Timing of

Paleoearthquakes on the

Northern Hayward Fault —

Preliminary Evidence in El

Cerrito, California

By the Hayward fault Paleoearthquake Group (HPEG)

1

Open-File Report 99-318

1999

This report is preliminary and has not been reviewed for conformity with U.S. Geological

Survey editorial standards or with the North American stratigraphic code. Any use of trade,

product, or firm names is for descriptive purposes only and does not imply endorsement by

the U.S. Government.

U. S. DEPARTMENT OF THE INTERIOR

U. S. GEOLOGICAL SURVEY

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J. J. Lienkaemper & D.P. Schwartz, USGS 977, 345 Middlefield Rd., Menlo Park, CA 94025;

 K.I. Kelson, W.R. Lettis, G.D. Simpson &, Wm. Lettis Assocs., 1777 Botelho Ave., Ste 262,

Walnut Creek, CA 94596;

 J.R. Southon, Center for AMS, L-397, Lawrence Livermore National Lab, 7000 East Ave.,

Livermore, CA 94551-9900;

 J.A. Wanket, Dept. of Geography, 501 McCone Hall, UC Berkeley, Berkeley, CA 94720

 P.L. Williams, Seismographic Station, 475 McCone Hall, UC Berkeley, Berkeley, CA 94720
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Abstract

The Working Group on California Earthquake Probabilities estimated that the northern

Hayward fault had the highest probability (0.28) of producing a M7 Bay Area earthquake in

30 years (WGCEP, 1990). This probability was based, in part, on the assumption that the

last large earthquake occurred on this segment in 1836. However, a recent study of historical

documents concludes that the 1836 earthquake did not occur on the northern Hayward fault,

thereby extending the elapsed time to at least 220 yr ago, the beginning of the written record.

The average recurrence interval for a M7 on the northern Hayward is unknown. WGCEP

(1990) assumed an interval of 167 years. The 1996 Working Group on Northern California

Earthquake Potential estimated ~210 yr, based on extrapolations from southern Hayward

paleoseismological studies and a revised estimate of 1868 slip on the southern Hayward

fault.

To help constrain the timing of paleoearthquakes on the northern Hayward fault for the

1999 Bay Area probability update, we excavated two trenches that cross the fault and a sag

pond on the Mira Vista golf course. As the site is on the second fairway, we were limited to

less than ten days to document these trenches. Analysis was aided by rapid C-14 dating of

more than 90 samples which gave near real-time results with the trenches still open. A

combination of upward fault terminations, disrupted strata, and discordant angular relations

indicates at least four, and possibly seven or more, surface faulting earthquakes occurred

during a 1630-2130 yr interval. Hence, average recurrence time could be <270 yr, but is no

more than 710 yr. The most recent earthquake (MRE) occurred after AD 1640. Preliminary

analysis of calibrated dates supports the assumption that no large historical (post-1776)

earthquakes have ruptured the surface here, but the youngest dates need more corroboration.

Analyses of pollen for presence of non-native species help to constrain the time of the MRE.

The earthquake recurrence estimates described in this report are preliminary and should not

be used as a basis for hazard estimates. Additional trenching is planned for this location to

answer questions raised during the initial phase of trenching.

Introduction

The northern Hayward fault extends for ~50 km, from San Leandro to beneath San Pablo

Bay, next to the most densely populated parts of the East [San Francisco] Bay Area. The

Working Group on California Earthquake Probabilities (1990; WGCEP90) assigned a

reliability ranking to the 30-yr probability of occurrence of major earthquakes on each of six

selected fault segments in the Bay Area. They gave the northern Hayward (Fig. 1) and

Rodgers Creek faults the lowest reliability rankings in the region, principally because these

segments lacked reliable data for the most recent event (MRE). The MRE for the northern

Hayward fault had been assumed to be a large earthquake in 1836 based on an unconfirmed

historical interpretation by Louderback (1947). However, a recent detailed study of historical

documents indicates this event occurred south of the Bay Area (Toppozada and Borchardt,

1998). Thus, the MRE for the northern Hayward fault is pre-1776, the date suggested by

Toppozada and Borchardt (1998) for the start of the regional historical record. Because

knowing the age of the MRE is essential for the calculation of time-dependent earthquake

probability, constraining the maximum age bound of the MRE is critical information for

forecasting major earthquakes on the Hayward fault. Another key objective of this research

is the development of a late-Holocene paleoearthquake chronology for the northern Hayward

fault. This would better constrain both the mean recurrence interval and the extent of

ruptures, essential parameters for increasing the understanding of how the fault behaves and

computing probabilities of future large earthquakes.
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Constraining the northern extent of earthquake ruptures on the southern Hayward fault,

including the M7 historical event in 1868, is required for evaluating fault segmentation and

establishing a more realistic probability model. The WGCEP90 assumed that the 1868

rupture extended 36 km, from Agua Caliente Creek to Mills College (AC to MC, Fig. 1),

based on information gathered 40 years after the earthquake (Lawson, 1908). A

paleoearthquake study in Oakland (Lienkaemper and others, 1995; Lienkaemper and

Williams, in press 1999) showed that surface rupture in 1868 extended at least as far north

as Montclair Park (MT, Fig.1), and a new analysis of 19th century triangulation data

suggested large slip at depth in 1868 as far north as Rocky Mound (RM, Fig.1; Yu and Segall,

1996). An estimated total length of 61 km or more for the 1868 subsurface rupture now

seems reasonable (CR to RM, Fig. 1). Thus, confirming or excluding the occurrence of 1868

surface rupture at various locations along the northern Hayward fault is another important

objective of our investigations.

This open-file report summarizes the results of the first phase of a paleoseismic trenching

study across the Hayward fault at the Mira Vista golf course in El Cerrito, California. We

present an overview of site selection, the methodology used, general stratigraphic

relationships observed, and the evidence for paleoearthquakes. We then discuss the

implications of these results with respect to the MRE, mean recurrence interval, and other

potentially useful constraints on the timing of historical and prehistoric earthquakes at this

site.

Trenching Results

Site selection

For site selection, we made a reconnaissance of the entire northern Hayward fault zone

using aerial photography and made field inspections of the most promising sites. We

concentrated our initial efforts north of Oakland to reduce possible complications from the

overlapping of northern and southern segment ruptures. Shallow hand coring was done at 3

locations to help choose a site having optimal sedimentary layering and to determine the

fault’s exact location. The Mira Vista Golf Course site (Figs. 1, 2 and 3) was selected as the

most favorable for having fine-scale stratigraphy across the active fault trace.

