I Berliner geowiss. Abh.1 (E) 9 293-329 113 Abb., 7 Tafeln Berlin 19931 Oldest entirely preserved sponges and other fossils from the Lowermost Cambrian and a new facies reconstruction ofthe Yangtze platform (China) M. STEINER, D . MEHL, 1. REITNER & B.-D. ERDTMANN Olelest entirely preserved sponges and other fossils from the Lowennost Cambrian and a new facies reconstruction of the Yangtze platform (China).- M. STEINER, D. MEHL, J. REITNER & B.-D. ERDTMANN, Berliner geowiss. Abh. (E) 9: 293-329, Berlin. Kunfiuaune: Eine Faziesrekonstruktion W1d Korrelation obersinischer-unterkambrischer Schichten der Yangtze-Plattform (Südchina) wird vorgestellt. Dabei wird zwischen geschütztem Becken, Schwelle W1d tiefem Becken unterschieden. Die unterkambrische Schwarzschiefer-Transgression, der "Badaowan" Event, wird als diachron gekennzeichnet. Nach Untersuchungen der Lithologie W1d Geochemie der unterkambrischen Sedimente, vorwiegend Schwarzschiefer des Profils Sansha (nahe Dayong. N-Hunan), kann zwischen Sedimenten, die unter teilweise anoxischen Bedingungen oder im stagnierenden Becken abgelagert wurden, unterschieden werden. Schwammnadeln sind im untersten Unterkambrium Zentralchinas weit verbreitet. Neufimde vollständiger hexactinellider Schwämme Sanshadictya microreticulata gen. et sp. 0., Hyalosinica archaica gen. et sp.o., Triticispongia diagonata gen. et sp. n., Solactiniella plumata gen. et sp. 0., Hunanospongia sp. QIAN & DING, 1988, Hexactinellida indet., eines fraglichen vertreters der Demospongiae, Saetaspongia densa gen. et sp. 0. sowie eines Vertreters der Malacostraca Perspicaris sp., W1d einer unbenannten A1genfonn, werden vorgestellt. Schwammnadeln wurden ebenfalls neu in Gesteinen des Shibantan Mb. (Dengying Fm., Ob. Proterozoikum) vom Straßenaufschluß Liantuo (nahe Yichang. S-Hubei) gefunden. Die Fauna vorwiegend hexactinellider Schwämme von Sansha wird im Zusammenhang mit den taphonornisch AhnIichen Spongienfaunen des Red Hil1s Quarry (Mitteldevon, Nevada) und des Arnager Kalkes (Kreide, Bomholm) diskutiert. Abstract: A facies reconstruction and correlation ofUpper Sinian - Lower Cambrian strata ofthe Yangtze platform (South China) is presented. Protected basin, uplift and deep basin development may be distinguished. The Lower Cambrian black shale transgression, the "Badaowan" Event, is characterized as diachronous. As a result of these investigations of lithology and geochemistry of the Lower Cambrian sediments (mainly black shales ofthe Sansha section, near Dayong. N. Hunan), sediments deposited under partially anoxic conditions or in a stagnant basin have been recognized. Sponge spicules are widely distributed in the lowennost Lower Cambrian of CentraI China. Recently discovered more or less complete sponges, including Sanshadictya microreticulata gen. et sp. 0., Hyalosinica archaica gen. et sp. 0. , Triticispongia diagonata gen. et sp. 0., Solactiniella plumata gen. et sp. 0., Hunanospongia sp. QIAN & DING, 1988, Hexactinellida indet., a questionable demosponge, Saetaspongia densa gen. et sp. 0., and the Malacostraca Perspicaris sp., and an unnamed a1ga are described. Sponge spicules additionally were found in rocks of the Shibantan Mb. (Dengying Fm., Upper Proterozoic) from the road section of Liantuo (near Yichang. S.Hubei province). The fauna ofmainly hexactinellid poriferans from Sansha is discussed with regard to the similar taphonomy ofthe sponge faunas from the Red Hills Quarry (MiddIe Devonian ofNevada) and from the Arnager Iirnestooe (Cretaceous, Bomholm). Keywonls: Porifera, China, Yangtze platfonn, Lower Cambrian, megaalgae, Malacostraca, black shales, facies, slnltigraphy Authon' adresses: M. STEINER & B.-D. ERDTMANN: Technische Universität Berlin, Institut fllr Geologie W1d Paliontologie, Sekr. ACK 14, Ackerstraße 71-76,1>-13355 Berlin, Germany I D. MEHL & J. REITNER: Institut fllr Paliontologie, Freie Universität Berlin, Malteserstr. 74-100, Haus D, 0-12249 Berlin, Germany 1. Introduction Tbe present paper includes OOt results of a palaeontologica1-sedimentologica1 correlation pro- ject on the Yangtze platform, China. Team members on the German side concentrate on the investigation of phosphogenesis and lithofacies correlation at the Precambrian - Cambrian transi- tion (SIEGMUND, TU Berlin) and on studies of the Precambrian-Lower Cambrian "mega-algae" (STEI- NER. TU Berlin). Additionally primary results con- cerning a palaeogeographiclfacies reconstruetion of the Yangtze platform, and the stratigraphie correlation, geochemistry and palaeontology of Lowermost Cambrian (Nemakit-Daldynian, Tommotian) strata are presented here. New tectonie data (CHEN et al., 1991; XING et al., 1992; pers. comm. R BREWER. Sept. 1992), a re- evaluation of literature (e.g. HE & YANG, 1982; CHEN, 1984; anonymous, 1987) and field observations in 1991 and 1992 elearly show that a simple palaeobathymetrie subdivision of the Upper Proterozoie-Lower Cambrian sediments of South China into shelf-platform-sediments, slope sediments and basin-sediments (e.g. Y ANG, CHENG & WANG, 1986; anonymous, 1987) is not satis- faetory. First doubts concerning the former model were expressed after initial palaeontologica1 and sedimentologica1 investigations by STEINER. ERDTMANN & CHEN (1992). San 1/29 Sanl/26- San lnS- '1 San 1/21- San 1/20- San 1/19- San 1/18- Sanl/17- not exposed + + 294 ,; '" '" '" ,; ,; /' '" '" Re /.,-- - - - '" -- ./ - - -. - --- ---.. •• .. - -. •• • (!::::::; 100 m Q -. . _. Sanl/14- --~~~~;:::-- --. ~n-l~4::::::::--"'--_ .-.-. San 1/12- San 1/10- ----- . - - --.. -- - - - -:: :::::~~r' not exposed ~ocm Ten-fig. 1: lnvestigated sections in N.Hunan and S.Hubei provinces (for explanation of fossil symbols see fig. 5). Fossil records from the Upper Precambrian- Lowermost Cambrian are of great interest because of the implication to the evolution of life and to a higher stratigraphical resolution. Small shelly fossils (SSF) and sponge spicules are the most widely distributed fossil remains near the Precambrian-Cambrian transition. Entirely preserved Porifera, the oldest ones described so far, are found in several horizons in an excellent preservation. They are fairly small specimens and are attributed mainly to the Hexactinellida. All taxa of Porifera here presented are analysed, described and documented by MEHL & REITNER (working group "Porifera", FU Berlin). The non-Porifera taxa are described by STEINER. Shuijingtuo ....... f.m. Yanjiahe Fm. ~ Baima- 2' .~ tuo ~ Fm. .................... ---- 295 rTnl-~ ____ 6 c E ~ u.. C'I 0 c-e 0 >- ..c. C'I 0 e :J Q) ...J ~O Cl ~ limestone ~ - - argiUaceous dolomite ~ dolomite 1- · ·1 ._.- si lty claystone .. phosphate • py.rite ~ -- claystone ·stone coal" Iii! organic - rich claystone .J2. slumpfolds ~ chert -- phosphatic nodules --- Ten-fig. 2: Lithology and location of sampies and fossiliferous horizons of the section ca. 1Ion SW of the traffic check point Sansha (near Dayong, N.Hunan province)(for explanation of lithological signs see fig. 1, for fossil symbols see fig. 5). 2. Geological setting 2.1 . General scope of study During field investigations in N.Hunan and S.Hubei five sections in the Wuling Mountain area and one section at Heziao near Changyang were measured and compared (fig. 1). One additionally section in the Huangshan area (S.Anhui), which exposes a similar facies as in the Liandaowan and Wenshanwan sections, and three sections in Jin- ning and Chengjiang county (Yunnan prov.) provided data for a facies reconstruction, roughly extending over the Yangtze platform. The stratigraphic sections, investigated most closely and described herein represents the Precambrian-Cambrian transition. A comprehen- sive correlation table over the complete Yangtze platform did not exist untill now. Previous correlation attempts between several provinces (e.g. anonymous, 1987, 1988, 1990) were based mainly on lithostratigraphy. Our recent investigations include studies of the Dengying Fm., Yanjiahe Fm. and Shuijingtuo Fm. in the Heziao section; the Dengying Fm., the Niutitang Fm. and Balang Fm. in the Luoyixi, Labazhou and Sansha sections; and the Liuchapo Fm. and Xiaoyanxi Fm. in the Wenshanwan and Liandaowan sections. The localities at Liandaowan, Wenshanwan and in the Huangshan area (S.Anhui) document that chert was deposited during the Uppermost Precambrian (Liuchapo Fm., Piyuancun Fm.), but in the regions farther to the N, e.g. in Sansha and Heziao, the sedimentation remained under car- bonatic influence (Dengying Fm.). Because of lateral facies changes, the Yangtze, Jiangnan and South~t regions have been distinguished (e.g. Y ANG, CHENG & W ANG, 1986). The investigated sections are situated along a traverse from the Yangtze region to the Jiangnan region. 