湖南张家界地区志留纪晚期地层新见兼论小溪组的时代

就华南板块而言,志留纪晚期(Ludlow世—Pridoli世)近岸浅海、非笔石相地层多分布在边缘海湾处,是否在扬子地台内部发育,以往尚无确凿记载。依据来自湘西北张家界—桑植地区新近发现的微体化石(主要指植物碎片),确认志留纪晚期地层在扬子地台内部确实存在。对原小溪组(又称小溪峪组)进行厘定,将它"一分为二":上部仍称小溪组,命名地在桑植瑞塔铺,发育最好的是张家界温塘剖面,岩性为黄绿色碎屑岩,富含大型虫管遗迹化石,时代为Ludlow晚期—Pridoli早期;下部称迴星哨组,归于Llandovery统Telychian阶上部。小溪组与迴星哨组之间为假整合接触,缺失Telychian末期、Wenlock世和Ludlow世早期地层。由此得出结论:在"扬子上升"后,扬子地台内部曾被志留纪晚期的海水侵漫;对其他地区迴星哨组与上覆地层的研究需要细化。     

四川广元志留系Ludlow统的再研究兼论车家坝组的含义

四川广元地区志留纪晚期地层曾被划分为金台观组、车家坝组和中间梁组,后被厘定合并为一个组,即车家坝组。通过对岩性组合特征和生物化石群面貌的分析,广元地区晚志留世地层在岩性、生物化石生物群面貌方面具有一致性,赞成将三组归入同一个岩石地层单元——车家坝组,代表近岸、正常浅海(平均浪基面以上)沉积(BA2—BA3)。对比分析表明,该组的牙形刺Ozarkodina crispa应鉴定为Ozarkodina snajdri。这是O.snajdri牙形刺带在中国的首次报道。依据牙形刺化石,车家坝组的时代被修订为中Ludlow世晚期—晚Ludlow世早期。该组上部发现几丁石Sphaerochitina sp.组合,可与O.snajdri牙形刺带和bohemicus tenus-kozlowskii笔石带进行对比。     

Graptolites from the Lower Elton Formation (Ludlow) of Shadwell Rock Quarry,Shropshire

Graptolites are recorded for the first time from the Lower Elton Formation of Shadwell Quarry, Wenlock Edge, Shropshire. The presence of Colonograptus colonus (Barrande) indicates that the formation here may be assigned to the lowermost Ludlow, either the nilssoni or lower scanicus graptolite biozone. Copyright © 1998 John Wiley & Sons, Ltd.     

The Ludlow-Downton transition at Kington,Herefordshire

Biostratigraphy and lithostratigraphy of some exposures of upper Ludlow and lower Downton rocks near Kington, Herefordshire are described in detail. Temporary exposures created during the construction of the new Kington by-pass are particularly informative. One small exposure of Lower Whitcliffe Formation is recorded. The Upper Whitcliffe Formation is well displayed in characteristically fossiliferous shelly siltstones. The Downton succession begins with the Ludlow Bone Bed Member. This and the succeeding Platyschisma Shale Member complete the local development of the Downton Castle Sandstone Formation.     

云南曲靖地区关底组的时代

近年来 ,珊瑚工作者和层序地层工作者分别提出云南曲靖地区关底组下部或岳家山段应属文洛克统 (Wen-lock)。但在关底组岳家山段发现的 Ozarkodina crispa (Walliser) beta Morph.仍属 Ozarkodina crispa带 ,证明岳家山段仍属 L udlow世的晚期。 O.crispa可上延到 Pridoli世的早期。层序地层工作者将上易剥页岩归入早泥盆世是不可取的     

Valentinagraptus a new genus of plectograptid graptoloid from the lower Ludlow (Silurian) of Barrandian,Bohemia

The new plectograptid—Valentinagraptus simplex gen. nov., sp. nov.,—(Family Retiolitidae) was recovered from the nilssoni and progenitor biozones (early Gorstian, Ludlow) of the Barrandian area of central Bohemia, Czech Republic. The new taxon is characterized by a sub‐oval form and considerably reduced rhabdosome framework. The rhabdosome is similar to Plectograptus, with a simple ancora umbrella with large proximal orifices, but has a simple ancora sleeve with horizontal lateral lists connecting ladder‐like ventral walls. Copyright © 2006 John Wiley & Sons, Ltd.