Nemagraptus Gracilis Research Articles

Ordovician chitinozoans of the Miaopo Formation at Zhenjin, Upper Yangtze Platform, South China

Chitinozoan investigations on the late Middle to early Late Ordovician in South China are limited. Documented chitinozoan occurrences are mainly from the Miaopo Formation on the Upper Yangtze Platform. The present study reports new data from the Miaopo Formation at the Zhenjin section in the Yichang area. In total, 13 genera and 33 species are recognised, and three new species are described: Spinachitina? coronifera sp. nov., Lagenochitina yichangella sp. nov. and Pellichitina confragosa sp. nov. The Baltoscandian index species, Laufeldochitina striata, is documented in the lowermost part of the formation. This is the first report of this species in South China. The L. striata Biozone is suggested for the basal part of the formation due to the presence of the eponymous species. The index species of the Laufeldochitina stentor Biozone, the Armoricochitina granulifera and Cyathochitina megacalix subzones adopted in the Jieling section, are also observed in the Zhenjin section. However, according to the new data obtained at Zhenjin, the first appearance datum of C. megacalix and A. granulifera coincides with that of L. striata. Therefore, the C. megacalix Subzone is kept but moved to the L. striata Biozone. Armoricochitina granulifera has stable occurrences in almost the entire Miaopo Formation, corresponding to the Nemagraptus gracilis graptolite biozone. It is slightly older than Baltic records but could be useful for recognising this time interval in South China.

Ordovician graptolite biostratigraphy of the Röstånga-2 drill core (Scania, southern Sweden)

ABSTRACT The graptolite biostratigraphy of the 116.11-m-long Röstånga-2 drill core from Scania, southern Sweden, includes the Darriwilian (Middle Ordovician) Holmograptus lentus, Nicholsonograptus fasciculatus, Pterograptus elegans, Pseudamplexograptus distichus and Jiangxigraptus vagus biozones, and the lower Sandbian (Upper Ordovician) Nemagraptus gracilis Biozone. The early Darriwilian Komstad Limestone was not reached. The succession includes numerous levels of brecciated rocks and slickensides, suggesting considerable tectonic deformation and possible gaps. The boundary between the Almelund Shale Formation (below) and the Sularp Shale Formation (above) has been identified at 19.55–19.70 m, where the Fågelsång Phosphorite Bed has been identified tentatively in the Jiangxigraptus vagus Biozone. The first specimens of Nemagraptus gracilis appear higher in the succession. The international correlation of the Darriwilian graptolite succession is discussed.

The δ13C chemostratigraphy of Ordovician global stage stratotypes: geochemical data from the Floian and Sandbian GSSPs in Sweden

ABSTRACTThe δ13C chemostratigraphy of five of the seven Ordovician global stages has been published previously but no such data have been available from the Floian GSSP and most of the Sandbian GSSP in Sweden. This lack of information has now been remedied by isotope data obtained from series of closely spaced shale samples collected from the Floian stratotype at Diabasbrottet in Västergötland and the Sandbian stratotype at Fågelsång in Scania. Although the bases of these stages cannot be precisely tied to levels of conspicuous δ13C excursions, that of the Floian Stage, which is marked by the appearance of the graptolite Tetragraptus approximatus, is between the closely spaced excursions named LTNICE and BFICE. The base of the Sandbian Stage, which is defined as the appearance level of the graptolite Nemagraptus gracilis, is just below a negative excursion previously known as the “Upper Kukruse Low”, which is nowadays known as the LSNICE. The relations between chemostratigraphy and graptolite and conodont biostratigraphy in the Swedish GSSPs and some coeval key sections in Baltoscandia, China, and America are briefly discussed. It is concluded that the data at hand indicate that there is good regional agreement in these relations.

Graptolite biostratigraphy of the Ordovician Almelund and Sularp Shale formations of the Fågelsång-3 drill core, Scania, Sweden

ABSTRACTThe upper Middle to basal Upper Ordovician succession (Darriwilian to Sandbian) of the Fågelsång-3 drill core provides new important information on the graptolite biostratigraphy of Scania, southern Sweden. The Scanian succession is known largely from drill cores and a few scattered outcrops exposing only parts of the interval. The Darriwilian Almelund Shale Formation overlies the Komstad Limestone Formation and has a thickness of more than 42 m in the Fågelsång-3 drill core. A seemingly complete succession through the Holmograptus lentus, Nicholsonograptus fasciculatus, Pterograptus elegans, Pseudamplexograptus distichus and Jiangxigraptus vagus biozones can be recognized. Some intervals are poorly documented by their respective graptolite faunas or show extensive post-depositional tectonic deformation. The Nemagraptus gracilis Biozone of earliest Sandbian age cannot be positively identified, even though fragments of Nemagraptus have been discovered in the uppermost part of the Almelund Shale below the Fågelsång Phosphorite Bed.