2.2. Localities Among the investigated sections in N.Hunan, S.Hubei (see text-fig. 1), the section ca. lkm SW of the trafik check point Sansha (text-fig. 2) was selected for a first closer examination because of its rich fossil content. In the Sansha section (text-fig. 2) phosphates, dark cherts, black shales with phosphatic nodules, and black metalliferous shales of Lower Cambrian age were deposited above a distinct and visible disconformity. In the subjacent Dengying Fm., SIEGMUND (in prep.) observed several weIl defined karst features. Locally ero- sional surfaces are refilled with transgressive phosphatic sediments. The thickness of the dark cherts and carbonaceous shales with phosphate 296 nodules above the erosional disconforrnity is highly variable, compensating for relief differences caused by karstification of the Dengying dolostones. Narrow and deep channels, eigther filled with carbonates that contain small chert nodules, or phosphate and carbonaceous shale that contain small phosphatic nodules, occur within the black cherts. These cherts contain the oldest sponge spicules in this section (SIEGMUND, in prep.; see plate 6, figs . 2-4). SSF could not be clearly iden- tified, but DING & QIAN (1988) reported SSF of the Protohertzina/ Conotheca' association and sponge spicules (Hunanospongia delicata QING & DING 1988) from basal phosphatic, carbonaceous silico- lites that contain silty carbonaceous shales and phosphatic concretions of the Lower Cambrian from Yangjiaping (Shimen, Hunan prov.). A carbonaceous shale with large phosphatic nodules was deposited above the cherts. It is called "the lower stonecoal bed" and is locally mined for lime-burning purposes. With a TOC of approx. 11 %, this bed has the highest organic content of the entire section. COVENEY & CHEN (1991) and COVENEY et al. (1992) reported nodular Ni-Mo-ore beds (2-15 cm) from Guizhou and Hunan provinces. These beds directly overlie the Lower Cambrian phos- phates in Hunan and a thin black shale bed above the phosphates in Guizhou province. Although we couldn't detect an ore layer with Ni and Mo enrichments in % scale, the carbonaceous shales with phosphatic nodules contain unusually high element enrichments ofV (up to 1,1 wt. %), Cr (up to 0,5 wt. %), Ba (up to 0,5 wt. %), Se, Mo, Cd, U and Ni (see figs. 3,4). The "lower stone coal" is succeeded at Sansha by 1-2 silty horizons with local mass occurrences of Perspicaris sp. and with isolated organic compressions of Porifera. The poor state of preservation of the bivalved arthropods, as weIl as the absence of mineralized spicules, support the hypothesis of their transportation into the depositional area by water currents' More than 12 m py,rite-rich black shales (TOC. 6-9%) were deposited above the fossili- ferous siltstones. Between 1,5 and 3 m above the top of the Sinian the black shale shows fine pyrite and barite bands spaced 1-2 mm apart. Such pyrite generation is regarded as primary, but pyrite nodules, lenses and nests, however, are regarded as secondary, probably diagenetic. Both generations are pure pyrite. COVENEY & CHEN (1991) demonstrated that both early and late pyrite generations coexist in the Ni-Mo-ore beds, with the later generation con- taining higher amounts ofNi, Se and Mo (7). 1/29 :' .. .. . .... / N; ~ a. E 0 .. 1/26 C! •••• 1/25 \. 1/23 '-In "- .......... Co ............. , 1121 1/20 1/19 1/18 1/17 1m 297 , , , . , \1010 ,'Se , , , " /ö t 1 1 1 1 • 1 1 I 1, , , , , , , , " "_ "_ ::: : ~. '0._ I-- Blaclc Sea ----I Text-fig. 3: Enrichment resp. depletion pattern of the elements Mn, Co, Ni, V, Mo and Se of the section lkm SW ofthe traffic check point Sansha (near Dayong, N.Hunan province) to anormal shale, low in TOC, with a comparison to enrichment patterns of these elements in Recent upwelling zones and the Black Sea (data for normal shale from WEDEPOHL, 1970; for data of Recent upwelling zones and of the Black Sea see compilation in BRUMSACK& THUROW, 1986). 1129 .. .. Ci. E a 1/26 1/25 1/21 1120 1/19 1118 1/17 "14 10-1 / i I 1 I I enrichment 100 I Zn / I / / Ba .' I I ) ~ / <:0., . .I '. f , . : , }) / /; .. .. ;'/ ;:~~ I:"'~ ~ , , ,Cd I , , I , I ~ 1 1 1 I • Ten-fig. 4: Enrichment resp. depletion pattern of the elements Zr, Ti, U, Zn. Cd, Ba and of Corg. of the section lkm SW of the traffic check point Sansha (near Dayong, N.Hunan province) to anormal shale, 10w in TOC (data for normal shale from TuREKlAN & WEDEPOHL, 1961; WEDEPOHL, 1970; for U the assumption of 4 ppm for anormal shale was choosen) Between 3 and 13 m above the top of the Sinian, mainly secondary pyrite occurs. At the top of the black pyrite-rich shales, secondary Cu-mine- rals (such as chrysocolla, malachite a.s.o.) were precipitated. Probably identical secondary minerals were observed in similar positions in the outcrops at Wenshanwan (Hunan) and Piyuan (S.Anhui). The black pyrite-rich shales are succeeded at Sansha by 40 m of dark shale (TOC. 3-4 %), rich in sponge spicules. Occasional thin carbonate horizons are intercalated. The black shales of the Niutitang Fm. conformally grade into the super- jacent fine, grey and yellowish weathering claystone of the Balang Fm. in the entire Wuling MOWltain area (e.g. Sansha, Luoyixi). The Balang Fm. is correlated with the Shuijingtuo Fm. of the Yichang and Changyang areas, based on trilobites. 2.3. Geochemical data and facies interpretation To obtain a facies interpretation of the Lower Cambrian black shales, three seetions were in- vestigated geochemically (Sansha, Hunan: Heziao, Hubei and Chengjiang, Yunnan). Enrichments in Ni and Mo (several wt. %) and to a lesser degree in As, V, Se, U, Zn, Ag, Au and PGE of Lower Cambrian black shales of South China have been known for a long time (e.g. CHEN et al., 1982; anonymous, 1987; COVENEY & CHEN, 1991; COVENEY et al., 1992). Element enrichments that are Wlusually high for black shales (VINE & TOURTELOT, 1970) were observed, both in the lower part of the Niutitang Fm. in Sansha (Se, Cd, Mo, V, Cr, Cu) and at a horizon of the Shuijingtuo Fm. near Heziao (Se, Cd, Mo, V). The latter is rich in hyo- lithids and yields some sponge spicules and trilobites. Areplacement of the original material by Zn-sulfide (with Cd) and by chalcopyrite in the outer part was detected in one of these sponge spicules. Enrichment pattern of trace metals in the investigated Lower Cambrian black shales can be best compared to those of Cenomanianffuronian (CTBE) black shales (BRUMSACK & THUROW, 1986; BRUMSACK, 1992). Text-figs. 3 and 4 show the enrichment resp. depletion of selected elements of the Sansha section compared with an average shale low in TOC (TUREKIAN & WEDEPOHL, 1961; WEDEPOHL, 1970). Although an actualistic model for the stratification ami/or distribution of water masses for the Lower Cambrian time is Wllikely, in text- fig. 3 a comparison to recent enrichment patterns in upwelling zones (e.g. Gulf of California) and stagnant basins (e.g. Black Seal is given (see also compilation in BRUMSACK & THUROW, 1986). Recent sediments, deposited under the influence of 298 upwelling, show enrichments only in Se. Cd, Mo and perhaps slightly in Cu. At the same time they are depleted in Co and Mn, a pattern attributed to an increasing mobility Wlder reducing conditions and their removal from the system. Nearly all elements may be enriched in re- cent deep sea clays (COLLEY et al .. 1984), but Cd. Se, Cr and V are not at all or only slightly enriched. In recent stagnant basins with extended anoxie conditions apart from the elements Se, Mo, Cd and Cu, which can Oe enriched in upwelling sediments too, additionally Co. V and Ni can have higher values than in normal shales. Unfortunately, only incomplete data are published for the largest recently existing stagnant basin - the Black Sea (see compilation in BRUMSACK & THUROW. 1986). Especially the basal part of the black shales, which is probably comparable to extremely Ni-Mo- rich horizons described by COVENEY et al. (1992) from other areas, is considerably enriched in V, Cr, Mo, Se, Cd, Zn and to a certain extent Ni is also enriched, in contrast to maximal values fOWld in recent stagnant mainly anoxie basins. Additional mechanisms, such as hydrothermal influence, diagenetic enrichment, or deep palaeokarst / weathering may explain these Wlusually high element enrichments. Although a meteoric impact was envisaged as an explanation for some element enrichments (FAN, 1983; FAN et al., 1984), an extraterrestrical influence appears wtlikely (COVE- NEY & CHEN, 1991; COVENEY et al. , 1992). In spite of the incomplete data base for comparison and the essential application of a probably anactualistic model for Cambrian times, the docurnented enrichment pattern may serve as a tool for facies interpretation. The basal transgressive phosphates, cherts (with channels) and basal black shales with phosphatic nodules (sampies San 1/3-1/7), indicate an established anoxie environment (Mn-Co-de- pietion). Completely anoxie conditions, however, were developed (normal Cr- · and Co-values and enrichment in V, Ni and Cu) during the accurnulation of the supeIJacent strata (sampies San 1/7-1/20). Diagenetic processes and palaeo- karst phenomena (SIEGMUND, in prep.) probably led to extreme element enrichments in Se, Mo, V, Cr, Ni and Zn in the basal black shales with phosphatic nodules. The distribution pattern of Zn (see text-fig. 4) in particular, probably points towards a mobilization by diagenetic processes. Especially Se, U, Cd and Mo are positively correlated with the organie content, although the distribution of U is not only dependent on the organie contents and Cd still can be secondarily enriched by Zn-sulfide (see text-figs. 3 & 4). &a >:!:t ~r(Q e.