排序方式： 共有22条查询结果，搜索用时 78 毫秒
1.
Douglas J. Cant 《Basin Research》1991,3(2):51-62
Geometric analysis shows that the angle of migration of coastal sedimentary facies is a function of the relative sea-level change and the thickness of sediment deposited or eroded. The angle of facies migration compared to the slopes on the sediment surface determines the degree of facies preservation and stratigraphic relationships to the surrounding facies. Vertical facies successions generated by radial migration of environments show a great deal of variety because the sediment surface in both marine and non-marine areas is concave-up. Both regressive and transgressive sequences with non-erosive marine-nonmarine contacts can be generated. Transgression at a slightly lower angle can form a ravinement surface cut on non-marine deposits with onlapping barrier sands or shallow marine deposits. Regression with relative sea-level drop generates a minor erosion surface with baselapping isolated shoreline deposits. Disequilibrium conditions occur when sea level varies at a rate exceeding the ability of the system to supply or redistribute sediment, with resulting changes in surficial slopes. Onlapping and downlapping stratal relationships across erosion surfaces result because of differences in slopes between marine and non-marine environments. These discontinuities are generally less than one degree, but could possibly be recognized on high quality multichannel seismic lines. Most of these discontinuities are probably not regionally extensive enough to be regarded as sequence boundaries. Tectonic tilting or differential subsidence of strata during depositional hiatuses is necessary to generate true regional unconformities or sequence boundaries. Where facies climb with respect to horizontal, erosion surfaces produced only by this migration may cut across lithostratigraphic units at higher angles, up to 3 or 4 degrees. Low-angle erosion surfaces relevant to the scales of sequence stratigraphic studies may result only from facies migration, even during a period of relative sea-level rise. 相似文献
2.
Emilio Rodríguez-Caballero José Raúl Román Sonia Chamizo Beatriz Roncero Ramos Yolanda Cantón 《地球表面变化过程与地形》2019,44(14):2771-2779
Biological soil crust, or biocrust communities, are the dominating life form in many extreme habitats, such as arid and semiarid badlands, where water scarcity and highly erodible substrates limit vegetation cover. While climate, soil and biotic factors have been described as environmental filters influencing biocrust distribution in such biomes, little is known about the effect of terrain attributes on creating specific microhabitats that promote or restrict biocrust colonization. This study aimed to identify the main terrain attributes controlling biocrust distribution in the driest badland system in Europe, the Tabernas Badlands (SE Spain). To do this, we analysed the influence of different terrain attributes related to landscape stability and microclimate formation on the spatial distribution of lichen and cyanobacteria, using field measurements and topographical information from a LiDAR survey. Our results showed that the spatial distribution of cyanobacteria-dominated biocrusts, which are physiologically and morphologically adapted to extreme drought and high UVA radiation, was mostly associated with areas of high potential incoming solar radiation. The exception was bare south-aspect hillslopes with very high sediment transport potential, where bare physically crusted soils were the dominant ground cover. Lichen-dominated biocrusts, in contrast, colonized near the top of north-aspect hillslopes, characterized by low potential incoming solar radiation and potential evapotranspiration, and their cover decreased downstream, as conditions became good enough for vascular plants. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd. 相似文献
3.
4.
Evaporative losses from soils covered by physical and different types of biological soil crusts 总被引：3，自引：0，他引：3
Evaporation of soil moisture is one of the most important processes affecting water availability in semiarid ecosystems. Biological soil crusts, which are widely distributed ground cover in these ecosystems, play a recognized role on water processes. Where they roughen surfaces, water residence time and thus infiltration can be greatly enhanced, whereas their ability to clog soil pores or cap the soil surface when wetted can greatly decrease infiltration rate, thus affecting evaporative losses. In this work, we compared evaporation in soils covered by physical crusts, biological crusts in different developmental stages and in the soils underlying the different biological crust types. Our results show that during the time of the highest evaporation (Day 1), there was no difference among any of the crust types or the soils underlying them. On Day 2, when soil moisture was moderately low (11%), evaporation was slightly higher in well‐developed biological soil crusts than in physical or poorly developed biological soil crusts. However, crust removal did not cause significant changes in evaporation compared with the respective soil crust type. These results suggest that the small differences we observed in evaporation among crust types could be caused by differences in the properties of the soil underneath the biological crusts. At low soil moisture (<6%), there was no difference in evaporation among crust types or the underlying soils. Water loss for the complete evaporative cycle (from saturation to dry soil) was similar in both crusted and scraped soils. Therefore, we conclude that for the specific crust and soil types tested, the presence or the type of biological soil crust did not greatly modify evaporation with respect to physical crusts or scraped soils. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
5.
