Current patterns and mass transport of clastic sediments in the near-shore regions of Monterey Bay

Title:: Current patterns and mass transport of clastic sediments in the near-shore regions of Monterey Bay
Abstract:: "Three definable current patterns existed in Monterey Bay during the summer and fall of 1966, and early part of 1967. During that time changes from one pattern to the next closely paralleled seasonal changes peculiar to the Monterey Bay area. Currents over the central shelf region flowed with remarkable symmetry about the axis of the Monterey submarine canyon. Currents within the canyon were complex and extremely variable with frequent short lived changes in direction and velocity. Station observations indicated a direction of mass transport both northeast and southwest, into and out of the canyon proper. In late summer and early fall, water masses diverged upon reaching the canyon head, forming one current which flowed toward the northwest, and another toward the south. However, in early winter, all currents over the central shelf region flowed from south to north passing over the Monterey Canyon and giving rise to a more persistent down-canyon current. Well-sorted dark gray-green very fine sand and silt predominate over the central shelf region. Sediments contoured on the basis of median diameters form zones which roughly parallel the isobaths. Water masses entering the north shelf region in mid-winter, flowed from west to east to south in directions parallel to the curving coastline and to the isobaths farther seaward. Grey-green, fine grained sediments cover much of the north shelf region and are best sorted offshore. Grouping of grain sizes forms bands which are essentially parallel to the curving shoreline and isobaths. Currents flowing over the south shelf during mid-winter and early spring originated from the northwest. As these currents came upon Point Pinos they diverged in two directions, one branch flowed southward parallel to the west coast of the Monterey Peninsula, the other southeastward along the northeast coast which then swung northward parallel to the curving coastline. Medium to very fine grey-green sands are widely distributed over the south shelf, with the finer grained and best sorted sediments in the deeper portions. Grouping of grain sizes indicated trends much the same as those characteristic of the north and center shelf regions. Application of current and grain size data to the diagram prepared by Hjulstrom (1939) in which current velocity and particle size are related to conditions of erosion, transportation, and deposition show that sediments in the Monterey Bay area are under conditions of transport. Correlation of grain size distribution with observed current directions indicate mass transport of clastic materials in directions parallel to the isobaths in most cases."
Supplemental_Information:: The boundaries on the area studied are the San Lorenzo River to the north and Point Pinos in the south. Several samples were taken in the high tide zone and have been given a water depth of '0'. Grain size analyses were performed only on phi sizes 1.0 to 10, although comments in the text refer to coarse sand (samples 51 and 55), pebbles (sample 51), and shells (sample 52). Data digitized by the USGS for inclusion into usSEABED (<http://walrus.wr.usgs.gov/usseabed>)

Range of values
Minimum:	0
Maximum:	140
Units:	Meters
Resolution:	0.1

Range of values
Minimum:	1.09
Maximum:	4.38
Units:	Phi
Resolution:	0.01

Range of values
Minimum:	1.4
Maximum:	4.16
Units:	Phi
Resolution:	0.01

Range of values
Minimum:	0.3
Maximum:	4.1
Units:	Phi
Resolution:	0.01

Range of values
Minimum:	1.12
Maximum:	1.59
Units:	Phi
Resolution:	0.001

Current patterns and mass transport of clastic sediments in the near-shore regions of Monterey Bay

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