SPODDS Affiliates La Jolla Trip Guidebook

106 Pages·2010·13.67 MB·English

by  Lisa Stright

18th ANNUAL REVIEW AND FIELD WORKSHOP

FIELD TRIP GUIDEBOOK:
CANYON- AND CHANNEL-FILL DEPOSITS OF
THE SOUTHERN CALIFORNIA COAST

3-6 OCTOBER 2010
La Jolla, California

DEPARTMENT OF GEOLOGICAL AND
ENVIRONMENTAL SCIENCES
STANFORD UNIVERSITY
FIELD GUIDE CONTENTS

CONTENTS . . . . . . . . . 2

INTRODUCTION . . . . . . . . 3

SCHEDULE . . . . . . . . . 4

DAY 1: Cretaceous strata of the La Jolla area . . . . 5

‘Turbidite sedimentology of the Upper Cretaceous Point Loma and Cabrillo
formations, San Diego, California,’ by T. H. Nilsen and P. L. Abbott, 1984,
reprinted from Pacific Section SEPM . . . . . 13

Field guide to La Jolla Cretaceous strata, by M.A. Arthur, E.L. Winterer, U. von
Rad, and M.F Kennedy, 1984, reprinted from Pacific Section SEPM . 37

DAY 2: Eocene of Black's Beach/Torrey Pines, La Jolla, CA . . 53

‘Eocene sedimentary history, San Diego, California: Overview and field trip
stops,’ by Martin H. Link and Patrick L. Abbott, 1991, reprinted from Pacific
Section Book 68. . . . . . . . 61

‘Field trip guide: Early to middle Eocene La Jolla Group of Black’s Beach, La Jolla,
California,’ by J. A. May, J. M. Lohmar, J. E. Warme, and S. R. Morgan, reprinted from
Pacific Section Book 68 . . . . . . . 75

‘Controls on the development of depositional sequences and facies in the Eocene
La Jolla Group, San Diego, California,’ by J.M. Lomar, S. R. Morgan, and K.M.
Campion, 1991, reprinted from Pacific Section Book 68 . . . 85

‘A coarse-grained, confined, deep-water-channel reservoir analog (Black’s Beach,
La Jolla, CA.)’ by Lisa Stright. . . . . . . 90

DAY 3: Capistrano Formation at San Clemente State Beach . . 104
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INTRODUCTION

The Annual Meeting of the Stanford Program on Deep-Sea Depositional Systems
(SPODDS) is organized as a field conference in order for industrial supporters of the
program to gain first-hand familiarity with SPODDS research sites; to increase their
catalogue of outcropping deep-water systems; and to foster the exchange of ideas that
typifies field trips. SPODDS 2010 differs from many other annual SPODDS meetings by
spotlighting several outcrop localities not previously analyzed in SPODDS graduate
dissertations. Thus, these outcrops afford an equal opportunity for everyone to share
observations and interpretations.

Submarine canyons and deep-water channels are the primary conduits for the transfer of
coarse sediments from the shallow shelf to deep-water settings and they are today major
targets for petroleum exploration. Southern California has had a long and complex
geologic history that has involved many episodes of deep-water sedimentation in a
variety of settings ranging from the Paleozoic passive margin of the North American
craton to Mesozoic forearc and arc settings to Cenozoic transform, pull-apart, and
continental borderland basins. All of these settings feature deep-water deposits in which
both large and small submarine channels played major roles as sediment transport routes
and sites of sedimentation.

We have selected three systems for examination on this field trip. These include in the
order that we will examine them: (1,) Cretaceous strata in coastal exposures in La Jolla,
(2) Eocene strata in sea cliffs north of Scripps Institute of Oceanography, and (3) the
Miocene-Pliocene Capistrano Formation at San Clemente State Beach, California. Both
the Capistrano and La Jolla areas today serve many groups as models for the proximal
parts of deep-water channels and channel evolution. We will see that three systems have
contrasting outcrop expressions, yet all have at least one thing in common - they have
been interpreted as channel-related systems. This commonality, real or imagined, should
provoke lively discussion and debate during the field trip!
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2010 SPODDS ANNUAL MEETINGAND FIELD WORKSHOP

SCHEDULE

Sunday, October 3

Evening: Arrive in La Jolla, California, at the Grande Colonial Hotel. Check-in at the
hospitality room, 6-9 p.m.

Monday, October 4

7:30 A.M. Field trip to Cretaceous rocks at La Jolla Cove and Tourmaline Beach

Noon: Lunch Picnic at Scripps Park, La Jolla Cove

1 P.M. SPODDS Annual Review, Part I

Evening free

Tuesday, October 5

7:30 A.M. Field trip to Black’s Beach/Torrey Pine Eocene strata

1 P.M. SPODDS Annual Review, Part II

Evening Free

Wednesday, October 6

8 A.M. Drive to San Clemente State Beach

Day will be spent at San Clemente State Beach with picnic lunch included. Discussions
likely will continue until mid-afternoon, but participants may leave as schedules require
at any point in the day.

