| Abstract: | Opening of the Neogene Los Angeles Basin began
abruptly about 17.4 Ma. Extensional rifting, with local basaltic
volcanism, began the process and accompanied its early stages.
Crustal detachment, followed by clockwise tectonic rotation
and translation of large crustal blocks has been shown by previous
paleomagnetic declination measurements in the western
Transverse Ranges Province northwest of the basin and by
large strike-slip and dip-slip separations on several major faults
transecting it. Successful palinspastic reconstruction of the
region to its arrangement before 17.4 Ma depends on understanding
and integration of many stratigraphic and structural
components.
Before 17.4 Ma, fluviatile, alluvial and floodplain deposits,
interstratified in the younger part with shallow marine to
deeper shelf transgressive equivalents, accumulated to thicknesses
as great as several kilometers. This report maps the
surface and subsurface extents, thickness variations, and facies
patterns of these strata, the Sespe plus Vaqueros and Trancas
Formations or equivalents. Separate southeast and northwest
sectors are revealed, each with distinctive internal thickness
and facies patterns, which must have been related before rifting
and transrotation. Terrestrial vertebrate and marine molluscan
and foraminiferal fossils, plus magnetostratigraphic
profiles of other workers and a few dates of igneous rocks,
provide timing for key depositional and structural events.
Our preliminary reconstruction of the region brings the
internal patterns of the northwest and southeast sectors toward
congruity but leaves unsatisfied discrepancies that suggest
important information is missing. The reconstruction focuses
attention on critical elements, specific uncertainties, and deficiencies
of prior reconstructions. It also provides a new foundation
for further work |
| Genre: | USGS Numbered Series |
| ProdID: | 56952 |
| Citation Author: | McCulloh, Thane H.; Beyer, Larry A. |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | 32 p. |
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| Citation Series: | Professional Paper |
| Citation Series Code: | PP |
| Citation Series Number: | 1690 |
| Citation Search Results Text: | Mid-Tertiary Isopach and Lithofacies Maps for the Los Angeles Region, California: Templates for Palinspastic Reconstruction to 17.4 Ma; 2004; PP; 1690; McCulloh, Thane H.; Beyer, Larry A. |
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| Citation Year: | 2004 |
| Type: | citation/reference |
| Text: | Mid-Tertiary Isopach and Lithofacies Maps for the Los Angeles Region, California: Templates for Palinspastic Reconstruction to 17.4 Ma; 2004; PP; 1690; McCulloh, Thane H.; Beyer, Larry A. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/pp_1690.jpg |
| URL (INDEX PAGE): | http://pubs.usgs.gov/pp/pp1690/ |
| Date Other: | Tue, 1 Jun 2004 00:00 -0500 |
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