直进演化抑或分支演化──中国的人类化石证据

和县、巢湖、周口店和金牛山的人类化石表明,直立人有可能延续到0．200MaB．P,智人至少可上溯到0．310MaB．P。考虑到郧县人类化石有可能是代表智人,而不是代表直立人,则智人的历史可提早到蓝田直立人的年代。直立人与智人在生存年代上的重叠,提示了人属成员的演化不是以“直进演化”的形式实现的,如果把直立人和智人看成是两个不同的种的话。     

The last deglaciation of Svalbard

Svalbard has been completely covered by an extensive ice sheet at least once, but not in the Late Weichselian (max. 18,000–20,000 years ago). Areas in the western and northwestern parts of Svalbard have been ice-free for more than 40,000 years. The extension and time of a Barents Shelf glaciation are questions still open for discussion. For most of the Svalbard area we do not know when the last deglaciation started, geographically and in time. The oldest datings for the interval 15,000 to 10,000 years B.P. have an age of about 12,600 years, and datings from between 11,000 and 10,000 years B.P. are rather frequent in the western and northern parts of Spitsbergen. No moraines from Younger Dryas have been found in Svalbard and the glaciers were probably less extensive 10,000 years ago than today. The maximum extension of glaciers in the Holocene took place only a few hundred years ago.     

北京房山世界地质公园中元古界雾迷山组地震-海啸序列及地质特征——以野三坡园区为例

野三坡园区中元古界(1800~1200Ma B.P)位于燕辽裂陷槽南部中轴断层南支(古紫荆关断裂)之东盘。野三坡雾迷山组笫二段白云岩中的地震序列自下而上分为：A.阶梯状断层与震碎角砾岩变形单元;B.微褶皱-微断层变形单元;C.液化均一变形单元;D.液化卷曲变形单元。这4个变形单元分别代表海底之下深度不足10m内已固结成岩—半固结—弱固结沉积层的变形特征,都经历了前震及主震期（P波和S波）不同程度的影响。海啸系列（海啸岩）自下而上为：E.津浪丘状层单元;F.丘-槽构造层单元和G.粒序均一层单元。海啸是在主震期数十秒后发生的。海底瞬时大幅度抬升,然后突然大幅度下降,使外海海水涌入,引发海啸,形成丘状层及有关变形。余震阶段的震荡流与一次沉降事件分别形成F和G单元。本区中轴断层（古紫荆关断层）是一条海底直立的断层带,对雾迷山组二段中的地震-海啸及沉积过程均起到激发与控制作用。此次震中位于中轴断层带西缘的白石山,震级为7.0~7.5里氏级,是震源浅、裂度大的海底地震。     

Glacial stratigraphy of East and Central Jutland

Glaciostratigraphic investigations at one key locality (Haldum), 9 major and about 160 minor localities in East and Central Jutland, Denmark, together with laboratory work, have led to the establishment of a stratigraphy consisting of 10 till units, usually separated by meltwater deposits. The stratigraphy is in some degree supported by thermoluminescence datings. The complete sequence includes one till unit with associated meltwater deposits of Menapian age, three till units with intercalated meltwater deposits of Elsterian age, marine sediments deposited during the Holsteininan, and three till units with intercalated of Elsterian age, marine sediments deposited during the Holsteinian, and three till units with intercalated glaciofluvial sedimants of Saalian age. Eemian deposits are present above this level, and the whole sequence is capped by till and meltwater deposits related to three glacial advances during the Weichselian.     

Relative dating of Late Quaternary deposits using cluster and discriminant analysis, Audubon Cirque, Mt. Audubon, Colorado Front Range

Holocene and Late Quaternary talus, lobate rock glaciers, and moraines within Audubon Cirque, Colorado Front Range, were assigned reltive ages using the following age-dependent criteria: fresh-weathered ratio, pitting, weathering rind development, angularity, and surface, oxidation of boulders, together with lichen cover and largest lichen diameter. Principal Component scores, yielding four major groups of deposits (relative age units C, R, E and V, from youngest to oldest). Tentative correlation with other Colorado Late Quaternary sequences suggests that unit C is of Gannett Peak age (100–300 years B. P.), unit R of Audubon age (950–1850 years B. P.) unit E of Early Neoglacial age (3000–5000 years B. P.), and unit V of Late Pinedale age (about 10,000 Years B. P.). Correlation is problematic due to differences in operationsl definitions of relative dating parametrs between workers, and because climatic and lithologic variations between areas may confound the date.     