~ 5) ' Ci 0) 0 § a ... 5)' e: t:". = 0 (JQ = Oe. VlVl ~ ... "- ~ . \0, ~b ':-"~ (1) ... i ::I. § I e. ~ i i g. a 1 g' e. i .g. 5ansha eg.~nshal1WQn Hubei Changyarg Yangtze G. Hunan S. Anhui E. Yunnan Strat. C N , S ~ .e · iij Yuanshan Mb.* Balang Fm E paper ' . Shuijingtuo Fm. u ~ c: :;J ,co.. . l.L.. shale .' '- ~ Dahai Mb. , ::.:::. Fm . 0 h :.~; .:.'::: v,anJ' ,'ahe ~ ~ -ci •• :: .- sole ;0;. ':::: o 8- Zhongyicun Mb. ' X .: 0.. ::.;;; Fm. --I' a@' ."0. • ..• ,+<@ _~z'---1 E ;:S:: + .. , <. Tianzhushm ll.. Xia~b~iloushan ,? . . tr[[~]tu u .- 0 N c 0 0 '- Q) c -- V) 0 '- a... Cl . . C Baiyanshao ' E upper c---- ----- - ~::::-.-. ::~:~:: >- ll.. cherl Cl Mb. ~ Dengying 0 ~ I Fm. o J iucheng Mb. ~ Donglongtan Mb. Wangjiawan Fm . Nantuo Fm. T ~~IJ[ Doushanluo Fm. Nanluo yFm , >- ~ Shibanlan ~ Mb. (r~+ Q) o Hamajing Mb. 1---IIIJI? D D Dl fO Doushantuo Fm. +? Nantuo Fm . T Australia Flinders Ranges Ajax f Wilka- willina + Limestone ~® Parachilna Fm. I ~, I 1---------1 Uratanna Fm. 1ft. ~ ITlllII ITITlIillfl- Rawnsley Quartzite IEdiacara Mb. {r Q Bonney Sandstone Wonoka Fm. {r Bunyeroo Fm. I ABC Range Quarlzile Brachina Fm. {r Nuccaleena Fm . ---- Elatina Fm. T - ~ trilobites V hyoli thids y glaciomarine deposit \T bivalved arthropods ~ megaalgae {( Ediaeara type fossils <9 sponges 0 siphonous megaalgae @ trace fossils + sponge spieules * loeation of Chengjiang fossils @ arehaeoeya thids , small shelly fossils T ti llite mmn hiatus ~ \0 10 Higher Ba-values occur throughout the entire section, exeept for the siltstones that contain mass occurrenee horizons of bivalved arthropods and sponges, and the basal mieritie phosphorites. The clastie influenees inerease in the upper part of the section (sampies San 1/23-1/29), indieated by inereased Zr and Ti values, that resulted from a heavy mineral input (see text-fig. 4). Only partially anoxie eonditions developed (Co, Mn, Ni de- pietion, normal values of Cr, V) in the upper part of the section (sampies San 1123-1129). Under these latter conditions sponges found a wide distribution. At the Heziao section fully anoxie eon- ditions were developed during the lower At- dabanian, for the first time. Such eonditions were never established in the Chengjiang region (Yunnan). 2.4. Summary of sedimentologieal, palaeogeo- graphical and geochemieal observations A correlation of Sinian-Lower Cambrian sediments of the E.Yunnan, Hunan, Hubei and S.Anhui provinces is proposed in text -fig. 5. It is based on all available palaeontological and sedimentologieal data and field observations. The first oceurrenee of trilobites, the distribution of different small shelly fossil (SSF) associations (HE & Y ANG, 1982; CHEN, 1984; Luo et al., 1982, 1984; DING & QIAN, 1988; QIAN, 1989; QIAN & BENGTSON, 1989), the distribution of Phycodes pedum, as weIl as other trace fossils (e.g. Luo et al., 1984; SUN, pers. -comm. Oet. 1991) and of aeritareh zones (ZANG, 1992) were eonsidered as important stratigraphie markers. Aecording to the IUGS Working Group on the Precambrian-Cambrian boundary (decision July 1991), the first appearanee of the tracefossil Phycodes pedum is indicative of the Precambrian- Cambrian boundary. The present eorrelation pro- posal exeeds previous eorrelation attempts, whieh were based on palaeontologieal and sedimento- logieal data and isotope geochemistry (e.g. SUN, 1989; BRASIER et al. , 1990; BRASIER, 1992a, b). A facies reconstruetion for the Yangtze platform during Lowermost Cambrian times, based on sedimentologieal and palaeontologieal data, is presented herein (text-fig. 6). A distinetion bet- ween protected basin, uplift (also ealled Jiangnan islands by other authors, as e.g. Y ANG, CHENG & WANG, 1986), and deep basin facies is proposed. New tectonie data and the oceurrence of melange-zones indieate a local subduetion of oceanie erust during Middle Proterozoie time (pers. comm. BREWER, Sept. 1992). This zone expanded to an elongate belt, but the subduetion eeased completely in Late Proterozoie time. But the geotectonie influenee upon sedimentation by eom- pensation movements and hydrothermal ex- 300 halations, was aetive weIl into the Palaeozoie Era. Whether this facies reeonstruetion (text-fig. 6) can be eompared to an island are tectonic situ- ation or not remains unanswered. To be eertain would require additional espeeially tectonic in- vestigations. Nevertheless, this hypothesis seems reasonable beeause sequenees of basic volcanie rocks, including pillow struetures, have been described from the Pre-Sinian of Sichuan provinee (anonymous, 1991). But results of rnagmatie ae- ivities were further rePOrted (anonymous, 1991 ) from Sw. and N. Siehuan for the Early Sinian, subsequent to the so ealled Jinning movement. The uplift belt (Jiangnan islands of Y ANG, CHENG & WANG, 1986), whieh existed in the Upper Sinian and Lowermost Cambrian, eould not be deteeted as clearly for the Lower Sinian as for the Upper Sinian times. But an uplift, not as morphologically significant as in Upper Sinian, eould weIl have existed before (see anonymous, 1987). The wide oceurrenee of blaek shales with element en- riehments of V, Ni, Cr a.s.o. in the Doushantuo Fm., Niutitang Fm., Yanjiahe Fm. and Shuijingtuo Fm., as weIl as the appearanee of phosphates during the whole SinianJLower Cambrian might also indieate inereased outerops of volcanites, as e.g. back are basin basalts or volcanie are basalts, during the Upper Proterozoie. Thus, submarine volcanites rnay have served as a souree for an additional supply of elements to the sea water. During fue Upper Sinian (post Nantuo glaciation), N and NW of the uplift-belt a protected basin developed. This protected basin prograded with a general tendency towards the NW at least until the Atdabanian. Maximum subsidenee oceurred during the Tommotian, with the de- pocenter situated in the Sichuan provinee. An increased subsidence of the protected basin from the beginning of the Cambrian onwards led to a widely distributed diachronous deposition of black shales, here called the "Badaowan" Event (see text- fig. 5). That event was possibly, but not necessarily, connected with · eustatie sea level ehanges. The diachronity (j>f the black shales is indicated by data of SSF (CHEN, 1984; DING & QIAN, 1988; QIAN & BENGTSON, 1989), of traee fossils, and by sedimentologieal data. The general palaeo-geographie situation appears to support this conclusion. Geochemical and palaeontological data clearly point out the existenee of a stagnant basin with an extended anoxie zone. The development of anoxie conditions was variable in both time and spaee. Life was possible at least sometimes, depending upon the environment. SSF and sponge spieules belong to the remains of life forms with widest distribution throughout the lowermost Lower Cambrian. However, the oceurrenee of these fossils is mainly allochtonous or parauthochtonous. I \ I '? 0 { " / ' ... -"" ,.......... middle Prolerozoic melange zone ....... xxx v upper Prolerozoic melange zone Ordovician sulure 301 TeIt-fig: 6: Fades re- construction for the Yangtze platform during Lowermost Cambrian times (location of platform margins, melange zones and of the Ordovician suture after BREWER, pers. comm. Sept. 1992; distri- bution of Ni-Mo-PGE-Au-rich ores, completed after COVE- NEY ,et al. , 1992). Working area, described in the text, framed (compare also fig. I). • Ni - Mo - PGE -Au-rich ores in Lower Cambrian black shales v- enrichmenl ) + Sponge spicules The clastic influence on the sedimentation in the protected basin increased during the Upper Tommotian. This, and probably decreasing rates of subsidence led to a shallowing of the protected basin. It became more and more aerated, and nutrients were readily accessible. Altogether, this led to a rapid radiation of life forms during the Upper Tommotian / Atdabanian time. The pre- servation of some Porifera from the Upper Niutitang Fm. of the Sansha section, described herein as weH as the spiculite rnats from the same strata, underline the authochtonous nature of the fauna in the Upper Niutitang Fm .. Magrnatic activities are indirectly detectable in Upper Sinian sediments. Tuffs were mentioned in the Doushantuo Fm. by FAN, YE & LUI (1992), as weH as by CHEN & XIAO (1992), and in the Lower Cambrian by COVENEY & CHEN (1991) and COMPSTON et al. (1992). During field investi- gations in 1992 SIEGMUND & STEINER (unpubl.) discovered probable synsedimentary rnagrnatic rocks within the fossiliferous Lantian Fm. in S. Anhui. An increased subsidence of the protected basin, connected with fracturing, is assumed for the period of deposition of the Dengying Fm. Slump folds in claystones and cherts of the Liuchapo Fm. (N.Hunan prov.) and Piyuailcun Fm. (S.Anhui prov.), as weH as channel~ -in the Jiucheng Mb. (Yunnan prov.; STEINER, unpubl.), which can be correlated with carbonates of the Dengying Fm. (N.Hunan prov., S.Hubei ' ptov.), support an in- creased subsidence in the area N of the uplift. Because of the fracturing, the