Post-Miocene stratigraphy and depositional environments of valley-fill sequences at the mouth of Tampa Bay, Florida

Post-Miocene sea-level low stands allowed rivers and karst processes to incise the exposed carbonate platform along the Gulf Coast of Florida. Few Miocene to mid-Pleistocene deposits survived erosion along the present coast except within incised valleys. Since their formation, these valleys have been filled and incised multiple times in response to sea-level changes. The thick sedimentary sequences underlying the mouth of Tampa Bay have been recorded as a range of depositional environments and multiple sea-level incursions and excursions during pre-Holocene time and subsequent to the accumulation of the Miocene carbonate sequences. Sediment analysis of cores collected from a north–south transect across the mouth of Tampa Bay has enabled the identification of lithofacies, ranging from well-sorted, quartz sand to dense, fossiliferous, phosphatic grainstone. These facies were deposited in freshwater, estuarine, and shallow, open marine environments. As a result of channel development and migration within the paleovalley, and cut-and-fill associated with individual transgressions and regressions, correlation of the lithofacies does not extend across the entire transect. Fining-upward sequences truncated by tidal ravinement surfaces that extend throughout the paleovalley can, however, be identified. Age determinations based on 14-C analysis, amino-acid racemization, and strontium isotope analysis dating of numerous samples yield ages of Miocene, Pliocene, early Pleistocene, and late Pleistocene, as well as Holocene for sequences that accumulated and were preserved in this valley-fill complex. Numerous inconsistencies in the stratigraphic organization of the age determinations indicate that there are bad dates, considerable reworking of shells that were dated, or both. For this reason as well as the lack of detailed correlation among the three relatively complete cores, it is not possible to place these strata in a sequence stratigraphic framework.     

地表剥蚀作用对地应力场反演的影响

岩体自重和剥蚀作用都是形成岩体初始应力场的重要因素。在地应力回归分析中，反演所得岩体重度往往大于实测重度。通过算例说明，地表剥蚀作用因素是导致该结果的主要原因，并分析了由此产生的一些工程应用问题。     

A pictorial comparison of interplanetary magnetic field polarity,solar wind speed,and geomagnetic disturbance index during the sunspot cycle

Observations of interplanetary magnetic field polarity, solar wind speed, and geomagnetic disturbance index (C9) during the years 1962–1975 are compared in a 27-day pictorial format that emphasizes their associated variations during the sunspot cycle. This display accentuates graphically several recently reported features of solar wind streams including the fact that the streams were faster, wider, and longer-lived during 1962–1964 and 1973–1975 in the declining phase of the sunspot cycle than during intervening years (Bame et al., 1976; Gosling et al., 1976). The display reveals strikingly that these high-speed streams were associated with the major, recurrent patterns of geomagnetic activity that are characteristic of the declining phase of the sunspot cycle. Finally, the display shows that during 1962–1975 the association between long-lived solar wind streams and recurrent geomagnetic disturbances was modulated by the annual variation (Burch, 1973) of the response of the geomagnetic field to solar wind conditions. The phase of this annual variation depends on the polarity of the interplanetary magnetic field in the sense that negative sectors of the interplanetary field have their greatest geomagnetic effect in northern hemisphere spring, and positive sectors have their greatest effect in the fall. During 1965–1972 when the solar wind streams were relatively slow (500 km s^-1), the annual variation strongly influenced the visibility of the corresponding geomagnetic disturbance patterns.Visiting Scientist, Kitt Peak National Observatory, Tucson, Arizona.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

A detailed comparison of theoretical wave spectra and wave forecasting methods

Conclusion The status of various results on the determination of the appropriate family of theoretical wave spectra to describe wind generated seas and the status of various wave forecasting methods have been reviewed. The spectra of Neumann appear to describe the sea more accurately than other theoretical spectra and the wave forecasting methods of Pierson, Neumann and James appear to be the most nearly correct for the widest variety of possible wave and weather situations.     

Ecological quality assessment of small estuaries from the Portuguese coast based on benthic macroinvertebrate assemblages indices

Benthic macroinvertebrates communities are the most consistently emphasized biotic component of aquatic ecosystems and are one of the biological indicators required for assessment by the European Water Framework Directive. In this context, several indices based on these communities have been developed in order to assess ecological quality of estuarine systems. In the present work we used AMBI, M-AMBI, BENTIX and BAT to distinguish ecological status of five small estuarine systems of the Portuguese south and southwest coasts. Although indices outputs did not differ between systems and sampling seasons, results indicated that the metrics in which these indices are based could differentiate community structures as a result of two main gradients that force these communities: the natural variability, and the anthropogenic impact.     

海南岛博鳌港沉积物的沿岸输送

分析了博港沿岸沉积牧粒度参数的沿岸变化，并应用沉积物粒径趋势分析模型（GSTA模型）对沉积物运动趋势进行了分析。GSTA模型结果表明，博鳌港沿岸的泥沙在横向上表现为：万泉河口以北岸段为由海向岸运动，近期处于淤积状态；万泉河口以南岸段即玉带滩大致以NNE走向到NE走向的转折点为界，北部主要是由岸向海运动，是侵蚀岸段，而南部则主要为由海向岸运动，有少量的淤积，博鳌港沿岸泥沙输送在纵向上表现为：万泉河口以北由南向北运动，万泉河口以南，北部是由北向南运动，南部是由南向北运动，其次还运用了经验公式对GSTA结果进行了验证，得到了通过万泉河口南部（玉带滩）3个断面的沿岸漂沙量，其沿岸漂沙方向主要为南北向，以上两种分析方法得出的结果和当地的许多地貌证据基本符合，而GSTA模型在玉带滩北部泥沙纵向输运方向与经验公式计算结果所表现出的一些差异，主要是由于研究时间尺度和所用的资料特征的差异性造成的。     