Graptolite and conodont faunas of Upper Ordovician (Sandbian) successions of the Argentine Precordillera: Biostratigraphic implications

Graptolites and conodonts are frequent fossils in Sandbian (Late Ordovician) outcrops of the Argentine Precordillera, where they present continuous and abundant records that enable detailed biostratigraphic studies. This work deals with the integration of previously available information on early Sandbian graptolites and conodonts, together with new paleontological data from the Las Aguaditas Creek (middle and upper members of the Las Aguaditas Formation), Las Chacritas River (Las Aguaditas Formation), and Cerro La Chilca (Los Azules Formation) sections from the Central Precordillera of the San Juan Province. The presence of the key graptolite Nemagraptus gracilis and the associated graptolite taxa allow for the documentation of the N. gracilis Zone. Specimens of N. gracilis and key conodont species, such as Pygodus anserinus coexist, along with a rich conodont fauna including Baltoniodus variabilis, whose range straddles the boundary between the Pygodus anserinus and the Amorphognathus tvaerensis zones. Detailed biostratigraphic ranges of the rich graptolite and conodont associations documented in the three study areas are provided. These records and an accurate taxonomic review allow a thorough description of the recognized zones. The use of conodont and graptolite zones from different areas of the Precordillera enables the verification of a diachronous contact, representing a hiatus that spans the middle to upper Darriwilian. Moreover, a brief taxonomic description of the identified graptolite species is provided.

Reconstruction of a shallow intraplatform depression by microfacies analysis of the Upper Ordovician Miaopo and Datianba formations in the northwestern Yangtze Region, China

The sedimentary environments of the Upper Ordovician (lower Sandbian) shale-dominated Miaopo Formation and the contemporaneous limestone-dominated Datianba Formation in the northwestern Yangtze Platform, China, are reconstructed using facies analysis incorporating microfacies and faunal indicators. These two lithological units are generally only a few meters thick but each spans an interval of the Nemagraptus gracilis Biozone (ca. 3–4 My). Accordingly, they are condensed sequences. The Datianba Formation, which consists of thin-bedded limestones containing a shelly fauna, was formed in a shallow, oxic setting on the outer-shelf. The Miaopo Formation shales are limited to depressions surrounded by the Datianba Formation, indicating the sporadic occurrence of anoxic marine environments on the sea floor. The Miaopo Formation contains a high-diversity, abundant benthic fauna in addition to planktonic graptolites. The presence of tube-shaped burrows within the Miaopo Formation further indicates an oxic sea floor favorable for survival of benthic fauna. These results indicate that during deposition of the two formations the sea floor was mainly oxic. During deposition of the Datianba and Miaopo formations, the sea floor was a relatively gentle ramp without steep slopes. The distinct facies of the Miaopo and Datianba formations are interfingered.

On the diachronous nature of the top of the Ordovician Kuniutan Formation on the Yangtze Platform: Implications of the conodont biostratigraphy of the Dacao section, Chongqing

The top part of the Kuniutan Formation in the Dacao section at Chengkou, Chongqing in the northern part of the Yangtze Platform contains the conodonts Baltoniodus variabilis (Bergström), B. variabilis(Bergström)-B. gerdae (Bergström) transitional form, B. cf. alobatus (Bergström), Complexodus pugionifer (Drygant), Dapsilodus viruensis (Fåhraeus), Panderodus gracilis (Branson et Mehl), Periodon aculeatus Hadding, Protopanderodus varicostatus (Sweet et Bergström), Scabbardella altipes (Henningsmoen), and Yangtzeplacognathus jianyeensis (An et Ding). This species association is referred to the B. variabilis Zone. The transitional form between Baltoniodus variabilis and its descendent B. gerdae is recorded for the first time in China but it has been reported previously from a thin (0.5m thick) interval at the top of the B. variabilis Subzone in Sweden and a coeval interval in much thicker successions in the Appalachians of eastern United States. This form is important because it is present in a vertically limited stratigraphic interval near the top of the Nemagraptus gracilis graptolite Zone. The new conodont data indicate that the top part of the Kuniutan Formation at the Dacao section is about three conodont zones higher than that of the same formation at the well-known Huanghuachang section in the Yichang area, Hubei and the Waigangou section at Tangshan in Nanjing, Jiangsu. This illustrates the conspicuous diachronous nature of the Kuniutan/Miaopo formation contact in the Yangtze Platform region, which has not been recognized previously in China. The widely present gap at the top of the Kuniutan Formation is at least due partly to the late Darriwilian eustatic event that can be recognized also in Baltoscandia, North America, and Argentina.