The favorable depositional environment at Mira Vista is due to a local anomaly in fault

strike with respect to regional tectonics. A closed depression or sag pond has formed

adjacent to the fault, presumably because the fault strikes N27°W locally. This strike is 8°

more northerly than the N35°W average strike for the Hayward fault as a whole

(Lienkaemper, 1992). This change in strike makes the fault more likely to have a sizeable

extensional and vertical component of slip at this site. The Hayward fault generally seems to

be well-oriented to release plate boundary motion as mainly strike-slip. Using regional strain

data, Lisowski and others (1991) determined that the maximum right-lateral shear direction

was N31.0°W ± 1.6° for the north Bay Area and N34.4°W ± 1.5° for the south and central

Bay Area. This result is corroborated by more recent VLBI results (Sierra Nevada blockPacific plate rotatation model, D. Argus, written commun., 1995) that give a net vector of

N31°W at the midpoint of the Hayward fault. These values are all similar to the N33°W

vector computed using the Nuvel-1A, Pacific- North America plate motion model, which spans

the last 3.5 million years (DeMets and others, 1994). Thus, the tectonic setting of the site is

well-suited to producing persistent vertical and extensional components of slip, that would

contribute both to high rates of deposition and to a normal-oblique slip style of faulting, both

of which greatly improve our ability to recognize paleoearthquakes in trench exposures

(Bonilla and Lienkaemper, 1990).
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Methodology

Because we were limited to only 10 days total for trench excavation, cleaning, logging,

sampling, backfilling, and for repair of the golf-course, we assembled a team of 6 geologists.

Many other personnel assisted in radiocarbon sampling, surveying, and photographing the

walls. We cut two trenches to maximize exposure of paleoearthquake evidence; making

trench 1 longer to expose a larger sample of the pond stratigraphy and explore for secondary

faulting (location: Fig. 2, Fig. 3; logs: Fig. 4, Fig. 5). Trenching was done in mid-July to lessen

ground-water problems. Although a permanent drain field had been installed, ground water is

always within 1-2 m of the surface, so frequent pumping was needed.

We sampled for radiocarbon dating in three stages to achieve the fastest possible

laboratory dating while the logging progressed. Samples taken in the first two days covered a

wide range of stratigraphic horizons and were processed in 2-3 days by Lawrence Livermore

National Laboratory’s Center for Accelerator Mass Spectrometry (LLNL-CAMS). This

allowed us to focus later stages of sampling on horizons most critical to dating the MRE and

on other horizons important to establishing a complete paleoearthquake chronology for the

past ~2,000 years. Altogether, about 90 radiocarbon samples were dated, predominantly on

detrital charcoal (Table A1).

Stratigraphy

Although bedrock units adjacent to the fault are mapped in general as serpentinite

southwest of the fault and as melange of the Franciscan Assemblage to the northeast

(Radbruch and Case, 1967; Dibblee, 1980; Graymer and others, 1995), in our trenching, we

found serpentinite on both sides of the main fault trace (Fig. 4). Southwest of the fault, the

serpentinite is weathered to clay and rock fragments and is overlain by colluvial units of

similar composition; below the northeasternmost pond sediments, the in situ serpentinite is

highly-weathered but retains some rock structure.

Sag pond deposits have accumulated for at least the last 6,000 years at the site at an

average rate of ~0.3 mm/yr. Deposition rates vary laterally and tend to be greater near the

fault, up to 0.46 mm/yr. The pond sediments are composed of organic-rich silts and clays that

are generally massive, but fine laminar structure is fairly abundant and variations in color

made it possible to map and correlate several strata between trench exposures (Fig. 5).

Drying of the pond deposits was essential to our recognition of sedimentary structure. Where

walls remained saturated in the lower part of the trenches, little structure was observed.

The most distinctive units are four wildfire ash layers (units: u8, u15, u18, u24) that

became the essential control strata for checking the overall correlation of the sequence.

Adjacent to the main fault, a series of colluvial packages interfinger with the pond deposits

and are derived principally from the intensely weathered serpentinite bedrock. Several minor

unconformities exist near the fault, but the stratigraphic record as a whole appears complete

and reliably dated for the ~2,200 years preceding the historic period. Units older than ~2,200

yr were saturated from the high water table, and few units were logged in detail or could be

correlated reliably between the trenches.

A major erosional unconformity exists between units u27 and u28. A clean gray silty clay

(u28) directly overlies the unconformity, and it is overlain by its more clast-rich equivalent

(u29). These units are generally thicker, more massive and less organic-rich than the

underlying pond deposits. Although we suspected that they were of historical age, we found

no historical artifacts in them. However, pollen analysis of the pond sequence, shows that

these gray units (u28, u29) both contain Eucalyptus, a tree that became widespread in the

region during the 1880s. The next overlying unit (u30) is rockier than the underlying units,
5

and probably is a fill applied as an improvement to the golf course which was built circa World

War I.

Paleoearthquakes

Paleoearthquakes are preserved in the stratigraphic record as relative changes in the

amount of deformation between two adjacent units (called event horizons). Younger units are

deformed less than older underlying units. Examples of features we interpret as evidence of

past surface-rupturing earthquakes include: upward terminations of fault traces, disrupted

strata, and discordant angular relations and scarp-derived colluvia. However, the occurrence

of surface creep along the fault increases the difficulty in defining event horizons associated

with coseismic surface rupture from paleoearthquakes. Because creep occurs on the Hayward

fault (Lienkaemper and others, 1991; Lienkaemper and Galehouse, 1997), it is important to

show that these increases in deformation downward derive from sudden, brittle surfacerupturing processes that we associate with large earthquakes, and not from gradual fault

creep. We found evidence for nine possible deformation events in the sag pond deposits that

we presently interpret as evidence of coseismic surface rupture. However, the ages of the

three early events E1, E2, E3 are poorly constrained and resolution of stratigraphic and

faulting features was much poorer in the lower, water-saturated stratigraphy, so we do not

include these events in our discussion of recurrence interval. The stratigraphic sequence is

reasonably well-dated for up to seven apparent ground-rupturing earthquakes, which we call

E4, E5, E6, E8, E9, E10 and E11. In Figure 6 and Table 1, we summarize various evidence for

each of these seven events in terms of its relative degree of certainty. Events E4, E6, E8 and

E11 have clear evidence in most exposures. Events E3, E9 and E10 require the aggregation

of more subtle evidence to suggest that they are distinct surface-rupturing events. Evidence

for event E5 is fairly strong, but is less widespread among the exposures. One event that

was initially interpreted, E7, was eliminated as our work correlating stratigraphic units

progressed. Thus, there seem to be seven surface rupture events since 392 BC to 54 BC, four

of which are more distinct (Tables 1 and 2), however this record could be incomplete for two

reasons. Firstly, when such pond deposits are submerged, surface rupturing may occur with

little or no brittle deformation and thus earthquake ruptures could either go undetected, or

evidence for them might appear less distinct than for those occurring during the dry season.

