南京地区栖霞组的界线和化石分带

南京地区早二迭世栖霞组化石丰富、种类繁多,是我国南方发育最为完整的地区之一。栖霞组最早称栖霞石灰岩(李希霍芬、1882年),泛指南京东郊栖霞山附近五通石英砂岩与龙潭煤系之间的一段海相地层,时代为泥盆纪。其后,经李四光和朱森,李四光,黄汲清,陈旭,李毓尧,李捷和朱森等人不断详细研究,才将船山灰岩与孤峰层之间的一套灰岩层确定为栖霞组范围,自下而上划分为臭灰岩、下硅质层、栖霞灰岩(狭义)、上硅质层四部分,并建立四个筵类和三个珊瑚化石带(见下表)。时代相当于早二迭世。     

苏皖地区的孤峰组

<正> 苏皖地区的孤峰组原称孤峰层,由“孤峰镇石灰岩”一名演变而来。叶良辅、李捷(1924)在安徽泾县孤峰镇进行煤田地质调查时,将相当于黄龙组、船山组及栖霞组的一套灰岩统称为“孤峰镇石灰岩”。孤峰层是朱森、李四光、李毓尧等(1930,1932,1935)重新厘订的,指出孤峰层“为黑色灰质页岩及硅质甚富之灰岩等,间于栖霞灰岩与龙潭煤系之     

安徽巢湖二叠系栖霞组碳酸盐岩斜坡沉积

长期以来,人们均认为下扬子地区广泛发育的栖霞组碳酸盐岩属于浅海碳酸盐岩台地沉积。但以巢湖地区为例研究表明,栖霞组主要为碳酸盐岩斜坡沉积。碳酸盐岩碎屑流沉积物形成了臭灰岩段和顶部灰岩段的层状石灰砾岩,分布于斜坡上部;等深流沉积物形成了上、下硅质层段的砂屑硅质粒泥灰岩,主要分布于斜坡下部。而上、下硅质层段中的钙、硅质页 (泥 )岩属于斜坡远端和盆地沉积;唯有本部灰岩段可能属于浅海碳酸盐岩台地沉积。这一认识不仅突破了传统观念,而且有助于重新认识下扬子板块二叠纪的古地理特征和盆地构造演化。     

南京地区栖霞阶早期环境

<正> 南京地区栖霞组臭灰岩段在含Misellina claudiae带之下,船山组Pseucloschwagerina带之上,广泛分布一层厚0.5—2.5m的页岩夹石灰岩层(以下简称为页岩层)。内含丰富的介形类、苔藓虫、双壳类、腕足类、有孔虫、珊瑚以及藻类等化石。笔者拟从沉积物中的生物标志、物理标志二方面阐明其环境意义。 代表剖面出露在南京城东20km的孔山北坡公路壁,自上而下层序如下:(图1)     

恩施剖面栖霞组下部贫氧-缺氧环境成因模式

我国华南地区二叠系栖霞组沉积了多套富有机碳的暗色岩系,是华南地区油气勘探的潜在烃源岩。其形成主要与水体的氧化还原以及古特提斯海洋洋流系统有关。然而,栖霞期水体的缺氧-贫氧的成因模式还需要更多的地质证据。本文选择湖北省恩施剖面栖霞组下部臭灰岩段钙质页岩及碳酸盐岩夹层为研究对象,开展稀土元素REE、微量元素Th/U比值以及碳酸盐矿物晶格内微量硫酸盐硫同位素组成分析。研究结果表明,栖霞组下部臭灰岩段的下部沉积水体主要为缺氧至贫氧条件,而臭灰岩段上部主要为贫氧至氧化条件。这些缺氧至贫氧沉积主要是由洋流的上涌造成。洋流的上涌将深水环境中缺氧、贫氧的底部水体涌至陆棚斜坡地带,造成斜坡浅水地带形成一个近似倒三角的缺氧-贫氧水体带,从而沉积了栖霞组暗色薄层石灰岩或钙质页岩。     

福建下二叠统栖霞组特征及沉积地理环境探讨

一、序言(代研究简史) 有关福建栖霞组层位的研究工作,可追溯到1930年王绍文创立的“曹远石灰岩”及1935年侯德封等使用的“栖霞灰岩”其均指福建现今划为林地组与文笔山组之间的一套灰岩地层。当时不知其中尚包含有中、上石炭统的黄龙组和船山组层位。至1941年陈旭等在清流沙芜塘采获晚石炭世(竹蜓)类后方告分晓并予划出。到此福建“栖霞灰岩”才名符其实地     