Enhanced microbial activity in carbon-rich pillow lavas, Ordovician, Great Britain and Ireland

There is extensive evidence for the microbial colonization of seafloor basalts in the modern ocean and in the geological record. The sulfur isotope composition of pyrite in the basalts commonly indicates marked isotopic fractionation due to microbial sulfate reduction. Sections through the Nemagraptus gracilis zone (Ordovician) in Great Britain and Ireland are characterized by both widespread pillow lavas and organic-rich seafloor sediment, allowing an exceptional opportunity to assess whether the availability of organic carbon influenced the extent of microbial activity in the basalts in deep geological time. Whole-rock data from basalts at 10 localities show that there is a relationship between sulfur isotopic composition and the carbon content of the basalt. At two localities where organic carbon was entrained in the basalt, isotopic compositions are heavy compared to compositions in carbon-poor basalt, implying that microbial activity exhausted the supply of seawater sulfate. In most basalt, microbial activity was limited by the supply of carbon, but where the basalt incorporated carbon during emplacement on the seafloor, microbial activity became sulfate limited.

Telephinaand Other Trilobites from the Pratt Ferry Beds, Ordovician of Alabama, U.S.A.

The Pratt Ferry beds are a three meter thick bioclastic carbonate unit containing thePygodus serrus–P. anserinusconodont zone boundary and lying just below theNemagraptus gracilisgraptolite zone at a single locality in Alabama.TelephinaMarek at Pratt Ferry and other eastern North American localities is represented by at least six species. These are judged widespread and in part conspecific with Scandinavian or Asian forms of similar age. Most of the fifteen Appalachian telephinid species proposed by Ulrich (1930) are reviewed and some synonymized.BevanopsisCooper is present, extending its stratigraphic range viaB. buttsi(Cooper). The original description ofCeraurinella buttsiCooper is augmented. Other recorded but poorly represented genera includeAmpyxina,Arthrorhachis,Calyptaulax,Hibbertia,Lonchodomas,Mesotaphraspis,Porterfieldia, andSphaerexochus. The entire faunule represents a mixture of ‘inshore’ and ‘offshore’ or planktonic faunal elements rarely seen elsewhere in the latest Middle Ordovician (Darriwilian) of eastern North America.

The oldest known occurrence of the Foliomena fauna in the uppermost Darriwilian (Middle Ordovician) of South China

The oldest Foliomena fauna was, until now, known from the middle–upper Miaopo Formation (Nemagraptus gracilis Biozone, lower Sandbian, basal Upper Ordovician) of South China. In this study, the oldest record of the fauna is set back to the latest Darriwilian (upper Hustedograptus teretiusculus Biozone), represented by Foliomena jielingensis and some typical constituents of the Foliomena fauna from the basal Miaopo Formation at Jieling, northern Yichang, western Hubei Province, central China. The Miaopo Formation is characterized by its organic-rich dark-grey shale facies, unique in its localized distribution on the Yangtze Platform, and distinguished by its rich and diverse benthic and graptolitic faunas. This suggests an origin of the Foliomena fauna in periodically oxygen-starved local depressions on the Yangtze Platform during the Middle–Late Ordovician transition.

Toward a stepwise Kwangsian Orogeny

The Kwangsian Orogeny originated along the southeast coast of China and stepwise developed in a northwest direction. It includes two stages, a long locally varying uplift from the Late Ordovician to the early Silurian and a finally tectonic movement near the Silurian and Devonian transition. The Kwangsian uplift event shows a stepwise delay northwestwards from the southeastern coast area in Nemagraptus gracilis Biozone (Sa1) to the south side of the Xuefeng Mountains in or later than Cystograptus vesiculosus Biozone (R3) to Coronograptus cyphus Biozone (R4). In the southern of Yangtze Platform, the Yichang Uplift was droved by the Kwangsian Orogeny forming a diachronous stratigraphical break through Rhuddanian and Aeronian. The distribution of the early Telychian lower marine red beds indicates a northwestward increase of the Cathaysian Oldland. Stratigraphical evidence may explain why the Kwangsian movement was marked by an angular disconformity during the Pridoli to earliest Devonian interval.