Secondly and perhaps even more important, an incomplete record of events can result simply

from hiatuses in deposition. Further trenching is the best means of corroborating this

preliminary event chronology and testing it for completeness.

Most Recent Event (MRE)

Because of the critical importance of the MRE to estimating the probability of future

earthquakes, considerable attention was given to documenting the character of faulting and

age constraints on event E11, which we judge to be the most recent event. We summarize

evidence for the event E11 in Table 1 and age constraints on it, in Figure 6 and Table 2. Some

of the most conspicuous evidence for brittle fault slip in this event (on fault F2 above the

u24/u25 contact, Fig. 5d) coincides with the best age control on the event (on unit u25). A

weighted average of 4 radiocarbon dates from u25 gives calibrated age ranges of AD 1640 to

1679 (61% probability) and AD 1768 to 1802 (34%), thus constraining at >95% confidence the

lower bound of the MRE (E11) to after AD 1640.

The upper-bound age for this event from radiocarbon data depends mostly on one sample

(1S-21) from colluvium (u26). It is weakly corroborated by another sample (2N-10) with an

identical radiocarbon date in a coeval silt unit (u27). However, this sample is from a

krotovina, or infilled burrow and thus may be younger than the colluvium that surrounds it.
6

Age estimates from these samples suggest the minimum age constraint for the MRE (E11)

is: 1) probably before 1821 (>88% confidence), 2) unlikely to be in 1868 (≤7% chance for

1837-1876), and 3) highly unlikely to be in 1836 (<<1%) (Table 2).

Equivocal or possible minor offsets on the major unconformity below the gray clay units

(u28, u29), primarily in the south wall of trench 2, suggest the possibility that another event

may have occurred after event E11. However, we believe that these features, such as an

apparent fissure fill above fault F4 and soil steps in the u27/u28 contact, are better explained

as resulting from erosion or fault creep. The soil steps on the u27/u28 contact in trench 2

(south wall) were logged schematically as abrupt steps but did not distinctly appear to be

fault offsets. This interpretation is strongly supported by laboratory work that shows

Eucalyptus pollen in the gray unit. Eucalyptus was not planted in the East Bay until the

1870s, and was not planted widely until the 1880s (see appendix for details on pollen

analysis and history). Thus, displacements, if any, on the u27/u28 contact result from slip that

has occurred after the 1868 earthquake, thus would almost certainly be due to aseismic slip.

The results of our study supports the hypothesis of Toppozada and Borchardt (1998), who

conclude that the 1836 earthquake did not occur on the Hayward fault. Rather, a careful

interpretation of the historical records of that period, suggests that there have been no large

earthquakes on the Hayward fault since at least 1776. Based on the results presented here,

we concur that 1776 is the best available estimate of minimum age for the MRE on the

northern Hayward fault.

Recurrence interval

We consider age control reliable only for the past 7 events (E4 through E11). Event E7

was dismissed by improved stratigraphic correlation. To compute a minimum value for the

mean recurrence interval, we use the minimum elapsed time for these seven or more events,

1627 years, which is derived from the 95% age bounds, AD 13 to 1640. This time period, 1627

yr divided by six intervals yields a minimum of <270 yr. Applying the less than symbol (<) to

the minimum recurrence reiterates our concern that events might be missing from our record.

At the other extreme, the four events with the most robust evidence (E4, E6, E8, E11)

occurred after 355 BC and before AD 1776, i.e., three intervals in 2131 yr, or a maximum of

710 years.

We emphasize that this investigation is still in progress, and that we need to corroborate

the paleoearthquakes thus far documented by logging other exposures and trenching other

sites. Especially important, we need to confirm the completeness of the event record, because

it is possible that some large earthquakes left no clear rupture evidence in the exposures

logged to date.

Conclusions

The most recent event (MRE) is well-constrained by radiocarbon dating to have occurred

after 1640. A single radiocarbon date supports the historical study of Toppozada and

Borchardt (1998), which indicates that the 1836 earthquake was not on the northern

Hayward fault and implies that the MRE was prehistoric or pre-1776. We observed no

evidence that surface rupture occurred here associated with the 1868 earthquake, although

some of the depositional record of this period is absent. A minimum of <270 yr for the mean

recurrence interval is indicated by our preliminary interpretation of 7 surface-rupturing

events, and allows that events could be missing. Using only the evidence for the 4 mostconspicuous paleoearthquakes gives a maximum mean recurrence time of <710 yr. More

trenching is needed to verify the number and timing of paleoearthquakes on the northern

Hayward fault. Existing radiocarbon constraints are not precise enough to indicate possible
7

clustering of events or to allow us to evaluate the variability in recurrence time. Recurrence

intervals from this first phase of this paleoseismic investigation should not be used as a

basis for computing hazard for the northern Hayward fault.

Acknowledgments

The National Earthquake Hazards Program of the U.S.G.S. funded both U.S.G.S. and

William Lettis & Associates. Pacific Gas & Electric Company supported this work,

especially in the reconnaissance phase, through its CRADA with the U.S.G.S. We thank so

many for their timely assistance: especially Tom Fumal, John Hamilton, Daniella Pantosti,

Chris Hitchcock, and many other staff and volunteers who lent a hand when it was most

needed. We gratefully acknowledge the essential support and encouragement of the

Directors, members and staff of the Mira Vista. Detailed and constructive reviews by

Suzanne Hecker and Tom Fumal greatly improved the clarity of this report.
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R e f e r e n c e s 

Bonilla, M. G. and Lienkaemper, J. J., Visibility of fault strands in exploratory trenches and

timing of rupture events, Geology 18, 153-156, 1990.

Byrne, R., S. Mensing, and E. Edlund, Long term changes in the structure and extent of

California Oaks, Final Report submitted to the Integrated Hardwood Range

Management Program, 128 pp., 1993.

DeMets, C., R.G., Gordon, D.F. Argus, and S. Stein, Effects of recent revisions to the

geomagnetic reversal of time scale on estimates of current plate motions, Geophys. Res.

Letts. 21, 2191-2194, 1994.

 Dibblee, T. W., Jr.. Preliminary geologic map of the Richmond quadrangle, Alameda and

Contra Costa Counties, California, U.S. Geol. Surv., Open-File Rep. 80-1100, 1980.

Faegri, K., and J. Iversen, Textbook of Pollen analysis, New York, Wiley, 328 pp., 1989.

Frankel, R. E., Ruderal vegetation along some California Roadsides, Berkeley, University of

California Press, 120 pp., 1967.

Gibbons, W.P., The redwood in the Oakland Hills, Erythea 1, 161-166, , 1893.

Graymer, R. W., D. L. Jones, and E.E. Brabb, Geologic map of the Hayward fault zone, U.S.