安徽巢湖地区石炭纪-早二叠世碳酸盐岩微相与沉积环境

安徽巢湖凤凰山剖面出露石炭系金陵组(C1j)、和州组(C1h)、黄龙组(C2h)、船山组(C2c)以及下二叠统栖霞组下部臭灰岩段(P1q)等5个含碳酸盐岩地层。本文在野外剖面实测的基础上,对这些碳酸盐岩进行了岩相与微相分析。通过对碳酸盐岩显微薄片的观察分析,共识别出14个微相,分属于干旱近海岸蒸发台地(潮坪)、局限海台地、开阔台地内部浅滩、开阔海台地等4种沉积环境。本文研究结果表明,石炭纪-早二叠世期间,巢湖地区主要为浅海碳酸盐台地环境,期间发生了3次比较大规模的海侵-海退旋回,并间隔有若干次小规模的海平面升降。     

试论梁山段和栖霞灰岩的关系

我国南方下二叠统下部普遍发育一套灰岩,即栖霞灰岩。灰岩之下至二叠系底部,常见一套碎屑岩,有的含煤,有的不含煤,一般称梁山组,也称梁山段或梁山煤系。栖霞灰岩和梁山组（段）同为早二叠世早期沉积。它们之间是什么关系,历来说法不一。有的认为,梁山组（段）是栖霞灰岩下部Stylido phyllum volzi带或Misellina clau-diae带的陆相代表,就是说彼此为相变关系。另有人则认为,梁山组(段)位于栖霞灰岩Misellina claudiae带之下,彼此为上下关系。笔者曾在陕南西乡县高川一带作过煤田地质调查,谨以这里的资料为依据,谈谈对栖霞 岩和梁山段关系的看法。      

安徽宿松坐山中二叠统栖霞组碳酸盐岩微相和黏土矿物特征及其对沉积相和古气候的指示

安徽宿松坐山剖面中二叠世地层发育,栖霞组、孤峰组和武穴组连续出露,为下扬子地区中二叠统的典型剖面之一。其中栖霞组主要为碳酸盐岩,其次为硅质岩和碎屑岩。栖霞组碳酸盐岩中共识别出9种微相类型,分别可以与Flügel整理的7种标准微相对比。栖霞组主要为斜坡沉积,其次为台地沉积,而斜坡相又可以进一步分为上斜坡相和下斜坡相。其中,上斜坡相主要出现在臭灰岩段的中部,该层位以产砾屑灰岩为特征,微相类型以MF3为主。其次出现在本部灰岩段的中偏上部,该处微相类型为MF3、MF8和MF9。此外,顶部灰岩上部发育灰岩砾石的层位中的微相类型主要为MF3和MF9,也属于上斜坡相。下斜坡相主要发育于上、下硅质岩段和本部灰岩段的顶部,主要特征为发育薄层硅质岩或长条状硅质结核,微相类型主要为MF4和MF5。台地相主要出现在本部灰岩中下部,其次出现在臭灰岩段的下部和上部及顶部灰岩段的下部,且其微相类型以MF1为主,其次为MF2、MF6和MF7,表明台地相整体属于开阔海台地。微相分析表明栖霞组整体形成于一个海侵过程中,期间经历了4次较明显的海退。黏土矿物分析显示栖霞组碳酸盐岩的黏土矿物以伊利石为主(平均含量为61.97%),高岭石次之(平均含量为27.25%),伊蒙混层(平均含量为9.43%)和绿泥石(平均含量为1.36%)较少。高岭石/(伊利石+绿泥石)的比值与伊利石的相对含量变化共同表明栖霞期由早期的相对干冷变为晚期的相对暖湿,期间发生了3次较为明显的气候变化周期。同时,栖霞期气候整体变暖湿、海平面整体上升的趋势与晚古生代冰川(LPIA)消融的时间对应,则暗示古气候变化导致的冰川消融事件控制了栖霞期的整体海平面变化。而沉积相变化所反映的栖霞期4次相对海平面变化与3次明显的气候波动能够较好的吻合,则显示出气候对海平面变化和沉积记录的控制作用。表现在气候变暖湿导致冰体融化,海平面上升,风化指数(WI)升高,主要发育碳酸盐斜坡相。气候变干冷、冰体增大导致海平面和风化指数(WI)的下降,以碳酸盐台地沉积为主。     

