Changes

[[file:M31F5.jpg|thumb|300px|{{figure number|4}}Photographs of bedding in a meander point bar. A. Cyclic flood deposits in a point bar. B. Small-scale cross-stratification and organic debris. C. Climbing ripple sequence capped by convolute laminations. D. Highly contorted bedding in point-bar deposits. E. Soil zones alternating with ripple laminations in upper part of point-bar deposits.<ref name=Colemanandprior_1981 />]]

[[file:M31F5.jpg|thumb|300px|{{figure number|4}}Photographs of bedding in a meander point bar. A. Cyclic flood deposits in a point bar. B. Small-scale cross-stratification and organic debris. C. Climbing ripple sequence capped by convolute laminations. D. Highly contorted bedding in point-bar deposits. E. Soil zones alternating with ripple laminations in upper part of point-bar deposits.<ref name=Colemanandprior_1981 />]]

Overlying the large-scale cross-bedding is a well-sorted sand sequence composed of repeated cyclic sedimentation units of climbing ripples, convolute laminations, and parallel well-sorted sand laminations ([[:file:M31F5.jpg|Figure 4A]]). Each of the cyclic units represents deposition during a single flood and a change from lower flow to upper flow regime. Such units range in thickness from 0.5 to over 1.5 m. In some areas the flood deposit is poorly sorted and consists primarily of silts and sands displaying small-scale ripple laminations ([[:file:M31F5.jpg|Figure 4B]]).

Overlying the large-scale cross-bedding is a [[Core_description#Maturity|well-sorted]] sand sequence composed of repeated cyclic sedimentation units of climbing ripples, convolute laminations, and parallel well-sorted sand laminations ([[:file:M31F5.jpg|Figure 4A]]). Each of the cyclic units represents deposition during a single flood and a change from lower flow to upper flow regime. Such units range in thickness from 0.5 to over 1.5 m. In some areas the flood deposit is poorly sorted and consists primarily of silts and sands displaying small-scale ripple laminations ([[:file:M31F5.jpg|Figure 4B]]).

During times of extremely high flooding, rapid deposition often takes place on the point bar because of river currents cutting across the meander loop, attempting to shorten its course. In those instances, thick sequences of rapidly deposited, well-developed climbing ripples capped by contorted laminations are common ([[:file:M31F5.jpg|Figure 4C]]). Deposition of 1 to 2 m can take place over only a few hours to a day. Most commonly the distorted bedding simply caps the sand unit, but the entirebed can be rendered into a fluid state and massive contortions can be present ([[:file:M31F5.jpg|Figure 4D]]). The zone of maximum contorted bedding often closely approximate the low-water river level and extends upward into the zone covered by flood waters. The uppermost unit of the meander point bar often consists of silt and sand beds (few centimeters thick) displaying ripple laminations alternating with silty-clay and clay beds exhibiting root burrows ([[:file:M31F5.jpg|Figure 4E]]). In these uppermost units iron oxide and calcium carbonate nodules usually are abundant.

During times of extremely high flooding, rapid deposition often takes place on the point bar because of river currents cutting across the meander loop, attempting to shorten its course. In those instances, thick sequences of rapidly deposited, well-developed climbing ripples capped by contorted laminations are common ([[:file:M31F5.jpg|Figure 4C]]). Deposition of 1 to 2 m can take place over only a few hours to a day. Most commonly the distorted bedding simply caps the sand unit, but the entirebed can be rendered into a fluid state and massive contortions can be present ([[:file:M31F5.jpg|Figure 4D]]). The zone of maximum contorted bedding often closely approximate the low-water river level and extends upward into the zone covered by flood waters. The uppermost unit of the meander point bar often consists of silt and sand beds (few centimeters thick) displaying ripple laminations alternating with silty-clay and clay beds exhibiting root burrows ([[:file:M31F5.jpg|Figure 4E]]). In these uppermost units iron oxide and calcium carbonate nodules usually are abundant.