The marine geology of San Miguel Gap off Point Conception, California

Metadata:

• Identification_Information
• Data_Quality_Information
• Spatial_Data_Organization_Information
• Spatial_Reference_Information
• Entity_and_Attribute_Information
• Distribution_Information
• Distribution_Information
• Metadata_Reference_Information

Identification_Information:

Citation:

Citation_Information:

Originator: Frederick Fanning Wright

Publication_Date: 1967

Title:

The marine geology of San Miguel Gap off Point Conception, California

Geospatial_Data_Presentation_Form: Paper

Publication_Information:

Publication_Place: Los Angeles, CA

Publisher: University of Southern California

Other_Citation_Details:

The Allan Hancock Foundation provided shiptime under a grant from the National Science Foundation. Much of the analysis and laboratory work was supported by a Penrose Bequest Research Grant from the Geological Society of America.

Description:

Abstract:

"San Miguel Gap is a submarine basin which intersects the continental slope southwest of Point Conception. It lies at the northwest limit of the California continental borderland. The basin is bounded by straight, steep slopes, which separate it from Arguello Plateau to the north and the Channel Islands and Santa Rose-Cortes Ridge to the east. A gentler, less regular slope to the south leads to the Patton Ridge. The basin is 30 x 35 km at a depth of 1500 m; it slopes gently seaward to breach the continental slope to a depth of 2500 m. "Sub-bottom acoustic reflection profiles across the Gap show pre- and post-orogenic generations of sedimentary fill, distinguished by mild peripheral folding in the older section. Assuming a sediment velocity of 2 km/sec, the basin contains a maximum thickness of 270 m of post-orogenic and 400 m of pre-orogenic fill. Beneath the basin, forming the continental slope, and outcropping on the ridges there is a unit termed "acoustic bedrock." Where sampled, this is Miocene (?) basalt or sedimentary rock. Acoustic bedrock correlates with the Channel Islands section of Cretaceous to Miocene sediments and volcanics. Possible boundary faults lie to the east and north, while to the south there is a possible downfold to form the Gap basin. "The Gap region is an elongate continental slope sedimentary environment, under terrestrial influence to the east and oceanic influence to the west. Terrestrial sands, near the islands, grade into glauconitic sands on the deeper slopes and hemipelagic clayey silt in the basin. Both sediment production and distribution are controlled by oceanographic agencies. In particular, strong currents influence the entire water column. Surface flows often exceed 200 cm/sec, and velocities averaging 5 cm/sec, peaking over 20 cm/sec, were measured at 727 m. Terrestrial sands come from the islands; they are controlled by wave action. Silts and clays, largely derived from the mainland, are distributed by winds, surface and bottom currents, and are concentrated in the basin. Foraminifers are extremely common in the sediment; their abundance is a function of surface organic productivity and bottom current winnowing. Glauconite is ubiquitous and contemporary; it constitutes over one-half the sediment where other deposition is inhibited. A probable authigenic sequence form precipitation in small shells to typical glauconite pellets can be identified in Gap sediments. Relative contributions of the major sediment constituents were determined for each section of the Gap area: Santa Rosa Ridge-Cortes Ridge: 50% terrestrial, 42% organic, and 7% authigenic; Central Basin: 76% terrestrial, 22% organic, and 2% authigenic; Deep slopes and terraces: 30% terrestrial, 27% organic, and 42% authigenic. "Sedimentation rates range from 13-15 mm/10e3 years on the deep slopes to 31 mm/10e3 years at the head of the basin and 54 mm/10e3 years in the central basin. Assuming constant rates, the observed fill thickness in the basin could have accumulated in 13.4 x 10e6 years, since Early Pliocene. All dates used in the estimates are based upon the sinistral-to-dextral coiling direction shift in the foraminifer, Globigerina pachyderma, at the end of the Pleistocene. Study of cores in the Gap region indicates no significant change in the sedimentary or oceanographic regimes since Late Pleistocene. "Two pronounced east-west structures, the Murray Fracture Zone of the Pacific basin and the Transverse Ranges of California, are aligned with the Gap. It has been suggested that this break in the continental slope represents an interaction of oceanic and continental structures. All evidence, however, indicates that San Miguel Gap is a borderland structure formed during Late Miocene, which has subsequently undergone little disturbance. No relation with the east-west structures is clear."

