1. Reinterpreted as an Ordovician volcanogenic massive and disseminated sulphide deposit.

2. Dichograptus species are very widespread in the early Ordovician rocks.

3. RioFinex examined the Ordovician volcanic rocks of County Tyrone for base metals but found only minor intersections of low-grade copper mineralisation.

4. By the end of the Ordovician they had already radiated into many of the niches they occupy today.

5. The Ordovician lithofacies and biofacies change greatly at different localities of the Yangtze Region, South China.

6. The weathering crust of Majiagou Formation in Ordovician of Changqing Gasfield in Ordos Basin is the major pay zone with the evaporated marginal sea facies.

7. Cambrian - Ordovician petroleum system is the most important system type in the northern region of Tarim basin.

8. Straddling the late Ordovician period and the early Silurian period, the Andean-Saharan ice age was marked by a mass extinction, the second most severe in Earth's history.

9. Mid-Lower Ordovician reservoir was characterized by early accumulation, early filling and high level of oil and gas evolvement. Late Ordovician-Silurian was main period for hydrocarbon accumulation.

10. Marine volcanics of Early Ordovician was found in Zhifang region.

11. In the Ordovician, Silurian Period, the Devonian, Carboniferous, the advent of low amphibians and ancient ancient reptiles.

12. Hydrocarbon in the Ordovician petroleum accumulation system originated from the Cambrian and Lower Ordovician source rocks.

13. Bryozoa was quite diversified in the Ordovician, but lacked fossil records in the Cambrian.

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14. At the end of the Ordovician period, 440m years ago, a mass extinction event wiped out almost all corals and fish, and 25% of all families of creatures.

15. The main reservoir types in Ordovician carbonate formation in Tahe Oilfield are dissolution fractures and caves.

16. Apart from conodonts, unequivocal evidence for fish does not occur until the Ordovician.

17. Like most other molluscan groups they rapidly diversified in the Ordovician.

18. Trinucleid trilobites, with various types of fringe, are characteristic of Ordovician rocks.

19. Five past extinctions: Some event near end of the Ordovician period, 440m years ago, wiped out almost all corals and fish, and 25 % of all families of creatures.

20. Among the multi - oil - generating beds, the Cambrian and Ordovician is the best one.

21. A systemic and integrated criteria is thus obtained for the Ordovician carbonates in the Tahe oilfield.

22. The third period of the Paleozoic era, the Silurian follows the Ordovician period and precedes the Devonian.

23. According to the data on the bitumen reflectance and inclusion homogenization temperature, it is shown that the organic matters in Lower Ordovician source rocks are in the high maturity stage.

24. The main water source is fracture - karst water in Middle Ordovician carbonate rocks.

25. Finally some views are presented that how to conduct further study on Ordovician reservoir, how to improve producing reserves extent and how to make optimum technical strategy etc.

26. The correlation between oil and source proved that the preserved commercial oil reservoirs of marine origin in the Tarim basin are mainly generated from the marl of the Middle Upper Ordovician.

27. The Tazhong paleo-uplift is a multiple oil-gas accumulation play, and medium-large scale reservoirs have been found in the Carboniferous, Silurian, Ordovician and Cambrian Systems.

28. The soluble rocks in this area are the carbonate rock constructions of the Sinian, the Cambrian and the Ordovician period.

29. The Bed G bauxite of Shanxi massif, a paleoresiduum bauxite underlying Bangou Formation of Upper Carboniferous, occurs on the fossil erosion surface of Middle Ordovician of Upper Cambrian.

30. Due to spreading of Helan and Qinling rift valleys during the Ordovician period, a L-shaped swell belt formed in the western and south- ern parts of the basin.

31. In Tazhong-88 Well, the conodont fossils in the late of Middle Ordovician and the early of Late Ordovician slope facies have been found for the first time.

32. At the end of Ordovician Period, a differential elevation occurred in the central Shanganning Basin due to the Caledonian Movement.

33. The Lower Ordovician in Tazhong area is dominated by marine carbonate.

34. Therefore, conventional seismic data can be used to effectively predict large fractured, fractured-cavern, carven and cave reservoirs of Ordovician carbonate in Central Tarim basin.

35. The Cambrian - Ordovician strata in Luxi Block are very continuous and well exposed.

36. The other one is between the Upper Ordovician Terekawat Formation and the underlying formations, which presents commonly as a parallel unconformity or an angular unconformity in some regions.

