Species diversity: benthonic foraminifera in Western north atlantic

Maximum species diversity occurs at abyssal depths of greater than 2500 meters. Other diversity peaks occur at depths of 35 to 45 meters and 100 to 200 meters. The peak at 35 to 45 meters is due to species equitability, whereas the other two peaks correspond to an increase in the number of species.     

Radiolarian skeletons: solution at depths

Radiolarian skeletons were placed at several depths on the taut mooring wire of a buoy in the central Pacific for 4 months. Recent radiolarian sediment dissolved at appreciable rates at depths shallower than 2000 meters; solution was greatest near the surface and decreased with depth. This pattern correlates with bathymetric distributions of dissolved silicon and of temperature. Siliceous Radiolaria from planktonic samples appeared to dissolve about eight times faster than those from sediment. Tripyleans seemed to be less resistant than polycystins. Acantharia dissolved completely at all depths.     

Ocean current monitoring employing a new satellite sensing technique

The very-high-resolution radiometer on the NOAA-2 (National Oceanic and Atmospheric Administration) satellite has recently obtained imagery in the visible channel containing sunglint over a major portion of the coastal waters off the eastern seaboard of the United States. An abrupt change in surface roughness has been observed at the shoreward edge of the Gulf Stream Current from Florida to Cape Hatteras that results from the opposition of waves propagating against the flow of the Gulf Stream.     

Vertebrate evidence of a low sea level in the middle pliocene

Marine and untransported terrestrial vertebrates of Middle Pliocene (Hemphillian) age occur together in well-sorted, sandy, phosphatic gravels at an elevation of 1.8 to 3 meters in Manatee County, Florida. If no crustal warping of the Late Cenozoic age has occurred in this part of Florida (as investigators generally agree), the sea must have approached its present level 4 to 7 million years ago.     

Quaternary raised coral-reef terraces on sumba island, indonesia

A spectacular sequence of coral-reef terraces (six steps broader than 500 meters and many minor substeps) is developed near Cape Laundi, Sumba Island, between an ancient patch reef 475 meters high and sea level. Several raised reefs have been dated with the electron spin resonance and the uranium-series dating methods. The uplift trend deduced from these reefs is 0.5 millimeter per year; most terraces, although polycyclic in origin, appear to correspond to specific interglacial stages, with the oldest terrace formed 1 million years ago. This puts them among the longest and most complete mid-Quaternary terrace sequences.     

Seasonality and interaction of biogenic and lithogenic particulate flux at the panama basin

Time-series sediment traps were deployed for an entire year at three depths (890, 2590, and 3560 meters) at a deepwater station (3860 meters) in the Panama Basin. The amount of horizontal and lithogenic particulate material arriving at the three depths was seasonally pulsed and directly reflected changes in surface primary production. Two spikes of organic flux were simultaneously recorded at all three depths: (i) a period of high productivity during regional upwelling in February through March and (ii) an unusual bloom of a single species of coccolithophorid during June through July. This latter spike delivered approximately 25 grams of coccolith per square meter of area at a depth of 3860 meters during less than 60 days. The flux of lithogenic particles increased with increasing depth and was seasonally correlated to surface production and current direction, and not to the detritus discharged in river flow. The data suggest that suspended clays are efficiently scavenged from the water column by rapidly sinking organic aggregates.     

U/Pb zircon geochronology and tempo of the end-permian mass extinction

The mass extinction at the end of the Permian was the most profound in the history of life. Fundamental to understanding its cause is determining the tempo and duration of the extinction. Uranium/lead zircon data from Late Permian and Early Triassic rocks from south China place the Permian-Triassic boundary at 251.4 +/- 0.3 million years ago. Biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the Changhsingian pulse of the end-Permian extinction, corresponding to the disappearance of about 85 percent of marine species, lasted less than 1 million years. At Meishan, a negative excursion in delta13C at the boundary had a duration of 165,000 years or less, suggesting a catastrophic addition of light carbon.     

A tsunami deposit at the cretaceous-tertiary boundary in Texas

At sites near the Brazos River, Texas, an iridium anomaly and the paleontologic Cretaceous-Tertiary boundary directly overlie a sandstone bed in which coarse-grained sandstone with large clasts of mudstone and reworked carbonate nodules grades upward to wave ripple-laminated, very fine grained sandstone. This bed is the only sandstone bed in a sequence of uppermost Cretaceous to lowermost Paleocene mudstone that records about 1 million years of quiet water deposition in midshelf to outer shelf depths. Conditions for depositing such a sandstone layer at these depths are most consistent with the occurrence of a tsunami about 50 to 100 meters high. The most likely source for such a tsunami at the Cretaceous-Tertiary boundary is a bolidewater impact.     

