HomeMy WebLinkAbout3184; CANNON ROAD WEST; FINAL PALEONTOLOGICAL MITIGATION REPORT; 1998-08-01SEP 1819
H
FINAL PALEONTOLOGICAL MITIGATION REPORT
CANNON ROAD WEST *
(LEGO DRIVE TO MACARIO CANYON)
CARLSBAD, CALIFORNIA
Prepared for:
CARLTAS COMPANY
5600 Avenida Encinas, Suite 100 -
Carlsbad, CA 92008
S
Prepared by:
DEPARTMENT OF PALEONTOLOGICAL SERVICES
San Diego Natural History Museum.
P.O. Box 1390
San Diego, CA 92112
Thomas A. Deméré, Ph.D.
Director
S FINAL PALEONTOLOGICAL REPORT
CANNNON-ROAD;WEST PROJECT
(LEGO DRIVE TOMACARm CANYON)
CARLSBAD, CALIFORNIA
INTRODUCTION
This report presents the results of the paleontological resource mitigation program.
conducted during grading for the Cannon Road West project (Lego Drive to Macario
Canyon), City of Carlsbad, San Diego County, California. The mitigation program was a requirement of the grading permit issued by the City of Carlsbad. Work was performed
for the Caritas Company.
Personnel
The field monitoring portion of the paleontological mitigation program was conducted by
Bradford 0. Riney of the Department of Paleontological Services.
METHODS
Field Methods
Field activities included monitoring of excavation operations, examination of temporary
and permanent. cut slopes and canyon clean-outs, and recovery of geologic, stratigraphic,
and paleontologic contextual data. Specific field methods are discussed more fully
below.
Monitoring Monitoring of mass grading operations was conducted during October, 1997
and involved physically following the earth-moving equipment and inspecting, freshly
exposed bedrock for unearthed fossil remains. Ideally, inspection would have involved
examination of every newly exposed surface but this was operationally impossible. The
pace and quantity of equipment in the cut determined how often the monitor could make
inspections. When the active excavations were/ too dangerous to enter because of a
narrow cut, short haul, and/or heavy traffic, an elevated vantage, point provided a secure
point from which to observe the progress of grading.
Safety procedures followed by field personnel included the wearing of appropriate
clothing (high-visibility vests, hard hats, and large hand-held flags), securing equipment
operator's acknowledgment before entering an active cut, and using caution when driving
on haul roads. Periodic attendance at safety meetings allowed the paleontological
monitor to discuss mutual safety issues with excavation personnel.
Geologic Mapping Geologic mapping was conducted throughout the course of the
monitoring program. Mapping was done through examination of outcrops exposed in
0
active cuts and finished slopes. The goal of mapping was to delimit the nature of
sedimentary rock units on the project site; their aerial distribution, lithcilbgic character,
upper and lower contacts and the location of structural deformation (faults and folds).
Data collected included lithologic descriptions (color, sorting, texture, structures, and
grain size), stratigraphic relationships (bedding type, thickness, and contacts), and
topographic position. Measurement of stratigraphic sections was done with a hand level
and six foot folding engineers rule.
RESIJLTS
Stratigraphy
Grading operations at the Cannon Road West project exposed a'rather complex
stratigraphic sequence of Pleistocene-aged and Eocene-aged sedimentary rock units. The
Eocene-aged deposits are assigned to the Santiago Formation (member C) of Wilson
(1972). This rock unit is unconformably overlain by an unnamed sequence of
Pleistocene-aged marine terrace deposits.
Pleistocene marine terrace deposits Pleistocene-aged sedimentary deposits were
exposed from the western terminus at Lego Drive to approximately Engineering Station . (ES) 51+00 The Pleistocene sequence consisted of approximately 22 feet of reddish-
orange, medium- to coarse-grained sandstone and conglomeratic sandstone deposited on
an elevated marine abrasion platform (sea floor). This abrasion platform, which
originally formed at sea level, now occurs at an elevation of 155 feet and is possibly
correlative with the Guy Fleming Terrace of Kern and Rockwell (1992) and the
Magdalena Terrace of Eisenberg (1985). No fossils were recovered from this rock unit.
Eocene fluvial deposits (Santiago Formation) Approximately 130+'feet of fine- to
coarse-grained sedimentary rocks of the Santiago Formation (member C of Wilson, 1972)
were exposed between approximately ES 51+00 and ES 64+00. This Eocene sequence is
divisible into a lower unit, approximately 40 feet-thick, of light gray, fine-grained, silty
sandstones with localized carbonate-cemented horizons; a middle unit, approximately 80
feet thick, of light brown, interbedded mudstones, siltstones, and fine-grained sandstones;
and an upper unit, approximately 10 feet thick, of gray to brown, coarse-grained gravels
and gritstones. The Eocene sequence was observed to be tilted and dipping
approximately 170 to the west. A single, pçorly-preserved fossil bone was observed in
the middle unit of the Santiago Formation.
Paleontology
No significant paleontological resources were discovered during. the monitoring phase of . this mitigation program. A single fossil bone was observed in canyon clean-out
exposures of the Santiago Formation at ES 60+00 (approximately elevation 90 feet).
2
. Golz, D J, and J A Lillegraven 1977 Summary of known occurrences of terrestrial
vertebrates from Eocene strata of southern California. University of Wyoming,.
Contributions to Geology 15:43-65.
Kern,. J.P. and T.K. Rockwell. 1992. Chronolcgy and deformation of Quaternary marine
shorelines, San Diego County, California. In, C.H. Fletcher, III and J.F.
Wehmiller (eds.). Quaternary Coasts of the United States: Marine and Lacustrine
Systems,.SEPM Special Publication 48, pp. 377-382.
Walsh, S. L. 1996. Middle Eocene mammal faunas of San Diego County, California. In,
Prothero, D. R., and R. J. Emry (eds.), The Terrestrial Eocene-Oligocene
Transition in North America, Cambridge University Press, pp. 75-119.
Wilson, K.L. 1972. Eocene and related geology of a portion of the San Luis Rey and.
Encinitas quadrangles, San Diego County, California. Unpublished M.A. thesis,
University of California, Riverside, 1.35 p.
4