Searching for stars in compact high-velocity clouds – II     

U. Hopp  R. E. Schulte-Ladbeck  J. Kerp 《Monthly notices of the Royal Astronomical Society》2007,374(3):1164-1168

  相似文献   

四川西部西康群新都桥组碳酸盐岩的锶同位素特征     

曾宜君  黄思静  易同富  郝雪峰  熊昌利  胡作维 《地球科学与环境学报》2007,29(2):126-129

四川西部松潘—甘孜地区广泛分布一套三叠系黑色砂板岩层系,由于其岩性单调、古生物化石贫乏,给该区地层划分、对比带来极大困难。因此,从锶同位素地层学基本原理出发,对甘孜北部西康群新都桥组中薄层状灰岩样品进行了锶同位素组成测定。结果表明,6件样品的N(87Sr)/N(86Sr)分别为0.708688、0.708659、0.708907、0.708223、0.708341、0.708266,平均为0.708514。表明该地层的碳酸盐岩样品可能遭受了不同程度的成岩蚀变,多数样品的锶同位素组成偏离同时代的全球海水锶同位素组成。  相似文献   

豫西狮子坪地区秦岭群中的斜长角闪岩-大理岩组     

杨家喜  王涛  雷泓晏 《地球科学与环境学报》1993,(Z1)

在河南卢氏狮子坪地区的秦岭群中出露一套变质地层,其组成特点与各地已知的秦岭群明显不同,主要岩石类型为斜长角闪岩、透辉斜长变粒岩和含石墨大理岩。在构造迭置关系上这套变质地层位于秦岭群条带状长英质片麻岩层和云母片岩层之上,原始接触关系已不明朗,内部也难以逐层恢复层序,但内部三部分的迭置关系是明确的。作者提出这套变质地层应当作为一个独立的填图单位,进而建立岩组,并认为这可能是一套迭置于秦岭群之上的较新地层,但曾与秦岭群一道遭受了变质变形改造。  相似文献   

关于辽南复州湾本溪群     

范炳恒  沈树忠 《国土资源》1993,(4)

复州湾地区石炭纪早期发展史及地层研究有待深入。本文通过有关岩石和化石内容,讨论了传统本溪组的一些问题,认为本溪组应改称本溪群,它代表自奥陶系石灰岩侵蚀面至砾状灰岩顶面一段沉积地层,砾状灰岩顶面标志——平行不整合面,据岩性组合本溪群分为上下两部分(有待建组)。化石资料修正了本溪组时代相当莫斯科期的观点,提出该区本溪群延续时限自早石炭世晚期(相当纳谬尔A期)或更早至莫斯科期中期(Profusulinella带上限),在区域上本溪群是一个明显的穿时单位。  相似文献   

Chemical evolution of dwarf spheroidal and blue compact galaxies     

Gustavo A. Lanfranchi  Francesca Matteucci 《Monthly notices of the Royal Astronomical Society》2003,345(1):71-85

  相似文献   

河南西峡含化石碎屑龟山组层位层序及时代探讨     

薛松鹤 《河南国土资源》1997,(1)

信阳群龟山组横贯北秦岭南缘及桐柏山—大别山，西延入陕西，为地质结构上的关键层位，部分地段为重要赋矿层位，因其为一套罕见化石的碎屑岩，故对其地质时代看法颇异。近年我队在西峡八庙矿区工作时，在岩石薄片中见有多门类化石碎屑，并作了报道。作者在报道的基础上，吸收前人和近年某些有关信阳群和刘岭组（群）的工作成果，就龟山组的层位、层序及时代进行探讨，并与邻区、邻省的相关层位进行对比：认为含动物化石碎屑的龟山组（周进沟组）与陕西省的牛耳川组及桐柏山—大别山北坡的大部分龟山组及二郎坪群和部分苏家河群的时代大体相当，其时代归属暂置早奥陶世—早泥盆世  相似文献   

唐古拉山中段开心岭群乌丽群的时代定义问题     

刘广才 《青海国土经略》1993,(1)

根据最新区域地质调查的代表剖面,在分析研究下二叠统开心岭群、上二叠统乌丽群的岩性组合特征、沉积类型、古生物面貌的基础上,将二叠系建立5个岩石地层单位和相应的5个生物地层单位,代表栖霞期—长兴期地层层序与生物序列;区内生物性质属特提斯动物群和华夏植物群;青南乌丽与藏北双湖及昌都妥坝属同一含煤建造,成煤期为龙潭中期—长兴期。  相似文献   

The tidal trail of NGC 205?     

A. W. McConnachie  M. J. Irwin  G. F. Lewis  R. A. Ibata  S. C. Chapman  A. M. N. Ferguson  N. R. Tanvir 《Monthly notices of the Royal Astronomical Society》2004,351(4):L94-L98

  相似文献   

陕西蓝田红门寺地区丹凤群构造变形特征     

王翔  张维吉 《地球科学与环境学报》1990,(3)

本文对蓝田红门寺地区丹凤群的变形特征,提出至少经历过三期主要构造变形及混合岩化作用。  相似文献   

Miocene provenance change in Himalayan foreland basin and Bengal Fan sediments,with special reference to detrital garnet chemistry     

Kohki Yoshida  Toru Nakajima  Yuki Matsumoto  Ai Osaki  Lalit Kumar Rai  Jarrett W. Cruz  Harutaka Sakai 《Island Arc》2021,30(1):e12408

Bengal Fan Miocene sediments were collected during International Ocean Discovery Program Expedition 354 and investigated using petrographic and detrital garnet chemistry analyses. The Miocene Siwalik Group, which is composed of sediments deposited in the Himalayan foreland basin, was also analyzed for comparison with the Bengal Fan data for the provenance change during the Miocene. Our petrographic analyses revealed that the Miocene sediments of the Bengal Fan and Siwalik Group consist predominantly of Higher Himalayan Crystalline (HHC)-derived detritus such as chloritoid, staurolite, sillimanite, and/or kyanite, which appear among the accessory minerals. The chemistry of the detrital garnet varies across the stratigraphy; most of the garnet is rich in almandine and poor in spessartine and pyrope. However, pyrope-rich garnet, which is considered to originate from the HHC core (granulite facies), was found in the lower to upper Miocene deposits. The deposition of HHC-derived detrital garnet began before the Middle Miocene (15 Ma) and before the Late Miocene (10–9 Ma) in the Siwalik Group. The Bengal Fan data, by contrast, indicated that pyrope-rich garnet appeared in the Early Miocene (17.3 Ma) and Late Miocene (8.5–6.5 Ma). We conclude that the Bengal Fan sediments record the erosion of the HHC zone since the Early Miocene that appears in the Siwalik sediments. Furthermore, we found that the HHC-derived inputs decreased from the late Middle Miocene (12 Ma) to the early Middle Miocene (10 Ma) in both the Nepal Himalaya foreland basin and the Bengal Fan. The disappearance of the HHC-derived detritus is probably the result of dilution by Lesser Himalayan detritus, which suggests that the Lesser Himalayan zone, which is composed of metamorphosed and unmetamorphosed sedimentary rocks, was uplifted.  相似文献