sedimentation was hydrotherrnally influenced. Thus, among others, stratiform Hg-ore-layers could have originated within the Dengying Fm. in the Hubei and Guizhou provinces (see e.g. Y AN & LIU, 1989; XING, 1989). COVENEY & CHEN (1991) and COVENEY et al. (1992) have proven a hydrotherrnal influence on the Lower Cambrian Mo-Ni-rich deposits. Cherts of the basal transgressive succession were assumed to be of exhalative origin by the latter authors, whereas BRASIER (1992a) described eherts in similar stratigraphie positions from other areas as spieulites. We consider the basal eherts of the "Badaowan" Event (see text-fig. 2) as exhalites. This opinion is supported by the high Ba-values of the eherts (up to 4500 ppm). Ba is an element that mainly indicates an endogenous origin (DILL, 1986). A barite-faeies of the Upper Sinian (anonymous, 1987), as weIl as the thiek eherts of the Liuehapo Fm. and Piyuaneun Fm. follows the uplift (see text-fig. 6) and were probably eontrolled by hydrothermal influences via marginal faults. The sediments of the Lower Cambrian strata are characterized by generally increased Ba-values, both in N.Hunan and S.Hubei, which indicates a possible continuous hydro- thermal influence. However, an increased input of reworked Ba-minerals coeval with increasing clastic influence in the depositional area must be additionally expected (see text-fig. 4). Tbe linear belt-like arrangement of the Ni- Mo deposits at the base of the Lower Cambrian black shales (see text-fig. 6) further supports the existence of basement fractures (COVENEY & CHEN, 1991). 3. Palaeontology 3.1 . Introduction With the progress of investigations into the Precambrian-Cambrian rocks, the Yangtze platform turned into focal attention for palae- ontological research. The discovery and description of a Lower Cambrian soft-body fauna from Cheng- jiang (e.g. ZHANG & Hou, 1985; Hou, 1987; CHEN, Hou & Lu, 1989; CHEN & ERDTMANN, 1991), the description of Ediacara-type fossils of the Shibantan Mb. from the Yangtze Gorges (DING & CHEN, 1981; SUN, 1986), the discovery ofhighly developed "mega-algae" in the Doushantuo and Dengying Fm. (ZHU & CHEN, 1984; CHEN & XIAO, 1991, 1992; STEINER, ERDTMANN & CHEN, 1992) and the evidence of diverse SSF associations (e.g. QIAN & BENGTSON, 1989; QIAN, 1989) certainly represents only a minor part of further discoveries still to be expected. With regard to the porifera, several records and doubtful documentations of sponge spicules from the Doushantuo Fm. and Dengying Fm. have been published. TANG, ZHANG & JIANG (1978) named questionable siliceous sponge spicules from thin sections of siliceous banded dolomites of the Doushantuo Fm. as Archaeoprotospongia and mentioned Protospongia from the Dengying Fm .. XING et al. (1985) and DING & XING (1988) also mentioned sponge spicules from the Precambrian 302 of S.Hubei province. They distinguished between ?Eospicula yichangensis and ?Hazelia Iia- ntuoensis. To the latter they also assigned Archaeoprotospongia of TANG, ZHANG & JIANG (1978). QIAN (1989) described spicules of Protospongia sp. from the Dengying Fm. (Maidiping Mb.) from Sichuan. Luo et al. (1982) reported Protospongia? sp. from bed 2 (= Dengying Fm., Xiaowaitoushan Mb.) of the Meishucun section and Calcihexactinia isophyllus from bed 13 (=base of Yuanshan Mb., Qiongzhusi Fm.) (Luo et al., 1984), hut similar observations were not confirmed in QIAN & BENGTSON (1989). Sponge spicules of Lower Cambrian black shales from Hunan and Hubei provinces (ano- nymous 1988, anonymous 1990) have been known for a long time. Most evidence comes from the protected basin facies (see text-fig. 6), but sponge spicules have also been reported from sand- stone/slate intercalations and from thin layered siliceous rocks and carbonaceous shales with phosphate nodules in the basal part of the deep basin in S.Hunan (anonymous, 1988). Entirely preserved Porifera were only known to date from the Atdabanian fossil lager- stätte Chengjiang (Yuanshan Mb.) in Yunnan. Recently discovered sponge spicules from the Shibantan Mb. of the Liantuo section (Hubei) and entirely preserved sponges from the base and the top of the Niutitang Fm. of the Sansha section are described herein. Associated with Poriferans, we discovered accumulation layers of Perspicaris sp. near the base of the black shales at Sansha. Remains of "mega-algae" in layers rich in sponge spicules from the top of the Niutitang Fm. at Luoyixi extend our knowledge of the fossil record from the Lowermost Cambrian . Because the Porifera constitute the phylogenetically most original group within the Metazoa (e.g. Ax, 1989; REITNER & MEHL, 1993) they are expected to be traced back very far within the fossil record. Actually, all major poriferan groups have been documented from the Early Cambrian, mainly as isolated spicules, but in ) isolated occurrences also as body fossils. In basal Cambrian strata, especially from China, triaxons of the Hexactinellida are by far the most common spicule type. From the Early Cambrian of South Australia BENGTSON et al. (1990) documented a diverse spicule association including various triaxons (especially hexact-, pectact- and stauractins) of the Hexactinellida. Also triaene most probably demospongiaen spicules (Dodeca- actinella cynodontota BENGTSON & RUNNEGAR, the authors interpret these spicules as calcarean) were found. Further, various Heteractinida (stern lineage representatives of the Calcarea) e.g. EifJe/ia W ALCOTI were documented. Definite sterraster spicules (Tetractinellida, Demospongiae) were documented from the Atdabanian of Flinders Range sections, South Australia by GRUBER & REITNER (1991). Some probably post-Tonunotian Early Cambrian Hexaetinellida and Demospongiae (?Protospongia. Hazelia, Leptomitus) in body preservation have been described from North America (RIGBY, 1987). From Sibiria also an Early Cambrian sponge body fossil (Lenica unica ?Demospongiae) has been reported (GoRJANSKY, 1977). The Middle Cambrian was a time of radiation within all poriferan major groups, and highly diverse sponge body fossil as weil as spicule associations have been documented from all over the world. The Middle Cambrian Burgess Shale of Canada brought about diverse faunas of many metazoan groups in body preservation (W ALCOTI, 1920) including sponge fossils of the Hexae- tinellida, the Demospongiae and the Calcarea (RIG- BY 1986). Middle Cambrian demosponges and hexaetinellids, in similarly good body preservation, were documented from the House Range and Drum Mountains in Utah (RIGBY 1983, 1990). An en- tirely preserved silieified heteraetinid sponge (Calcarea), Jawonya gurumal KRUSE, 1987, was published from the Middle Cambrian of North Australia (originally misinterpreted as a "sphineto- zoan", later revised by RIGBY, 1991: p. 84, REIT- NER,1992). In Middle Cambrian sediments of the Georgina Basin, Northem Territory, Australia, also the oldest hitherto known representative of the Anthaspidellidae, "Lithistida", has been published (KRusE, 1983). Further, a highly diverse poriferan spieule assemblage in phosphatie preservation is found. From these sediments van KEMPEN (1990) deseribed various spieules from hexaetinellides and demosponges (e.g. ealthrops and different triaenes). A detailed description and documen- tation of the very rieh spieule association of the Georgina Basin is eurrently in preparation by one ofthe authors (MEHL). Preservation state and stratigraphie distribution About 50 pieces of dark shale (some as part and counterpart) with spieule impressions of sponges. Some of these obviously are fossilized entire sponge bodies. The sponge fossils are pereieveable by naked eye as few em large, dark spots on the shale surfaces. Most of the specimens San 100-150 also eontain spieules, whieh are mainly preserved as intemal moulds ofaxial canals or entire spieules in secondarily silieified preservation, but weathered specimens (on yellowish shale surfaees) often only eontain hollow spicule impressions. Part of the spieules from the paratype of Hyalosinica archaica (San 106B) were analysed by EDAX, the anylysis eonfirmed that the material is siliea. The spieules must have been silieified secondarily from solutions invading the sediment, after dissolution of the original skeletal opal, dissoltions whieh 303 normally occurs during very early diagenesis. Exeept questionable demosponges and Porifera indet., the fossils of this collection are all Hexaetinellida. Some of the sampies, (e.g. San 107 A,B; PI.5, Fig. l), obviously are hexaetinellide spieules aeeumulated unsorted and without any visible orientation. They are interpreted here as spieule mats, whieh were formed on the ocean bottom after the decay of sponges and their deeomposition in situ. Similar spicule aeeumu- lations are observed in ~he present to form in situ spiculites at the Aretie Vesterisbanken (HENRICH et al., 1992). Older sampies San 050-060 show dark round spots, similar to those desribed above, but with no definite spieules and only very indistinet "ghosty" linear impressions, whieh indieate that spieules were originally present (e.g. San 50B; pI.5, fig.3). From the basal ehert, definite hexaetinellide spieules (hexaetins) are found in thin section (pI.6, figs.2-4). The presense of spieules here may be due to better preservation potiential and to accumulation in the eourse of a possible transportation. Precambrian spieule remains Hexaetinellid sponges and may be demosponges are thus definitely documented from the basal "Badowan" event. Their phylogenetie history, however, reaehes baek far beyond this. In a dolomitie limestone of the Dengying Formation, Shibantan Member (Ediacara Member equivalent, compare text-fig. 5) from the Liantuo section (Hubei Provinee, about 200 km N' of Sansha), spieules are frequently observed in thin section. These are preserved as moulds seeondarily filled with sparitie cements and then silieified. Most of them are monaxone, whose attribution is uncertain, because eentral eanals are only exeeptionally ob- served. A few of these moulds, however, appear to be rather definite "erosses", whieh are interpreted, with some eaution as paratangential rays of isolated hexaetine spieules ,(pI. 7). Material This material is still under study. The Porifera collection is eurrently kept at the Institut fur Paläontologie of the Freie Universität Berlin, and the sampies, so far, still have their original field numbers. 