江西中部石炭—二叠系界线

<正> 江西中部晚石炭世至早二叠世地层为连续的海相碳酸盐岩沉积,在船山组Sphaero-schwagerina带之上,栖霞组Misellina claudiae带之下有一套深灰色中至厚层生物泥晶灰岩,含(竹蜓)、牙形刺及珊瑚,厚度一般为40—60m。以高安鸡公岭出露良好,故命名鸡公岭组,用以代表江西中部下二叠统最低层位。     

巢县二叠系栖霞组臭灰岩段异地成因碳酸盐岩

下扬子地区二叠系栖霞组臭灰岩段广泛发育。以巢县为例 ,研究表明组成臭灰岩段的石灰砾岩并非正常沉积。剖面特征 ,岩石学、沉积学和地球化学特征的分析结果 ,显示了石灰砾岩的砾石来源于浅海碳酸盐台地 ,它们作为碳酸盐岩碎屑流的产物 ,沿着台地边缘的斜坡 ,被搬运到半深海—斜坡处再沉积。环绕于砾石周围的胶结物和砾岩层之间的薄层硅质粒泥灰岩 ,主要是由等深流沉积物组成。因此 ,臭灰岩段碳酸盐岩主要是异地成因 ,沉积环境属于碳酸盐台地周缘水体较深的斜坡。     

安徽巢北地区栖霞组臭灰岩段富有机质成因探讨

以安徽巢北地区二叠纪栖霞组臭灰岩段为研究对象,从岩石学、古生物学及沉积学特征出发,探讨臭灰岩段富有机质与风暴事件沉积之间的关系。臭灰岩段岩性整体为灰黑色中厚层状石灰岩,层间夹数毫米至数厘米厚灰黑色钙质泥岩,整套岩层富含有机质;其中生物化石丰富,整体为热带、亚热带正常盐度浅水生物组合为特征;为正常浅海碳酸盐岩台地沉积,沉积期表现为一个明显的海侵过程,并受风暴作用的频繁扰动。臭灰岩段沉积环境并非“贫氧或缺氧”条件,而是正常富氧环境。富有机质特征一方面得益于沉积期较高的生物产率,同时还与风暴事件沉积作用密切相关,即在风暴作用下,沉积物发生快速堆积,有机质未来得及与富氧水体发生长期接触即被埋藏覆盖,从而导致有机质被良好保存,形成臭灰岩段富有机质特征。风暴作用频发与研究区臭灰岩段沉积期所处的低纬度特征有关。     

山东淄博地区石炭纪含(竹蜓)地层

<正> 石炭纪含(竹蜓)地层在山东境内出露比较广泛,包括淄博、章邱、峄县、莱芜等地,以淄博及章邱一带出露较好。石炭纪含(竹蜓)地层可分为上石炭统本溪组和上石炭统太原组二部份,含(竹蜓)石灰岩的层数和厚度在山东各地不一,变化较大。谭锡畴(1922)在淄川、博山地层柱状图中,将含(竹蜓)石灰岩作为博山组(Poshan Formation)的下部,相当于山西的太原组。李四光、赵亚曾(1926)在山东境内找到三处石炭纪含(竹蜓)地层,即:章邱煤田、博山煤田及峄县煤     

Lithofacies and stratigraphy of the Ordovician Guniutan Formation in its type area,China

The Lower to Middle Ordovician Guniutan (Kuniutan) Formation in the eastern Yangtze Gorges, China has been demonstrated to be similar to the ‘Orthoceratite Limestone’ in Baltoscandia with respect to facies, stratigraphic development and conodont biostratigraphy. Thus the ‘Orthoceratite Limestone’ appears to be a much more widely distributed and characteristically Ordovician facies than has hitherto been assumed. Five lithostratigraphic subdivisions of the Guniutan Formation are here defined in ascending order as the Nanya, Puxi, Wuguixi, Daping and Niangjiafang members. It is shown that these members, which represent considerable spans of time as indicated by their conodont stratigraphy, may be fairly thin but nevertheless regionally extensive. A new conodont zone, with Eoplacognathus crassus as the zonal fossil, is established to accommodate the precise dating of the Wuguixi and Puxi members. Microfacies data from the Guniutan Formation, available for the first time, show that its dominant component particles are sand-sized echinoderm and arthropod debris, as in the Baltoscandian ‘Orthoceratite Limestone’.     