Geol. Surv., Open-File Rep. 95-597, 1995.

Hayward Fault Paleoearthquake Group, The northern Hayward fault, CA: preliminary timing

of paleoearthquakes, EOS, Trans. Am. Geophys. Union 78, 439, 1997.

Hendrey, G. W., Adobe brick as a historical source, Agricultural History 8 , 64-71, 1931.

Lanson, J. A., Eucalyptus in California: its distribution, history, and economic value, MA

Thesis, University of California, Berkeley, 210 pp., 1952.

Lawson, A. C., The earthquake of 1868 in A. C. Lawson, ed., The California earthquake of

April 18, 1906, Report of the State Earthquake Investigation Commission (Volume I),

Carnegie Institution of Washington Publication No. 87, 434-448, 1908.

Lienkaemper, J. J., Map of recently active traces of the Hayward fault, Alameda and Contra

Costa Counties, California, U.S. Geological Survey Miscellaneous Field Studies Map

MF-2196, map scale 1:24,000, 13 p., 1992.

Lienkaemper, J. J., and G. Borchardt, Holocene slip rate of the Hayward fault at Union City,

California, J. Geophys. Res. 101, 6099-6108, 1996.

Lienkaemper, J. J., G. Borchardt, and M. Lisowski, Historic creep rate and potential for

seismic slip along the Hayward fault, California, J. Geophys. Res. 96, 18,261-18,283,

1991.

Lienkaemper, J. J., and J. S. Galehouse, Revised long-term creep rates on the Hayward Fault,

Alameda and Contra Costa Counties, California, U.S. Geol. Surv., Open-File Rep. 97-

690, 18 p., 1997.

[http://quake.wr.usgs.gov:80/hazprep/NCEP/HF_creep/OF97_690dwnlod.html]

Lienkaemper, J.J., and P.L. Williams, New evidence in north Oakland of minor ground rupture

on the Hayward fault and major rupturing in prehistoric earthquakes, Geophys. Res.

Lett., in press 1999.

Lienkaemper, J. J., P. L. Williams, P. Taylor, and K. Williams, New evidence of large surfacerupturing earthquakes along the northern Hayward fault zone, SEPM (Society of

Economic Paleontologists and Mineralogists) Pacific Section, 70th Annual Meeting, San

Francisco, California, SEPM, p. 38, 1995.

Lisowski, M., J. C. Savage, and W.H. Prescott, The velocity field along the San Andreas fault

in central and southern California, J. Geophys. Res. 96, 8369-8390, 1991.

 Louderback, G.D., Central California earthquakes of the 1830's, Bull. Seismol. Soc. Am. 34,

33-74, 1947.
9

Nowak D. J., Historical vegetation change in Oakland and its implications for urban forest

management, Journal of Arboriculture 19, 313-319, 1993.

Oppenheimer, D. H., I. G. Wong, and F. W. Klein, The seismicity of the Hayward fault,

California, Calif. Div. of Mines and Geol. Spec. Publ. 113, 91-100, 1993.

Radbruch, D. H. and Case, J. E., Preliminary geologic map of Oakland and vicinity, California,

U.S. Geological Survey Open-file Report 67-183, 1967.

Savage, J. C., and M. Lisowski, Inferred depth of creep on the Hayward fault, central

California, J. Geophys. Res. 98, 787-793, 1993.

Stuiver, M., and H. A. Polach, Discussion: Reporting of 14C data, Radiocarbon 19, 355-363,

1977.

Stuiver, M., and P. J. Reimer, Extended 14C database and revised CALIB radiocarbon

calibration program, Radiocarbon 35, 215-230, 1993.

Toppozada, T. R., and G. Borchardt, Re-evaluation of the 1836 "Hayward Fault" earthquake

and the 1838 San Andreas Fault earthquake, Bull. Seismol. Soc. Am., 88, 140-159.

Williams, P. L., Geologic record of southern Hayward fault earthquakes, Calif. Div. of Mines

and Geol. Spec. Publ. 113, 171-179, 1993.

Working Group on California Earthquake Probabilities, Probabilities of large earthquakes

occurring in the San Francisco Bay Region, California, U.S. Geol. Surv., Circular 1053, 51

p., 1990.

Working Group on Northern California Earthquake Potential, Database of potential sources

for earthquakes larger than magnitude 6 in northern California U.S. Geol. Surv., OpenFile Rep. 96-705, 53 p., 1996. [http://quake.wr.usgs.gov:80/hazprep/NCEP/]

Yu, E., and P. Segall, Slip in the 1868 Hayward earthquake from the analysis of historical

triangulation data, J. Geophys. Res. 101, 16,101-16,118, 1996.
10

A p p e n d i x : P o l l e n a n a l y s i s a n d a g e o f g r a y c l a y , u n i t 2 8 

Bulk wall samples taken during trenching at Mira Vista allowed for laboratory work on

sedimentary pollen and organic content to determine whether the units surrounding the major

erosional unconformity at the base of unit 28 are of historic age. We subsampled at 1-cm

intervals a continuous section (see PS-3 at 6.2 m in trench 2 south wall, Fig. 5d) containing a

12-cm thick portion of unit 28 and a 4-cm thick portion of unit 25. Loss on ignition was

performed to determine organic content, and standard acid digestion procedures (Faegri and

Iversen, 1989) were used to prepare the samples for pollen analysis. After replacing sample

depths with codes to ensure blind testing, all 16 samples were analyzed for organic content

and scanned for non-native pollen types. In eight samples, four from each unit, at least 300

pollen grains were identified to the family, genus, or species level and plotted as a percentage

of total aquatic or non-aquatic pollen. A total of 35 taxa were identified in the samples.

Figure A2 shows key results from laboratory work. We found no non-native pollen types

in the unit below the unconformity. While this alone does not demonstrate a pre-historic age

for the unit, the high organic content, abundance of Sequoia pollen, and relatively low levels of

Poaceae and Brassicaceae pollen argue for a pre- or early-Spanish age for the unit (e.g. Byrne

et. al., 1993). The presence of Erodium and Eucalyptus pollen throughout unit 28, above the

unconformity, confirms that the unit is of historic age. Erodium cicutarium became naturalized

in the San Francisco Bay Area soon after Spanish arrival in 1772 and is the likely source of

the pollen (Hendrey, 1931; Frankel, 1967). Erodium at the base of unit 28 thus assigns an

earliest date of 1772 to the sediments. Eucalyptus pollen throughout the top 3/4 of the unit

imply a younger age for the majority of the unit. Eucalyptus species were not introduced to

California until 1857 and were not planted in the East Bay until the 1870s (Lanson, 1952).