New data of early Late Ordovician chitinozoans from the Miaopo Formation at Jieling, Yichang, central China

Chitinozoans from the uppermost Darriwilian–lower Sandbian Miaopo Formation at Jieling of western Hubei Province are reported, for the first time, including 30 species of 14 genera from 10 collections which are much more diverse and abundant than previously known. Two chitinozoan assemblages are recognized: the Laufeldochitina cf. striata Assemblage and the Eisenackitina cf. rhenana Assemblage. The L. cf. striata Assemblage is correlative to the upper Hustedograptus teretiusculus graptolite biozone. The base of the E. cf. rhenana Assemblage coincides with the base of the Nemagraptus gracilis graptolite biozone, indicating that E. cf. rhenana has the potential for recognizing the base of Upper Ordovician.

On the integration of Ordovician conodont and graptolite biostratigraphy: new examples from Gansu and Inner Mongolia in China

Wang, Z.H., Bergström, S.M., Zhen, Y.Y., Chen, X. & Zhang, Y.D., 2013. On the integration of Ordovician conodont and graptolite biostratigraphy: New examples from Gansu and Inner Mongolia in China. Alcheringa 37, 510–528. ISSN 0311-5518.Few Ordovician successions in the world contain both biostratigraphically highly diagnostic conodonts and graptolites permitting an integration between standard biozones based on these fossil groups. The Sandbian Guanzhuang section in the vicinity of Pingliang in the Gansu Province has an outstanding graptolite record through most of the Nemagraptus gracilis and Climacograptus bicornis graptolite biozones. Calcareous interbeds in the succession yield biostratigraphically important conodonts, including some species used for biozonations in Baltoscandia and the North American Midcontinent. Likewise, the middle–upper Darriwilian Dashimen section in the Wuhai region of Inner Mongolia hosts both diverse graptolites of the Pterograptus elegans, Didymograptus murchisoni and lowermost Nemagraptus gracilis biozones, and conodonts of Midcontinent and Baltoscandic types. The distribution patterns of these index fossil groups provide an unusual opportunity to closely correlate conodont and graptolite biozones in the middle to upper Darriwilian to Sandbian interval. For instance, the base of the C. bicornis Biozone is approximately coeval with the base of the Baltoscandic B. gerdae Subbiozone and a level near the middle of the North American P. aculeata Biozone.Zhi-hao Wang [zhwang@nigpas.ac.cn] Xu Chen [xu1936@gmail.com], and Yuan-dong Zhang [ydzhang@nigpas.ac.cn], Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China; Stig M. Bergström [stig@geology.ohio-state.edu], School of Earth Sciences, Division of Earth History, The Ohio State University, Columbus, OH 43210, USA; Yong Yi Zhen [yongyi.zhen@austmus.gov.au], Australian Museum, 6 College Street, Sydney NSW 2010, Australia.

Gastropods and tergomyans from the Upper Ordovician (Viru–Harju) of the Fågelsång area, Scania, southern Sweden

A diverse tergomyan and gastropod assemblage is described from the Global Boundary Stratotype Section and Point (GSSP) section of the Sandbian Stage, Upper Ordovician, in the Fågelsång area, Scania, southern Sweden. Deep water graptolitic mudstone and shale comprise the succession, and previously only one gastropod species was known. The new material spans the Sularp Formation through the Lindegård Mudstone (Nemagraptus gracilis–Dicellograptus complanatus biozones). Fourteen species are described: two tergomyan, five bellerophontoid gastropods, and seven anisostrophically coiled gastropods. Three species are new: Peelerophon hodites, Tetranota scanica and Lophospira sandbiana. Three taxa (Tritonophon subtrilobatus, Tetranota scanica and Holopea mobergi) are found high in the Lindegård Mudstone (Vormsi–Pirgu stages). Cyrtodiscus, Peelerophon and Tritonophon are recorded for the first time in Baltoscandia. Some taxa may have been transported from shallower water settings, whereas species of Peelerophon, Joleaudella, Mestoronema and Sinuites may have been part of the local benthos. Except for Bucania erratica, no species are shared with the fauna of the coeval Dalby Limestone in Sweden. Deaechospira elliptica, common in the Dalby Limestone, is not recorded at Fågelsång, although two closely related species are found (Deaechospira rotunda and Deaechospira? sp.). The Fågelsång assemblage has more in common with the older to coeval fauna of the Elnes and Arnestad formations in the Oslo Region, Norway (e.g. sharing Joleaudella, Sinuites, Mestoronema and Pararaphistoma). The Sandbian fauna of Fågelsång includes peri-Gondwanan taxa, e.g. Cyrtodiscus, Peelerophon and Deaechospira. Nevertheless, cluster analysis reveals that the faunas of Baltica and Laurentia were most similar, whereas faunas from Perunica and Baltica remained distinct and separated during the Darriwilian–Sandbian. The few similarities may result from spread of a temperate fauna supplementing rather than replacing taxa in deep water assemblages. The main Fågelsång assemblage coincides both with the Baltoscandian Middle Caradoc Faunal Turnover and the Gutenberg Carbon Isotope Excursion. http://zoobank.org/urn:lsid:zoobank.org:pub:093F6504-B3FA-42A4-94C2-FF460D549F18