The Pliocene‐Pleistocene boundary in Southeastern Australia

In southwest Victoria thin sequences of upper Cainozoic marine to non‐marine mainly calcareous sediments occur at Portland and in the Glenelg River valley near Dartmoor. At Portland the Whalers Bluff Formation is shown to lie wholly within foraminiferal zone N19 (early Pliocene) which has age limits of about 3.0 to 4.8 m.y. Basalts overlying this formation give consistent K‐Ar ages averaging 2.51 ± 0.04 m.y.

In the Glenelg River valley, subaerial basalts yielding K‐Ar ages of 2.24 to 2.46 m.y. are overlain by shallow neritic sands and littoral calcarenites which belong to the type Werrikooian of F. A. Singleton, here included in the Werrikoo Limestone. Some distance above the base of the Werrikoo Limestone, Globorotalia truncatulinoides appears, the incoming of which defines the base of planktonic foraminiferal zone N22. The base of zone N22 closely approximates the beginning of the Pleistocene defined as the base of the Calabrian stage in Italy, and has an age of about 1.7 m.y. Thus the Werrikoo Limestone was deposited during late N21 and N22 time, straddling the Pliocene‐Pleistocene boundary and providing a reference standard for southeastern Australia as a whole.

It is shown that the Whalers Bluff Formation and the Werrikoo Limestone are separated in both space and time, contrary to the conclusions of earlier workers.     

Correlation of Mississippian (Upper Viséan) foraminiferan,conodont, miospore and ammonoid zonal schemes,and correlation with the Asbian–Brigantian boundary in northwest Ireland

The microbiota of the upper Viséan (Asbian–Brigantian) rocks in the Lough Allen Basin in northwest Ireland is analysed. The Middle Mississippian sequence studied extends from the upper part of the Dartry Limestone/Bricklieve Limestone formations of the Tyrone Group to the Carraun Shale Formation of the Leitrim Group. The rocks have been traditionally dated by ammonoid faunas representing the B_2a to P_2c subzones. The Meenymore Formation (base of the Leitrim Group) also contains conodont faunas of the informal partial‐range Mestognathus bipluti zone. The upper Brigantian Lochriea nodosa Conodont Zone was recognized by previous authors in the middle of the Carraun Shale Formation (Ardvarney Limestone Member), where it coincides with upper Brigantian ammonoids of the Lusitanoceras granosus Subzone (P_2a). Foraminifera and algae in the top of the Dartry Limestone Formation are assigned to the upper Cf6γ Foraminifera Subzone (highest Asbian), whereas those in the Meenymore Formation belong to the lower Cf6δ Foraminifera Subzone (lower Brigantian). The Dartry Limestone Formation–Meenymore Formation boundary is thus correlated with the Asbian–Brigantian boundary in northwest Ireland. For the first time, based on new data, a correlation between the ammonoid, miospore, foraminiferan and conodont zonal schemes is demonstrated. The foraminiferans and algae, conodonts and ammonoids are compared with those from other basins in Ireland, northern England, and the German Rhenish Massif. Historically, the Asbian–Brigantian boundary has been correlated with several levels within the P_1a Ammonoid Subzone. However, the new integrated biostratigraphical data indicate that the Asbian–Brigantian boundary in northwest Ireland is probably located within the B_2a Ammonoid Subzone and the NM Miospore Zone, but the scarcity of ammonoids in the Tyrone Group precludes an accurate placement of that boundary within this subzone. Copyright © 2006 John Wiley & Sons, Ltd.     

