摘要
事件地层学(Event Stratigraphy)的概念由英国学者D.V.Ager(1973)首先提出。它利用地质历史上稀有的、突发的短暂事件及其地层记录来划分对比地层,按照自然特征确定地层界线。我国学者对事件地层学的研究起步较晚。徐道一于1980年和1982年首先提出了古生物绝灭与超新星爆发的关系并介绍了新灾变假说。近年来由杨遵仪教授主持的IGCP第203项目,对华南地区二叠-三叠系界线研究已取得可喜成果。刘本培等(1986)从事件地层学角度探讨了东亚陆相侏罗-白垩系界线。吴思本于1984年和1986年首先发现并研究了多伦陨石坑的陨击事件。张勤文等于1984年对我国南方震旦-寒武系界线上的地质事件进行了研究。但是,目前对其它地层界线上的地质事件及生物事件研究甚少。
Data on occurrences of Late Devonian rugose corals suggest a major worldwide extinction of platform- and reef-dwelling corals occurring near the end of Frasnian time. The basin-dwelling corals, however, were virtually unaffected by the Late Frasnian event.
The Daminshan district in the central Great Xing'an Ranges of NE China is one of the very rare localities in the world, where the Frasnian shallow-water corals and the Early Famennian basinai corals were well-developed. The Frasnian sediments called the Lower Daminshan Formation containing the corals Hexagonaria zarubinskiensis (Ivania), Temnophyllum rectum (Walther), T. densum sp. nov., and Hinganastraea daminshanensis gen. nov. While in the Famennian strata called the Upper Daminshan Formation, the corals are all small and solitary with thin and simple skeletal elements, reflecting a semipelagic basinal environment, such as Petraiella sp., Barrandeophyllum zhaduenheense sp. nov., Guerichiphyllum daminshanense (Guo), Friedbergia sinensis sp. nov., Amplexocarinia sp., Gorizdronia simplex (Guo), G. minor sp. nov., Kozlowskinia sinensis sp. nov., Tabulophyllum tenuis sp. nov., Famennelasma sinensis sp. nov., etc. Their age may be bounded by the associated ammonoids corresponding to the Cheiloceras and Platyclymenia zones.
The collisional suture between the Sino-Korean and the Siberian plates extends roughly along the border line of China with Mongolia, about 350km south of the Daminshan district. In the author's (1986) interpretation, the convergence of the two paleoplates started in Late Devonian, and so the orogenic movement and volcanic activities caused by the collisional process might be the direct reason of the Late Frasnian extinction in this region. Of course, this requires further study on the stratigraphic sections to find the iridium anomaly and to determine the isotopes.
Description of New Genus and Species Barrandeophyllum zhaduenheense sp. nov. (P1. Ⅲ, figs. 1, 2; text-fig. 7) 1980 Barrandeophyllum perplexum, Guo, p. 110, p1. 48, fig. 7.
Subcylindrical solitary corallum 8—11mm in diameter, with a deep calicular pit. Marginal stereozone 1.2—1.3mm in width. Major septa 20 in number, moderately thick, with their axial ends withdrawing from axis, but contiguous to form anincomplete and irregularly round aulos with an inner radius of 2mm and surrounded by thinner wall. Minor septa 17 in number, 1/3—1/2 as long as the major ones and contingent. Tabulae generally complete, concave in the middle and curved abaxially on edges, with 5—6 of them visible in a distance of 5mm in the longitudinal section where the aulos is indistinet.
Comparison: Morphologically the new species is similar to Barrandeophyllum bohemicum Prantl from the Zlichovian of Czechoslovakia, but the latter has a greater diameter (20mm) of corallum, more major septa and longer minor septa, thinner marginal stereozone and thicker wall of aulos.
Occurrence and horizon: Southern bank of Zhaduen River, Xuguit Qi, Inner Mongolia;Upper Devonian Upper Daminshan Formation. Holotype Ru 1032; Paratype Ru 1032a.
Friedbergia sinensis sp. nov. (P1.Ⅳ, fig. 4; text-fig. 9)
Small, solitary rugose coral. In early stages, corallum 5mm in diameter; major septa of cardinal quadrants 8 in number, strongly thickened and curved, unequal in length; those of counter quadrants thin, 8—9 in number and curved around axial space to form a half aulos>1mm ininner radius; cardinal fossula shallow, but counter one obscure. In later stages corallum 7—8mm in diameter; septa in cardinal quadrants thinned and 10 in number, withdrawing from axial space; those of counter quadrants 12—13 in number, with half aulos becoming indistinct; cardinal fossula slightly obvious.
Comparison: The present new type differs from the type species Friedbergia bipartita Rozkowska from the upper part of Famennian in the Holy Cross Mrs. of Poland which shows more intervals between the thickened septa of cardinal quadrants in early stages and rhopaloid axial ends of septa to form a thicker half aulos in later stages.
Occurrence and horizon: The same as the preceding species. Holotype Ru 1238. Gorizdronia minor sp. nov. (P1. Ⅳ, fig. 3; text-flg. 11)
Cylindro-conical, small solitary corallum with a diameter of 3.5—4mm. Epitheca thin. Major septa 16 in number, thin and straight, slightly withdrawing from axis, with some axial ends of neighbouring septa conjoined. A short cardinal septum present in shallow fossula. Minor septa undeveloped. Tabulae complete and flat, slightly convex in the middle, evenly spaced with intervals of 1mm. Few amplexoid septa visible in longitudinal section.