37. And the strong karstification in the same direction as layer and cataclasis create by tectonic stress are the control factors of Ordovician carbonate karst reservoir development.

38. The Ordovician system carbonate rock reservior in Tahe oilfield lies deep in the earth. Having high temperature there, the reservior has many difficulties in acid filtering and acid rock reaction.

39. Study shows that the Ordovician carbonate formation in this area has the characteristic of very low groundmass porosity.

40. A rift trough along Mianxian - Lueyang ophiolitic melange belt was formed from Ordovician to Silurian.

41. Study shows that the Ordovician carbonate formation in this area characteristic of very low groundmass porosity.

42. A lot cephalopoda fossils were found in the section of dolomite with limestone, which belong to early Ordovician.

43. The clastic rock reservoirs of Upper Devonian and Silurian and the carbonate reservoirs of Middle and Lower Ordovician are mainly distributed in the peri-cline area around central Tarim basin.

44. Because hard shells fossilise, and are therefore more readily preserved than soft tissue(sentence dictionary), scientists had an incomplete and biased view of the marine life that existed during the Ordovician.

45. The major storage space and fluid channel of Ordovician reservoir is hypogenous fracture-cavern. It can make high production after erodent buildup.

46. A great thickness of evaporite strata were developed in the Ordovician in eastern Ordos Basin. Quite a few researchers have proposed different views about their genesis.

47. This achievement provides the microfossil materials for the study of the lower ordovician in Northern Guizhou.

48. Comprehensive researches have concluded that the Heishan ophiolite was formed in Nanhua Ordovician period and its structural location in Silurian period early Middle Devonian epoch.

49. This was the result from the large - scale regression in the Late Ordovician.

50. Benxi water tunnel in the limestone is the Ordovician period under the EC-Hill Group and the EC in the Majiagou group, the role of a rock from development.

51. Late trias, the up-and-down configurations of Ordovician weathered crust peak are high on the west-north and low on the east-south, oil-gas moved to west-north.

52. The clastic rock reservoirs of Upper Devonian and Silurian and the carbonate reservoirs of Middle and Lower Ordovician are mainly distributed in the pen- dine area around central Tarim basin.

53. And think pinching belt of mid - up Ordovician is exploration area of oil and gas in future.

54. The Tahe reservoir Ordovician carbonate rock belongs to the type reservoir that this is special.

55. Look at these two folds. One is convex upward with older rock of Ordovician limestone toward the center of curvature.

56. It is based on the present writers' achievements of study and mapping of quantitative lithofacies palaeogeography of the Cambrian and Ordovician in North China, South China and Northwest China.

57. It consists of Archaeozoic and Paleozoic strata in which Cambrian and Ordovician are dominated by limestone. The tectonism and weathering make it become a good reservoir.

58. In 1992 , the author found fossil crinoid stems in crystalline limestone at Xia-zhuang, Wenchuan, which were determined to be of Ordovician age.

59. The middle and upper Ordovician was characterized by clastic rock of turbidity facies in bathyal sea.

60. The major structure in the area is the NE-NNE folded belt consisting of Banxi Group of the Middle Proterozoic era to the Ordovician system of the Early Paleozoic era.

61. The generation of hydrocarbons of the Ordovician source is different from that of Mesozoic nd Cenozoic sources since there were on high plants in the Ordovician Period.

62. Late Ordovician organic reefs composed of cyanophyta and calcareous sponge were firstly discovered in northern Tarim basin.

63. The natural geography of the Ordovician period is that: the Hannan paleocontinent and the Bashan Mountain rise at the north, and the wide epicontinental sea basin lies in the south.

64. In this paper, the straticulate dolostone and spatulate dolostone in Lower Ordovician strata of Well Tazhong 1 were studied using petrologic and geochemical methods.

65. The Middle Ordovician Llandovery rugose corals are abundant in the Yangtze region, especially in the Early Silurian.

66. The Cambrian and Ordovician are important exploration target strata in Leshan - Longnvsi paleo - uplift area.

67. The Ordovician and Devonian rocks did not yield reliable character remanence due to either too weak magnetization or dispersal remanent directions.

68. There is abundant karst fissure water in the limestone and dolomite of Cambrian and Ordovician.

69. Many coal mine in our country suffers from the Ordovician period Karst containing water inrush frequently due to the complex geology condition, Water inrush is a serious disaster in coal mining.