Yolanda Cantón Luis Villagarcía María José Moro Penelope Serrano-Ortíz Ana Were Francisco Javier Alcalá 《水文科学杂志》2013,58(5):737-753
Abstract This paper analyses the temporal dynamics of soil water balance components in a representative recharge area of the Sierra de Gádor (Almeria, southeastern Spain) in two hydrological years. Two approaches are used to estimate daily potential recharge (PR): Approach 1 based on deriving PR from the water balance as the difference between measurements of rainfall (P) and actual evapotranspiration (E) obtained by eddy covariance; and Approach 2 with PR obtained from the dynamic pattern of the soil moisture (θ) recorded at two depths in the site's thin soil (average 0.35 m thickess). For the hydrological year 2003/04, which was slightly drier than the 30-year average, E accounted for 64% of rainfall and occurred mainly in late spring and early summer. The PR estimated by Approach 1 was 181 ± 18 mm year-1 (36% of rainfall), suggesting an effective groundwater recharge in the study area. In the unusually dry hydrological year 2004/05, E was about 215 mm year-1, close to the annual rainfall input, and allowing very little (8 ± 12 mm year-1) PR according to Approach 1. Estimation of PR based on Approach 2 resulted in PR rates lower than those found by Approach 1, because Approach 2 does not take into account the recharge that occurs through preferential flow pathways (cracks, joints and fissures) which were not monitored with the θ probes. Moreover, using Approach 2, the PR estimates differed widely depending on the time scale considered: with daily mean θ data, PR estimation was lower, especially in late spring, while θ data at 30 min resolution yielded a more reliable prediction of the fraction of total PR resulting from the downward movement of soil water by gravity. Citation Cantón, Y., Villagarcía, L., Moro, M. J., Serrano-Ortíz, P., Were, A., Alcalá, F. J., Kowalski, A. S., Solé-Benet, A., Lázaro, R. & Domingo, F. (2010) Temporal dynamics of soil water balance components in a karst range in southeastern Spain: estimation of potential recharge. Hydrol. Sci. J. 55(5), 737–753. 相似文献
6.
7.
DOUGLAS J. Cant 《Basin Research》1989,2(2):73-81
Abstract An equation to relate the thickness of sediment deposited (ΔSed), eustatic sea-level change (ΔE), and subsidence (ΔSub), to changes in depth of water (ΔD) is: ΔSub +ΔE-ΔSed =ΔD.
Using existing sea-level curves, the equation shows that some transgressive-regressive sequences in a foreland basin and a composite seismic facies sequence on a passive margin cannot result solely from eustatic variation. In each case, the space created by subsidence is greater than that provided by eustatic rise. However, eustatic variation could have triggered sequence development if superimposed on a basin with relatively constant values of the other parameters. Short-period sea-level fluctuations with high rates of change, exceeding 70–100 m Myr-1 for periods less than 2–3 Myr, affect the stratigraphy and sedimentology more than longer period, higher amplitude variations.
Clinoforms are generated because of lateral variations in sedimentation rate compared to the rate of creation of accommodation space. These variations may result from differing sedimentation rates, subsidence rates, or rates of eustatic change, superimposed on a basin with lateral sediment supply. Clinoform slopes and curvatures are interpre table in terms of these variables as well as the type of sediment supplied and the energy distribution in the basin.
These equations put some well-known geological principles on a simple quantitative basis. They force precision in definition of variables, and may lead to further development of quantitative techniques in stratigraphy and sedimentology. 相似文献
Using existing sea-level curves, the equation shows that some transgressive-regressive sequences in a foreland basin and a composite seismic facies sequence on a passive margin cannot result solely from eustatic variation. In each case, the space created by subsidence is greater than that provided by eustatic rise. However, eustatic variation could have triggered sequence development if superimposed on a basin with relatively constant values of the other parameters. Short-period sea-level fluctuations with high rates of change, exceeding 70–100 m Myr
Clinoforms are generated because of lateral variations in sedimentation rate compared to the rate of creation of accommodation space. These variations may result from differing sedimentation rates, subsidence rates, or rates of eustatic change, superimposed on a basin with lateral sediment supply. Clinoform slopes and curvatures are interpre table in terms of these variables as well as the type of sediment supplied and the energy distribution in the basin.
These equations put some well-known geological principles on a simple quantitative basis. They force precision in definition of variables, and may lead to further development of quantitative techniques in stratigraphy and sedimentology. 相似文献
8.
9.
Francisco J. Alcalá Yolanda Cantón Sergio Contreras Ana Were Penélope Serrano-Ortiz Juan Puigdefábregas Albert Solé-Benet Emilio Custodio Francisco Domingo 《Environmental Earth Sciences》2011,62(3):541-557
In the high-permeability, semiarid carbonate aquifer in the Sierra de Gádor Mountains (southeastern Spain), some local springs
draining shallow perched aquifers were of assistance in assessing applicability of the atmospheric chloride mass balance (CMB)
for quantifying total yearly recharge (R
T) by rainfall. Two contrasting hydrological years (October through September) were selected to evaluate the influence of climate
on recharge: the average rainfall year 2003–2004, and the unusually dry 2004–2005. Results at small catchment scale were calibrated
with estimated daily stand-scale R
T obtained by means of a soil water balance (SWB) of rainfall, using the actual evapotranspiration measured by the eddy covariance
(EC) technique. R
T ranged from 0.35 to 0.40 of rainfall in the year, with less than a 5% difference between the CMB and SWB methods in 2003–2004.
R
T varied from less than 0.05 of rainfall at mid-elevation to 0.20 at high elevation in 2004–2005, with a similar difference
between the methods. Diffuse recharge (R
D) by rainfall was quantified from daily soil water content field data to split R
T into R
D and the expected concentrated recharge (R
C) at catchment scale in both hydrological years. R
D was 0.16 of rainfall in 2003–2004 and 0.01 in 2004–2005. Under common 1- to 3-day rainfall events, the hydraulic effect of
R
D is delayed from 1 day to 1 week, while R
C is not delayed. This study shows that the CMB method is a suitable tool for yearly values complementing and extending the
more widely used SWB in ungauged mountain carbonate aquifers with negligible runoff. The slight difference between R
T rates at small catchment and stand scales enables results to be validated and provides new estimates to parameterize R
T with rainfall depth after checking the weight of diffuse and concentrated mechanisms on R
T during moderate rainfall periods and episodes of marked climatic aridity. 相似文献
10.