The top 3/4 of the unit are thus assigned an age no earlier than 1870. However, it is quite

possible that the bottom 1/4 of the unit is also post-1870, as Eucalyptus was not planted on a

grand scale in the East Bay until the 1880s. The lower part of the gray clay unit is uniform in

texture and lacks stratification, hence may suggest rapid deposition. Thus the appearance of a

single grain of Eucalyptus pollen solely in the fourth of the lowest seven intervals may

suggest only that the pollen density of Eucalyptus is quite low during this era. The sharp

increases in Poaceae and Brassicaceae pollen in unit 28 reflect historic invasion of native,

largely perennial grasslands by annual grasses and associated herbs. Other well-dated sites

in the California coast ranges show marked increases in Poaceae and Brassicaceae pollen

after 1860 (Byrne et. al., 1993). The abrupt decline in Sequoia pollen in the gray unit is an

expected result of widespread cutting of redwood stands in Oakland in the 1840s (Gibbons,

1893). The markedly lower organic content of unit 28 is likely due to grazing impacts on soils

surrounding the site.

That unit 28 was deposited over a period of time and in an aquatic environment rather

than as a massive fill event is supported by the aquatic pollen stratigraphy (Figure A3).

Declining values of Sagittaria pollen and increasing values of Cyperaceae pollen are

consistent with hydroseral succession in an infilling pond. Declining pollen concentration and

organic content toward the top of the unit indicate an increasing sedimentary rate throughout

the period of deposition, perhaps as a result of increasing grazing pressure. Pollen

concentration at the bottom of the unit is roughly double that at the top, suggesting that the

sedimentation rate doubled over the period of deposition.

In summary, unit 28 is firmly established to be of historic age, with the majority if not all of

the sediments deposited after 1870 based on the occurrence of non-native Eucalyptus pollen.

Although the base of the unit was not found to contain Eucalyptus pollen, the record of

terrestrial tree and herb pollen is consistent with a late 19th century date of sediment
11

deposition. The aquatic pollen record, organic content, and pollen concentration in the unit

indicate that it was not deposited as a massive fill but over time in a pond environment. The

terrestrial pollen record in unit (?) below the unconformity suggest that the unit is pre- or

early-Spanish (i.e. pre-1800). The amount of time represented by the unconformity is probably

no less than 60 years (1800-1860). Sampling deeper in the gray clay is needed to determine

more reliably the lowest stratigraphic level that contains Eucalyptus pollen.

Figure Captions

Figure 1. Location of trench site and other points along the Hayward fault. Currently known

extent of 1868 surface rupture shown as solid gray band; dashed where subsurface extent

of rupture is inferred. Stars indicate localities discussed in text. Creeping trace extends at

least 68 km from P, Point Pinole to AC, Agua Caliente Creek. Trenching sites: MV, Mira

Vista (Hayward Fault Paleoearthquake Group, 1997); MT, Montclair (Lienkaemper et

al., 1995); MH, Masonic Home (Lienkaemper and Borchardt, 1996); TP, Tule Pond

(Williams et al., 1993). Other localities: RM, Rocky Mound, key triangulation point of Yu

and Segall (1996); BT, BART tunnel; CR, near Calaveras Reservoir, the branching point

of northern Calaveras fault from faster-creeping southern Calaveras fault (Working Group

on Northern California Earthquake Potential, 1996).

Figure 2. Orthophoto view of trench site on second fairway. Fault indicated by double

dashes. Thick gray line shows approximate outline of sag pond; trench locations shown in

detail in Figure 3.

Figure 3. Detailed topographic map of trench site. Hachured line shows extent of closed

elevation contours, formerly a seasonal sag pond.

Figure 4. Logs of trenches showing area of detailed drafting (see Fig. 5). Darkest gray

shading indicates weathered bedrock and colluvium derived from it. Light units are pond

deposits that lie below thickest black line, which indicates major unconformity of

historical age. Faults, principally near vertical, shown by intermediate line weights.

Outside detail area, radiocarbon dates (uncalibrated yr BP) and sample numbers shown

in boxes adjacent to samples (hexagons).

Figure 5. Detailed logs of trenches. Shading same as Figure 4. Ash-containing units 8, 15, 18

and 24 (u8, u15, u18, u24) shown with “v” pattern where ash is most concentrated (i.e.,

less disturbed). Units 1 through 31 (u1,...,u31), numbered in hexagons to distinguish from

events 1 through 11 (i.e., paleoearthquakes, E1, ..., E11), numbered in squares. Fault

traces numbered (e.g., F1, F2,...) to show approximate correlation across each trench and

for discussion. Radiocarbon sample locations, marked by circles, show uncalibrated dates

(in yr BP) and sample numbers. Heaviest solid line indicates major erosional

unconformity underlying gray units (u28, u29). Next heaviest lines, mainly subhorizontal,

indicate inferred approximate horizons at time of paleoearthquake ruptures. Intermediate

line weights (mostly vertical) show fault traces: dashed where approximate, dotted

where inferred, queried where uncertain. Colluvial units also labelled C1, C2, ...

Figure 6. Age constraints on paleoearthquakes. Event numbers shown above each event

symbol, elongated ovals; calibrated age data given in Table 2. Age constraints all at 95%

confidence, except event E11 (MRE) has upper bound limited by introduced pollen and

pre-1776 historical limit of Toppozada and Borchardt (1998). Squares show ages of

radiocarbon-dated units; weighted averages (method of Stuiver and Reimer, 1993) used

wherever possible. P1, P2 and P3 indicate probability ranges described in Table 2.

Appendix Figure Captions
12

Figure A1. Trench logs showing field linework. Same description as for Fig. 5, but for clarity omits

inferred event horizons and interpretative shading on stratigraphic units. Stratigraphic units, fault trace

numbers and radiocarbon information kept to aid comparison.

Figure A2. Profile of unit 28 and unit25, showing variations in pollen frequencies and organic content.

Dashed lines indicate sample positions, gray solid line indicates contact between units. Values for

Erodium and Eucalyptus are numbers of grains found by scanning prepared slides, while values for

Poaceae, Brassicaceae, and Sequoia are frequencies based on full (300+ grains) pollen counts.

Figure A3. Profile of unit 28 and unit 25, showing trends in organic content, pollen frequencies, and pollen

concentration. Values for Sagittaria and Cyperaceae are based on full pollen counts and expressed as

percent of total aquatic pollen. Aquatic pollen is defined here as including Sagittaria, Cyperaceae, Typha

latifolia, Typha/Sparganium, and Azolla.
San Francisco

 Pablo

 Bay

1868

MH

TP

Oakland

Hayward

Fremont

San Francisco Bay

Hayward f.

Richmond

No. Calavera

San Andreas f.