Evidence of high sea level during the mid- Holocene on the southwest coast of Sri Lanka

A well-developed extensive buried coral reef at Akurala, north of Hikkaduwa, is deposited on a low plateau of decomposed crystalline rocks of Precambrian age. Radiocarbon age datings from three coral quarries in the area reveal that the branching and massive corals, in a position ofgrowth, were gradually deposited between 6, 110 ± 80 B.P. and 5,500 ± 80 B.P. in a bay or a lagoon as isolated patches, and their heights vary from 1.4m to 3.9m below mean sea level (MSL). Four radiocarbon age datings of emerged coral reef patches at Akurala and Akurala- Telwatte vary from 6,170 ± 70 B.P. to 5,350 ± 80 B.P. and at levels between 10cm and 70cm above MSL respectively. The present living corals in front of the southwest coast thrive from mean low water spring (MLWS) tidal level to 4m in depth in lagoonal reef areas. From the level of pesent living coral it is inferred that sea level was above the present level about 50cm at 6,110 ± 80 B.P. and 1m or more at 5,560 ± 80 B.P. The in situ position and condition of the materials show that they were not accumulated by catastrophic events such as storm waves.     

Stratigraphy of late Quaternary estuarine deposits and amino acid stereochemistry of oyster shells beneath San Francisco Bay,California

The sequence of Quaternary deposits beneath the floor of San Francisco Bay includes four to seven noncontemporaneous estuarine units intercalated with alluvium and dune sand. Units L (0–10,000 B.P.), M (>40,000 B.P., probably ca. 80,000–140,000 B.P.), and N (older than unit M) are distinctly superposed. The dominant molluscan fossil in each of these three units is Ostrea lurida Carpenter, the native oyster along much of the pacific Coast of North America. Despite a lamellar structure that suggests vulnerability to contamination, O. lurida shells generally yield amino acid enantiomeric ratios that are analytically reproducible and stratigraphically consistent. The kinetics of racemization in O. lurida conceivably resembles that of Protothaca and Saxidomus, other bivalves whose kinetics of racemization are relatively well understood. Assuming such a resemblance, enantiomeric ratios in O. lurida imply that (1) unit M is the same approximate age as estuarine terrace deposits bordering San Pablo Bay and Carquinez Strait, providing that the terrace deposits have been at diagenetic temperatures 1°-2°C warmer than unit M; and (2) the age of unit N is about four times greater than that of unit M, providing that both units have been at the same approximate diagenetic temperature.     

Forced regression and its sedimentary response to continental lacustrine rift basin: A case of the Member 3 of Shahejie Formation in Laizhouwan sag,Bohai Bay Basin

Falling stage systems tract(FSST)is an offlap strata with strong relationship with hydrocarbon exploration,which is driven by relative lake-level fall and developed above the highstand systems tract and below the lowstand systems tract of a new sequence. It has no relationship with sediment supply. Based on the theory of sequence stratigraphy and sedimentology,3D seismic data,drilling core data,and well-logging data were comprehensively analyzed. The study showed that the FSST strata was formed in the Member 3 of Shahejie Formation in the Laizhouwan sag. The FSST can be divided into three units,namely as units P1,P2,and P3 from bottom to top. The P1 is the first unit of progradation downlap the bottom of the FSST. The top of the unit P3 is a sequence boundary exhibits subaerial unconformity. The seismic profile along the source direction is characterized by the low-angle oblique progradation reflection that downstream the center of lake basin from west to east. Incised valleys developed on the top of the FSST perpendicular to the source direction. Gamma-ray logging response is manifested by a series of funnel-shaped complex,indicating that the sedimentary response of the FSST was a cycle of coarsening-upward parasequence sets. Comprehensive studies on core interpretation and well-logging analysis showed that the FSST was a fluvial-delta sedimentary system with slumped fan deposits associated with the delta front. Consequently,the FSST is a common result of relative dry climate and falling of lake level,considering regional tectonic evolution,sediment supply,and paleo-climate change. The discovery of the FSST in the Laizhouwan sag has an important geological significance for the sedimentological interpretation,and it offers a guidance for further oil exploration in the study area. In addition,it also serves as a significant reference for future research on the FSST development and exploration in the continental lacustrine rift basin.     

