Supplementary material for Time-averaged field at the Equator: complete data
and results from the Galapagos Islands, Ecuador.
S.Gromme, E.A.Mankinen, and M.Prevot.
Copy of Allan Cox’ undated transcriptions on file cards of the site-by-site
geologic information in his field notes taken by him on his 1964 and 1965
expeditions to the Galapagos Islands, Ecuador. These transcriptions were
evidently made by Cox while on sabbatical leave at the U.S.G.S. in the mid1970’s. They are abstracted from the field notes, which are about twice to
three times as detailed and include many Polaroid black-and-white photographs.
The entries (one per sampling site) are grouped by island, and are in
numerical order by anticipated or realized publication number (Gnnn) for each
island. The field/laboratory numbers (4Cnnn, 5Cnnn, 5Vnnn) are also given,
where the digit 4 or 5 represents the year of collection, the C refers to Cox,
and the V refers to Verne (Allan Cox’ middle name). (The switch from C to V
was necessitated by limitation of laboratory data format, as it was not
designed to accomodate more than 999 oriented cores collected by one person in
one year.) At nearly all sites, eight oriented cores were collected, and Cox
also usually collected a ninth unoriented core for radiometric dating. In the
field/laboratory numbering system, a site is designated by the number of the
first oriented core collected. Not all the field numbers are in sequence, and
some intervals are missing. The missing intervals represent unoriented rock
samples collected by Cox. The curious reader will note that Cox returned to
some islands more than once.
The islands are arranged in alphabetical order using the currently accepted
names. Original English-language names are shown in parentheses. The site
coordinates were transcribed from Cox’ original maps and field notes by E.A.
Mankinen in 1994. The coordinates are in the usual geomagnetic convention:
degrees and decimals, with longitude reckoned positive eastward. Some of
these cards also contain notes on the preliminary paleomagnetic data, which
are omitted here unless marked by an asterisk. Note that “flow” refers to
basaltic lava flow. Statements in brackets are by Gromme; comments regarding
later laboratory work refer to demagnetizations done by E.A. Mankinen in 19651968, and to those done by Mankinen, Michel Prevot, and Gromme in 1994.
Numerical analyses of similarity or difference of site-mean magnetization
directions were done by Gromme in 2000. In a few instances where Cox’
handwriting was indecipherable, photostats of the original field notes were
consulted.
Compiled by Sherman Gromme
30 Jan 2008
BALTRA
G11
4C090
0.433°S, 269.715°E
Geology: "S." side of bay at Baltra. Thick, massive flow capping low
fault(?) scarp. [Coordinates are for the north side of Caleta Aeolian
(Aeolian Cove), probably at the boat landing site shown on the navigational
chart.]
G30
4C263
0.474°S, 269.736°E
Geology: Massive lava flow capping cliff at NE end of South Channel. [Canal
de Itabaca] May dip 3 to 7° to NE. Local landsliding.
DARWIN (Culpepper)
G8
4C060
1.663°N, 267.997°E
Geology: From sequence near top of cliff on NW corner of island.
ft. th[ick] sequence of thin lava flows.
1
From a 6
ESPANOLA (Hood)
G34
4C300
1.371°S, 270.256°E
Geology: Flow exposed in high cliff section.
Upper flow at “blow hole”.
G35
4C310
1.371°S, 270.256°E
Geology: Underlies G34, separated by red rubbly zone. Irreg[ular] up[per]
surface  probably lots of time between G34 & G35.
*Mag: Mag[netic] directions of G34 and G35 are almost identical.
G36
4C317
1.371°S, 270.256°E
Geology: Underlies G35, separated by thin limey[sic] zone.
same flow.
*Mag: Different direction from G35.
G140 5C904
1.347°S, 270.338°E
Geology: Irregular coast line suggests flow is young.
and has heavy vegetation. Comes from vent to the N.
G141 5C913
[No other notes.
of Floreana.]
May or may not be
However it is faulted,
1.345°S, 270.351°E
Gardner Is.
This Gardner Is. is not the same as the Gardner Island east
G142 5C922
1.345°S, 270.351°E
Geology: Overlies G141, separated by calcareous rubbly layer.
small crater a few hundred meters to the north. Heavy brush.
*Mag: G142 = G141
G143 5C931
1.385°S, 270.380°E
Pta Cevallos
Geology: Surface relief of flow has been obliterated.
high cut into flow.
Comes from
Cliff 10 to 15 meters
G144 5C940
1.380°S, 270.373°E
Geology: Light-colored deposits, possibly marine, are contained in cracks in
the flow  possibly higher stand of sea. Overlain by a red weathered zone.
*Mag: G144  G143 but very close.
G145 5C949
1.379°S, 270.373°E
Geology: Overlies G144. Appears to be separate from G146  youngest flow on
Hood.
G146 5C958
1.371°S, 270.375°E
Geology: Youngest flow on Hood. Covered by vegetation that appears about as
mature as the R [reversely polarized] flows at C. Cevallo. Front trimmed by
surf, which runs high. Numerous barrancas covered with lichen on upper
surface.