Purpose:

"The specific objectives of this study are (1) to describe the geology of an anomalous segment of the continental margin and to relate this to the regional geology, and (2) to explain the distribution of the contemporary and the sub-recent sediments of the area in terms of the observed and postulated physico-chemical environment."

Supplemental_Information:

Data digitized by the USGS for inclusion into usSEABED (<http://walrus.wr.usgs.gov/usseabed>)

Time_Period_of_Content:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 1967

Currentness_Reference: Publication date

Status:

Progress: Complete

Maintenance_and_Update_Frequency: None planned

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -121.100

East_Bounding_Coordinate: -120.100

North_Bounding_Coordinate: 34.136

South_Bounding_Coordinate: 33.675

Keywords:

Theme:

Theme_Keyword_Thesaurus: None

Theme_Keyword: University of Southern California

Theme_Keyword: Allan Hancock Foundation

Theme_Keyword: Double pipe dredge

Theme_Keyword: Single pipe dredge

Theme_Keyword: Phleger corer

Theme_Keyword: Piston corer

Theme_Keyword: Shipek sampler

Theme_Keyword: Shipek grab sampler

Theme:

Theme_Keyword_Thesaurus: ISO 19115 Topic Category

Theme_Keyword: Oceans and Estuaries

Theme_Keyword: Location

Theme_Keyword: GeoscientificInformation

Theme:

Theme_Keyword_Thesaurus:

NASA/Global Change Master Directory (GCMD) Earth Science Keyword. Version 5.3.3

Theme_Keyword: Marine Sediments

Theme_Keyword: Sediment Composition

Theme_Keyword: Sedimentary Structures

Theme_Keyword: Sedimentary Textures

Theme_Keyword: Terrigenous Sediments

Place:

Place_Keyword_Thesaurus: Geographic Names Information System (GNIS)

Place_Keyword: California

Place_Keyword: Tomales Bay

Place_Keyword: Channel Islands

Place:

Place_Keyword_Thesaurus: None

Place_Keyword: Continental

Place_Keyword: Borderland

Place_Keyword: San Miguel Gap

Place_Keyword: San Miguel Basin

Place_Keyword: Arguello Plateau

Place_Keyword: Arguello Basin

Place_Keyword: Insular Ridge

Place_Keyword: Santa Rosa-Cortes Ridge

Place_Keyword: Patton Ridge

Place_Keyword: Patton Escarpment

Access_Constraints:

None. Thesis is available at the USGS library and other libraries.

Use_Constraints:

Cite Frederick F. Wright and the University of Southern California as originators of the data.

Point_of_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: University of Southern California

Contact_Address:

Address_Type: Physical

Address: Zumberge Hall

Address: 3651 Trousdale Parkway

City: Los Angeles

State_or_Province: CA

Postal_Code: 90089

Contact_Voice_Telephone: 213-740-6106

Browse_Graphic:

Browse_Graphic_File_Name: Wright_PhD_1967

Browse_Graphic_File_Description:

Sample distribution with coastline and bathymetry for reference.

Browse_Graphic_File_Type: .jpg

Data_Set_Credit:

Frederick Fanning Wright at the University of Southern California for the collection and analysis of data. For inclusion into usSEABED: digitization: Carolynn Box and Jennifer Mendonca (USGS); Formatting corrections: Jane Reid (USGS) and Chris Jenkins (University of Colorado).

Native_Data_Set_Environment:

Tkme: Another editor for formal metadata by Peter N. Schweitzer (U.S. Geological Survey, Reston, VA 22092), version 2.9.13, Microsoft Windows Version 5.1; Microsoft Word 2000 9.0

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report:

No estimate made for the accuracy of the data in the original report. Data digitized by the USGS and partners were visually compared to the source data, and corrected. Where appropriate, data were tested for completeness using MS Excel. Locations checked using GIS.

Logical_Consistency_Report:

Data fall within normal ranges for analytical results. The locations listed for the rocks samples taken from 10097AHF (Appendix IV) are different from the locations given in Appendix I. The locations given in Appendix I were used.

