山东海阳断裂东石兰沟段晚更新世以来地表断错特征与最大潜在地震估计

海阳断裂是胶东半岛NE向牟平 -即墨断裂带东部一条规模较大的断裂 ,尽管晚更新世以来该断裂的地表断错活动总体上已基本停息 ,但东石兰沟段在晚更新世晚期以来仍有断错地表的活动。最后一次断错地表的活动发生在距今 3 7～ 1 2万年 ,但接近 1 2万年。地表破裂长度约6 5km ,活动段长度 8km。地表断错以走滑活动为主 ,可见最大倾滑位移 0 2m ;根据断层擦痕侧伏角推测最大水平位移 1 13m。最后一次断错地表的活动若以距今 1 2万年计算 ,则最大平均倾滑速率为 0 0 17mm/a ;最大平均右旋走滑速率为 0 0 94mm/a。野外观测到该活动段的断错活动表现为突发断错 ,根据地震地表破裂参数、活动段长度与地震的关系 ,估计其最大潜在地震为 6 级     

New Early Cretaceous paleomagnetic results from Qilian orogenic belt and its tectonic implications

Lower Cretaceous red sedimentary rocks from the depositional basin of East Qilian fold belt have been collected for a paleomagnetic study. Stepwise thermal demagnetization reveals two or three components of magnetization from dark red sandstones. Low-temperature magnetic component is consistent with the present Earth Field direction in geographic coordinates. High-temperature magnetic components are mainly carried by hematite. The mean pole of 19 sites for high-temperature magnetic components after tilt-correction is λ=62.2°N, φ=193.4°E, A95=3.2°, and it passes fold tests at 99% confidence level and reversal tests at 95% confidence level. The paleopole is insignificantly different from that of Halim et al. (1998) from the same sampling area at the 95% confidence level. Compared with paleomagnetic results for North China, South China, and Eurasia, our results suggest that no significant relative latitudinal displacement has taken place between Lanzhou region and these blocks since Cretaceous time. Remarkably, the pole of Lanzhou shows a 20° clockwise rotation with respect to those of North China, South China, and Eurasia. Geological information indicates that the crustal shortening in the western part of Qilian is greater than that in eastern part. In this case, the clockwise rotation of sampling area was related to India/Eurasia collision, and this collision resulted in a left-lateral strike-slip motion of the Altun fault in north Tibetan Plateau after the Cretaceous.     

Late Glacial and Holocene environmental history of the Pirin Mountains (SW Bulgaria): a paleolimnological study of Lake Dalgoto (2310 m)

Diatoms, Cladocera, and chironomids preserved in the sediments of Lake Dalgoto were studied to reconstruct the history of the lake ecosystem in the context of the vegetation history as represented by the pollen stratigraphy. Younger Dryas silty sediments at the base of the core are characterized by low diversity of aquatic organisms. The transition to the Holocene is indicated by a sharp change from silt to clay-gyttja. The migration and expansion of trees at lower elevations between 10200 and 8500 ¹⁴C-yr BP, along with higher diversities and concentrations of aquatic organisms and the decreased proportion of north-alpine diatoms, point to rapidly rising summer temperatures. After 6500 ¹⁴C-yr BP the expansion of Pinus mugo in the catchment coincides with signs of natural eutrophication as recorded by an increase of planktonic diatoms. In the late Holocene (4000–0 ¹⁴C-yr BP) Pinus peuce and Abies are reduced and Picea expands. Cereal grains and disturbance indicators suggest late-Holocene human modification of the vegetation.     

延边汪清一带的二叠纪浊积岩特征

根据典型剖面研究,该套浊积岩系由一套轻微区域变质的中细砂岩、粉砂岩、粉砂质泥岩组成,局部夹碳酸盐岩。剖面结构多种粒度不同的碎屑岩在宏观上有规律地交替出现形成韵律层系,单个韵律层系厚度一般20～60cm。此浊积岩具明显的粒序性、发育较清楚的平行纹层及扰动层理,具较典型的浊积岩特点,鲍玛层序发育。     

羌塘盆地最大规模沥青脉的发现及其意义

在羌塘盆地已经发现了190余处油气显示。近年笔者在盆地北部晚侏罗世地层中发现了迄今最大规模的沥青脉。研究结果表明，该沥青脉产出于上侏罗统索瓦组地层之中，地层下部系与沥青脉的形成有一定关系的中株罗统夏里组局部含油气显示的盐丘。沥青族组分(％)为：饱和烃5．72、芳烃18．46、沥青质52.37、非烃23．45，说明核沥青脉经过了运移、氮化的过程。同时，沥青脉产出于复背斜范围内，利于油气聚集成藏。这一发现对于羌塘盆地的油气地质的作用具有现实意义。     

辽宁庄河鞍子山超单元岩浆侵位变形构造

鞍子山超单元由4个单元组成，各单元不同程度地发育岩浆侵位变形构造。侵位变形构造主要由叶理构造组成，闪长质包体，钾长石斑晶总体按优选方位定向，三者产状一致，平行接触带分布。从早期单元至晚期单元，随着岩浆侵位叶理构造变形强度减弱，闪长质包体数量减少，压扁变形程度降低，钾长石斑晶从明显按优选方位定向到杂乱分布。根据上述特征，将该超单元浆侵位变形、中等侵位变形、弱侵位变形及基本无侵位变形4个带。     

贵州关岭生物群海百合Traumatocrinus的再研究

在前人的研究基础上，通过对大量新发掘的贵州关岭地区晚三叠世海百合化石标本的再研究，肯定了Trauma-tocrinus的有效性。根据目前的材料，认为该属只有1个有效种，即Traumatocrinus hsui；而根据化石的埋藏学特征，认为幼年体Traumatocrinus hsui营假浮游生活，成年体是否能够适应底栖生活环境尚需进一步证实。     

Re-Os Age of Cu-Ni Ores from the Huangshandong Cu-Ni Sulfide Deposit in the East Tianshan Mountains and Its Implication for Geodynamic Processes

An isochron age of 282±20 (95% conf. limit) Ma of the sulfide ores in the Huangshandong Cu-Ni sulfide deposit, the East Tianshan Mountains has been obtained through Re-Os isotopic measurement. The age implies that the Cu-Ni sulfide deposit and other related deposits in the same area occurred in a Permian extensional environment of post-collision instead of Devonian-Early Carboniferous ophiolite-related oceanic or island arc environments inferred before. It shares the same ages with the orogenic and epithermal gold deposit systems in the same area. An initial 187Os/188Os ratio of 0.25±0.04 (1σ) and a γos value of 99 on average display the participation of large quantities of crustal components into the rock-forming and ore-forming system during mineralization and magmatic emplacement.     

泥盆纪最早期牙形刺带化石在蒙古南戈壁幕使盖(Mushgai)地区"尕屋(Gavuu)"段的首次发现

在蒙古南戈壁的Bayan—Khoshuu Ruins剖面原归入到志留系Mandalovoo组尕屋(Gavuu)段的地层中发现了牙形刺Caudicriodus woschimidti woschmidti，这是泥盆纪最早期牙形刺带化石在蒙古的首次发现。尕屋(Gavuu)段的下部属志留系，但其上部，即采集牙形刺样品M-9～M-12的层位肯定属下泥盆统(下洛霍考夫阶)，而不是下志留统。Mandalovoo组应当改为Mandalovoo群，它的三个段应提升为三个组。