Biostratigraphic correlation of the Ordovician black shales in Tarim Basin and its peripheral regions

Ordovician black shales are widely distributed in the Tarim Basin and its peripheral regions, and some of them may serve as potential hydrocarbon source rocks. The present study of the Ordovician graptolite fauna from these shales, together with the yielded conodonts and chitinozoans etc., permits a refined correlation of the rocks. Based mainly on a new collecting of the graptolites and a study of the faunas in Kalpin and Kuruktag regions, and the successful identification of the new graptolite material from a few drill cores within the basin, we are able to update our knowledge of the Ordovician in the regions, and draw some conclusions: (1) The most widespread distribution of the black shales in the Tarim Basin and its peripheral regions, which correspond to the Nemagraptus gracilis Zone, may be related to a global sea-level rise during this time interval. (2) Black shales of Ordovician occur most frequently and extensively in the Kuruktag (also spelled as Quruq Tagh) region in eastern Tianshan Mountains, spanning Tremadocian to mid-Katian (D. spiniferus Zone) temporally and extending southeastwards into Manjiaer Depression. The black shales of the D. spiniferus Zone may even extend into the central Tarim Basin. (3) Three different bio- and litho-facies belts (Bachu: carbonate platform and reef belt; Kalpin-Aksu: marginal platform and upper slope belt; Wushi: slope belt) are recognized in the northwestern Tarim Basin. (4) The internationally well-correlated Saergan black shale, which has been considered to possess high potential for hydrocarbon source rock, may possess a restricted distribution in the Kalpin and Aksu areas.

Climacograptus pungensRuedemann, 1904 and the definition of the Darriwilian (Ordovician) graptolite genusArchiclimacograptusMitchell, 1987

The genus Archiclimacograptus represents one of the earliest taxa of axonophoran graptolites with geniculate thecae, but its current status and evolutionary relationships are difficult to access even after a number of cladistic analyses have been executed. Archiclimacograptus? pungens (Ruedemann), a poorly known little species from the lower Darriwilian of eastern North America is interpreted as a possible member of the genus. The species belongs to a group of axonophorans with highly asymmetrical proximal end and pattern C astogeny, characterized by the lack of an apertural spine on th12, ranging from the Levisograptus dentatus Biozone (Darriwilian) to the Nemagraptus gracilis Biozone (Sandbian). Specimens are common in North America and the Argentinian Precordillera, but have not been reported from any Atlantic Faunal Realm localities. The distribution of the group indicates a restriction to the Pacific Faunal Realm, providing the earliest indication of a developing biogeographic differentiation of axonophoran graptolites after their origin in the oceanic biofacies during the Upper Dapingian to lower Darriwilian time interval. Archiclimacograptus? ambiguus is described as a new species.

The Dawangou auxiliary GSSP (Xinjiang autonomous region, China) of the base of the Upper Ordovician Series: putting global chitinozoan biostratigraphy to the test

Abstract. The Dawangou section, an auxiliary Global Stratoype Section and Point (GSSP) for the base of the Upper Ordovician Series, was sampled for chitinozoans. The 32 samples taken from the black shales of the Saergan Formation, spanning the Pterograptus elegans, Didymograptus murchisoni and Nemagraptus gracilis graptolite biozones, yielded 6536 chitinozoan vesicles. In addition to a diverse endemic assemblage, species important for international correlation were recovered, which enables the subdivision of the Saergan Formation into two chitinozoan biozones, one subzone and one provisionally recognized biozone: the Baltoscandian Laufeldochitina striata Biozone and the Laurentian Lagenochitina sp. A (sensu Achab, 1984) (/Belonechitina hirsuta) Biozone, and the Belonechitina tuberculata Subzone are recognized based on the presence of the index species, while the Baltoscandian Laufeldochitina stentor Biozone is provisionally recognized on the presence of Laufeldochitina sp. A aff. striata sensu Grahn et al., 1996 which has a range confined to the latter biozone. One new chitinozoan species is described: Cyathochitina giraffa sp. nov. and two species were assigned to a different genus: Belonechitina tuberculata comb. nov. and Hercochitina seriespinosa comb. nov.