Figure 1

CALIFO

P

AC

RM

MIRA VISTA

TRENCH SITE

MC

SL

0 5

 kilometers

10

MT

BT

?
TRENCH 1

TRENCH 2

Arlington Blvd

Pinehurst

Court

2nd

hole

2nd

tee H A Y W ARD

FAUL

 Mira Vista Golf 100 

 Course, El Cerrito 

Hayward Fault

Paleoearthquake Site

Figure 2
@

@

@H

H

.

F

@

@

F

..

H

H

H

H

H

^

^

^

^^

^

.

H

H

@

@

@

@

@

@

@

H

H

^

^

^

^.

@

@

@H

H

.

F

@

@

F

..

H

H

H

H

H

^

^

^

^^

^

.

H

H

@

@

@

@

@

@

@

H

H

^

^

^

^.

TRENCH 1

TRENCH 2

HAYWARD FAULT
?

?

5910 19

5850 12

6120 13

?

H20

SUMP PUMP

K

K

K

K?

K

K

CAVED IN AREA

10 m 12 m 14 m

H20

SUMP PUMP

CAVED IN AREA

v

1690 7-7/9 1770, 1810 8
k

-4 m

10 m 12 m

2620 7

2130, 2090 8

230 6

3700 5

k? k?

1960 5

2120 4 

k

k


h wall, trench 2, Mira Vista trench site

k

k

k

k

k k

k

k

6 m 

C4C8

? ? ?

?

?

?

?

1

?

8

21

1719

24

18

16

22

28

3130

2

10

12 13 11

6

39

4

14

7

58

15

2325

29

1234569

10

11

8

F3

F4

F5 F6

3120 3

1470 4

 

1120 17

1180 21 1100 18

10 15 20 25

T PALEOEARTHQUAKES, MIRA VISTA

P 1P 2P 3

MORE CERTAINTY

LESS CERTAINTY

UNIT/EVENT

d.

PENULTIMATE

MOST RECENT EVENT time for sedimentation

1 1

1 0

9

8

5

6

4

ence



?

?

?

400 8

10

530 11

2

1130 15

340 16

1260 19

250, 210 2a,b

1430 3

6

360 7

320 20

270 21

1130 23

250 24

"1110"

"2090"

?

6 m

4 m

C1

C2

C3

1 3

2

4 5

6

8

7

?

?

? ?

?

?

k

k?

?

9

10

13 12 14

15

?16

17

19

20

26

21

22

23

24

25

27

313029

28

C6

C8

C5

C4

C7

C9?

C10?

F1

F2

F3

F4

?

?

?

nch 2, south wall, DETAIL

? ?

?

?

?
45

POACEAE

0 15 30

MIRA VISTA SELECTED POLLEN AND LOSS ON IGNITION

Erodium

01234

Eucalyptus

0123

Organic Content

0 15 30

BRASSICACEAE

5 10

Sequoia

0 5 10

1

 2

34

56

7

8

9

centimeters

10

11

1213

1415

unit 28 unit 25

Figure A2
Organic Content

0 10 20 30 40

MIRA VISTA SELECTED AQUATIC POLLEN AND LOSS ON IGNITION

Sagittaria

0 20 40 60

CYPERACEAE

0 20 40 60 80

Pollen Concentration: Grains/cc

0 50 100 150

% aquatic pollen X 1000 % dry weight

1

 2

34

5678

9

centimeters

10

11

1213

1415

Figure A3

unit 28 unit 25
Table 1. Evidence for paleoearthquakes.

EVENT more certainty intermediate certainty less certainty

11 [2s]: on faults F1 & F2 more

deformation below top

of u25

[2n]: folding in u23 [1n]: C9, fault termination

[1s]: C9, u23 ends abruptly

at fault F1

[2n]: C9, 4 weak fault

terminations

& fissure fill

[2s]: probable C9 & fault

termination

10 [1n & 1s]: much more

deformation below u23

near F2 and westward

[1s]: abrupt terminations of

pond sediments (u21) &

faulting covered and

infilled by C8

[1n,1s,2n,2s]: C8 colluvium

[2s]: fault termination

[1s]: 2 fault terminations

9 [2s]: 3 extremely distinct

fault terminations

below u21

[2n]: much more deformation

below u21 (folding

between faults F1a &

F1b)

[1n,2n,2s]: C9 colluvium

[2n]: 2 fault terminations

8 [1s, 2s]: strong deformation of

u15 (ash 2)

[1n]: 2 distinct fault

terminations

[2n, 2s]: C6, large, distinct

colluvium

[2n]: 2 fault terminations

[1s]: 4 fault terminations

6 [1n]: 3 distinct fault

terminations & "thrust"

faulting between &

above F5 to F7

[1s]: u10 much more deformed

(folded above fault F4)

than u14 (flat-lying)

[2s]: 2 fault terminations

[2n,2s]: fault termination

5 [1n]: abrupt fault termination

& u11 much more

deformed than u13

[2n, 2s]: C5, large & distinct

colluvium at event

horizon

4 [1n,1s,2n,2s]: intense

deformation of u8 (ash

1)

[1n]: major "thrust" faulting

[1s]: u8 (ash 1) in fissure

[1n,2n,2s]: C4 colluvium

[1n,1s]: 3 fault terminations in

each wall

Abbreviations: [1n, 1s, ...], trench 1 north wall, south wall; u1, u2, ..., unit 1, 2, ...
 calendric dates (AD positive) and 95% probability ranges for units and paleoearthquakes

P2L P2U P3L P3U Comment

1713 1821 1837 1876 Sum of P1 (25.6%) + P2 (62.8%) + P3 (7.0%) = 95.4%

Most recent event. P1U, historical age constraint after Toppazada and Borchardt (1998)

1768 1802 Sum of P1 (61.3%) + P2 (34.1%) = 95.4%

Ash 4 is u24

Ash 3

Ash 2

Ash 1

Age of u5 needs verification, much older dates also possible.

ges P1L to P1U represent 2 standard deviations calculated with program of Stuiver and Reimer (1993) except for units 25-26

epts exist in calibration curve, see comment column above for probabilities associated with each intercepted age range.
Table A1. Radiocarbon data

CAMS Sample 14C age Calibrated age Fraction

# name (yr BP) ± Unit (cal yr) (2σ) d13C Modern ± D14C ±

38508 1S-07-7/9 1690 60 30 fill -26.0 .8107 .0054 -189.3 5.4

38509 2N-07 2620 70 30 " -26.0 .7219 .0055 -278.1 5.5

38511 1S-17 260 50 28 historical pond,

gray clay unit,

-25.9 .9680 .0051 -32.0 5.1

38512 2S-20 320 70 28 see appendix -26.0 .9615 .0075 -38.5 7.5

38513 2S-12 480 50 28 on pollen -25.7 .9423 .0052 -57.7 5.2

38514 1S-03 760 50 28 analysis -26.0 .9094 .0051 -90.6 5.1

Major historical-aged unconformity

38515 2N-10 190 50 27 k –– -25.0 .9766 .0054 -23.4 5.4

38516 2N-14 350 40 27 –– -26.4 .9577 .0044 -42.3 4.4

38517 2N-23 410 80 27 k –– -28.7 .9501 .0092 -49.9 9.2

38518 2S-06 1110 90 27 ? –– -26.0 .8706 .0090 -129.4 9.0

38510 1S-06 150 50 26 ? –– -26.9 .9810 .0055 -19.0 5.5

38519 1S-21 190 40 2 6 1652-1706 (26%)

