River-evolution and tectonic implications of a major Pliocene aggradation on the lower Colorado River: The Bullhead Alluvium
River-evolution and tectonic implications of a major Pliocene aggradation on the lower Colorado River: The Bullhead Alluvium
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科罗拉多河下游上新世主要加积作用的河流演化和构造影响：布尔海德冲积层
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发表时间：
2015
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影响因子：
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通讯作者：
P. Pearthree
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作者：
K. Howard;P. House;R. Dorsey;P. Pearthree
大峡谷下游科罗拉多河下游沿着厚约200 m的河床式牛头冲积层记录了上、下游科罗拉多河流域整合后大量上新世早期沉积物的加积。加积沉积物的分布和范围记录了：（1）河谷纵向剖面的演变，对河口和三角洲位置的变化有影响;（2）早期快速流域侵蚀和沉积物供应的脉冲;（3）对区域和局部变形的限制。牛头冲积层沿沿着基底侵蚀不整合嵌入到Hualapai组和Bouse组中。它的基础定义了一个纵向剖面，被解释为科罗拉多河通过湖泊盆地整合后的切割最终结果。随后的牛头加积，在约。4.5-3.5 Ma，形成宽达50 km的辫状平原，使科罗拉多河的水位升高。我们解释的加积记录峰值沉积物供应时，河流整合和基准面下降不稳定和侵蚀残留景观和第三纪基岩在科罗拉多河的巨大集水区。牛头冲积层的纵向剖面表明，米德湖上部区域的牛头后相对断层隆起≥200 m，布莱斯盆地的局部沉降>100 m，索尔顿海槽沿着太平洋-北美板块边界的相关三角洲层序的沉降更深。然而，从区域来看，从亚利桑那州尤马到亚利桑那州米德湖和内华达州的河流走廊，沿着>500公里，牛头冲积层顶部似乎既没有隆起也没有倾斜，向下游倾斜0.5-0.6 m/km，就像较小的晚更新世加积序列的梯度一样。栖息露头暂定分配到附近的圣安德烈亚斯断层系统项目的牛头冲积层上新世海岸或海湾线的两倍远（300-450公里），无论是现代河口或构造恢复4.25马古海岸。我们的结论是，牛头加积达到峰值后4.25马，延长了三角洲平原向海的速度超过了2毫米/年的三角洲沉降和43-45毫米/年的转换断层偏移的三角洲。后Bullhead退化开始前3.3马，这意味着河流剖面降低和缩短，因为沉积物供应下降，并addation是无法跟上沉降和板块运动的三角洲。
The ∼200-m-thick riverlaid Bullhead Alluvium along the lower Colorado River downstream of Grand Canyon records massive early Pliocene sediment aggradation following the integration of the upper and lower Colorado River basins. The distribution and extent of the aggraded sediments record (1) evolving longitudinal profiles of the river valley with implications for changing positions of the river’s mouth and delta; (2) a pulse of rapid early drainage-basin erosion and sediment supply; and (3) constraints on regional and local deformation. The Bullhead Alluvium is inset into the Hualapai and Bouse Formations along a basal erosional unconformity. Its base defines a longitudinal profile interpreted as the incised end result after the Colorado River integrated through lake basins. Subsequent Bullhead aggradation, at ca. 4.5–3.5 Ma, built up braid plains as wide as 50 km as it raised the Colorado River’s grade. We interpret the aggradation to record a spike in sediment supply when river integration and base-level fall destabilized and eroded relict landscapes and Tertiary bedrock in the Colorado River’s huge catchment. Longitudinal profiles of the Bullhead Alluvium suggest ≥200 m post-Bullhead relative fault uplifts in the upper Lake Mead area, >100 m local subsidence in the Blythe Basin, and deeper subsidence of correlative deltaic sequences in the Salton Trough along the Pacific–North American plate boundary. However, regionally, for >500 km along the river corridor from Yuma, Arizona, to Lake Mead, Arizona and Nevada, the top of the Bullhead Alluvium appears to be neither uplifted nor tilted, sloping 0.5–0.6 m/km downstream like the gradient of a smaller late Pleistocene aggradation sequence. Perched outcrops tentatively assigned to the Bullhead Alluvium near the San Andreas fault system project toward a Pliocene seashore or bayline twice as distant (300–450 km) as either the modern river’s mouth or a tectonically restored 4.25 Ma paleoshore. We conclude that Bullhead aggradation peaked after 4.25 Ma, having lengthened the delta plain seaward by outpacing both 2 mm/yr delta subsidence and 43–45 mm/yr transform-fault offset of the delta. Post-Bullhead degradation started before 3.3 Ma and implies that the river profile lowered and shortened because sediment supply declined, and progradation was unable to keep up with subsidence and plate motion in the delta.
影响因子：
4.2
作者：
P. Ballato;D. Stockli;Mohammad Reza Ghassemi;A. Landgraf;M. Strecker;J. Hassanzadeh;A. Friedrich;S. Tabatabaei
通讯作者：
P. Ballato;D. Stockli;Mohammad Reza Ghassemi;A. Landgraf;M. Strecker;J. Hassanzadeh;A. Friedrich;S. Tabatabaei
影响因子：
2.8
作者：
C. Plattner;R. Malservisi;T. Dixon;P. LaFemina;G. Sella;J. Fletcher;F. Suárez‐Vidal
通讯作者：
C. Plattner;R. Malservisi;T. Dixon;P. LaFemina;G. Sella;J. Fletcher;F. Suárez‐Vidal