A glacial chronology for northern East Greenland

In East Greenland between 75 and 76N three different glacial episodes can be identified: (1) An early period with more or less total ice cover and in which the ice reached out onto the continental shelf - the Kap Mackenzie stadial; (2) a period with glaciation of intermediate extent, when nunataks and a few ice-free lowland areas existed - the Muschelbjerg stadial; and (3) a final period with glacial advance, when the glaciers were mainly restricted to fjords and larger valleys - the Nanok stadial. Each of these stadials was followed by a period with general deglaciation, from which marine shell-bearing sediments have been found; the Hochstetter Forland interstadial, the Peters Bugt interstadial and the Flandrian interglacial, respectively. The marine limit sank with each of these ice-free periods; probably an isostatic effect of the decreasing amplitude of the glacial advances. The deglaciation after the Nanok stadial began about 9500 B.P. It is not known for certain when this glacial advance started, but 13,000 B.P. or earlier is suggested. According to ¹⁴C datings the Peters Bugt interstadial dates from at least 45,000 B.P. and the Hochstetter Forland interstadial from at least 49,000 B.P. However, amino acid analyses indicate a distinct age difference between these two interstadial, and Th/U datings give age estimates of 70,000–115,000 B.P. for the Hochstetter Forland interstadial, which therefore seems to be of Early Weichselian age although a pre-Weichselian age cannot be excluded. The same applies to the preceding Kap Mackenzie stadial. The correspondence between the present glacial chronology and similar tripartite ones on Bafffin Island, Ellesmere Island and Svalbard seems reasonably good     

陆相断陷湖盆强制湖退及沉积响应:以莱州湾凹陷沙三段为例*

强制湖退体系域(FSST)是由相对湖平面下降驱动、发育于相同层序高位体系域之上及新层序低位体系域之下、在相对湖平面下降时期形成的、与油气勘探关系密切的一种退覆地层,与沉积物供给的变化无关。基于三维地震、钻井岩心和测录井资料,在层序地层学和沉积学理论指导下,发现莱州湾凹陷古近系沙河街组三段发育一套强制湖退体系域地层,垂向上可划分为3期,自下而上命名为P1、P2和P3,P1向湖盆中央终止于FSST底界面,P3顶部为显著不整合的层序界面。顺物源方向地震响应特征为缺失顶积层的低角度斜交前积反射,该反射自西向东推进到湖盆中央;在垂直物源方向的地震剖面上,可见下切谷地震响应。测井响应GR曲线呈漏斗状的复合体,表明沉积响应为上粗下细的反旋回。岩心及测井相分析结果表明,该FSST为一套河流—三角洲沉积体系,三角洲前缘伴生滑塌湖底扇沉积体。综合盆地区域构造演化、沉积物供给和气候变化等因素,认为该套沉积体系是气候相对干旱和绝对湖平面下降的共同产物。莱州湾凹陷沙三段FSST的发现对其沉积解释具有重要地质意义,对研究区进一步的油气勘探开发具有指导意义,也对研究陆相断陷湖盆FSST的形成与发现具有借鉴意义。     

Indications of late medieval earthquakes in the Talas-Fergana Fault Zone,Tien Shan

A paleoseismological study in the Talas-Fergana Fault Zone of the Tien Shan was accompanied by age determination of ancient seismic events. The calibrated radiocarbon datings of recent and buried soils allowed us to recognize the fault segments reactivated during strong earthquakes that occurred in the 14th- 16th centuries A.D. The magnitude of the paleoseismological event in the 16th century was no lower than 7.0 and no lower than IX in seismic intensity.     

Constraint on the eclogite age of the Sanbagawa metamorphic rocks in central Shikoku,Japan

ABSTRACT

To constrain the timing from the accretion to the subduction-related metamorphism of the protolith in the Sanbagawa eclogites, we performed zircon U–Pb datings and REE composition analyses on pelitic schist of the Seba eclogite-facies region in the Besshi area in central Shikoku, Japan. The detrital igneous cores of the zircons show ages from ca. 2000 to 100 Ma, and the metamorphic rims show ca. 90 Ma. These results show that the protolith was accreted at ca. 100–90 Ma, which is significantly younger than the previously reported accretion age of ca. 130 Ma of other eclogite-facies regions in this area. And, the metamorphic rim domains show HREE decrease without Eu anomalies, suggesting that they were formed at ca. 90 Ma eclogite-facies metamorphism. Our results combined with previous reports for the tectonics of the Sanbagawa metamorphic rocks suggest that there are at least two eclogite-facies units with different accretion ages in the Besshi area; ca. 130 Ma unit (Besshi unit) and ca. 100–90 Ma unit (Asemi-gawa unit), which structurally contact with each other. It is likely that the older unit was subducted into a depth of over 50 km and stagnated until the younger unit was subducted to the same depth. Probably, both units were juxtaposed at a mantle depth and began to exhume to the surface at the same timing after ca. 90 Ma. The juxtaposition and exhumation process might have relation to multi-factors such as tectonic erosion along the subduction zone, shallowing subduction angle of the hotter slab, backflow in the mantle and fluid infiltration along exhumation route.     