1713-1821 (63%)

1837-1876 (7%)

-25.7 .9770 .0048 -23.0 4.8

38543 2N-01 290 40 26 –– -26.1 .9643 .0043 -35.7 4.3

38544 2S-07 360 70 26 ? –– -29.5 .9560 .0079 -44.0 7.9

38545 1N-02 370 50 26 –– -26.7 .9554 .0053 -44.6 5.3

38546 2N-01

repeat

370 50 26 –– -26.1 .9555 .0054 -44.5 5.4

38547 1S-20 800 120 26 –– -26.0 .9047 .0127 -95.3 12.7

38548 2S-02

repeat

210 50 2 5 wa 1640-1679 (61%)

1768-1802 (34%)

-26.0 .9743 .0055 -25.7 5.5

38549 2S-02 250 50 2 5 wa " -26.0 .9691 .0054 -30.9 5.4

38551 2S-24 250 40 2 5 wa " -26.8 .9699 .0042 -30.1 4.2

38552 2S-21 270 150 25 (±150 yr age err.) -26.0 .9666 .0169 -33.4 16.9

38553 2S-16 340 60 25 ? –– -26.4 .9586 .0060 -41.4 6.0

38554 2S-08 390 40 25 ? –– -26.0 .9528 .0044 -47.2 4.4

38556 2S-25 580 80 25 –– -26.0 .9300 .0084 -70.0 8.4

38555 2S-11 530 70 2 3 AD 1294-1496 -26.0 .9362 .0075 -63.8 7.5

38557 1N-22 1150 50 23 –– -26.0 .8671 .0044 -132.9 4.4

38558 1N-05 1130 50 22 ? –– -26.0 .8683 .0049 -131.7 4.9

38502 1S-12 900 50 21b AD 1027-1479 -26.0 .8944 .0052 -105.6 5.2

38503 1S-10 1040 50 21a wa AD 892-1008 -26.0 .8782 .0050 -121.8 5.0

38504 1S-11 1060 60 21a wa " -26.0 .8758 .0060 -124.2 6.0

38505 2N-18 1100 50 21a wa " -26.0 .8723 .0052 -127.7 5.2

38506 2N-17 1120 40 21a wa " -26.0 .8699 .0040 -130.1 4.0

38507 2S-23 1130 50 21a wa " -26.0 .8683 .0048 -131.7 4.8

38559 2S-15 1130 50 2 0 AD 785-1014 -26.0 .8683 .0048 -131.7 4.8

38560 2N-13 1510 120 20 –– -26.0 .8286 .0116 -171.4 11.6

38561 2N-21 1180 50 1 9 AD 718-985 -26.0 .8637 .0047 -136.3 4.7

38562 2S-19 1260 100 19 –– -26.0 .8551 .0103 -144.9 10.3

38617 1N-03 1150 50 1 8 wa AD 784-967 -25.8 .8664 .0048 -133.6 4.8

38618 2N-26 1160 50 1 8 wa " -26.0 .8656 .0048 -134.4 4.8
Table A1. Radiocarbon data (continued)