G147 5C967
1.363°S, 270.363°E
Geology: Flow prob[ably] from small cone that forms a cliff several hundred m
to the NE. Densely vegetated. Trimmed by surf.
G148 5C976
1.362°S, 270.358°E
Geology: Partially vegetated. Mottled on air photos  lighter patches are
rock with lichen.
2
G149 5C985
1.353°S, 270.344°E
B[ahia] Gardner
Geology: Densely vegetated. Top of flow in place, bottom broken up!
G150 5V001
1.350°S, 270.351°E
Geology: Flow from a small cone, half of which has been removed by sea. Half
covered with vegetation. Prominent N30E fault. [This site is on a small
unnamed islet in the strait between Isla Espanola and I. Gardner; the strait
is the narrowest part of Bahia Gardner.]
G151 5V011
1.345°S, 270.305°E
Geology: Flow from vent several hundred m to the NE.
area of the vent, and flow heavily vegetated.
Cliff 10 m high in the
FERNANDINA (Narborough)
G12
4C100
0.264°S, 268.555°E
Geology: Young flow. Little erosion.
forest.
Espinoso Pt.
Cactus, well-developed mangrove
G13
4C109
0.264°S, 268.551E
Geology: Very young flow, generally aa.
Pahoehoe where sampled.
G50
5C036
0.469°S, 268.389°E
Cabo Hammond
Geology: Pahoehoe flow, very sparse vegetation. 3 to 4 m sea cliff.
of beach boulders 4 to 5 m higher than flow.
Ridge
G51
5C045
0.465°S, 268.389°E
flow N of Hammond
Geology: Layers of fluid lava, capped with rough aa flow. Absolutely no
vegetation, but cut by cliff.
G52
5C054
0.465°S, 268.601°E
Geology: Flow with rough surface and no vegetation.
form cliff as much as 3 m high.
G53
5C063
0.449°S, 268.614°E
Pta Mangle
Geology: Low pahoehoe flow slopes gently to the sea.
but sand beaches and extensive mangrove forests.
Sea has nicked front to
Little or no erosion,
G54
5C071
0.436°S, 268.611°E
Pta Mangle
Geology: Very young flow. Only a few [....?} cactus and a few mangroves
where it joins G53. Upper surface broken and rough.
G55
5C080
0.394°S, 268.622°E
Geology: Pahoehoe broken into this slabs.
Little or no erosion by sea.
*Mag: Same dir[ection] as G54.
Extremely sparse vegetation.
G56
5C088
0.335°S, 268.620°E
Geology: Pahoehoe. Thick mangrove forest, almost no erosion.
luxuriant than Pta Espinosa.
Trees more
G57
5C097
0.279°S, 268.494°E
N. Coast
Geology: Cliff exposure. Top of flow at high tide level, overlain by red
cindery deposit, then by 10 to 12 m of flows.
G58
5C106
0.279°S, 268.494°E
Geology: Overlies G57. Both G57 and G58 were formed prior to cliff erosion.
*Mag: Direction same as G57
G59
5C115
0.279°S, 268.494°E
Geology: This flow pours over the wave cut cliff in G57 and G58.
3
Younger.
*Mag: Different direction from G57 and G58.
G60
5C124
0.294°S, 268.440°E
Geology: Flow with top 1 m above high tide. Upper surface trimmed off by the
sea. Calcareous algal (?) deposits between this and G61.
G61
5C133
0.294°S, 268.440°E
Geology: Overlies G60. Clff 2 to 3 m high.
Top young with no vegettion.
G62
5C141
0.296°S, 268.377°E
Geology: Thin pahoehoe flows exposed along a cliff 30 m high.
G63
5C150
0.296°S, 268.377°E
Geology: Undelies G62.
*Mag: Same direction as G62.
G64
5C160
0.295°S, 268.420°E
Geology: Cliff exposure of thin lava flow about 8 m high.
section, in intertidal zone.
At bottom of
G65
5C168
0.295°S, 268.420°E
Geology: Overlies G64
*Mag: Slightly different from G64.
FLOREANA (Charles)
G37
4C325
1.280°S, 269.510°E
Geology: Point S of Fondeadaro Black Beach.
surface. Well-developed vegetation.
Pahoehoe with preserved upper
G38
4C333
1.294°S, 269.505°E
Geology: S of Rada Black Beach. Covered with vegetation.
*Mag: Direction similar to G37.
G39
4C341
1.299°S, 269.502°E
Geology: Lava flow forming cliff 10 to 12 m high 1/2 to 1 mile S of Rada
Black Beach. May or may not be the same as G38.
*Mag: Yes, it is the same. [This estimate not borne out by later lab work.]
G40
4C349
1.314°S, 269.489°E
Saddle Point
Geology: Lava flow several hundred [m?] NE of Saddle Point. Appears rather
young, but there is plant cover. Wave-cut cliff 10 to 15 m high.
*Mag: Same direction as G38-40[sic]. {Not subsequently confirmed.]
