The influence of 70 and 120 kHz tonal signals on the behavior of harbor porpoises (Phocoena phocoena) in a floating pen     

Kastelein RA  Verboom WC  Jennings N  de Haan D  van der Heul S 《Marine environmental research》2008,66(3):319-326

Two harbor porpoises in a floating pen were subjected to five pure tone underwater signals of 70 or 120kHz with different signal durations, amplitudes and duty cycles (% of time sound is produced). Some signals were continuous, others were intermittent (duty cycles varied between 8% and 100%). The effect of each signal was judged by comparing the animals' surfacing locations and number of surfacings (i.e. number of respirations) during test periods with those during baseline periods. In all cases, both porpoises moved away from the sound source, but the effect of the signals on respiration rates was negligible. Pulsed 70kHz signals with a source level (SL) of 137dB had a similar effect as a continuous 70kHz signal with an SL of 148dB (re 1muPa, rms). Also, a pulsed 70kHz signal with an SL of 147dB had a much stronger deterring effect than a continuous 70kHz signal with a similar SL. For pulsed 70kHz signals (2s pulse duration, 4s pulse interval, SL 147dB re 1muPa, rms), the avoidance threshold sound pressure level (SPL), in the context of the present study, was estimated to be around 130dB (re 1muPa, rms) for porpoise 064 and around 124dB (re 1muPa, rms) for porpoise 047. This study shows that ultrasonic pingers (70kHz) can deter harbor porpoises. Such ultrasonic pingers have the advantage that they do not have a "dinner bell" effect on pinnipeds, and probably have no, or less, effect on other marine fauna, which are often sensitive to low frequency sounds.  相似文献   

Can sediment supply variations create sequences? Insights from stratigraphic forward modelling     

Jinyu Zhang  Peter M. Burgess  Didier Granjeon  Ronald Steel 《Basin Research》2019,31(2):274-289

Classic sequence stratigraphy suggests depositional sequences can form due to changes in accommodation and due to changes in sediment supply. Accommodation‐dominated sequences are problematic to define rigorously, but are commonly interpreted from outcrop and subsurface data. In contrast, supply‐dominated sequences are much less commonly identified. We employ numerical stratigraphic forward modelling to compare stratal geometries forced by cyclic changes in relative sea level with stratal geometries forced by sediment discharge and water discharge changes. Our quantitative results suggest that both relative sea‐level oscillations and variations in sediment/water discharge ratio are able to form sequence‐bounding unconformities independently, confirming previous qualitative sequences definitions. In some of the experiments, the two types of sequence share several characteristics, such as an absence of coastal‐plain topset deposits and stratal offlap, something typically interpreted as the result of falling relative sea level. However, the stratal geometries differ when variations in amplitude and frequency of relative sea‐level change, sediment/water discharge ratio, transport diffusion coefficient and initial bathymetry are applied. We propose that the supply‐dominated sequences could be recognised in outcrop or in the subsurface if the observations of stratal offlap and the absence of coastal‐plain topset can be made without any strong evidence of relative sea‐level fall (e.g. descending shoreline trajectory). These quantitative results suggest that both supply‐dominated and accommodation‐dominated sequences are likely to occur in the ancient record, as a consequence of multiple, possibly complex, controls.  相似文献   

AMS 14C age constraints on geoglyphs in the lower colorado river region,arizona and california     

Jay Von Werlhof  Harry Casey  Ronald I. Dorn  Glenn A. Jones 《Geoarchaeology》1995,10(4):257-273

Giant ground figures are widespread in the lower Colorado River area of southwestern North America, yet their chronology has remained unconstrained by numerical ages. Thirteen AMS ¹⁴C measurements reported here indicate that geoglyphs were made from before ˜A. D. 1200 to before ˜900 B. C. We account for potential contamination from prior organics in weathering rinds. All other potential errors point to ¹⁴C dates being minimum-limiting ages for the manufacturing of geoglyphs. Although these ages indicate considerable chronological complexity among geoglyphs, our data are consistent with the linguistic hypothesis that the Yuman people in the desert of southeastern California migrated from Baja California—rather than from the north. These results must, however, be placed under the cloud of uncertainty that hangs over the entire field of AMS dating of rock art: the untested assumption surrounding contemporeneity of organics in a surface context. © 1995 John Wiley & Sons, Inc.  相似文献   

Clinoform growth and sediment flux into late Cenozoic Qiongdongnan shelf margin,South China Sea     

Si Chen  Ronald Steel  Hua Wang  Rui Zhao  Cornel Olariu 《Basin Research》2020,32(2):302-319

The South China Sea continental margin in the Qiongdongnan Basin (QDNB) area has incrementally prograded since 10.5 Ma generating a margin sediment prism more than 4km-thick and 150–200 km wide above the well-dated T40 stratigraphic surface. Core and well log data, as well as clinoform morphology and growth patterns along 28 2D seismic reflection lines, illustrate the evolving architecture and margin morphology; through five main seismic-stratigraphic surfaces (T40, T30, T27, T20 and T0) frame 15 clinothems in the southwest that reduce over some 200 km to 8 clinoforms in the northeast. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east. Vertical sediment accumulation rate increased significantly across the entire margin after 2.4 Ma, with a marked increase in mud content in the succession. Furthermore, an estimate of sediment flux across successive clinoforms on each of the three selected seismic cross sections indicate an overall decrease in sediment discharge west to east, away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The QDNB Late Cenozoic continental margin growth, with its overall increased sediment flux, responded to the climate-induced, gradual cooling and falling global sea level during this icehouse period.  相似文献   