CAMS Sample 14C age Calibrated age Fraction

# name (yr BP) ± Unit (cal yr) (2σ) d13C Modern ± D14C ±

38619 2N-25 1210 50 1 8 wa " -26.0 .8597 .0048 -140.3 4.8

38620 2S-13 1320 50 18 –– -26.0 .8483 .0047 -151.7 4.7

38621 1N-24 1190 50 1 7 AD 708-979 -26.0 .8619 .0050 -138.1 5.0

38622 1N-04 1380 50 17 –– -26.0 .8419 .0046 -158.1 4.6

38623 1S-23 1440 50 17 –– -26.0 .8361 .0049 -163.9 4.9

38624 2N-04 1470 50 17 ? –– -26.0 .8332 .0047 -166.8 4.7

38625 2N-16 1230 60 1 6 AD 667-968 -26.0 .8580 .0058 -142.0 5.8

38626 2N-24 1440 60 16 –– -26.0 .8360 .0053 -164.0 5.3

38627 2S-03 1430 70 1 5 AD 534-756 -26.0 .8367 .0072 -163.3 7.2

38628 2S-10 2090 60 15 –– -26.0 .7711 .0054 -228.9 5.4

38629 1S-08 1770 50 13 ? –– -26.0 .8025 .0041 -197.5 4.1

38630 1S-08

repeat

1810 60 13 ? –– -26.0 .7986 .0054 -201.4 5.4

38631 2N-12 2460 50 12 ? –– -26.0 .7358 .0041 -264.2 4.1

38632 1N-08 2000 50 1 1 104 BC - AD 121 -26.0 .7792 .0042 -220.8 4.2

38633 1N-16 2120 50 11 –– -26.0 .7684 .0042 -231.6 4.2

38634 2N-09 2250 60 11 k –– -26.0 .7561 .0053 -243.9 5.3

38635 2N-06 230 40 10 k –– -26.0 .9716 .0046 -28.4 4.6

38636 1N-20 2040 50 1 0 wa 152 BC - AD 13 -26.0 .7760 .0046 -224.0 4.6

38637 1S-05 2050 50 1 0 wa " -26.0 .7746 .0043 -225.4 4.3

38638 1S-04 2070 40 1 0 wa " -27.9 .7729 .0035 -227.1 3.5

38639 2N-08

repeat

2090 50 10 k –– -26.0 .7709 .0046 -229.1 4.6

38640 2S-01 2110 50 10 ? –– -26.0 .7694 .0043 -230.6 4.3

38641 2S-04 2120 50 10 ? –– -26.0 .7684 .0043 -231.6 4.3

38642 2N-08 2130 50 10 k –– -26.0 .7667 .0044 -233.3 4.4

38643 1N-11 2410 70 10 –– -26.0 .7411 .0057 -258.9 5.7

38644 1N-01 2390 50 9 –– -25.3 .7428 .0042 -257.2 4.2

38645 2N-02 2450 50 9 ? –– -26.0 .7373 .0042 -262.7 4.2

39123 1S-16 2110 50 8 wa 355 BC - 54 BC -26.0 .7688 .0045 -231.2 4.5

39124 1S-14 2190 50 8 wa " -26.0 .7613 .0040 -238.7 4.0

39125 1N-09 2240 40 8 –– -26.0 .7571 .0038 -242.9 3.8

39126 1S-13 2420 50 8 –– -26.0 .7402 .0041 -259.8 4.1

39127 1N-14 3090 50 7 –– -26.0 .6810 .0037 -319.0 3.7

39128 1N-17 2230 50 5 392 BC- 173 BC -26.0 .7572 .0042 -242.8 4.2

39129 1N-21 2980 50 5 –– -26.0 .6901 .0040 -309.9 4.0

39130 1N-18 3070 50 5 –– -26.0 .6825 .0038 -317.5 3.8

39131 2S-05 1960 60 4 ? –– -29.6 .7831 .0054 -216.9 5.4

39132 2N-03 3120 50 4 1464 BC - 1261 BC -26.0 .6781 .0038 -321.9 3.8

39133 1N-07 3190 50 3 1526 BC - 1323 BC -26.0 .6725 .0038 -327.5 3.8

39134 2N-11 3370 50 3 ? –– -26.0 .6573 .0038 -342.7 3.8

39135 2N-05 3700 50 2 2203 BC - 1928 BC -26.0 .6310 .0035 -369.0 3.5

39136 1S-15 4830 50 3703 BC - 3389 BC -26.0 .5482 .0032 -451.8 3.2

39137 1N-15 5170 50 4210 BC - 3911 BC -26.0 .5257 .0029 -474.3 2.9

39138 1N-10 5600 50 4533 BC - 4344 BC -26.0 .4982 .0029 -501.8 2.9
Table A1. Radiocarbon data (continued)

CAMS Sample 14C age Calibrated age Fraction

# name (yr BP) ± Unit (cal yr) (2σ) d13C Modern ± D14C ±

39139 1N-12 5850 50 (caved after

sampling, location

± 0.5? m)

-26.0 .4829 .0029 -517.1 2.9

39140 1S-01 5890 40 wa 4843 BC - 4722 BC -26.3 .4801 .0023 -519.9 2.3

39141 1N-19 5910 50 wa " -26.0 .4790 .0027 -521.0 2.7

39142 1S-02 5940 50 wa " -26.0 .4773 .0027 -522.7 2.7

39143 1N-13 6120 60 (caved after

sampling, location

± 0.5? m)

-26.0 .4670 .0030 -533.0 3.0

39144 1S-07 7/8 6230 50 (caved after

sampling, location

highly uncertain)

-26.0 .4605 .0025 -539.5 2.5

1) Delta 13C values are the assumed values according to Stuiver and Polach (Radiocarbon, v. 19, p.355, 1977)

when given without decimal places. Values measured for the material itself are given with a single decimal

place.

2) The quoted age is in radiocarbon years using the Libby half life of 5568 and following the conventions of

Stuiver and Polach (ibid.).

3) Radiocarbon concentration is given as fraction Modern, D14C, and conventional radiocarbon age.

4) Sample preparation backgrounds have been subtracted, based on measurements of samples of 14C-free coal.

Backgrounds were scaled relative to sample size.

5) Letter codes used: k = krotovina, sampled from infilled burrow; wa = included in weighted average for unit;

? = unit identity highly uncertain 

6) Calibrated ages computed only for samples identified as being in stratigraphic sequence and having

meaningfull ages. Some ages are clearly rejectable based on having prehistoric radiocarbon in historical-aged

units, others are judged inconsistent for appearing to be out of sequence by more than 100 yr.
Table A2. Loss on ignition data for unit 28 and unit below unconformity

Sample

interval

cruc

empty

cruc+wet

sed

wet sed cruc +

dry sed

dry sed cruc +

min

min LOI

0-1 cm 8.8588 9.9836 1.1248 9.6752 0.8164 9.5962 0.7374 9.68%

1-2 cm 8.6387 9.7713 1.1326 9.4411 0.8024 9.3573 0.7186 10.44%

2-3 cm 8.6279 9.7973 1.1694 9.4813 0.8534 9.4010 0.7731 9.41%

3-4 cm 7.5164 8.6386 1.1222 8.3214 0.8050 8.2434 0.7270 9.69%

4-5 cm 8.7828 9.9004 1.1176 9.5753 0.7925 9.4972 0.7144 9.85%

5-6 cm 8.9256 10.0496 1.1240 9.7856 0.8600 9.6976 0.7720 10.23%

6-7 cm 8.2910 9.3823 1.0913 8.9943 0.7033 8.9103 0.6193 11.94%

7-8 cm 8.0705 9.1227 1.0522 8.7514 0.6809 8.6695 0.5990 12.03%

8-9 cm 8.2242 9.3438 1.1196 8.9563 0.7321 8.8699 0.6457 11.80%

9-10 cm 8.8529 9.9797 1.1268 9.5642 0.7113 9.4712 0.6183 13.07%

10-11 cm 8.9223 10.0768 1.1545 9.6798 0.7575 9.5879 0.6656 12.13%

11-12 cm 8.7139 9.7958 1.0819 9.3402 0.6263 9.2373 0.5234 16.43%

12-13 cm 8.8465 9.6773 0.8308 9.2058 0.3593 9.0974 0.2509 30.17%

13-14 cm 8.6720 9.4298 0.7578 8.9072 0.2352 8.8104 0.1384 41.16%

14-15 cm 6.9804 7.7685 0.7881 7.2342 0.2538 7.1287 0.1483 41.57%

15-16 cm 8.4559 9.1999 0.7440 8.6964 0.2405 8.5928 0.1369 43.08%

All weights in grams
Table A3. Pollen scan data for unit 28 and upper part of unit 25

Sample

interval

Pollen type Magnification

0-1 cm Erodium 100X

Erodium 100X

Eucalyptus 400X

1-2 cm Erodium 100X

2-3 cm Erodium 100X

Erodium 100X

Erodium 100X

Eucalyptus 400X

Eucalyptus 400X

3-4 cm Erodium 100X

Erodium 100X

Erodium 100X

Erodium 100X

Eucalyptus 400X

4-5 cm Erodium 100X

Eucalyptus 400X

Eucalyptus 400X

Eucalyptus 400X

5-6 cm Erodium 100X

Erodium 100X

6-7 cm none noted

7-8 cm Erodium 100X

Erodium 100X

8-9 cm Erodium 100X

Eucalyptus 400X

9-10 cm Erodium 100X

10-11 cm Erodium 100X

Erodium 100X

11-12 cm Erodium 100X

12-13 cm none noted

13-14 cm none noted

14-15 cm none noted

15-16 cm none noted

Microscope magnification at which grain was first noted