Sink or swim: strategies for cost-efficient diving by marine mammals

Locomotor activity by diving marine mammals is accomplished while breath-holding and often exceeds predicted aerobic capacities. Video sequences of freely diving seals and whales wearing submersible cameras reveal a behavioral strategy that improves energetic efficiency in these animals. Prolonged gliding (greater than 78% descent duration) occurred during dives exceeding 80 meters in depth. Gliding was attributed to buoyancy changes with lung compression at depth. By modifying locomotor patterns to take advantage of these physical changes, Weddell seals realized a 9.2 to 59.6% reduction in diving energetic costs. This energy-conserving strategy allows marine mammals to increase aerobic dive duration and achieve remarkable depths despite limited oxygen availability when submerged.     

East pacific rise crest: a near-bottom geophysical profile

A deep-towed magnetometer profile made across the East Pacific Rise crest shows many anomalies with about 1000-gamma amplitudes and 500-meter wavelengths and has larger amplitude changes corresponding to magnetic field reversals. This profile across contacts between normal and reversely magnetized crustal blocks is interpreted to place an upper limit of 4700 years on the time required for field reversals and an upper limit of 280 meters on the width of the intrusion center at the rise crest. This intrusion center may occasionally shift several kilometers laterally with respect to the rise axis. The magnetometer records are compatible with the hypothesis that the magnetic field has undergone many fluctuations of short period and small intensity in the past 2 million years. Sediment accumulation increases from less than 2 meters at the rise crest axis to about 20 meters at the western end and 10 meters at the eastern end of the profile. This increase in accutmiulation appears to be the result of ocean-floor spreading.     

Rates of late cenozoic uplift, baldwin hills, los angeles, california

Radiocarbon ages for the marine late Pleistocene stratigraphic units of the Baldwin Hills are 36,200 +/- 2,750 years and 28,450 +/- 2,600 years, respectively, defining the termination of marine deposition in this area of the Los Angeles Basin at less than 28,000 years ago. Faunas of the older sample suggest that water depths were about 100 meters at the time of deposition. Shoaling of waters by deposition resulted in very shallow marine to nonmarine conditions about 28,000 years ago. The average rates of uplift for the past 36,000 years have been between 0.5 and 0.8 meter per 100 years.     

Clathrate hydrates of air in antarctic ice

Measurements of the dissociation pressure of nitrogen hydrate and oxygen hydrate show that the clathrate hydrate of air with the formula (N(2), O(2)) 6H(2)O should exist below about 800 meters in the Antarctic ice sheet. This accounts for the disappearance of gas bubbles at depths greater than 1200 meters. The hydrate should exist from this depth to prise 0.06 percent of the ice.     

Reduction of permeability in granite at elevated temperatures

The addition of hydrothermal fluids to heated, intact granite leads to permeability reductions in the temperature range of 300 degrees to 500 degrees C, with the rate of change generally increasing with increasing temperature. The addition of gouge enhances the rate of permeability reduction because of the greater reactivity of the fine material. Flow rate is initially high in a throughgoing fracture but eventually drops to the level of intact granite. These results support the fault-valve model for the development of mesothermal ore deposits, in which seals are formed at the base of the seismogenic zone of high-angle thrust faults. The lower temperature results yield varying estimates of mineral-sealing rates at shallower depths in fault zones, although they generally support the hypothesis that such seals develop in less time than the recurrence interval for moderate to large earthquakes on the San Andreas fault.     

Lithologic Control of the Depth of Earthquakes in Southern California

The depth distribution of southern California earthquakes indicates that areas underlain by schist basement rocks have a shallower (4 to 10 kilometers) maximum depth of earthquakes than do areas with other types of basement rocks. The predominant minerals in the schists become plastic at lower temperatures, and thus at shallower depths, than the minerals in the other basement rocks. The lateral variations in lithology will control the depth extent (and thus the magnitudes) of potential future earthquakes; these depths can be determined from the depth of the current background seismicity.     

两品系萼花臂尾轮虫的生活史特征和受精率研究

应用单个体培养和群体培养方法,在25℃条件下,对萼花臂尾轮虫Brachionus calyciflorus南京品系(NJ)和美国佛罗里达品系(FL)的幼体发育时间、胚胎发育时间、繁殖量、种群增长参数及品系间、品系内受精率进行了研究.结果表明:萼花臂尾轮虫FL品系与NJ品系的幼体发育时间、第一个幼体孵出时间和繁殖量之间均无显著性差异(P＞0.05),而NJ品系的胚胎发育时间比FL品系显著缩短6.9％(P＜0.05); NJ品系的净生殖率(R0)、内禀增长率(rm)、世代时间(T)和生命期望(e0)均显著大于FL品系(P＜0.05);萼花臂尾轮虫FL和NJ品系雌雄交配试验结果表明,两品系间的受精率低于各自品系内交配的受精率.本研究表明,南京品系和佛罗里达品系萼花臂尾轮虫的发育和种群增长参数存在显著差异,但两品系之间不存在完全的生殖隔离,未形成姐妹种.     