Comparison: This new species is somewhat similar to Gorizdronia profunda tenius Rozko wska from the Famennian in the Holy Cross Mts. of Poland in septal number and flatness of tabulae. But in the latter, the corallum is 7mm in diameter, with shorter and thinner septa and more closely and irregularly spaced tabulae.
Occurrence and horizon: The same as the preceding species. Holotype Ru 1231.
Kozlowskinia sinensis sp. nov. (P1. Ⅳ, figs. 5, 6; text-fig. 12)
Subcylindrical small solitary corallum 7mm in diameter, with a narrow marginal stereozone. Major septa 17—20 in number, thin and slightly curved, reaching 1/2 way to the axis. Minor septa rare and short. Dissepiments in 1—2 rows, with outer ones subhorizontally based and declined abaxially, while inner ones unequal in size and gently declined adaxially. Lateral dissepiments invisible in transverse section. Tabularium wide; tabulae moderately complete, slightly convex or concave, added by some tabellae, with 12 tabulae visible in a vertical distance of 5mm.
Comparison: The type species Kozlowskinia flos Rozkowska from the lower Famennian of the Holy Cross Mrs. in Poland differs from our new species in the larger size of corallum, more and longer septa, wider dissepimentarium and distinct lateral dissepiments.
Occurrence and horizon: The same as the preceding species. Holotype Ru 1232; Paratype Ru 1237.
Tabulophyllum tenuis sp. nov. (P1. Ⅳ, figs. 8, 9; text-fig. 14) 1980 Tabulophyllum rectum, Guo, p. 139, p1. 13, fig. 4.
Cylindro-conical corallum 14mm in diameter, with a weak marginal stereozone. Major septa 28 in number, thin, reaching 2/3—3/4 way to the axis. Minor septa stunted or poorly developed. Septa partly disrupted by large lonsdaleoid dissepiments. 2—3 rows of elongate dissepiments steeply declined in longitudinal section. Tabularium wide; tabulae mostly complete, flat-topped with a few peripheral tabellae. Intervals between spaced tabulae 1mm on the average.
Comparison: The present species differs from Tabulophyllum rectum Fenton et Fenton from the Frasnian of Iowa, United States which shows longer minor septa and a wider lonsdaleoid marginarium with bigger cystosepiments disrupting most septa.
Occurrence and horfizon: West of Daminshan, Xuguit Qi, Inner Mongolia; Upper Devonian Upper Daminshan Formation. Holotype Ru 1052; Paratype Ru 1242. Temnophyllum densum sp. nov. (P1. Ⅰ, figs. 1, 2) 1980 Temnophyllum rectum, Guo, p. 124, p1. 47, fig. 9.
Ceratoid corallum 12—18mm in diameter. Septa (26—31)×2 in number, thickened in dissepi-mentarium to contiguity, forming a 3—4mm wide stereozone, in Which a few dissepiments may emerge. Major septa long and straight, thinned into tabularium, with their axial ends slightly withdrawing from axia or conjoined at axis. Minor septa restricted only to dissepimentarium and mostly covered by stereozone. Dissepiments numerous, subglobose. Tabulae incomplete, flat-topped and closely spaced, with 12—13 of them observable in a vertical distance of 5mm. Monocanthine septal trabeculae coarse, directed upwards and inwards at 30°.
Comparison: The new species is similar to the type species Temnophyllum latum Walther in the dense and wide stereozone, but in the latter, the tabulae are concave and sporadically spaced. The present species differs from Temnophyllum ornatum Walther from the upper part of Middle Devonian in Germany in the narrower marginal stereozone and longer minor septa of the latter.
Occurrence and horizon: Southern bank of Zhaduen River, Xuguit Qi of Inner Mongolia; Upper Devonisn Lower Daminshan Formation. Holotype Ru 1048; Paratype Ru 1223.
Hinganastraea gen. nov.
Type species: Billingsastraea daminshanensis Guo, 1980
Astreoid corallum with large corallites. Septa radially arranged, straight and carinate, with predominantly yard-arm carinae formed by lateral fibrous extension of fine monocanthine trabeculae. Major septa fusiform in transverse section, thickest in inner part of dissepimentarium and withdrawing from axis. Minor septa thinner, restricted to dissepimentarium. Dissepimentarial floors subhorizontal and steeply declined near inner margin of dissepimentarium; thus trabeculae arranged in a broad asymmetrical sector. Dissepiments small, numerous and subglobose. Tabulae complete, horizontal or slightly convex and concave, with a supplementary peripheral tabellae.
Comparison: The new genus is similar to Asterobillingsia Oliver, 1974 from Lower-Middle Devonian of North America in the type of compound corallum, corallite size, dissepimentarial and tabularial floors. But the latter has attenuate septa, bigger and lowly arched dissepiments. The difference between the new genus and Marisastrum Rozkowska, 1965 from the Frasnian of West Europe lies in the latter's cerioid corallum with smaller corallites.
Age and distribution: Early Late Devonian (Frasnian), North China.
Famennelasma sinensis sp. nov. (P1. Ⅲ, fig. 5; text-fig. 15)
Small, conical solitary corallum 6—6.5mm in diameter, with a moderately thick marginal stereozone. Major septa 18—19 in number, somewhat arranged in bilateral symmetry, with their axial ends slightly dilated and withdrawing from axis. Minor septa very short or undeveloped. Cardinal septum shortened in shallow fossula. Tabulae declined abaxially.
Comparison: The type species Famennelasma rhen
出处
《古生物学报》
CAS
CSCD
北大核心
1990年第4期427-446,517-520,共20页
Acta Palaeontologica Sinica
基金
国家自然科学基金资助课题