Completeness_Report:

For usSEABED, Appendices I, III, IV, V, and VII were completely digitized. Foraminiferal data (Appendix VI) were not digitized. Some information from the report text may also be included in usSEABED.

Positional_Accuracy:

Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:

For the Allan Hancock Foundation samples aboard the Velero IV, navigation was by radar and dead reckoning. Due to strong currents in the area, station locations are accurate to about 2 km (1 nautical mile) over most of the area, but there may be even greater errors in the positions of some of the more remote stations. For the USNOTS and USNCEL data, navigation was by Loran-A, Loran C, and some of the stations were positioned by the commercial Raydist system, which is accurate to a few tens of meters. Locations are given to minutes, seconds.

Vertical_Positional_Accuracy:

Vertical_Positional_Accuracy_Report:

Depth determination by Precision Depth Recorder echograms. Water depths to nearest meter. Some dredged samples had a range of depths associated; the midpoint of those depths are included in usSEABED.

Lineage:

Process_Step:

Process_Description:

Samples were disaggregated by a treatment of 50 ml of 15 percent H2O2. Samples were desalted by alternate distilled water washing and centrifugation. Samples were wet sieved on a 62-micron screen to separate the sand fractions, which was dried and weighed. The washings, containing the finer fraction, were given an abbreviated pipette analysis. Grain counts were performed under a binocular scope on the coarse fraction on 150 to 250 individual grains. Rocks were thin-sectioned, and identified tentatively on the basis of textural and the more obvious mineral constituents.

Process_Date: Unknown

Source_Produced_Citation_Abbreviation: Wright_PhD_67

Process_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: University of Southern California

Contact_Address:

Address_Type: Physical

Address: Zumberge Hall

Address: 3651 Trousdale Parkway

City: Los Angeles

State_or_Province: CA

Postal_Code: 90089

Contact_Voice_Telephone: 213-740-6106

Spatial_Data_Organization_Information:

Direct_Spatial_Reference_Method: Vector

Point_and_Vector_Object_Information:

SDTS_Terms_Description:

SDTS_Point_and_Vector_Object_Type: Entity point

Point_and_Vector_Object_Count: 88

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Geographic:

Latitude_Resolution: 0.00028

Longitude_Resolution: 0.00028

Geographic_Coordinate_Units: Decimal degrees

Entity_and_Attribute_Information:

Detailed_Description:

Entity_Type:

Entity_Type_Label: Point

Entity_Type_Definition: SDTS point

Entity_Type_Definition_Source: Source report

Attribute:

Attribute_Label: Station numbers

Attribute_Definition: Station number

Attribute_Definition_Source: Source report

Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: AHF

Enumerated_Domain_Value_Definition: Collected by the Allan Hancock Foundation

Enumerated_Domain_Value_Definition_Source: Source report

Enumerated_Domain:

Enumerated_Domain_Value: D

Enumerated_Domain_Value_Definition:

Collected for this study by USNOTS (U.S. Naval Ordnance Test Station)

Enumerated_Domain_Value_Definition_Source: Source report

Enumerated_Domain:

Enumerated_Domain_Value: JD and MH

Enumerated_Domain_Value_Definition: Samples furnished by USNCEL (U.S. Naval Civil Engineering Lab)

Enumerated_Domain_Value_Definition_Source: Source report

Attribute:

Attribute_Label: Interval

Attribute_Definition: Subsample depth interval

Attribute_Definition_Source: Source report

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0

Range_Domain_Maximum: 1.95

Attribute_Units_of_Measure: Meters

Attribute_Measurement_Resolution: 0.01

Attribute:

Attribute_Label: Gravel

Attribute_Definition: Gravel

Attribute_Definition_Source: Source report

Attribute_Domain_Values:

Unrepresentable_Domain:

Gravel was not specifically analyzed; however, in the petrographic analyses, three samples noted gravel presence and rough estimation of presence, up to 20 percent.

