Three-dimensional numerical simulation of wind-induced barotropic circulation in the Gulf of Patras

The barotropic, wind-induced circulation, which develops in the Gulf of Patras in Western Greece during the winter, is studied using three-dimensional numerical simulations. The simulations are performed using the numerical code MIKE 3 FM (HD). The Gulf's basin is bracketed between two sills, one on the west at the opening with the Ionian Sea and the other on the east at the Straits of Rio-Antirio at the opening with the Gulf of Corinth. The simulations show that the wind-induced flow creates strong currents near the coasts, which determine the sense of rotation of the gyres that develop in the Gulf. Strong currents are also created at the Rio-Antirio Straits. The wind-induced, barotropic currents do not seem to contribute to the direct replenishment of bottom waters, which recirculate between the two sills. Depending on the wind-speed forcing of the flow, the residence time of the waters in the Gulf of Patras is estimated to range from one week to one month.     

Reprint of: Diagenetic controls on evolution of porosity and permeability in lower Tertiary Wilcox sandstones from shallow to ultradeep (200–6700 m) burial,Gulf of Mexico Basin,U.S.A.

Reservoir quality is a critical risk factor in deep to ultradeep reservoirs at depths >4.5 km. Analysis of Paleogene Wilcox sandstones on the upper Texas Gulf Coast provides insight into the evolution of reservoir quality during shallow to ultradeep burial diagenesis. Reduction of porosity and permeability with burial in Wilcox sandstones was evaluated using subsurface samples from 200 to 6700 m, at temperatures of 25–230 °C. Diagenesis and petrophysical properties were interpreted from petrographic data and core analyses. Wilcox sandstones are mostly lithic arkoses and feldspathic litharenites having an average composition of Q₅₉F₂₂R₁₉. Provenance did not change significantly during Wilcox deposition in this area, nor does average sandstone composition vary among lower, middle, and upper Wilcox sandstones. However, composition does vary with sequence-stratigraphic position; lowstand slope-fan deposits contain more rock fragments than do deposits from highstand or transgressive systems tracts. Given observations from this onshore dataset, Wilcox sandstones deposited in deepwater environments in the Gulf of Mexico are likely to contain more rock fragments than their linked highstand equivalents.     

Calibration and use of continuous heat-type automated seepage meters for submarine groundwater discharge measurements

Submarine groundwater discharge (SGD) assessments were conducted both in the laboratory and at a field site in the northeastern Gulf of Mexico, using a continuous heat-type automated seepage meter (seepmeter). The functioning of the seepmeter is based on measurements of a temperature gradient in the water between downstream and upstream positions in its flow pipe. The device has the potential of providing long-term, high-resolution measurements of SGD. Using a simple inexpensive laboratory set-up, we have shown that connecting an extension cable to the seepmeter has a negligible effect on its measuring capability. Similarly, the observed influence of very low temperature (≤3 °C) on seepmeter measurements can be accounted for by conducting calibrations at such temperatures prior to field deployments. Compared to manual volumetric measurements, calibration experiments showed that at higher water flow rates (>28 cm day⁻¹ or cm³ cm⁻² day⁻¹) an analog flowmeter overestimated flow rates by ≥7%. This was apparently due to flow resistance, turbulence and formation of air bubbles in the seepmeter water flow tubes. Salinity had no significant effect on the performance of the seepmeter. Calibration results from fresh water and sea water showed close agreement at a 95% confidence level significance between the data sets from the two media (R² = 0.98). Comparatively, the seepmeter SGD measurements provided data that are comparable to manually-operated seepage meters, the radon geochemical tracer approach, and an electromagnetic (EM) seepage meter.     

Suspended particulate matter in the St. Lawrence estuary and Gulf surface layer and development of a remote sensing algorithm

Remote sensing of chlorophyll concentration is potentially affected by the presence of inorganic matter in the water column. Seasonal variability of total suspended particulate matter (SPM) concentration and its partition into organic and inorganic fractions was thus measured in the estuary and Gulf of St. Lawrence during five cruises. These measures were made in the surface layer down to the depth of the 0.1% light level. Results indicate that vertical variability was small for the entire study area. Data analysis lead to the definition of two main regions having different SPM characteristics: 1) the estuary zone characterized by a strong spatial variability, intermediate SPM concentrations and a clear spring phytoplankton bloom that is combined to an increased inorganic matter load; 2) the gulf region characterized by a relatively low SPM concentration and phytoplankton blooms in the spring and fall periods. Combined with in situ measurements of remote sensing reflectances, the database was used to validate existing inorganic matter retrieval algorithms and develop a new one better adapted to the low concentrations encountered in the St. Lawrence estuary and Gulf.     

Ecosystem-based management institutional design: Balance between federal,state, and local governments within the Gulf of Mexico Alliance

We present a case study of the organizational framework of the Gulf of Mexico Alliance (GOMA), which was implemented to promote the use of ecosystem-based management (EBM) at a regional level. GOMA is a state-led initiative formed to protect and restore coastal and marine resources of the Gulf of Mexico. Representatives of the US Gulf States, together with their federal partners, clearly defined ecological, social, and economic short- and long-term objectives to be reached through regional collaborations. The aim of this paper is to show how GOMA, and particularly the Ecosystem Integration and Assessment Priority Issue Team, in its attempt to apply ecosystem approaches to manage marine resources, modified the common organizational scheme by implementing partnerships at various governmental (federal, state, local) and nongovernmental levels. We address the following major points considered to be of importance for EBM implementation: (1) multilevel cooperation, (2) stakeholders’ involvement, (3) sharing of information, (4) bridging science and policy, and (5) consensus-based decision making.     