The Triassic of Timor: Lithostratigraphy, chronostratigraphy and palaeogeography

The palaeontologically rich and lithologically diverse Triassic successions of Timor provide a key stratigraphic and palaeontological link between northwestern Australia and other terranes of former eastern Gondwana (present-day Southeast Asia). Timor is now located in the zone of collision between the northern margin of the Australian continent and island arc terranes bordering the Eurasian plate, with the Triassic successions exposed in a fold-and-thrust belt and an extensive mélange complex. Three formal lithostratigraphic units have been defined previously within the main Triassic succession in Timor (Niof, Aitutu and Babulu formations), with a fourth, the Wai Luli Formation, primarily Jurassic in age but extending down into the Triassic. The Niof Formation (Anisian to Ladinian, possibly also Early Triassic) is a fine-grained deepwater succession, succeeded conformably by the Aitutu and Babulu formations (Ladinian to Norian/Rhaetian), which were deposited contemporaneously, with the Aitutu Formation continuing locally into the Lower Jurassic. The Aitutu Formation consists of deep shelf limestones interbedded with shales and marls, while the Babulu Formation is a deltaic to turbiditic siliciclastic succession. The Late Triassic to Jurassic Wai Luli Formation is characterised by marine shales and marls.Informal stratigraphic units include the Cephalopod Limestone Facies, a Rosso Ammonitico-type deposit, which contains an extremely rich fossil fauna (particularly ammonoids) and ranges through the entire Triassic; and the Fatu Limestone and Pualaca Facies which consists of shallow to marginal marine carbonates (mud mounds, oolitic limestones and reefs) restricted to the Late Triassic. Facies diversity was low during the Early Triassic and Anisian, but became more pronounced from the Ladinian and continuing through the Late Triassic, probably as a consequence of renewed tectonic extension. Triassic extension was not associated with major volcanism, unlike a previous phase of extension in the Early Permian.The Cablac Limestone Formation, originally defined as a Miocene stratigraphic element, is now recognised to be at least partly Late Triassic–Early Jurassic in age, with lithologies comparable to parts of the Fatu Limestone. The stratigraphy of these shallow marine carbonate sequences is clearly in need of rigorous revision, but it is not yet possible to suggest appropriate redefined formations.     

Biostratigraphy of Dinantian limestones and associated volcanic rocks in the Limerick Syncline,Ireland

Rocks of Courceyan to Brigantian age are exposed in the Limerick Syncline. However, a complete Courceyan succession is known only from two boreholes which correlate closely, both faunally and lithologically, with a standard Limerick Province succession in the Pallaskenry Borehole on the Shannon estuary. This is followed by a thick Waulsortian sequence (the newly defined Limerick Limestone Formation) of late Courceyan to early Chadian age and overlying cherty micrites (the newly defined Lough Gur Formation) of early to late Chadian age, whose top is younger to the east. The Lough Gur Formation is succeeded by lavas and tuffs of the Knockroe Volcanic Formation whose upper part is interbedded with and overlain by shallow water oolites and algal-rich bioclastic limestones of the Herbertstown Limestone Formation. The higher part of the latter is in turn interbedded with lavas and tuffs of the Knockseefin Volcanic Formation. The Herbertstown Limestone has rich and diverse coral/brachiopod and foraminiferal assemblages of late Chadian to Asbian age. Its base is markedly diachronous: late Chadian in the west of the syncline and Holkerian in the east. Both the base and top of the Knockroe Volcanic Formation are thus shown to be markedly diachronous and volcanism extends from the Chadian to early Asbian. The Knockseefin Volcanic Formation is entirely of Asbian age. The highest limestones (Dromkeen Limestone Formation) have a diagnostic late Asbian–early Brigantian fauna and are overstepped by mid-Namurian shales.     

山西柳林成家庄剖面太原组碳酸盐岩沉积相的特征及其意义

山西柳林成家庄剖面太原组发育7层灰岩,从下到上依次为半沟灰岩、吴家峪灰岩、庙沟灰岩、下毛儿沟灰岩、上毛儿沟灰岩、斜道灰岩和东大窑灰岩。通过详细的野外观测和室内镜下薄片研究,确定了各层灰岩的沉积相类型,恢复了当时的沉积环境和各层灰岩沉积时相对水体深度的变化。其中庙沟灰岩属中缓坡相沉积,吴家峪灰岩、下毛儿沟灰岩、上毛儿沟灰岩、斜道灰岩和东大窑灰岩均属浅缓坡相沉积,半沟灰岩属后缓坡相沉积。7层灰岩的相对水体深度关系为:庙沟灰岩>斜道灰岩>东大窑灰岩>下毛儿沟灰岩>上毛儿沟灰岩>吴家峪灰岩>半沟灰岩。在太原组内识别出6次沉积间断、7次小型沉积旋回,总体构成2次明显的相对海平面升降旋回。