3.2. Systematic palaeontology Protoctista Division, Order, Family unknown unnamed alga (Plate 2, figs. 3 a,b, 4) Description: Irregular coaly imprint with stalk-like appendages. The appendages end up in funnel- shaped extensions. Dimensions: Total length of the irregular body 5 nun; length of the stalklike appendages 0,5-0,9 nun with an approx. width of 50-75 J.lIIl; maximum width ofthe funnel-shaped extensions 0,2-0,25 nun Material: 2 specimens (Luo 025, Luo 027) from the top of the Niutitang Fm. of Luoyixi near Wangchun (Hunan prov.) Discussion: Speculations about the biology of the organism are premature because only one specimen can be clearly placed ioto the unnarned Forma. If the funnel-shaped extensions of the appendages are only destructional remains of protoplasm filled bladders, this organism could represent a siphonous organized alga. Animalia Malacostraca LATREILLE 1806 Phyllocarida PACKARD 1879 Vanadaspidida NOVOZHILOV in ORLOV 1960 Perspicarididae BRIGGS 1978 Genus Perspicaris BRIGGS 1977 Perspicaris sp. (plate 1, figs.I-5, Plate 2, fig. 5, Plate 3, fig. 4) Diagnosis (from BRIGGs, 1977, p.597): "Carapace with hinge line, valves sub-oval, tapering anteriorly, rostral plate absent. Peduncuiate eyes large, borne on an elongate projection of the cephalon. Abdominal somites lacking appendages, teison not posteriorly produced, caudal furca spinose." Description: bivalved carapace of suboval outline, hinge line slightly convex, with a short postero- dorsal process. Carapace surface smooth apart from secondary folds and destruction structures. The border of carapace shows a thin rim. Dimensions: maximum length 6-14 nun; maximum heigth 4-8 nun Material: 22 specimens from the 10wermost Niutitang Fm. from Sansha near Dayong (Hunan prov.). Discussion: The genus Perspicaris was errected by BRIGGS in 1977 on the base of specimens with soft parts. The present material from Sansha does not show these diagnostically important soft parts. Thus, the taxonomical classification remains unclear to some degree. The isolated carapaces are 304 possibly closer related to P. dictynna (SIMONETf A & DELLE CA VE) BRIGGS 1977 than to other species, including P.? laevigata Hou & BERGSTRÖM 1991 from the Chengjiang Lagerstätte (Yunnan). The carapaces of Perspicaris sp. occur in mass layers within a limited horizon (see text-fig. 2). The sedimentology and geochemistry of this horizon, as weIl as the fragmentary state of pre- servation of these fossils, support the assumption of an drag transportation into the depositional environment by water currents. Several decom- posed carapaces are oniy preserved as circular closed ribbons, representing the more resistant borders of the carapaces (see plate 3, fig. 4). The specimen San 003 (plate 1, fig. 5 a,b) shows a possible rounded injury. Porifera GRANT, 1836 The poriferan taxa are described by MEHL & REITNER. Hexactinellida SCHMIDT, 1870 Reticulate Hexactinellid Sponges (Dictyo- spongiidae BALL, 1884) Sanshadictya n.g. (pI. 2, fig. 2; text-fig. 7) Derivatio nominis: Sanshadictya: Dictyosponge like hexactinellid from the type locality Sansha. Type species: Sanshadictya microreticulata. Diagnosis: Spicules are thin diactins and stauractins arranged in parallel bundles and forming a regular network with at least three orders of very fine quadrules. The sponge possessed coarse, probably anchoring spicules. Description: See the type species. Sanshadictya microreticulata n.g., n.sp. Derivatio nominis: microreticulata (la1.) refers to the small dimensions of reticulate meshes. Description: Fragment of sponge wall, only 5 x 7 nun, characterized by small quadrules of bundled diactins, partly in body preservation and partly only as impressions. The crosSing points are visible as dark spots, probably limonitic. Three orders of quadrules can be recognized, of which the largest is only about 1 nun long. The best preserved regions show very thin diactins in parallel bundles, between 5 and 7 spicules can be identified, but probably there were originally more. A few stauractins appear to be present in the best preserved area of the framework (plate San 117 B). Part of a thick monaxon, 4.5 nun long and about 100 J.lIIl in diameter, projects from the fragmentary sponge wall. Ten-fig 7: Sanshadictya microreticuJata, holotype (San 117); scale 5 mm. Probably, it represents the proximal part of a basal anchoring spicule, by means of which the sponge was originally attached. Discussion: The large Palaeozoic group of the Dictyospongiidae HALL is especially weH-known from the Devonian of New York (HALL & CLARKE, 1898), however, representatives of this group are found throughout the Palaeozoic since the Silurian. The youngest definite dictyospongiide was described from the Permian of Texas as Stereo- dictyon FINKS, 1960. According to the diagnosis given by HALL & CLARKE (1898) the Dictyo- spongiidae are characterized by a regular meshwork composed of vertical and horizontal bundles of diactins, normally with an outer layer of stauractins, forming quadrate or rectangular meshes in several orders of size. At the present stage of knowledge it is uncertain, whether this spicule organization characterizes a monophyletic group of hexactinellids, or if such regular reticulate patterns evolved several times convergently. Taking into consideration that dictyosponges S.str. are, so far, unknown from Later Cambrian and Ordovician strata, it is unlikely that the reticulate spiculation of Sanshadictya may have evolved independently of that of the Dictyospongiidae sensu HALL (1870). The meshwork of Sanshadictya microreticuJata shows diactins and stauractins in rectangles of three size orders, however, the largest meshes only measure about 1 mm across. Thus, reticulation is considerably finer than in any Dictyospongiidae known. Although only a small fragment is preserved, this sponge is significant, because it shows a derived type of spicule organization, and it might even be the oldest 305 representative of the Dictyospongiidae described so far. Since the basic spicules of Hexactinellida are neither diactins nor stauractins, but hexactins (MEHL, 1991), the dictyospongids must be con- sidered an already derived type of hexactinellide sponges. Material: The holotype is an unicate: San 117 A, B (plate + counterplate) Hexactinellida incertae sedis Hyalosinica n. g. (pI. 4, figs. la, b; text-fig. 8) Derivatio nominis: hyaJos (gr.) = transparent, clear., refers to the stalk of 10ng twisted spicules, like a "glas-rope" similar to that of the recent HyaJonema GRAY, 1835. Type species: HyaJosinica archaica Diagnosis: Stalk and root tuft consisting of coarse anisoactine, triaxial spicules loosely twisted in clock direction. Remark: Sponge body, except the tuft and few triaxial spicules in its proximal end, is unknown Description: See the type species. Hyalosinica archaica n. g., n. sp. Derivatio nominis: archaios (gr.) primary, original, these sponge are the oldest representatives oflyssacine stalk-bearing hexactinellids. Description: Only fragmentary twisted rootJstalk tufts of these sponges have been found. The tuft pieces are broken at both ends, thus it cannot be deterrnined, whether the spicules are diactins or monactins. The incompletely preserved spicules were originally longer. The holotype (text-fig. 8) is a tuft, 5.5 cm long, with rays twisted in clockical direction. Individual spicules are about 250 J.UD in maximal diameter and show no sign of com- paction. As a result of twisting, the spicules diverge and thus one end of the tuft measures ca. 7 mm and the opposite one only 4 mm across. In additionally to the long spicules, smaller triaxons hexacts, pentacts and staurncts, about 300 to 500 J.UD are scattered over the surface of the tuft, especially at its proximal end. About 7 mm under the inferred proximal edge of this tuft, several short rays perpendicularly