A mapping of the electron localization function for the silica polymorphs: evidence for domains of electron pairs and sites of potential electrophilic attack

The electron localization function, η, evaluated for first-principles geometry optimized model structures generated for quartz and coesite, reveals that the oxide anions are coordinated by two hemispherically shaped η-isosurfaces located along each of the SiO bond vectors comprising the SiOSi angles. With one exception, they are also coordinated by larger banana-shaped isosurfaces oriented perpendicular to the plane centered in the vicinity of the apex of each angle. The hemispherical isosurfaces, ascribed to domains of localized bond-pair electrons, are centered ～0.70 Å along the bond vectors from the oxide anions and the banana-shaped isosurfaces, ascribed to domains of localized nonbonding lone-pair electrons, are centered ～0.60 Å from the apex of the angle. The oxide anion comprising the straight SiOSi angle in coesite is the one exception in that the banana-shaped isosurface is missing; however, it is coordinated by two hemispherically shaped isosurfaces that lie along the bond vectors. In the case of a first-principles model structure generated for stishovite, the oxide anion is coordinated by five hemispherically shaped η-isosurfaces, one located along each of the three SiO bond vectors (ascribed to domains of bonding-electron pairs) that are linked to the anion with the remaining two (ascribed to domains of nonbonding-electron pairs) located on opposite sides of the plane defined by three vectors, each isosurface at a distance of ～0.5 Å from the anion. The distribution of the five isosurfaces is in a one-to-one correspondence with the distribution of the maxima displayed by experimental Δρ and theoretical ??²ρ maps. Isosurface η maps calculated for quartz and the (HO) ₃ SiOSi(OH) ₃ molecule also exhibit maxima that correspond with the (3,?3) maxima displayed by distributions of ??²ρ. Deformation maps observed for the SiOSi bridges for the silica polymorphs and a number of silicates are similar to that calculated for the molecule but, for the majority, the maxima ascribed to lone-pair features are absent. The domains of localized nonbonding-electron pair coordinating the oxide anions of quartz and coesite provide a basis for explaining the flexibility and the wide range of the SiOSi angles exhibited by the silica polymorphs with four-coordinate Si. They also provide a basis for explaining why the SiO bond length in coesite decreases with increasing angle. As found in studies of the interactions of solute molecules with a solvent, a mapping of η-isosurfaces for geometry-optimized silicates is expected to become a powerful tool for deducing potential sites of electrophilic attack and reactivity for Earth materials. The positions of the features ascribed to the lone pairs in coesite correspond with the positions of the H atoms recently reported for an H-doped coesite crystal.     

Stratigraphy of total metals in PIRLA sediment cores

Sediment cores from 30 low-alkalinity lakes in northern New England (NE), New York (NY), the northern Great Lakes States (NGLS) of Minnesota, Michigan, and Wisconsin, and Florida (FL) have been dated by ²¹⁰Pb and analyzed for water and organic content, eight major elements (Al, Ti, Fe, Mn, Ca, Mg, Na, K) plus four trace metals (Pb, Zn, Cu, and V). Variations in the percentages of major elements through time are dominated by long-term independent variations in the abundance of SiO₂, FeO, and to a lesser extent Ca and Al. Additional variations are caused by varying proportions of inorganic matter. Major variations in chemistry are generally unrelated to documented distrubances in the watersheds; most disturbances are minor fires or selective logging.Accelerated accumulation of Pb from atmospheric sources into sediment first occurs in sediment dated between 1800 and 1850 in NY and NE, slightly later in the NGLS region, and about 1900 in FL. Modern accumulation rates in all areas are comparable (ca. 1 to 4 g cm^–2 yr^–1). Accumulation rates of Pb in some lakes have declined significantly from 1975 to 1985. Atmospheric deposition of anthropogenic Zn and Cu is also indicated by generally increasing accumulation rates in sediment cores, but the record is not as clear nor are chemical profiles in all lakes parallel to the trends in atmospheric emissions inferred on the basis of fossil fuel consumption, smelting, and other industrial activities. Inter-lake variations in profiles of Cu and Zn are large. Vanadium accumulation rates increase by the 1940s in NY and NE, but not until the 1950s in the NGLS region. This timing correlates with regional trends in the combustion of fuel oil, a major source of atmospheric V.Acidification of some of the lakes is suggested by decreases in the concentration and accumulation rates of Mn, Ca, and Zn in recent sediment, relative to other elements of catchment origin. The decreases generally occur slightly before the onset of acidification as indicated by diatoms. Increased sediment accumulation rates for Fe may indicate the acidification of watershed soils. The use of the accumulation rate of TiO₂ as an indicator of rates of erosion and for normalization of trace metal accumulation rates is in question for lakes where the flux of TiO₂ from the atmosphere varies and is a significant fraction of the total flux of TiO₂ to the sediment.This is the thirteenth of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D. F. Charles and D. R. Whitehead are guest editors for this series.     

断层EDF技术在复杂断块构造研究中的应用

复杂断块构造具有断层复杂,小断层广泛发育,断层识别难度大,储层分布及连通性复杂,地震成像不清、资料品质较差等特征。对于此类问题,常规地震资料无法满足断层解释精度要求。提出了一种新的断层EDF解释性处理技术,将地震资料处理与解释融为一体,以提高资料的信噪比和断层的识别能力。断层EDF解释性处理技术是利用扩散滤波和中值倾角滤波相结合的断层增强滤波方法来提高资料的信噪比,突出断层和地层的接触关系,再在滤波后的地震资料数据体上进行分频处理,选择最佳成像频带,突出识别不同规模的断层。通过在涠洲A油田的应用,取得了良好的效果。