complex;the latter was deposited unconformably on the continental margin of the subducting Indian plate and then involved in the subduction complex during the continental collision.Typical lithologies of trench-basin fills include abyssal chert,siliceous shale,silty to sandy turbidites,debris flows deposits,and slump deposits without carbonate.Detritus feeding these basins were chiefly from the uplifted terrane in the upper plate.This paper summarizes the geological features of trench basins developed in southern Tibet and proposes criteria for recognizing trench-basins in collisional orogens.

Sedimentology and sequence stratigraphy of the Nkporo Group(Campanian-Maastrichtian),Anambra Basin,Nigeria

Integration of sedimentologic and sequence stratigraphic interpretations of the Nkporo Group has provided the basis for a basin-wide framework for prediction of potential source,seal and reservoir rocks in the Anambra Basin,Nigeria.Lithofacies and biostratigraphic data show that the Nkporo Group in the Anambra Basin contains three main facies associations(fluvio deltaic facies,estuarine central basin/shallow shelf facies and estuarine channel fill facies) that determine the reservoir containers,flow units and seals.The units are arranged to form two stratigraphic sequences represented by the Nkporo Shale-Owelli Sandstone and Owelli Sandstone-Enugu Shale successions,respectively.The transgressive systems tract in each sequence comprises coarse grained fluvio deltaic sandstone and an overlying open marine black carbonaceous mud rock.The highstand systems tracts comprise delta front deposits with average porosity,permeability and net-to-gross values estimated in the ranges of 30%,3000 md and 0.9,respectively.The fluvio deltaic and delta front facies which are encased in organically rich estuarine central basin/shallow shelf mud rocks are likely the potential reservoirs.Trapping capacity is enhanced by the presence of several N-S trending normal faults,and other microstructures related to the post-Santonian tensional regime in the Benue.The new information presented in this paper on potential seal,source and reservoir lithofacies within the Nkporo Group should serve as a useful contribution to the geological modelling of reservoirs within the Late Cretaceous-Paleocene succession in the Anambra Basin.