project from its surface. The short rays clearly appear to be projecting from the long spicules directly, and more short rays pro- jecting in right angles to each other seem to be present at the same location as weH. Thus, the tuft spicules of HyaJosinica archaica may weH be true triaxons with two greatly prolonged rays and with their 4 paratangential rays projecting from the spicule centre. In all specimens, the spicules are in body preservation, but some of them are weathered out, so only hoHow impressions are left. Text-fig. 8: HyaJosinica archaica, holotype (San 109); seale 10 mm. Discussion: HyaJonema GRAY is the only recent hexactinellide sponge that is elevated above the sediment on a 10ng stalk of spirally twisted monactine (and some associated diactine) spicules. The HyaJonema tuft, which can be more than one meter long, is twisted generally counter-clockwise. According to the divergence of the tuft spicules in HyaJosinica archaica, a decision about the probable orientation of the tuft in respect of the sponge body is possible: The twisting of stalks in recent and fossil lyssacine hexactinellids becomes looser towards the distal ends. Thus, the narrow 4 mm end is interpreted here as proximal, whereas the looser 7 mm end was probably closer to the outer terminal anchoring point. One of the para- types, (San 106A), measures ca. 8 cm in total length. This tuft appears more tightly twisted in one, preswnably the proximal end (about 7.5 mm across), than the opposite, probably distal end (about 10 mm across). Using this inferred orientation, the twisting of the tuft is again in a clockwise direction. So far, a tuft with the main sponge body attached to it has not been found. 306 However, the proximal half part the holotype tuft is covered by many smaller triaxons (hexacts, pentacts and stauracts). Because similar spicules occur scattered all over the sediment, it cannot be certain that they really belong to the sponge. However, the small triaxons occur much more commonly on and in between the tuft -spicules than outside of it, and additionally they are concentrated almost exclusively in the proximal half of the tuft. Thus, it seems most probable that the small triaxons were originally part of the sponge body, which might have been tom off from the tuft. The tuft spicules of HyaJonema are monactins with the axial cross and five rudimentary, atrophied rays located terminally form an anchor. A few Early Palaeozoic sponges, which possessed similarly long twisted stalks, were deseribed in entirely preserved body fossils as Retifungus RIETSCHEL, 1970, from the Lower Devonian H~rück Slate (Germany), and some Cambrian Protospongia div. sp. described by DAWSON (1889) from Quebec (Canada). The 30 cm long stalk of Retifungus rudens is twisted counter-clockwise (compare Figs. by RIETSCHEL, 1970 and KOTT & W lJITKE, 1987) and thus similar to that of the recent HyaJonema GRAY. The Protospongia specimens of the DAwsoN-collection possess long anchoring spicules, but they are only very few in number and hardly twisted at all (MEHL, pers. obs. 1992). HyaJosteJia ZITTEL from the Carboniferous of England is a hexactinellide sponge with a tuft of long anchorate basalia, which according to the material available so far, shows no clear twisting. A stalk-like tuft was documented also from the Upper Cretaceous Arnager limestone (Denmark) by MEHL (1992: p1.5, fig.8) and attributed to the recent genus, HyaJonema GRAY. According to the systematic classification by SCHUlZE (1887), HyaJonema belongs to the Amphidiscophora. Since so far, no miroscleres have been found associated with any of the fossil stalks, their systematic position within the Hexactinellida cannot be established with absolute certaincy. HyaJosinica archaica is the oldest stalk-bearing sponge reported from the fossil record. lsolated long root- tuft spicules were found in sarnple San 1/24 (see text-fig. 2), which represents the earliest do- cumentation of this type of sponges. Material: Holotype: San 109 A,B (plate + counterplate). Paratypes: San 111 ; San 106 A, B. Triticispongia n. g. (pI. 3, fig. 3; text-fig. 9) Derivatio nominis: triticum (lat.) = grain ofwheat, refers to the outer shape and the small size of this sponge. Type species: Triticispongia diagonata . Text-fig 9: Triticispongia diagonata, holotype (San 143-x); scale 5 mm. Diagnosis: Sponge body hardly exceeds 10 mm total size. Spicules are small triaxons, mainly stauracts with their paratangentialia in a diagonal arrangement. Description: See the type species. Triticispongia diagonata n.g., n.sp. Derivatio nominis: diagonata refers to the diagonal orientation of its spicules. Description: Sponge body round to vase-shaped and very small, maximal diameter about 1 cm. Only impressions of spicules are preserved. The rays of these measure about 0.5 mm to 1.5 mm in length, they clearly show the paratangential rays, which are generally in a diagonal orientation to the outlines of the sponge body. In the crossing points of the paratangentialia of some of the spicules, holes from vertical, proximaVdistal rays can be observed. Part of the spicules of this sponge thus may be reconstructed as hexactins additionally to the stauractins. Discussion: Triticispongia diagonata is small in its total body size and spicules, these sponges may be juveniles. However, no similar larger sponges were found, to which they may be attributed. So far, no young buds or juvenile sponges from strata of the Lowermost Cambrian have been reported. From the Upper Cambrian of Queensland BENGTSON 307 (1986) documented tiny (only about 250 JUD) globular bodies apparently consisting of siliceous, triaxial spicules fused into a rigid framework: Echidnina runnegari, and he interpreted them as juvenile hexactinellide sponges. Provided that these fossils are not radiolarians, which in our opinion cannot be definitely excluded, they would be the only planktic rigid buds known within fossil or recent Porifera. Material: Holotype, San 143-x, and one paratype, San 118A,B (plate and counterplate). Hunanospongia QIAN & DING, 1988 ?Hunanospongia sp. (PI. 4, fig.2; text-fig. 10) Description The most conspicuous feature of the incomplete specimen are six large (5-10 mm across) spicule impressions that all occur in the same orientation. Each of these possesses four long rays that point in the same overall direction, they are arranged bilaterally symmetrically in two pairs with about 450 in between. A fIfth short ray that points in the opposite direction, can be observed in two of these six spicules. Scattered among these large spicule impressions, smaller (1-2 mm) hexactinellide spicules occur, mainly stauractins some of which show small holes within the ray junctions indicating the former presence of proximal / distal rays. Discussion: The large impressions are interpretet here as derived triaxial spicules with their four, probably paratangential, rays all "bent" in one direction, whereas the fifth short ray still shows its original orientation, and the sixth one is atrophied. The smalIer triaxons might not belong to the same sponge as these large spicules, since the smaller ones are found all over the surface of plate San 118. However, they are in a much denser con- centration among the larger impressions than outside these, so they may weH belong to the sponge. No recent nor fossil sponges in body preservation with a type of ~n spicules similar to the large ones are known so far, but a few isolated similar spicules from the fossil record have been described. Isolated spicules , with four rays that point in the same overall direction are reported from probably the same stratigraphical level in Yangjiaping called Hunanospongia deJicata QIAN & DING, 1988 (figured in DING & QIAN, 1988). Similar isolated spicules have been found also in Middle Cambrian sediments of the Georgina Basin, South Australia (MEHL, in prep.) and in a few clusters they have been observed on plate surfaces of Upper Cretaceous Arnager limestone (MEHL, in prep.). Material: This specimen is an unicate (San 118 A, sponge Z). 