Trace fossils in middle to late triassic fluvial redbeds,pranhita‐godavari valley,south India

Several morphological varieties of trace fossils abound in Middle and Late Triassic fluvial redbeds in the Pranhita‐Godavari Valley, south India, including Skolithos, Palaeophycus, Taenidium, escape burrows, and a type of trace very similar to ‘small stuffed burrows’ from the Triassic of Greenland. Burrow morphology was influenced by local hydrodynamic conditions. The distribution of burrows was facies controlled; some forms are restricted to channel deposits whereas others occur only in floodplains. Vertical dwelling burrows (Skolithos) occur in both channel and floodplain deposits. Horizontal structures representing deposit feeding (Taenidium) are confined to nondepositional surfaces within parallel‐laminated sandstones having parting lineations that represent catastrophically emplaced sand‐sheets in channels and proximal floodplains. Vertical escape burrows are confined to what were slowly but continually accreting parallel‐laminated sands of channel bars. Horizontal dwelling burrows (Palaeophycus) and ‘small stuffed burrows’ are virtually restricted to the smaller sandsheets of floodplain drainage systems.

The burrow assemblages do not occur as recurrent associations throughout the redbed sequence, and variations in different stratigraphic levels seem to be controlled by minor differences within a broadly similar environment. The entire assemblage has components of both the Scoyenia and Rusophycus ichnocoenoses reported from East Greenland but may be considered as the Scoyenia ichnofacies characteristic of redbeds deposited in extensive floodplains dissected by small streams, even though no Scoyenia individuals are present.     

Commentary

A new ichnotaxon is recognized in the Perkasie Member of the Passaic Formation (Upper Triassic) at the Smith Clark Quarry, Milford, New Jersey. Spongeliomorpha milfordensis is a small trace fossil possessing sharply incised partial wall striations which form a distinctive angle with the axis of the burrow. It is construed as a deposit‐feeding structure possibly formed by aquatic insect larvae along the margin of a lake.     

渤海沿岸临清坳陷堂古5井中三叠统轮藻化石与地层划分对比

在临清坳陷堂古5井发现轮藻化石Stenochara和Stellatochara两属7种,证实该区存在三叠世地层。根据地层层序、岩石地层特征和区域地质资料分析,该区亦应存在下三叠统,并建议参照区域方案将该区中、下三叠统红层划分为刘家沟组、和尚沟组和二马营组。     

Ichnologic note

The brittle star Taeniaster bohemicus was found in association with the trace fossil Asteriacites lumbricalis in the Upper Ordovi‐cian of central Bohemia. Morphological features of the trace, coupled with spatial interrelationships between trace and body fossils, provide evidence that the brittle star represents the trace‐maker of this Asteriacites. The cubichnial burrows probably represent negative phototaxis among the ophiuroids.     

弱硅化腕足类化石酸处理方法的改进

本文介绍了一种获取灰岩中弱硅化腕足类化石的酸处理方法.以四川省布拖县浪珠乡万吨山剖面上奥陶统铁足菲克组近顶部的生屑灰岩为实验对象,通过准备样品、悬吊样品、配酸解液、酸解样品等实验流程,配合遮盖液(如二乙酸纤维素丙酮溶液)的使用,可获得保存精美的、弱硅化的腕足类实体化石,且该化石保存有主突起、铰齿和匙形台等重要的细小结构...     

Vagorichnus,a new ichnogenus for feeding burrow systems and its occurrence as discrete and compound ichnotaxa in Jurassic lacustrine turbidites of Central China

A new ichnogenus, Vagorichnus, is figured and described from Jurassic lacustrine turbidites of the Anyao Formation, Henan Province, Central China. Vagorichnus consists of complex burrow systems composed of discontinuous curved to meandering segments in which irregular networks are formed. The ichnospecies V. anyao covers burrow systems characterized by constricted and irregularly annulated segments, and ridge‐like knobs. Although traces are preserved as hypichnial ridges on the sole of turbidite sandstones, several lines of evidence indicate that these ichnofossils record the activity of a post‐event infauna. Vagorichnus occurs as discrete and compound ichnotaxa. In the latter case, it grades into Gordia and Tuberculichnus. Vagorichnus is interpreted as invertebrate feeding structures (Fodinichnia).     

Ichnologic note

Palaxius salataensis, an anomuran microcoprolite, is described from Cretaceous deposits of the MIT Guyot in the northwest Pacific, about 1500 km southeast of Japan. This is the first report of the ichnogenus in this area and the first report of the ichnospecies in Cretaceous deposits. The range of P. salataensis is thus very long, from Permian to Cretaceous.     