Extending the sub-sea-floor biosphere

Sub-sea-floor sediments may contain two-thirds of Earth's total prokaryotic biomass. However, this has its basis in data extrapolation from ~500-meter to 4-kilometer depths, whereas the deepest documented prokaryotes are from only 842 meters. Here, we provide evidence for low concentrations of living prokaryotic cells in the deepest (1626 meters below the sea floor), oldest (111 million years old), and potentially hottest (~100 degrees C) marine sediments investigated. These Newfoundland margin sediments also have DNA sequences related to thermophilic and/or hyperthermophilic Archaea. These form two unique clusters within Pyrococcus and Thermococcus genera, suggesting unknown, uncultured groups are present in deep, hot, marine sediments (~54 degrees to 100 degrees C). Sequences of anaerobic methane-oxidizing Archaea were also present, suggesting a deep biosphere partly supported by methane. These findings demonstrate that the sub-sea-floor biosphere extends to at least 1600 meters below the sea floor and probably deeper, given an upper temperature limit for prokaryotic life of at least 113 degrees C and increasing thermogenic energy supply with depth.     

福建省乡村道路林种群分布及结构特征研究

运用分层随机抽样法,对福建省88个乡村的道路林进行调查。结果表明:福建省乡村道路林植物组成较为丰富,包括41科、64属、79种;种类组成呈现沿海型平地型半山型山区型的变化规律,山区型乡村道路林数量明显不足,而半山型、平地型和沿海型数量相对较多。道路林植物以观赏性乔木为主,主要使用树种有木荷、楠木、含笑、杜英、圆柏、枫香、乐昌含笑、紫薇、龙眼、黄金榕、降香黄檀、意杨、香樟、天竺桂、垂叶榕等。道路林分布以主干道最多,其次为村内路,而进村路最少,且道路林分布的特点是以单侧分布较多,而两侧分布较少。分布结构以整条分布最多,而零散分布较少;分布长度以50 ｍ以下最多,其次为200 ｍ以上,而50～200 ｍ之间最少。道路林乔木以小径级为主,且多数平均高度均在5 m以下。道路林植物健康状况较差,不健康植物所占比重高达35.57%      

Foraminiferal ooze: solution at depths

Samples of foraminiferal ooze were exposed to ocean water at various depths for 4 months, attached to the taut wire of a buoy in the central Pacific. Appreciable solution took place below 1000 meters and increased rapidly below 3000 meters and below 5000 meters. The fact that samples from different locations appear to dissolve at different rates suggests that the previous history of a sample determines its solubility. Solution is selective; it changes species composition, size distribution, content of damaged shells, and average particle weight of an assemblage.     

Spatial Variability of Turbulent Mixing in the Abyssal Ocean

Ocean microstructure data show that turbulent mixing in the deep Brazil Basin of the South Atlantic Ocean is weak at all depths above smooth abyssal plains and the South American Continental Rise. The diapycnal diffusivity there was estimated to be less than or approximately equal to 0.1 x 10(-4) meters squared per second. In contrast, mixing rates are large throughout the water column above the rough Mid-Atlantic Ridge, and the diffusivity deduced for the bottom-most 150 meters exceeds 5 x 10(-4) meters squared per second. Such patterns in vertical mixing imply that abyssal circulations have complex spatial structures that are linked to the underlying bathymetry.     

Radioactive waste disposal in thick unsaturated zones

Portions of the Great Basin are undergoing crustal extension and have unsaturated zones as much as 600 meters thick. These areas contain multiple natural barriers capable of isolating solidified toxic wastes from the biosphere for tens of thousands to perhaps hundreds of thousands of years. An example of the potential utilization of such arid zone environments for toxic waste isolatic is the burial of transuranic radioactive wastes at relatively shallow depths (15 to 100 meters) in Sedan Crater, Yucca Flat, Nevada. The volume of this man-made crater is several times that of the projected volume of such wastes to the year 2000. Disposal in Sedan Crater could be accomplished at a savings on the order of $0.5 billion, in comparison with current schemes for burial of such wastes in mined repositories at depths of 600 to 900 meters, and with an apparently equal likelihood of waste isolation from the biosphere.