308 Text-fig. 10: Hunanospongia sp. (San 118-z); scale 5 mm. ?Hexactinellid sp. (p1..3 , fig.2; text-fig. 11) This small sponge fragment, is a dark, limonitie ernst whieh eontains some silieified spieules. The fossil shows a subconieal outline and measures 22 x 6 mm maximal size. Spieules inside are a few coarse diaetins associated with some smaller and very badly preserved relies, partly as impressions only, of monaxons and a few questionable stauraetins. The coarse diaetins, the largest of whieh measures 16 mm in length and ea. 200 J.UIl in diameter, more or less follow the direction of the long axis of the subconieal body fossil. Their pointed ends lie within the limonitie area and point towards the assumed base of the sponge. Because their opposite ends are all broken, none of the large diactins is eomplete in its entire length. Close to the margin of the assumed proximal end of the sponge fossil, a short spieular ray points out of the bedding surface (Text-Fig 11, arrow). It seems to belong one of the large spieules, from whieh it appears to project in a perpendieular direction. If this interpretation holds true, at least some of the apparent diactins would be of true triaxial nature. The smaller spicules are preserved as "ghoasty" impressions only, some of whieh seem to be triaxones. These are questionable stauraetins, whieh measure about 250-400 J.UIl in total size, they are all in a diagonal orientation to the eoarse diaetins. Discussion: Because of the apparent stauraetins, as well as the possible triaxial nature of some "diaetins" (as discussed above), this sponge most probably belongs to the Hexaetinellida. However, the ineomplete specimen, whieh is the only representative of this type within the eollection, in a bad preservation state, so no definite systematie assignment can be established. The eoarse diaetins all seem to end within the outline of the limonitie ernst. This implies that they most probably did not projeet beyond the sponge wall. For this reason, the diaetins cannot be interpreted as marginal prostalia or anehoring root spieules, and it is hard to understand their funetion, except as some kind of main vertieal supporting elements stabilizing the ) sponge. Sueh eoarse spieules that sre eompletely integrated within the sponge wall are observed in the Devonian hexaetinellide Taleolaspongia RIGBY & MEHL (in press), in whieh similar spieules of triaxial origin run through the wall in a longitudinal direction. However, these Devonian sponges are of rather large size and possess round pores in the wall, and they show no further similarities to the sponge here described. Material: The specimen (San 105) is an unicate. Ten-fig. 11: Hexactinellide sponge indet. (San 105); scale 5 nun. Porifera incertae sedis Soltu:tiniella n. g. (pI. 2, fig. 1; text-fig. 12 ) Derivatio nominis: sol (lat.) = the sun, actin (lat.) = ray; refers to tbe radial sun-like arrangement of diactine spicules. Type species: SolactinieUa plumata. Diagnosis: Spicu1es are mainly, or exclusively, coarse diactins, which are organized in bundles and radiate towards and protude beyond the margins ofthe sponge body. Description: See the type species. Solactiniella plumata n.g., n. sp. Derivatio nominis: plumos (lat.) = feather-like, fluffy; refers to the divergence of the spicu1ar bundles towards the margins. Description: Tbe sponge, which appears to be a fairly complete specimen, measures 3-4 cm in dia- meter, and shows no oscu1ar cavity. The spicu1es are maioIy impressions, some of which still contain internal mou1ds of secondarily thickened central canals, probably in limonitic preservation. OoIy diactins and a few questionable stauractins are observed. Tbe diactins are rather large, up to 20 mm, but mostly 5-10 nun, in total length. The 309 Ten-fig. 12: Solactiniella plumata, holotype (San 101); scale 10 nun. spicule orientation seems fairly accidential, but especially the peripheral diactins tend to radiate towards and project from the margin in a plumose arrangement. Discussion: At a first view, this fossil looks like an accidential, dense accumu1ation of spicules in a chaotic arrangement. However, the preferred radial orientation and the fact that ooIy one, maybe two, types of spicu1es indicate that this spiculation belongs to one and the same sponge body. It is not definitely established whether this sponge belongs to the Hexactinellida or to the Demospongiae, since we cannot determine, whether or not stauractins were also originally presen~. Even if the spicule impressions were all origißaIly diactins, they may weIl belong to a lyssacine hexactinellide sponge. On the other band, Demospongiae of similar outline are known from the Middle Cambrian Burgess Shale. Choia W ALCOTI possesses large diactins exclusively, which radiate from the center and project from the margin of the sponge body. Tbe plumose, radiating spiculation must be considered as a very ancient pattern of the Demo- spongiae. However, the radial spicu1e arrangement of Choia is much more regular than in Solactiniella, and the large coarse spicu1es of the latter do point towards an attribution to the Hexactinellida. Text-fig. 13: Saelaspongia densa, holotype (San 102-1); scale 10 mm. Material: The Holotype, San 10 IA, B (plate and counterplate) is the only body fossil that is de- finitely assigned to this species. Diactins of the size documented here seem to be a major component of spicule mats described above (like in San 107, pI. 5, fig. I). Saetaspongia o. g. (pI. 3, fig. I ; text-fig. 13) Derivatio oomiois: saeta (lat.) = bristly hair; refers to the very thin hair-like spicules. Type species: Saetaspongia densa (pI. 3, fig. I ; text-fig.13) Diagnosis: Dense accumulations of very thin hair- like diactins arranged in serniparalles bundles throughout the sponge body. The spicules line, but do not protude beyond the well-defined outer margin of the sponge body. Description: See the type species. Saetaspongia densa n.g., o. sp. Derivatio oominis: densus (lat.) = tight; refers to the dense accumulation of spicules, appearently without peripheral apertures. Description: The holotype, an almost circular, probably fairly complete impression of a sponge body measures about 3 x 4 cm. No oscular cavity is visible, but the dermal margins are partly pre- served. The impressions of thin, hair-like diactins (probably originally about 25 ~ in diameter) are only 1-2 mm long. The spicule impressions, most of which are pointed in both ends, are arranged in serni-parallel, sometimes also plumose bundles, 310 which generally radiate towards the periphery. However, they do not protude beyond the outer surface of the sponge body, but they line the outer margins as tangential dense bundles. Impressions of thicker-appearing spicules (about 50-100 ~ in diameter) occur, and some are in a perpendicular orientation, visible as round holes, scattered among the bundled diactins. These larger spicules appear to be mainly monactins and diactins, but a few of them rnight be tri-, tetr- or even hexactins. Discussion: The principalia of this sponge appear to be all diactins, the mode of preservation does not allow any definite statements, as to whether or not spicules with more than one axis were originally present. Thus, the systematic position of this sponge cannot be definitely deterrnined. The radial, sometimes plumose arrangement of diactins in- dicates a demospongian rather than a hexac- tinellide affinity. However, sponges with hair-like, mainly diactine spicules in a similar orientation are known also from Palaeozoic hexactinellids, e.g. the Devonian Rufospongia triporata RIGBY & MEHL (in press). Rufospongia, However, possesses clearly spicule delirnited pores in the body wall, and it has definitely hexactinelIide spicules as weIl. The larger spicule impressions may not belong to this sponge, since similar impressions are also common on the surface of the sampIe (e.g. on the paratype, San 104) outside the outline of the fossils. Material: Holotype: San 102-L; Paratype: San 104 3.3 Fossil poriferan faunas showing similar ta- phonomy: Red HilI (Middle Devonian, Nevada) and Arnager limestone (Upper Cretaceous, Denmark) These sponge fossils from Hunan Province are preserved mainly as spicule impressions on the surface of the dark shale. Although the spicules are unfused, they seem to be more or less in their original position within the sponge bodies. Although most siliceous sponges from the Early Palaeozoic possessed non-rigid skeletons of loose spicules (except the "Lithistida", common in Ordovician and Silurian strata), such good pre- servation is exceptional in the fossil record of non- rigid sponges. Normally, the small rnineralized, siliceous or calcitic spicules will fallout of the decaying soft tissues and can be found as isolated spicules only, scattered within the sediment. For this reason, the fossil record of these non-rigid poriferan groups is poor compared to their from an actualistic viewpoint assumeably worldwide do- minance within most sponge faunas. This is true especially to the Hexactinellida, since so-called dictyonal forms with rigid siliceous skeletons of fused spicules did not become an important faunal element until the Late Triassic (e.g. in Northem Sichuan, China; WENDT et al, 1989 and in the Camian Cassian beds, Italy; KEUPP et al., 1989). Because of a few fossilization "windows", such as the Cambrian Burgess Shale (W ALCOTI, 1920) or the Middle Devonian Red HilI (RIGBY & MEHL, in press) faunas, we know of at least some non-rigid, entirely preserved sponges from the Early Palaeozoic. In such cases, a rapid embedding prior to decay prevented these sponges from falling apart, and thus the exceptional documentation of spicules in situ is possible. Even in Mesozoic strata, the hexactinellids are probably generally under-represented within the fossil record due to the fact that the non-rigid, so-called "lyssacines", which are dominant among the Hexactinellida to- day, normally would not be documented. From the Coniacian Amager limestone (Bornholm, Den- mark), lyssacine hexactinellids known from isolated spicules only, such as the Rossellidae, were documented only recently as body fossils (MEHL, 1992). Common