Taphonomy of a Baurusuchus (Crocodyliformes,Baurusuchidae) from the Adamantina Formation (Upper Cretaceous,Bauru Basin), Brazil: Implications for preservational modes,time resolution and paleoecology

Upper Cretaceous vertebrate accumulations from the Adamantina Formation are known due to their high taxonomic diversity. On the other hand, taphonomic analyses still are rare, limiting the understanding of processes related to the biostratinomic and fossildiagenetic histories of this lithostratigraphic unit. In 2005, fossils were collected from an outcrop located at Jales municipality, state of São Paulo, southeastern Brazil. From this outcrop, a well-preserved Baurusuchus was recovered, which displays a peculiar set of taphonomic signatures. This paper identifies and interprets taphonomic features of a specimen of Baurusuchus (Crocodyliformes, Baurusuchidae; UFRJ DG 418-R) from the Adamantina Formation (Upper Cretaceous of the Bauru Basin), in Jales municipality, state of São Paulo. Brief taphonomic comparisons with other specimens previously studied (crocodiles and dinosaurs) and a lithofaciological analysis of the outcrop were undertaken in order to enhance the knowledge of the stratigraphy and paleoenvironment and improve the time resolution for the Adamantina Formation in the region of Jales. Furthermore, paleoecological data were interpreted based on the taphonomic analysis.The fossil is composed of an articulated segment of vertebral column, ribs, part of the pelvic girdle and gastralia. There is no hydraulic equivalence between both the specimen of Baurusuchus and the size of quartz grain predominant in the fossiliferous layer, suggesting death in situ or short transport as a “water carcass”. Teeth marks identified on the pubes were assigned to a small/juvenile baurusuchid crocodyliform or a theropod dinosaur. The repositioning of some elements (ribs and dorsal osteoderms) is suggestive of mummification. Desiccation marks were observed and attributed to the stage 1 of weathering. These features suggest subaerial exposure of the carcass prior to burial, however, probably after the mummification. On the other hand, the subaerial exposure was short, because the individual was not fully disarticulated. Furthermore, the degrees of articulation and preservation of the specimen nullify the hypothesis of reworking.Lithofaciological and taphonomic analyses suggest a well-drained floodplain as the burial environment and an arid or semi-arid climate in the region of Jales outcrop. In addition, the taphonomic signatures seem to indicate a time resolution about 10⁰–10⁴ years for the layer where the crocodyliforms were collected, but it seems to have, within this time limit, temporal-mixing among terrestrial crocodiles and dinosaurs collected from the same layer, suggesting time-averaging in this outcrop.     

Impacts of Coastal Reclamation on Natural Wetlands in Large River Deltas in China

Little information is available on the impacts of coastal reclamation on wetland loss in large-river deltas at a regional scale.Using remote sensing data of coastal wetland and reclamation in four deltas in China from 1978 to 2014, we tracked their continuous area changes in four periods: 1978–1990, 1990–2000, 2000–2008, and 2008–2014. The areal relation between wetland loss and reclamation was quantified and used to identify coastal reclamation mode intensity coupled with another three indicators: reclamation rate,accretion rate and land-use intensity of coastal reclamation. The results showed that coastal reclamation driven by economic development reduced, or even reverse the original growth of delta which was determined by the offset between wetland acceleration rate and wetland loss rate. Generally, the area of reclamation showed a positive linear correlation with the area of wetland loss. The findings imply that human activities should control reclamation rate and intensity to alleviate total wetland loss and maintain wetland ’net gain’.Inappropriate coastal reclamation modes can magnify total wetland loss;therefore, coastal reclamation with a slow increment rate and low impervious surface percent is of great importance for sustainable development in future coastal management.     

