Stream channel convexity induced by continuous base level lowering, the Dead Sea, Israel

被引:28
作者
Bowman, Dan [1 ]
Shachnovich-Firtel, Yonit [1 ]
Devora, Shlomo [1 ]
机构
[1] Ben Gurion Univ Negev, Dept Geog & Environm Dev, IL-84105 Beer Sheva, Israel
关键词
base level; longitudinal stream profile; headward entrenchment; Dead Sea - Israel;
D O I
10.1016/j.geomorph.2007.02.009
中图分类号
P9 [自然地理学];
学科分类号
0705 ; 070501 ;
摘要
The Dead Sea level has dropped from -388.4 in in 1896 to -417.2 m in 2004 and continues to fall rapidly, reaching a record of 1 m/y drop. Such a dramatic base level fall, on time scales of several tens of years, makes the Dead Sea area a unique field laboratory. The aim of this study is to examine the effect of the lowering Dead Sea, as a base level, on the longitudinal profiles of channels, on the formation of knick points, and on the sinuosity. Field studies were made along the lower courses of creeks which drain lakeward. Precise longitudinal profile measurements and their fitting to linear and logarithmic curves, show they are planar to slightly convex. The short convexity, the absence of hydrological or lithological control, and former experimental results of profile response to base level fall, suggest that the convexity results from the recent continuous rapid drop of the Dead Sea. The convexity is also an inheritance of the paleo morphology, i.e., the original convex front of the fan deltas and coastal scarps following channel incision, slope displacement and diffusion. The erodible substrate and the high stream power prevented preservation of nickpoints along the main channels. Sinuosity of the meandering thalwegs remained low 1.1-1.2, indicating no response to the base level lowering along the steep slopes. Although the stream channels are incised in soft sediments, the base level-induced entrenchment dies out within 1000 in or less from the receding shoreline. The channel profiles demonstrate different phases of adjustment to the lowering base level. The uniqueness of the Dead Sea case is that, contrary to former field and experimental studies, the system is in a continuous relaxation period without reaching a final adjustment. The channels are "trapped" in their convex form following a rapid on going base level fall upon exposed paleo fan deltas. (c) 2007 Elsevier B.V. All rights reserved.
引用
收藏
页码:60 / 75
页数:16
相关论文
共 91 条
[1]  
ANATI DA, 1989, ISRAEL J EARTH SCI, V38, P29
[2]  
ANATI DA, 1987, ISR J EARTH SCI, V8, P109
[3]  
ASHBEL D, 1965, MADA, V9, P255
[4]   Lake levels and sequence stratigraphy of Lake Lisan, the late Pleistocene precursor of the Dead Sea [J].
Bartov, Y ;
Stein, M ;
Enzel, Y ;
Agnon, A ;
Reches, Z .
QUATERNARY RESEARCH, 2002, 57 (01) :9-21
[5]  
BARTOV Y, 1999, THESIS HEBREW U JERU
[6]   DEVELOPMENT OF LONGITUDINAL PROFILES OF ALLUVIAL CHANNELS IN RESPONSE TO BASE-LEVEL LOWERING [J].
BEGIN, ZB ;
MEYER, DF ;
SCHUMM, SA .
EARTH SURFACE PROCESSES AND LANDFORMS, 1981, 6 (01) :49-68
[7]  
BEGIN ZB, 1997, 79GSI42 GEOL SURV
[8]  
BENZVI A, 2006, 20063 HYDROL SURV
[9]   CHARACTER OF HEADWATERS ADJUSTMENT TO BASE-LEVEL DROP, INVESTIGATED BY DIGITAL MODELING [J].
BONNEAU, PR ;
SNOW, RS .
GEOMORPHOLOGY, 1992, 5 (3-5) :475-487
[10]   Late Holocene lake levels of the Dead Sea [J].
Bookman, R ;
Enzel, Y ;
Agnon, A ;
Stein, M .
GEOLOGICAL SOCIETY OF AMERICA BULLETIN, 2004, 116 (5-6) :555-571