to the Cretaceous Amager fauna, the Devonian Red HilI sponges, and our Tommotian ones described here is the preservation of non-rigid sponges, especially lyssacine hexactinellids, in fairly large quantities. The sponges do not appear accumulated in certain layers, but occur more or less scattered throughout the sequences. Beds of the Red HilI section (Givetian) are 2-10 cm thick and consist of mainly dolomitized wacke- and packstones with a constant terrigenous input of fine to medium grained quartz sand. Generally, the sponges are preserved as hematite, probably resulting from metasomatosis of the pyritic pseudomorphosis of originally siliceous spicules. Qnly small sponges, Teganiella ovata RIGBY & MEHL, in press, are found as entire body fossils. They commonly accumulated in monospecific clusters (up to 35 specimens were counted on a piece of limestone that measures less than 10 X 10 cm). Sponges larger than about 5 cm, such as dictyospongiids or Rujospongia RIGBY & MEHL, in press, are generally fragmental, but occationally occur as large, almost complete specimens up to 10-20 cm size. These large fossils of the fragile sponge walls most probably were subject of rapid burial more or less in situ . Common to most sampies from the Red Hill- section is the fact that a sponge-bearing bedding surface typically contains only one species of sponge fossils. Interestingly, such "taxonomical sorting" with accumulations of a large number of sponge fossils of one single species, e.g. Choia ridJeyi WALCOTI, 1920, on shale surfaces are commonly observed also in sampies of the Middle Cambrian Burgess Shale collection (MEHL, pers. obs. 1992). This taphonomy can be explained only by assuming that the sponges concemed during their lifetime were already settled in monospecific groupings. Maybe this is due to their often non- sexual mode of reproduction, and/or to the short larval phases of sexual generations. Also, species- 311 specific ecological requirements often cause larvae to settle, where other specimens of the same species are already successfully growing. Another example is the Upper Cretaceous (Coniacian) Amager limestone (Bornholm, Denmark). The beds of this section consist of 5-15 cm thick lime mud- and wackestones that wedge out over lateral distances of 10-20 m. They contain sponges in large quantities, predominantly lyssacine hexactinellids and common root tufts, often found in living position as documented by MEHL (1992) and preserved as cristobatite' silica, pyrite or limonite pseudomorphs, or as hollow impressions of spicules. The extraordinary preservation of non- rigid hexactinellids as entire body fossils with their spicules in place implies a rapid fossilization of these sponges prior to the decay of soft tissues. Presumably, turbidity currents occasionally em- bedded the living sponges. The lobe deposits of the Amager beds further confmns the interpretation of these sediments as the result of sudden events. 4. Conclusions 1. According to investigations of the lithology and trace element geochemistry analysis, the Lowermost Cambrian sediments of the San- sha section were deposited under partly anoxic conditions, or in a stagnant basin, respectively. 2. Upper Sinian and Lower Cambrian strata of Hunan and Anhui provinces are bio- and lithostratigraphically correllated with E- Yunnan and Hubei provinces for the first time. 3. During Upper Sinian and Lowermost Cambrian time, within the Yangtze plat- form following facies types can be distin- guished: protected basin, uplift area, deep basin. 4. The "Badaowan" event is diachronous. 5. Exceptionally well-preserved fossils extend the record of entirely preserved Hexac- I tinellida and probably also Demospongiae down to the basal Tommotian. 6. The occurence of derived representatives of the sponges, such as the reticulate Hexacti- nellida, in strata of the basal Cambrian con- firms the phylogenetic assumption that the Porifera are an original and very old group ofMetazoa. 7. lsolated, definitely poriferan, hexactinellid, and other types may be with demospongean affinities, spicules are documented from Upper Precambrian (Sinian) strata probably stratigraphically equivalent to the Ediacara Member are documented for the first time. 8. Thus follows that the documentation of en- tire sponges as body fossils from strata of the Upper Proterozoic is now rnerely a question of time and effort. 5. Acknowledgernents The authors thank Prof. Dr. CHEN Junyuan, Dr. ZHANG Yunming, Dr. ZHU Maoyan and Mr. LI Guoxian (all Nanjing) for guidance and assistance in the field. We are endepted to Prof. Dr. 1.K. RIGBY for discussion and for valuable comments and suggestions on the manuscript. Special thanks are due to Hendrik SIEGMUND (Berlin) for valuable discussions and joint field work in 1991 and 1992. Hendrik SIEGMUND and Dr. 1. MALETZ (Buffalo) are acknowledged for the critical reading of the manuscript. Hendrik SIEGMUND supplied the photos for pI 6, figs. 2-4. Thanks to Mrs. GROßKOPF and Mr. KLEEBERG (Berlin) for the photographic documentation for the plates. DM. gratefully acknowledges many stirnulating dis- cussions with Prof. H. KEUPP (Berlin). MS. thanks Dr. MATIHEIS (Berlin) for RFA analyses, Prof. W ANG Xiaofeng (Yichang) for translations frorn the Chinese and Dr. R BREWER (Nanjing) and Dr. H. GELDSETZER (Caigary) for discussions and literature assistance. Mrs. DUNKER (Berlin) ex- pertly drew figs. 1-6. The research was funded by MPG, Munich and DFG under grant no. Er 96/7/1-3 with con- tributions by NIGPAS. The field trip of MS to China in 1992 was supported by DAAD, Bonn. 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(1984): On the discovery of macrofossil algae from the Late Sinian in the eastern Yangtze Gorges, South China. (in Chinese, with an English abstract)- Acta Botanica Sinica. 26(5): 558-560. 316 Plate 1 Locality for specimens of plate 1-6 1 km southwest of trafik checkpoint Sansha Algae from the Niutitang formation of the Louyixi section. Fig.l Perspicaris sp., mass accumulation of carapaces Scale: 5 mm. Fig.2 Perspicaris sp. , isolated carapace Scale: 5 mm Fig. 3 Perspicaris sp. , isolated carapace Scale: 5 mm. Fig. 4 Perspicaris sp., isolated carapace Scale: 5 mm. Fig. 5a Damaged Perspicaris carapaces one with an injury (arrow) Scale: 5 mm. Fig. 5b Enlargement of injury offig. 5a. Scale: 500 ~. 317 318 Plate 2 Fig.1 Soiactinella piumata n.gen.n.sp., h010type (SAN 107a,b) Seale: 1 em. Fig.2 Sanshadictya microreticuiata n.gen.n.sp., h010type (SAN 117a,b) Seale: 250 J.lIll. Fig.3a Unnamed alga linked with a sponge spieule (open arrow) Seale: 1 mm. Fig.3b Enlargement offig. 3a dose to blaek arrow with appendages offunnel-shaped extensions Seale: 300 J.lIll. Fig.4 Unnamed alga. Seale: 1 mm. Fig.5 Perspicaris sp. , carapaee, Seale: 5 mm. 319 320 Plate 3 Fig.l Saetaspongia densa, n.gen.n.sp., holotype (SAN 102). Taxon with demosponge features . Scale: 5 mm. Fig.2 Young hexaetinellid with two marginaliarge monaxonie spieules. Scale: 1 em. Fig.3 Triticispongia diagonata n.gen.n.sp., holotype (SAN 143) Seale. 250 Jilll. Fig.4 Damaged and partly decayed Perspicaris earapaees. Scale: 5 mm. 321 322 Plate 4 Fig.la HyaJosinica archaica n.gen.n.sp., holotype (SAN 109a,b) Seale: 5 mm. Fig.lb Enlargement ofthe spieule root tuft of HyaJosinica archaica. Scale: 5 mm. Fig.2 Hunanospongia sp. (QIAN & DING, 1988). Maybe remains of adermal spieule layer. Seale: 5 mm. 323 324 Plate 5 Fig.l Thin spiculite layer of hexactinellid scleres. these layers may have a lateral extension of some square meters. Young sponges are often settled on these layers (SAN 107) Scale: 1 mm. Fig.2 Young hexatinellid sponge with imprints ofstauractins (SAN 108) Scale: 2 mm. Fig.3 Relatively large rounded black fossils near the base ofthe Sansha region (SAN 50b). These structures exhibit sometimes remains of small spicules. Therefore they are interpreted as sponge remains, maybe with demosponges affinities. Scale: 5 mm. Fig. 4 Very young hexatinellid sponge growing on a large hexactine. Scale: 250 J.I.Ill. 325 326 Plate 6 Fig.l Accumulation ofyoung hexactinellids partly growing on large spicules (SAN 143) Scale: 2 mm. Fig.2 Cluster ofhexactinellid spicules from the basal chert ofthe Sansha section above sampies SAN 1/4 (Lower Tommotian). Scale: 250 ~. Fig.3 lsolated monaxonic spicules with remains of spines (acantho-) Scale: 500 ~. Fig.4 Spicule cross section with diagenetically enlarged central canal and outer spines. Scale: 1O~. 327 328 Plate 7 Spicules from the Precambrian Shiobantan Member (Dengying Formation) of the road seetion of Liantuo of sponges. Fig.l Overview of the spicule bearing wackestone. The spicules are secondarily silicified. Scale: 200 ~. Fig.la Spicule with triane affinities. Arrow marks remains of an axial canal (enlargement of fig. I) Scale: 50~. Fig.lb Diagenetically altered stauractine spicules with affinities to hexactinellids (enlargement offig.l) Scale: 20~. Fig.2 Oxeote spicule (demospnge ?) Scale. 50~. Fig.3 Style spicule (demosponge ?) Scale: 50~. Fig. 4. Stauractine spicule (hexactinellid) Scale: 75~. Fig. 5 Remain of a spicule axial canal. Scale: 20~. 329