Younger Dryas end moraines between Hardangerfjorden and Sognefjorden, Western Norway

End moraines (called the Herdla Moraines) from the Younger Dryas Stadial arc morphologically mapped along the western coast of Norway, from Hardangerfjorden to north of Sognefjorden. The submarine position of the moraines are found by means of a conventional echo sounder. Stratigraphieal studies with many C¹⁴ datings are used for age determination, giving Late Younger Dryas (10,000–10,500 C¹⁴ years B.P.) for the Herdla Moraines. The moraines are correlated with the Ra-Salpausselkä Moraines. Isobases for the Younger Dryas are obtained from marine terraces formed contemporaneously with the moraines.     

胶东半岛中生代构造演化的几何学和运动学

据岩石的变质相及变形特征可把胶东半岛分为5个地质单元,其构造几何关系由高至低为:1)板岩——砂岩单元;2)高压片麻岩——石英岩单元;3)大理岩——角闪岩单元;4)超高压变质单元,它经历了超过150km的深俯冲作用并快速折返至地表;5)片理化的混合岩穹隆单元,其为超高压变质单元叠加了混合岩化作用。这些构造单元均经历了相同的变形,具有NW指向的剪切特征。对比大别山构造学的研究结果,这种变形特征代表了超高压变质地体在折返过程中的运动学表现。混合岩穹隆中所残余含柯石英榴辉岩表明了胶东半岛和苏鲁地区具有相同的构造演化过程,烟台——青岛——五莲断裂不是华南板块与华北板块间的缝合带。     

关中活断层和地裂缝的年代学研究

取该区活动断裂中的断层泥,并首次在几个断层面附近的劈理化黄土中取样测出热释光年龄。12个断层热释光年龄数据在20-240ka B P之间变化,证实中更新世晚期和晚更新世期间断层曾有一次活动,为本区断层的活动性提供了证据。本研究成果也为西安地裂缝的活断层与人工抽水双重成因提供了证据。      

Palaeoecology and post-Weichselian shore-level changes on the coast of Møre, western Norway

Pollen analysis, macrosubfossil determinations and radiocarbon datings from a 0.95 m thick peat deposit resting on sand and buried by a 1.3 m thick beach ridge at Haramsøy (an outer-arc island off the coast of Møre og Romsdal province), reveal changes in the local vegetation and in the groundwater level of the landward lagoon-like area. These are considered to reflect the relative shore-level changes between late Preboreal and early Atlantic times: an initial section with a high groundwater level reflecting the early Boreal high shore level, an intervening section with a low groundwater level, from the time of the Boreal regression minimum, and a final section, with a rising groundwater level, reflecting the late Boreal eustatic rise in sea level, which led to complete burial of the peat and the formation of an extensive Tapes beach ridge. Radiocarbon dates reveal that the basal sand (approx. 8 m above sea level) rose above sea level at approx. 9500 B. P. and that the top of the peat (approx. 9 m above sea level) was transgressed by the sea at approx. 7300 B. P. The spread of alder ( Alnus ) within the area may have been delayed by a thousand years compared with other regions in south Norway.     

论地震地层的等时特征

地震地层有波系、波组、地震层序、同相轴等几种单元,规模较大的波系、波组可与年代地层学中的统、系甚至界相对应,是等时的地层单元。地震层序以各种不整合作为划分地层的依据,所划的地层不但不穿时,而且具成因意义。同相轴为等时的、平整的、具波阻抗差的古沉积表面的反射所形成,而不是人为想象的、不平整的、具波阻抗差的岩性界面的反射。在它所代表的地层厚度的规模上(通常为30～50m),同相轴可看成一个等时的地层单元,而对小于这一规模的地层来说,同相轴则可能穿时。地震地层对比除具等时性特征外,还有其它一些优越性及局限性。     

