Morphology of step-pools in a wilderness headwater stream: The importance of standardizing geomorphic measurements

The morphology of step-pools and cascades reflect the geological and climatic factors affecting channels in mountain watersheds. This study uses longitudinal and cross-section surveys to describe a headwater stream in the Boston Mountains of the Ozarks Plateau region in Arkansas and develop morphological relationships for comparisons with other regions. In the Bowers Hollow Creek watershed (3.5 km²), located within the boundaries of the Upper Buffalo Wilderness Area, step height and wavelength relationships are generally similar to those reported from other regions. Step-pool reaches were widely distributed in a discontinuous manner throughout the watershed. Average values of the sampled reaches are: reach slopes, 0.105 m/m; width, 6.10 m; crest particle sizes, 440 mm; step heights, 0.87 m; and step wavelengths, 6.62 m. The mean step steepness for the watershed was 0.13, whereas the mean length of a reach step to height ratio was 9:1. A comparison of morphological definitions found that the values of step height and steepness can vary by > 30% according to how step parameters are defined. Step height is particularly sensitive; thus, comparison of step height-based relationships from published data requires great care.     

Fossil nothofagaceous leaves from the Eocene of western Antarctica and their bearing on the origin, dispersal and systematics of Nothofagus

Fossil leaves resembling Nothofagaceae have been investigated from the Eocene of western Antarctica and a new form genus Nothofagofolia is proposed for these kinds of fossils. Some new specimens belonging to this form genus are described. They were collected from the Fossil Hill locality of Fildes Peninsula, King George Island, South Shetland Islands, western Antarctica. Two new species, two new combinations and an unnamed species are reported. A number of published Nothofagus leaf fossils from the same locality are discussed and revised. As a result of these studies of Nothofagus leaf morphology, we conclude that (1) Nothofagus probably originated in high latitudes of the Southern Hemisphere during the middle-late Late Cretaceous and diversified, dispersed gradually to the lower latitudes of the same hemisphere; (2) leaf morphological characters are significant for the systematics of the family Nothofagaceae, especially at the intrageneric level; and (3) extant species of Nothofagus known from southern temperate areas have more primitive leaf morphological characters and lower leaf ranks than those from tropical mountains as well as those of the Fagaceae and Betulaceae. Supported by the Foundation of State Key Laboratory of Palaeobiology & Stratigraphy, Nanjing Institute of Geology and Palaoentology, Chinese Academy of Sciences (Grant No. 013106), the National Natural Science Foundation of China (Grant No. 30670159) and the Fund of Innovation Program by Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences     

Morphology of the Itapeva to Tramandai transgressive dunefield barrier system and mid‐ to late Holocene sea level change

The surface morphology of the transgressive dunefield barrier extending from Itapeva to Tramandai along the northern littoral of Rio Grande do Sul, is examined and an attempt is presented to link morphological changes across the barrier to Holocene sea level changes. The 4·5 km wide Holocene barrier displays two typical morphologies: an inner part dominated by large‐scale, continuous alongshore, overlapping dunefield phases comprising sand sheets, dunes, deflation plains and precipitation ridges; and an outer part dominated by discontinuous, medium‐ to small‐scale, triangular to lobate transgressive dunefield phases, cut by both active and relict (palaeo‐) creeks or washouts. Holocene sea level in the region rose to c. +1 to +3 m above present reaching a maximum around 5100 years bp and then progressively fell to the present level. We argue that the effect on barrier development was to suppress the development of a drainage system during the rising and maximum stages, and encourage the development of an organized drainage system in the form of regularly spaced washouts during the falling period, and that this change in sea level from rising to falling therefore produced the large‐scale differences in barrier morphology. Copyright © 2006 John Wiley & Sons, Ltd.     

Transport and deposition of large woody debris in streams: a flume experiment

Large woody debris (LWD) is an integral component of forested streams of the Pacific Northwest and elsewhere, yet little is known about how far wood is transported and where it is deposited in streams. In this paper, we report the results of flume experiments that examine interactions among hydraulics, channel geometry, transport distance and deposition of floating wood. These experiments were carried out in a 1.22-m-wide×9.14-m-long gravel bed flume using wooden dowels of various sizes as surrogate logs. Channel planforms were either self-formed or created by hand, and ranged from meanders to alternate bars. Floating pieces tended to orient with long axes parallel to flow in the center of the channel. Pieces were deposited where channel depth was less than buoyant depth, typically at the head of mid-channel bars, in shallow zones where flow expanded, and on the outside of bends. We hypothesize that the distance logs travel may be a function of the channel's debris roughness, a dimensionless index incorporating ratios of piece length and diameter to channel width, depth and sinuosity. Travel distance decreased as the ratio of piece length to both channel width and radius of curvature increased, but the relative importance of these variables changed with channel planform. Large pieces can move further than our debris roughness models predict if greater than 50% of the active channel area is deeper than the buoyant depth of the piece, or if momentum is high enough to carry pieces across shallows. Our debris roughness model allows first-order prediction of the amount of wood transport under various channel geometries.     