广东流沙湾4个测站2个周日潮流观测的准调和分析

采用短期资料的潮流准调和分析方法,对水深为4.4～17.0 m的流沙湾4个测站2个周日潮流观测获得的表、中、底层的潮流资料进行了分析,分别计算了4个测站O1、K1、M2、S2、M4、MS4共6个主要分潮的潮流调和常数,并给出了各观测站位在各层的潮流椭圆要素.计算结果表明：流沙湾主要为日潮流海区,其中湾外为规则日潮流,湾内为不规则日潮流;湾外主要分潮流的北分量一般大于东分量,而湾内主要分潮流的北分量一般小于东分量.观测期间余流的流向主要呈西北向,最大余流流速出现在湾内地形突然收窄处,且在湾内中层余流流速要大于表、底层余流流速.整个海区潮流的可能最大流速表层在57～107 cm/s之间,中层在53～106 cm/s之间,底层在34～98 cm/s之间.流沙湾湾外潮流主要为顺时针的旋转流运动,湾内为带有旋转流的往复流运动.     

墨西哥湾南部晚侏罗纪主力烃源岩的形成条件

通过对墨西哥湾不同时代可采储量的分布特征和油源对比资料的分析认为,晚侏罗纪烃源岩是墨西哥湾南部最主要的烃源岩。资料显示,晚侏罗纪优质烃源岩形成的主控因素是稳定的构造和沉积条件以及超咸的还原环境,其中,"世界顶级"的晚侏罗纪提塘阶烃源岩主要形成于超咸的碳酸盐岩和/或蒸发岩沉积环境,属半深海还原环境,有机质以藻类为主,推测烃源岩中的有机质可能与极端干旱气候条件下的藻类勃发有关。     

Late Quaternary stratigraphy and sedimentology of the inner part of southwest Joseph Bonaparte Gulf

Joseph Bonaparte Gulf is a large embayment on the northwestern continental margin of Australia. It is approximately 300 km east‐west and 120 km north‐south with a broad continental shelf to seaward. Maximum width from the southernmost shore of Joseph Bonaparte Gulf to the edge of the continental shelf is 560 km. Several large rivers enter the gulf along its shores. The climate is monsoonal, sub‐humid, and cyclone‐prone during the December‐March wet season. A bedrock high (Sahul Rise) rims the shelf margin. The sediments within the gulf are carbonates to seaward, grading into clastics inshore. A seaward‐thinning wedge of highstand muds dominates the sediments of the inner shelf of Joseph Bonaparte Gulf. Mud banks up to 15m thick have developed inshore. Coarse‐grained sand ridges up to 15 m high are found off the mouth of the Ord River. These overlie an Upper Pleistocene transgressive lag of mixed carbonate and gravelly siliciclastic sand. Four drowned strandlines are present on the inner shelf at depths of 20, 25, 28 and 30 m below datum. These are interpreted as having formed during stillstands in the Late Pleistocene transgression. Older strandlines at great depths are inferred as having formed during the fall in sea‐level following the last highstand. For the most part the Upper Pleistocene‐Holocene marine sediments overlie an erosion surface cut into older Pleistocene sediments. Incised valleys cut into this erosion surface are up to 5 km wide and have a relief of at least 20 m. The largest valley is that cut by the Ord River. Upper Pleistocene sediments deposited in the incised valleys include interpreted lowstand fluvial gravels, early transgressive channel sands and floodplain silts, and late transgressive estuarine sands and gravels. Older Pleistocene sediments are inferred to have been deposited before and during the 120 ka highstand (isotope stage 5). They consist of sandy calcarenites deposited in high‐energy tide‐dominated shelf environments. Still older shelf and valley‐fill sediments underlie these. The contrast between the Holocene muddy clastic sediments and the sandy carbonates deposited by the 120 ka highstand suggests that either the climate was more arid in the past, with less fluvial transport, or that mud was more effectively trapped in estuaries, allowing development of carbonate depositional environments inshore.     

Dedolomitization of dolocrete deposits in Kuwait,Arabian Gulf

Dedolomitization of a dolocrete profile hosted in Mio-Pleistocene siliciclastic deposits in the area of Kuwait City, Arabian Gulf was investigated. Dolocrete dolomite crystals vary considerably in size, shape and internal structure; however, they are mostly zoned. Zonation is usually due to the alteration of cloudy and clear zones. The cloudy zones, which are mostly formed of disordered metastable dolomite, are more susceptible to dedolomitization than the stable, well ordered clear zones. Two modes of dedolomitization were recognized; the first involves complete dissolution of the metastable dolomite followed by precipitation of intracrystalline cavity-filling calcite. The second is a pseudomorphic replacement of dolomite by calcite. This replacement takes place by the simultaneous dissolution of dolomite and precipitation of calcite in such a manner that the original dolomite fabrics are inherited in the dedolomite. Exposed and near-surface dolocrete profile (less than 5 m deep) are almost completely dedolomitized and altered to secondary calcrete whereas subsurface profiles are slightly dedolomitized. Dedolomitization of the sub surface dolocrete profiles may indicate the effect of flushing by fresh groundwater; which flows from west to east, whereas the alteration of the exposed dolocrete profile could be attributed to be an effect of meteoric water. A new mode of calcrete genesis by dedolomitization and/or complete calcitization of precursor dolocrete is suggested.