The last deglaciation (20,000 to 11,000 B. P.) on Andoya, northern Norway

Cores representing a 5.5m long sequence recovered from lake Æråsvatnet have been investigated for lithostratigraphy, micro- and macrofossils and radiocarbon chronology. For the first time in Fennoscandia the maximum Weichselian advance has been closely bracketed with radiocarbon datings (19,000–18,500 B.P.). A continuous stratigraphy from 18,500 B.P. and onwards, partly marine and partly lacustrine, discloses the local shoreline displacement, the palaeovegetation, the palaeoclimate and, together with other data, the deglaciation history. Two phases with a prevailing High Arctic climate have occurred: 18,000 to 16,000 B.P. and 13,700 to 12,800 B.P. Important climatic amelioration accelerating the deglacial recession occurred 16,000, 12,800 and 12,000 B.P. The continental ice sheet was situated close to its maximum position until about 16,000 B.P. The following deglaciation was interrupted by (a minor ?) readvance/halt about 15,000 B.P. (the Flesen event), 13,700-13,000 B.P. (the D-event), 12,500 B.P. (the Skarpnes event) and 11,000–10,000 B.P. (the TromsØ-Lyngen event). The deglaciation chronology and pattern can be correlated with the suggested deep-sea-stratigraphy-based stepwise pattern relying on the old age alternative for termination IA.     

Late Weichselian–Early Holocene shore displacement west of Mt. Billingen, within the Middle Swedish end-moraine zone

Fourteen lake basins on and west of Mt. Billingen have been analysed with respect to different stratigraphic methods: pollen, diatoms, other microfossils, ¹⁴C datings, lithology, grain-size distribution and chemical characteristics. The aim has been to establish a well-dated pollen stratigraphy for the area in order to date when lakes west of Mt. Billingen were raised above sea level. Previous studies and results from the area have also been included in the study. Distance diagrams, with different tilting directions, have been constructed. A shore displacement curve from c . 11,300 to c . 9,300 B.P., based on the most probable tilting direction, shows a complex uplift picture. A rather low regression gradient (3–4 m/100 years) during c . 1,000 years was, at c . 10,200 B.P., followed by a distinctly increasing gradient (8–9 m/100 years) followed by a marked gradient decrease at c . 9,500 B.P. The latter was possibly caused by a distinct sea level transgression on the Swedish West Coast. Indications of a short transgression around 10,000 B.P. as well as the possibly complicated course of isolation of Lake Vänern from the sea are also discussed. Finally the shore displacement is related to the deglaciation of the area and the supposed two drainages of the Baltic Ice Lake.     

Exhumation of the Saualpe eclogite unit, Eastern Alps: constraints from 40Ar/39Ar ages and structural investigations

Summary The Cretaceous Eclogite-Gneiss unit and its tectonic overburden (Micaschist, Phyllite and Lower Magdalensberg units) and the underlying Preims subunit of the Saualpe, Eastern Alps, have been investigated in order to constrain the mode of exhumation of the type locality of eclogites. ⁴⁰Ar/³⁹Ar ages of white mica from the eclogite-bearing unit suggest rapid, uniform cooling and exhumation between 86 and 78 Ma (Santonian-Campanian). Overlying units show upwards increasingly older ages with an age of 261.7 ± 1.4 Ma in the uppermost, low-grade metamorphic unit (Lower Magdalensberg unit). We consider this Permian age as geologically significant and to record a Permian tectonic event. Rocks of phyllite and micaschist units along western margins of the Saualpe block yield amphibole and white mica ages ranging from 123 to 130 Ma. These are considered to closely date the age of nappe stacking, whereas a single biotite age of 66–68 Ma from a shear zone is interpreted to date retrogression during normal faulting. Biotite and amphibole of Micaschist and Eclogite-Gneiss units show variable contents of extraneous argon. Consequently, their ages are in part geologically meaningless whereas other samples yield meaningful ages. The white mica ages from the Eclogite-Gneiss unit range from 78 to 85 Ma and argue for cooling through ca. 400 °C during the time as the westerly adjacent Upper Cretaceous Krappfeld collapse basin formed. The Preims subunit with paragneiss and marbles is considered to represent a large synmetamorphic shear zone at the base of the overthrusting Eclogite-Gneiss unit. The unit comprises a flat-lying foliation and a SE-trending lineation. This zone is interpreted to represent a zone of top-NW thrusting. A major ductile low-angle normal fault with top to ESE shear has been detected between the Eclogite-Gneiss and overlying units, and between the Micaschist and Phyllite units. The ductile thrust at the base and the low-angle normal fault at the top are considered to confine a NW-ward extruding high-pressure wedge. The new observations argue for rapid exhumation of a subducted high-pressure wedge within a subduction channel. Rapid surface erosion of the exhuming wedge might have facilitated exhumation. Eroded sedimentary rocks are preserved within adjacent Gosau basins, although only pebbles of low-grade metamorphic rocks of the uppermost tectonic unit can be found in these basins.