Meteoritic and bedrock constraints on the glacial history of Frontier Mountain in northern Victoria Land, Antarctica

In 2001, a small H4 chondrite, Frontier Mountain (FRO) 01149, was found on a glacially eroded surface near the top of Frontier Mountain, Antarctica, about 600 m above the present ice level. The metal and sulphides are almost completely oxidized due to terrestrial weathering. We used a chemical leaching procedure to remove weathering products, which contained atmospheric ¹⁰Be and ³⁶Cl in a ratio similar to that found in Antarctic ice. The FRO 01149 meteorite has a terrestrial age of 3.0 ± 0.3 Myr based on the concentrations of the cosmogenic radionuclides ¹⁰Be, ²⁶Al and ³⁶Cl. This age implies that FRO 01149 is the oldest stony meteorite (fossil meteorites excluded) discovered on Earth. The noble gas cosmic ray exposure age of FRO 01149 is ~ 30 Myr. The meteorite thus belongs to the 33 Myr exposure age peak of H-chondrites.The bedrock surface on which FRO 01149 was found has wet-based glacial erosional features recording a former high-stand of the East Antarctic ice sheet. This ice sheet evidently overrode the highest peaks (> 2800 m a.s.l.) of the inland sector of the Transantarctic Mountains in northern Victoria Land. We argue that FRO 01149 was a local fall and that its survival on a glacially eroded bedrock surface constrains the age of the last overriding event to be older than ~ 3 Myr. The concentrations of in-situ produced cosmogenic ¹⁰Be, ²⁶Al and ²¹Ne in a glacially eroded bedrock sample taken from near the summit of Frontier Mountain yield a surface exposure age of 4.4 Myr and indicate that the bedrock was covered by several meters of snow. The exposure age is also consistent with bedrock exposure ages of other summit plateaus in northern Victoria Land.     

Reef margin collapse, gully formation and filling within the Permian Capitan Reef: Carlsbad Caverns, New Mexico, USA

An area of reef margin collapse, gully formation and gully fill sedimentation has been identified and mapped within Left Hand Tunnel, Carlsbad Caverns. It demonstrates that the Capitan Reef did not, at all times, form an unbroken border to the Delaware Basin. Geopetally arranged sediments within cavities from sponge–algal framestones of the reef show that the in situ reef today has a 10° basinwards structural dip. Similar dips in adjacent back-reef sediments, previously considered depositional, probably also have a structural origin. Reoriented geopetal structures have also allowed the identification of a 200-m-wide, 25-m-deep gully within the reef, which has been filled by large (some  >15 m), randomly orientated and, in places, overturned blocks and boulders, surrounded by finer reef rubble, breccias and grainstones. Block supply continued throughout gully filling, implying that spalling of reef blocks was a longer term process and was not a by-product of the formation of the gully. Gully initiation was probably the result of a reef front collapse, with a continued instability of the gully bordering reef facies demonstrated by their incipient brecciation and by faults containing synsedimentary fills. Gully filling probably occurred during reef growth, and younger reef has prograded over the gully fill. Blocks contain truncated former aragonite botryoidal cements, indicating early aragonite growth within the in situ reef. In contrast, former high-magnesian calcite rind cements post-date sedimentation within the gully. The morphology of cavern passages is controlled by reef facies variation, with narrower passages cut into the in situ reef and wider passages within the gully fill. Gully fills may also constitute more permeable zones in the subsurface.     

Palaeoclimatic cycles, global environmental changes and new glacial periods induced by the impact of extraterrestrial bodies

In terms of Earth-Sun geometry, the Milankovitch theory has successfully explained most of the cyclic palaeoclimatic variations during the history of the Earth, especially in the Quaternary. In this paper, the authors suggest that the impact of extraterrestrial bodies on the Earth may be another mechanism to cause palaeoclimatic cycles, global environmental changes and new glacial periods. Based on geological and geochemical records in the boundary layers produced by six huge Cenozoic bolide-impact events (65, 34, 15, 2.4, 1.1, 0.73 Ma B.P.), including those at 34, 15, 1.1 and 0.73 Ma B. P. which are represented by four famous tektite-strewn fields, the process and mechanics of palaeoclimatic cycles and global environmental catastrophes induced by extraterrestrial impact are discussed in detail. Impact-generated dust, soot and aerosol floating in the stratosphere could result in short-term (<1 year), rapid drop in temperature immediately after impact. Through self-regulation of the Earth’s climate system, the temperature at the surface slowly went up within 100a and maintained stable for a long time at 250K. If there were no other factors leading to the break-down of the newly-established equilibrium, a new glacial pound would be initiated. Estimating from the thickness of δ¹³C and δ¹⁸O anomalies in sediments across the impact boundary layer and deposition rate, the duration of two stages of the palaeoclimate cycle in the form of cold weather—greenhouse effect—normal weather was 10⁴ – 10⁵a, respectively. The conclusion deduced from the above model is supported by palaeotemperature change recorded by oxygen isotope in sediments across the impact boundary layer. The study was granted by the Scientific and Technological Bureau of Resources and Environment, Chinese Academy of Sciences (KZ952-J1-031) and the National Natural Science Foundation of China.     

菊花石及其他两种放射状形貌对比研究

通过天青石菊花石形貌与红柱石菊花石钟乳石截面放射状形貌的对比,找出它们形成的共同规律,并从形貌细节差异上分析了其形成机制和条件的差别。     

有毒甲藻Coolia monotis Meunier的研究 Ⅰ.甲板形态

经NaClO解离处理,得到Cooliamonotis的甲板板式如下：Po,3’,7”,6c,6s,5”’,2””。电镜照片显示,其甲片表面光滑,分布有圆形或椭圆形的小孔,此外无其他纹饰。     

海洋腹毛目纤毛虫—束状全列虫的形态学以及与相近种的比较

报道了一种采自青岛沿岸养殖水体的自由生纤毛虫——束状全列虫。文中对其形态学作了重新描述,利用蛋白银技术研究了其纤毛图式,并与其它相近种作了比较。     

南极威德尔海冰层下的砂壳纤毛虫

本文依据壳体的形态特征,对采自南极威德尔海冰层下的１１种砂壳纤毛虫进行了分类学描述（包括一未定种拟波膜虫Ｐａｒｕｎｄｅｌａｓｐ．）,它们是柱状拟铃虫、船生孔环虫、亚圆原波纹虫、杯状波缘杯虫、梵氏波缘杯虫、简单原纹虫、短原纹虫、变形条纹虫、针状平顶虫和截短角口虫