安徽早三叠世巢湖动物群的研究进展:生物面貌、地层分布和古生态学意义*

巢湖动物群主要分布在安徽巢湖及邻近地区下三叠统奥伦尼克阶南陵湖组中上段地层中,以保存大量完整且精美的巢湖龙化石为特点,伴生有鳍龙类、鱼龙形类、鱼类及多门类的海生无脊椎动物。巢湖动物群的研究始于20世纪70年代,近年来基于巢湖动物群中大量新材料的系统研究为二叠纪–三叠纪大灭绝发生之后三叠纪海洋生态系统的快速复苏过程提供了新的依据。本文梳理了巢湖动物群的地质背景、研究简史、生物组合特征、地层分布与时代特征、稳定同位素地球化学等方面取得的进展,并就其群落生态组成进行初步探讨。这项工作对建设巢湖动物群相关国家地质公园、开展科普教育工作、旅游开发等有着积极的意义。     

新疆托克逊晚三叠世昆虫

记述了新疆托克逊晚三叠世昆虫化石14属17种。这一昆虫群代表了我国北方三叠纪昆虫的面貌,也是我国最丰富的三叠纪昆虫群之一。从其生态习性分析,这个昆虫群以生活于水中和岸边环境的种类为主,说明当时托克逊地区为一水域环境,气候也很适宜昆虫的生存。     

Bichordites monastiriensis from the Pleistocene of southeast Jamaica

Bichordites monastiriensis Plaziat and Mahmoudi 1988, produced by burrowing spatangoid echinoids, is figured and described from shallow marine siliciclastic strata of the Pleistocene Old Pera Beds (Coastal Group) of southeast Jamaica. Its occurrence there represents only the second formal recording of this monospecific ichno‐taxon and extends its geographic range from the Mediterranean region to the Caribbean. The spatangoid species that produced this trace fossil is unknown, but, unlike examples from other areas, it is unlikely to be Echinocardium.     

西南极乔治王岛早第三纪遗迹化石

南极乔治王岛始新统化石山组含多种类型遗迹化石,常与鸟类足迹相伴产出。记述的１新遗迹属及所属的５新遗迹种,从遗迹化石形态两侧对称,纵向延伸,缺乏疣足及其它附肢构造等特征看,推测造迹者为软体蠕虫类,很可能属于寡毛纲的动物。这些化石反映了浅水河湖的沉积环境。     

The identification of fossil angiosperm pollen and its bearing on the time and place of the origin of angiosperms

Studies in the 1970's reporting the occurrence of fossil pollen types in the Cretaceous, coupled with surveys of extant pollen morphology of primitive flowering plants, laid the foundation for proposing a Lower Cretaceous origin of angiosperms. Over the last 30 years, morphological, ultrastructural, and ontogenetic studies of both extant and fossil pollen have provided an array of new characters, as well as greater resolution in defining character polarities. Moreover, a range of fossil pollen types exhibiting angiosperm characters occur in low frequency within Triassic and Jurassic sediments. The pollen data provide evidence of a pre-Cretaceous origin of angiosperms. Speciation and extinction rates were likely equal during the Triassic and Jurassic, resulting in the paucity of angiosperm pollen types from different geographic areas in the Atlantic – South American/African rift zone. It was not until the Lower Cretaceous that origination rates exceed extinction rates, resulting in the subsequent diversification of angiosperms and the origin of the eudicots.     

Trace fossils from the Podhale Flysch Basin, Poland - an example of ecologically-based lithocorrelation

Certain ichnogenera from the Podhale Flysch Basin do not occur randomly, but are grouped in distinct horizons, which are useful in mapping. The position of certain tuffite beds proves an approximate isochronism of those trace fossil horizons. Changes of the life conditions, among them especially oxygenation of the sea bottom, were responsible for that ichnologic differentiation. Profuse Occurrences of Taphrhelminthopsis are mainly connected with the presence of lighter, bluish shales, which indicates a well-oxygenated bottom. More distal and frequent sedimentation of turbidites could positively influence the preser-vational potential of the surface forms (very good state of preservation of Taphrhelminthopsis suggests that preservation of surface forms was frequent in the flysch basin), but the O₂ condition was the main controlling factor for the occurrences of ichnofauna. Most discriminating were trace makers of pre-depositional (mud-dwelling) Taphrhelminthopsis , and they were most probably irregular echinoids, while soft-bodied trace makers of pre- and post-depositional Planolites (post-depositional means sand-dwellers) were the most tolerant ones. An increased level of biological activity connected with a shift in the OMZ could have been the reason why Taphrhelminthopsis became so profuse in one period. Concerning preservational problems, some complications in determining pre- and post-depositional forms in the case of composite beds are presented.