Attribute:

Attribute_Label: Sand

Attribute_Definition: Sand

Attribute_Definition_Source: Source report

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 2.1

Range_Domain_Maximum: 99.48

Attribute_Units_of_Measure: Percent

Attribute_Measurement_Resolution: 0.01

Attribute:

Attribute_Label: Silt

Attribute_Definition: Silt

Attribute_Definition_Source: Source report

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0.12

Range_Domain_Maximum: 85.25

Attribute_Units_of_Measure: Percent

Attribute_Measurement_Resolution: 0.01

Attribute:

Attribute_Label: Clay

Attribute_Definition: Clay

Attribute_Definition_Source: Source report

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0

Range_Domain_Maximum: 56

Attribute_Units_of_Measure: Percent

Attribute_Measurement_Resolution: 0.01

Attribute:

Attribute_Label: Median

Attribute_Definition: Median grainsize distribution

Attribute_Definition_Source: Source report

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 2.22

Range_Domain_Maximum: 8.2

Attribute_Units_of_Measure: Phi

Attribute_Measurement_Resolution: 0.01

Attribute:

Attribute_Label: Lithologic descriptions

Attribute_Definition: Lithologic descriptions of rock samples

Attribute_Definition_Source: Source report

Attribute_Domain_Values:

Unrepresentable_Domain: Written descriptions

Attribute:

Attribute_Label: Sand fraction analyses

Attribute_Definition: Petrographic analyses of the sand fraction

Attribute_Definition_Source: Source report

Attribute_Domain_Values:

Unrepresentable_Domain:

Generally rough estimations (including trace presence) of planktonic, benthic, and arenaceous foraminifera, bryozoa, carbonaceous fragments, chiton fragments, diatoms, dark minerals, echinoid fragments, fish bones, glauconite, glauconite foraminiferal casts, mica, mollusk fragments, manganese fragments, phosphorite, radiolarian, sponge spicules, tar, terrestrial sand, volcanic rubble, volcanic debris, volcanic glass, and gravel.

Distribution_Information:

Distributor:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: University of Southern California

Contact_Address:

Address_Type: Physical

Address: Zumberge Hall

Address: 3651 Trousdale Parkway

City: Los Angeles

State_or_Province: CA

Postal_Code: 90089

Contact_Voice_Telephone: 213-740-6106

Resource_Description: Wright_PhD_1967

Distribution_Liability:

Although this dataset has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data. Users of the data should be aware of limitations of the data due to possible imprecision due to navigational inaccuracies and limitations of the statistical data.

Standard_Order_Process:

Non-digital_Form: Report is available at libraries.

Fees: None

Distribution_Information:

Distributor:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: U.S. Geological Survey

Contact_Address:

Address_Type: Mail and physical

Address: 345 Middlefield Road

City: Menlo Park

State_or_Province: CA

Postal_Code: 94025

Contact_Voice_Telephone: 650.329.5026

Contact_Electronic_Mail_Address: men_lib@usgs.gov

Resource_Description: Wright PhD 1967 203 (050)W932m

Distribution_Liability:

Although this dataset has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data. Users of the data should be aware of the limitations of the data due to possible imprecision due to navigational inaccuracies, statistical limitations, and digitizing errors.

Standard_Order_Process:

Non-digital_Form:

Report is available for viewing or checkout at the USGS library, Menlo Park, and at other libraries.

Fees: None

Technical_Prerequisites: None

Available_Time_Period:

Time_Period_Information:

Single_Date/Time:

Calendar_Date: 1959

Metadata_Reference_Information:

Metadata_Date: 2005

Metadata_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: U.S. Geological Survey

Contact_Person: Jane A. Reid

Contact_Position: Geologist

Contact_Address:

Address_Type: Physical and mail

Address: 400 Natural Bridges Drive

City: Santa Cruz

State_or_Province: CA

Postal_Code: 95060

Contact_Voice_Telephone: 831-427-4727

Contact_Electronic_Mail_Address: jareid@usgs.gov

Contact_Instructions: Email preferred

Metadata_Standard_Name: CSDGM Version 2

Metadata_Standard_Version: FGDC-STD-001-1998

Metadata_Access_Constraints: None

Metadata_Use_Constraints:

Metadata was written by a user of the data. Any information contained in the physical report is authoritative and supercedes any information given here.