黄陵穹隆周缘岩溶水流系统特征及成因

岩溶水流系统特征研究有助于地下水资源的合理评价和开发利用。借鉴水文学的研究方法,统计并量化了典型岩溶水流系统的空间特征以及其水文动态响应、温度场和电导率特征。划分了扇状、树枝状、平行状、梳状4种地下水系来综合反映岩溶水流系统的地表-地下岩溶特征,前两者主管道垂直于地层走向,构造裂隙起汇水作用,后两者主管道平行于地层走向,层面裂隙起汇水作用。黄陵穹隆西北翼、西翼和南翼以平行状和树枝状为主,东翼和北翼则以扇状水系和平行状水系为主。不同地下水系结构的形成及区域差异与含水系统和水系的空间关系和级次性密切相关,并表现出不同的动态特征。扇状和平行状岩溶水流系统对降雨响应最为敏感,而梳状水系岩溶水流系统响应和衰减过程最慢;基于岩溶地下水温度与出露高程和循环深度显著相关的关系建立了鄂西山区地下水温度线。这一基础性研究可为岩溶地下水流系统研究和当地工程实践提供一定的理论支持。     

上扬子晚古生代海相地层锶同位素曲线的LOWESS拟合

目前仍难以有一种具体的函数关系来描述随时问或随地层厚度变化的地质数据,L0wESS方法被证明是拟合这类数据的较为有效的方法.采用LOWESS方法对我国上扬子地区晚古生代98个海相碳酸盐的锶同位素数据进行科学的拟合,使拟舍得出的曲线具有更好的全球可对比性,从而提高我国锶同位素地层学的研究水平,并使之与相应的国际研究接轨.同时,还从数学角度讨论参数回归和非参数回归的区别,并对影响拟合结果的两个参数和误差范围进行讨论.     

碧口古陆周边锰矿找矿分析

前震旦系碧口群,属四川古陆核西北缘,中新元古代发育的岛弧型建造,经晋宁运动碰撞拼贴,组成扬子地台的一部分,本身固结成为古陆.在其周边及东部成带分布了含锰岩系.目前各含锰矿带上的锰矿床,具体层位归属有蓟县纪、震旦纪、寒武纪等之不同认识.经分析研究认为,含锰岩系均属前震旦纪摩大岭复背斜褶皱带(即碧口古陆)之上的盖层型震旦寒武纪沉积,大致应为同一时代,即晚震旦世.由于各带所处地质构造背景、沉积环境的不同,锰矿特征明显有异,南含锰矿带临接扬子地台,为弱还原地质环境相对稳定,以优质锰矿类型为主;北含锰矿带紧邻秦岭地槽,凹陷较深为还原环境,以高磷锰矿为主.在该带含锰岩系的构造岩性有利部位,易形成风化淋积型锰矿床.故在寻找锰矿过程中,应区别对待,注意优质锰矿的辨认,并对本区锰矿找矿标志及找矿方向提出建议.     

水资源开发利用引起的环境负效应——以玛纳斯河流域为例

通过对玛纳斯河流域环境负效应研究,确定了水资源开发利用过程中引起环境负效应的制约因子,引入地下水动态均衡方法进行半定量分析,明确地下水量的变化为引起环境负效应的直接因素,为定量进行水资源综合开发与利用、防止环境负效应的产生提供方法和依据。     

黄河山东段南北展宽区的经济现状及发展对策

20世纪70年代由于防洪、防凌的需要,黄河两侧修建了南、北展宽区,受防洪的限制,展宽区内群众的经济发展相对落后。小浪底水库建成运用后,南北展宽区失去其防洪作用,该文分析了南北展宽区内经济现状和资源的优劣势,针对如何利用现有条件就资源开发、优势互补等方面提出了设想和建议。     

长江中下游地区地下水卤素元素的形成及其分布规律

本文以丰富的实际资料，论证了地下水的卤素元素（F、Cl、Br、I）的形成、含量及其分布规律与含水介质成分、上覆岩土性质、地下水退流条件、氧化还原环境、地下水矿化度之间的关系。根据江汉平原东部区和鄱阳湖区地下水中Br、I元素的调查研究结果及它们形成的控制因素与分布规律，结合长江三角洲南部区水文地球化学环境条件分析对比，指出该区是一个形成Br、I矿泉水的有利地区。     

The flood of the Nenjiang river and the Songhua river in 1998 and the comprehensive management of the river basins

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