Clinoforms and clinothems: Fundamental elements of basin infill     

Claudio Pellegrini  Stefano Patruno  William Helland-Hansen  Ronald J. Steel  Fabio Trincardi 《Basin Research》2020,32(2):187-205

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Climatically controlled lacustrine clinoforms: Theory and modelling results     

Jinyu Zhang  Cornel Olariu  Ronald Steel  Wonsuck Kim 《Basin Research》2020,32(2):240-250

Lacustrine basins and their deposits are good paleoclimate recorders and contain rich energy resources. Shelf-margin clinoforms do exist in deep lacustrine basins, but with striking differences from those in deep marine basins, caused by a correlation between the river-derived sediment supply and the lake level. This study uses empirical relationships to calculate the water and sediment discharge from rivers and coeval lake level during wet–dry cycles at 10 s of ky time scale. Sediment supply and lake-level changes are used for a stratigraphic forward model to understand how lacustrine clinoforms develop under different climate conditions. The results show that both wet and dry cycles can be associated with thick deep-water fan deposits, supporting the existing climate-driven lacustrine model proposed based on field data (e.g. Neogene Pannonian Basin and Eocene Uinta Basin). The wet period with high sediment supply and rising lake level creates the highly aggradational shelf, progradational slope and thick bottomset deposits. This is contrary from marine basin settings where the presence of rising shelf-margin trajectory commonly indicates limited deep-water fan deposits. This work suggests marine-based stratigraphic models cannot be directly applied to lacustrine basins.  相似文献   

Study on the performance of the micropile-mechanically stabilized earth wall     

Zhi-chao Zhang  Ronald Y. S. Pak  Yu-min Chen  Han-long Liu 《山地科学学报》2018,15(4):825-844

The Micropile-Mechanically Stabilized Earth (MSE) wall, specially designed for mountain roads, is proposed to improve the MSE wall local stability, global stability and impact resistance of roadside barriers. Model tests and the corresponding numerical modeling were conducted to validate the serviceability of the Micropile-MSE wall and the reliability of the numerical method. Then, a parametric study of the stress and deformation of Micropile-MSE wall based on the backfill strength and interfacial friction angle between backfill and backslope is conducted to evaluate its performance. The test results indicate that the surcharge-induced horizontal earth pressure, base pressure and lateral displacement of the wall panel of Micropile-MSE wall decrease. The corresponding numerical results are nearly equal to the measured values. The basic failure mode of MSE wall in steep terrain is the sliding of backfill along the backslope, while A-frame style micropiles are capable of preventing the sliding trend. The maximum resultant displacement can be decreased by 6.25% to 46.9% based on different interfacial friction angles, and the displacement can be reduced by 6% ~ 56.1% based on different backfill strengths. Furthermore, the reduction increases when the interfacial friction angle and internal friction angle of backfill decrease. In addition, the lateral displacement of wall panel, the deformation of backfill decrease and the tension strain of geogrid obviously, which guarantees the MSE wall functions and provides good conditions for mountain roads.  相似文献   

Projectile preservation during oblique hypervelocity impacts     

Ronald T. Daly  Peter H. Schultz 《Meteoritics & planetary science》2018,53(7):1364-1390

Impact angle plays a significant role in determining the fate of the projectile. In this study, we use a suite of hypervelocity impact experiments to reveal how impact angle affects the preservation, distribution, and physical state of projectile residues in impact craters. Diverse types of projectiles, including amorphous silicates, crystalline silicates, and aluminum, in two sizes (6.35 and 12.7 mm), were launched into blocks of copper or 6061 aluminum at speeds between 1.9 and 5.7 km s⁻¹. Crater interiors preserve projectile residues in all cases, including conditions relevant to the asteroid belt. These residues consist of projectile fragments or projectile-rich glasses, depending on impact conditions. During oblique impacts at 30° and 45°, the uprange crater wall preserves crystalline fragments of the projectile. The fragments of water-rich projectiles such as antigorite remain hydrated. Several factors contribute to enhanced preservation on the uprange wall, including a weaker shock uprange, uprange acceleration as the shock reflects off the back of the projectile, and rapid quenching of melts along the projectile–target interface. These findings have two broader implications. First, the results suggest a new collection strategy for flyby sample return missions. Second, these results predict that the M-type asteroid Psyche should bear exogenic, impactor-derived debris.  相似文献   

Performance of community-based coastal resource management (CBCRM) programs in the Philippines: A meta-analysis     

Ronald J. Maliao  Robert S. Pomeroy  Ralph G. Turingan   《Marine Policy》2009,33(5):818-825

Community-based coastal resource management (CBCRM) is a major conservation and fisheries management strategy in the tropics. In this study, the performance of 16 CBCRM programs in the Philippines was assessed using a meta-analysis of eight indicators that represented the perceptions of local resource users. Overall, the CBCRM programs in the Philippines were perceived to have a significant positive impact. However, the performance of each of the indicators was mixed. Although the CBCRM programs were perceived to be effective in empowering the local fishing communities, their perceived impact on improving the state of the local fisheries resources remained limited. This highlights the importance of incorporating ecological and socio-economic considerations in setting fisheries management regimes.  相似文献   

The bottom sediments of the Amazon shelf and tropical Atlantic Ocean     

Ronald J. Gibbs 《Marine Geology》1973,14(5):39-45

Analytical results of bottom sampling of the equatorial Atlantic Ocean affected by the Amazon River show a concentration of material smaller than 2 μ along the shore northwest of the mouth of the Amazon River for 2000 km. A zone having a high percentage of material coarser than 20 μ extends outward from the Amazon River and along the outer continental shelf northwestward for 2000 km. Areas having high carbonate percentages are encountered only on the outer shelf and in deep water.  相似文献