中、低空机载成像光谱图像的几何校正研究

本文针对我国上海技术物理所研制的OMIS机载128道成像光谱系统试飞所获取的图像、定位和飞行姿态等数据，进行了图像几何修正处理和衫软件开发研究。详细分析了该系统所获取的定位与飞行姿态数据及存在的问题，并制定了相应的处理方案。根据该系统提供的各种参数，建立了航空高光谱图像单因素几何校正模型和几何畸变综合校正方法。对该系统在辽东湾地区试验飞行获取的10条航带图像进行几何校正和多航带镶嵌处理，效果理想。     

Location and height of intertidal bars on macrotidal ridge and runnel beaches

Previous studies devoted to the morphology and hydrodynamics of ridge and runnel beaches highlight characteristics that deviate from those initially postulated by King and Williams (Geographical Journal, 1949, vol. 113, 70–85) and King (Beaches and Coasts, 1972, Edward Arnold). Disagreements on the morphodynamics of these macrotidal beaches include the position of the ridges relative to the mean neap and spring tide levels, the variation in the height of the ridges across the intertidal profile and, most importantly, whether the ridges are formed by swash or surf zone processes. The morphological characteristics of ridge and runnel beaches from three locations with varying wave, tidal and geomorphic settings were investigated to address these disagreements. Beach profiles from each site were analysed together with water‐level data collected from neighbouring ports. It was found that the ridges occur over the entire intertidal zone. On one site (north Lincolnshire, east England), the ridges are uniformly distributed over the intertidal beach, whereas on the two other sites (Blackpool beach, northwest England, and Leffrinckoucke beach, north France) there is some indication that the ridges appear to occur at preferential locations. Most significantly, the locations of the ridge crests were found to be unrelated to the positions on the intertidal profile where the water level is stationary for the longest time. It was further found that the highest ridges generally occur just above mid‐tide level where tidal non‐stationarity is greatest. These findings argue against the hypothesis that the ridges are formed by swash processes acting at stationary tide levels. It is tentatively suggested that the ridges are the result of a combination of swash and surf zone processes acting across the intertidal zone. Elucidation of the morphodynamic roles of these two types of processes, and other processes such as strong current flows in the runnels, requires further comprehensive field measurements complemented by numerical modelling. Copyright © 2001 John Wiley & Sons, Ltd.     

论地质作用中元素间的相关性及制约因素

本文把地质作用中元素间的相关性划分为曲线相关、准线性相关和线性相关三种类型;并在建立反映岩浆、沉积作用过程中元素间相关关系的数学模型及其它工作的基础上,详细讨论分配系数、源区成分和作用过程等方面对地质作用中元素间相关关系的制约作用。进而获得批式熔融、结晶分异、岩浆混合、化学沉积、碎屑沉积等过程中元素间呈线性和(?)线性关系的一般特征和应用前景。最后还给出La/Ce相关性的应用实例。     

Sea ice thickness measurement and its underside morphology analysis using radar penetration in the Arctic Ocean

Sea ice, as an important component of the Arctic climate system, has drawn significant sci-entific interest. Sea ice thickness and its morphology have dramatic impacts on ocean-atmos- phere-ice interactions[1—4], which directly affect the exchange proces…     

现代植物炭屑形态的初步分析及其古环境意义*

通过对23种现代植物炭屑的观察、测量以及对草本、木本炭屑模拟破碎试验后的测量统计发现:现代植物炭屑形态根据其长宽比(L/W)和形态特征可以分为3个类型:1)草本型炭屑,L/W最大,平均为10.2±1.3, 呈长-薄条型、针型、簇纤维型,边缘及断口截然,棱角分明,有些具有气孔构造,很少有不规则的形态出现; 2)木本型炭屑(灌木+乔木),L/W较小,平均3.1±0.2,多呈方~长方型或立方体型,边缘多参差不齐,有些横向断口有粗大木纤维露出,相对致密; 3)阔叶类植物叶片炭屑,L/W最小,平均1.7±0.1,薄片状、网状,絮状,易碎。进一步通过对6个典型草原和森林表土样品的实验室分析,发现现代土壤中的炭屑颗粒大小相对现代植物炭屑颗粒大小总体有所减小,但草原土壤中炭屑长宽比相对森林土壤炭屑仍然较大,土壤中炭屑形态和部分结构鉴别特征仍能保留。表明L/W值与炭屑结构特征可以用来区分多数草本与木本植物炭屑。在此基础上,通过对黄土高原渭南剖面S₁以来不同层位12个地层样品的炭屑形态分析,初步研究了不同草本、木本植物炭屑形态变化的特点和环境意义。     

基于形态重构的图像去噪方法研究

应用数学形态学中的形态重构滤波,对噪声图像进行了处理,在去除噪声的同时,也保持了边缘及细节信息。