End of SPODDS 2010
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Day 1
October 4, 2010

La Jolla and Vicinity

Rocks of Eocene and Late Cretaceous age exposed in the La Jolla area (Fig. 1)
provide some of the best known and most extensively visited outcrops of the
proximal portions of sand-rich and gravelly submarine canyon fill. We will
examine some of the Cretaceous sandstone and conglomeratic units in La Jolla
itself on Day 1 and the classic Torrey Pines section of Eocene submarine canyon
fill north of La Jolla at on Day 2 (Fig. 2).

Fig. 1. Map of coastal southern California.

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DAY 1 La Jolla, CA (Fig. 2)

Upper Cretaceous rocks of the La Jolla area include both shallow- and deep-
water facies. The deep-water units belong to the Point Loma and Cabrillo
Formations. We will examine these units in La Jolla (STOP 2) and farther south in
the area between Bird Rock and Tourmaline Surfing Beach (STOP 1),
corresponding to Stops 5 and 6 in the following articles by Arthur et al. (1984)
and Nilsen et al. (1984), respectively. These rocks have been interpreted in terms
of classical submarine fan facies, and it will be interesting to discuss their
sedimentology and depositional settings in terms of more modern concepts of
deep-water systems.

Safety issues. Potential hazards of sea cliff outcrops include:

(1) Waves. We will be visiting coastal outcrops at very low tide states, but
never take the sea for granted. Rogue waves can occur. Stay alert to the
ocean.
(2) Footing. Wet and slippery patches of cobbles and surf-zone outcrops
occur locally in the areas visited on Days 1 and 2. Watch where you step
and wear good ankle support.
(3) Falling rocks. Rock-falls are always possible, and pose the greatest
hazard on Day 2. Hard-hats will be available, but do not linger directly
beneath cliffs.

STOP 1. Cretaceous strata in the sea cliff north of Tourmaline Surfing Beach.

Gather in the Grande Colonial Hotel lobby at 7:30 and organize for the short ride
to STOP 1. Proceed south on Prospect Avenue to its intersection with La Jolla
Boulevard and turn right (Fig. 2). Continue south on La Jolla Boulevard to
Tourmaline Street (about 15 minutes). Turn right on Tourmaline and drive
downhill to the Tourmaline Surfing Beach parking lot. Park and walk north
along the beach to prominent conglomeratic strata exposed in the greatest recess
of the cove. STOP 1 includes both the Point Loma and Cabrillo formations. The
latter shows multiple coarse conglomeratic units (Fig. 3) previously interpreted
to represent inner fan channels.

After observations and group discussion, return to the vehicles and return to the
hotel by the same route, park, and re-assemble for a short walk to STOP 2.

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Figure 2. Location maps for Day One stops. Stop 1 at Tourmaline Beach (bottom map) and Stop
2 (lunch) at Ellen Scripps Browning Park (middle map). SPODDS hotel (Grande Colonial) is
indicated by #1 in purple circle.
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Figure 3. Sandy and conglomeratic scour-fill complex
exposed in the sea cliffs north of Tourmaline Surfing Beach,
San Diego. Top photo is south-looking perspective view;
bottom photo shows detail of cut-and-fill relations.

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Figure 4. Detail of the scour-fill complex exposed in the sea
cliffs north of Tourmaline Surfing Beach, showing inverse
grading in conglomerate and dish-like features in the
underlying sandstone. Zane Jobe for scale.

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DAY 1, STOP 2.

Thick-bedded sandstone of the Cretaceous Point Loma Formation underlies La
Jolla Village and is exposed in the sea cliffs within easy walking distance of the
Grande Colonial Hotel.

Walk as a group from the entrance to the hotel north on Prospect Street and turn
right on Girard to its intersection with Coast Boulevard. Turn right on Coast and
walk across Ellen Scripps Browning Park to the northernmost point of land, the
headland that bounds La Jolla Cove on the west. STOP 2 focuses on this
headland and the sea cliffs for 50-100 meters to the southwest.

These strata are noteworthy for well-exposed dish structures and other
indications of soft-sediment mobility, as well as trace fossils (Figs. 5, 6).
Literature from the 1980s and 1990s interpreted these strata as reflecting middle
fan channel environments (Nilsen and Abbott, 1984). Today’s discussion will
focus on alternative interpretations, given the benefit of two or three decades of
additional experience with sand-rich deep-water systems.

2010 SPODDS