Ordovician graptolite-bearing strata in southern Jiangxi with a special reference to the Kwangsian Orogeny

The Ordovician graptolite sequence of the Yongxin-Chongyi area in southern Jiangxi was suggested as a standard for the correlation of Ordovician in the Zhujiang region of South China. Based on a restudy of the Upper Ordovician graptolites, the Shikou and Huamianlong formations are recognized herein as a part of the Hanjiang Formation, corresponding only to the Diplacanthograptus caudatus-Diplacanthograptus spiniferus Zone. Two graptolite zones in the Longxi Formation of Yongxin and Chongyi, the Nemagraptus gracilis Zone and Climacograptus bicornis Zone, are redefined here. A rapid replacement of facies from the typical deep-water graptolitic black shale of Longxi Formation to the rapidly-accumulated, shallow-water clastic deposits of Hanjiang Formation indicates the tectonic initiation of the Kwangsian Orogeny. The thick clastic deposits of the Hanjiang Formation are proposed to come from a nearby source area that rose during the Kwangsian Orogeny. The D. caudatus-D. spiniferus graptolite Zone of the Hanjiang Formation indicates the initiation time of this tectonic event.

Early Sandbian (Late Ordovician) conodonts from the Yenwashan Formation, western Zhejiang, South China

Zhen, Y.Y., Zhang, Y.D. & Percival, I.G., June, 2009. Early Sandbian (Late Ordovician) conodonts from the Yenwashan Formation, western Zhejiang, South China. Alcheringa 33, 133–161. ISSN 0311-5518. Conodonts are documented from the basal Yenwashan Formation at the Huangnitang Section (the GSSP section for the base of the Darriwilian), exposed near Changshan County town in western Zhejiang. The fauna consisting of 14 species is dominated by Pygodus anserinus, Periodon aculeatus, Protopanderodus cooperi, Costiconus ethingtoni and Dapsilodus viruensis. Both P. anserinus and P. cooperi are revised as having a septimembrate apparatus. The Pa element of P. anserinus has a morphology that varies from the primitive form with node-like denticles of the fourth row only developed on the distal part of the platform, to the advanced form with a well-developed fourth row of denticles. Association of these two morphotypes of P. anserinus, and the absence of P. serra and P. xinjiangensis in the basal Yenwashan Formation, suggests correlation of this level with the upper part of the P. anserinus Biozone (earliest Late Ordovician). This age determination agrees with the FAD of Nemagraptus gracilis immediately below in black shales intercalated with thinly bedded limestones at the very top of the underlying Hulo Formation, and provides new data for correlation with the graptolite biozone.

Advances in the Ordovician graptolite biostratigraphy of the St Petersburg area, Russia

The Ordovician shallow-water shelf deposits rich in benthic fauna are exposed along the Russian part of the Baltic- Ladoga Klint. Graptolites occur only at some stratigraphic levels, being comparatively numerous in marls and clays and very rare in carbonate layers. Since the 19th century graptolites have been collected from exposures of the Pakerort, Hunneberg, Billingen, and Volkhov regional stages (Tremadocian-Dapingian), while in the Uhaku-Idavere stratigraphic interval (Darriwilian-lower Sandbian) rare graptolites have been found in boreholes. Up to now, only some collections have been systematically studied. On the basis of new graptolite finds, recently the Pterograptus elegans Biozone was established in the upper Aseri Stage and the Nemagraptus gracilis Biozone in the lower Kukruse Stage. Detailed sampling of the Shundorovo Formation (upper Idavere Stage) resulted in the discovery of numerous diplograptids at five stratigraphic levels, in association with various dendroids. These diplograptids were provisionally assigned to ?Archiclimacograptus antiquus lineatus Elles & Wood. A systematic description of the late Darriwilian and early Sandbian diplograptids is under preparation.