G41
4C356
1.234°S, 269.552°E
Post Office Bay
Geology: S side of P.O. Bay. Waves have removed 2 m of flow and there is
vegetation cover, but appears rather young.
G42
4C364
1.239°S, 269.521°E
Pt. Daylight
Geology: Prob[ably] from source at Daylight Cone. 3m high cliff along sea
front. Vegetation cover.
G43
4C371
1.240°S, 269.521°E
Geology: 300 m S of G42. May be related to either of two local cones.
vegetation on surface.
*Mag: Direction is different from G42.
Dense
G44
4C379
1.245°S, 269.517°E
Geology: Lava flow forming high cliff with columnar joints on W side of cone
497. [Cone 497 is SSW from the cone forming Pta. Dalight; these two breached
cones dominate the NW corner of Floreana.]
4
G45
4C389
1.252°S, 269.514°E
Geology: Lava flow between G44 and [Fondadero] Black Beach.
front, vegetation on top.
3 m cliff on sea
G123 5C756
1.231°S, 269.535°E
P.O. [Post Office] Bay
Geology: Flow coming from Pta. Daylight. Pahoehoe top eroded at most one m
by surf. Locally ropey[sic] surface intact. Dense vegetation including
trees.
[Subsequent laboratory work shows that G123 and G43 have the same
magnetization direction, though the two sites are on opposite sides of the
cone forming Pta. Daylight.]
G124 5C765
1.237°S, 269.541°E
P.O. Bay
Geology: Flow S of long beach at P.P. Bay. Densely vagetated.
of 2 m.
G125 5C774
1.226°S, 269.557°E
Geology: Thin pahoehoe flow between P.O. Bay and Pta. Cormorant.
covered by vegetation. No erosion by sea. Very young.
Surf erosion
About half
G126 5C783
1.228°S, 269.577°E
Geology: Flow that forms the peninsula between Pta. Cormorant and Floreana.
The flow has turned brown, abundant lichens, some vegetation, some beaches,
but general appearance is young.
*Mag: G126 = G125 [Not confirmed by later laboratory work.]
G127 5C792
1.222°S, 269.580°E
Geology: Flow from tuff cone of Cerro Cormorant. Lava appears to be last
phase of eruption, following tuff. Heavy vegetation. 3 m of flow eroded by
surf.
*Mag: G127  G126
G128 5C801
1.233°S, 269.584°E
Geology: Lava flow on a cinder cone S of Pta Cormorant. It has cut a bay
into the cone to form a cliff 30 to 40 m high. Little erosion of the flow by
the sea. Vegetation including trees, 10 to 20% of flow bare.
*Mag: G128  G127
G129 5C810
1.244°S, 269.608°E
Geology: Massive flow adjacent to prominent creek.
15% bare. 2 m surf erosion.
*Mag: G129  G128
Densely vegetated, 10 to
G130 5C819
1.243°S, 269.605°E
Geology: Flow SW of creek. May be same as G130 but prob.[ably] different,
with creek between two flows. Covered with cactus and low brush. Surf has
removed rubble but cut less than into G129.
*Mag: G130  G129 [Later lab work shows that they have the same
paleomagnetic direction.]
G131 5C828
1.237°S, 269.616°E
I[sla] Champion
Geology: Top flow of a sequence of thin basalts. Dense vegetation, including
trees, but about half surface is rock! Steep cliffs 30 m high.
G132 5C837
1.236°S, 269.613°E
Champion I.
Geology: Vent of scoria and agglomerate with a long cut into it. Thin flows,
apparently contemporaneous with vent. About 50% covered with vegetation. Red
soil.
*Mag: G132 = G131 [Not borne out by later lab work.]
5
G133 5C460
1.257°S, 269.630°E
Los Cuevos [Not named on
navigational chart; see below]
Geology: Flow underlying massive deposits of palagonite. Cliffs 20to 25 m
high.
G134 5C847
1.249°S, 269.623°E
Geology: Pahoehoe flow. Covered with brush and cactus, 5% rock.
covered with lichen.
*Mag: G134  G133
Well
G135 5C856
1.258°S, 269.638°E
H 731 [H731 refers to the cone close
to the shore SW from this site, also known as Los Cuevos.]
Geology: Moderate veg. cover including acacias, 20 percent rock.
G136 5C867
1.271°S, 269.647°E
Geology: Pta Ayora and the island to the N are the flanks of a cone now
removed by the sea. Present samples [sites G136 and G137] are on flanks of
cone to the W.
G137 5C876
1.271°S, 269.647°E
Geology: Underlies G136. Separated by layer of orange to red scoria, with
calcareous veins  time interval?
*Mag: G136 = G137 {Not borne out by later lab work.]
G138 5C886
1.259°S, 269.635°E
Geology: Underlies tuff. See G135.
that G138 is older than G135.]
Los Cuevos
[Significance obscure.
Evidently means
G139 5C895
1.259°S, 269.635°E
Los Cuevos
Geology: Sill or flow within the tuff.
*Mag: G139  G135 [Later lab work confirms that G139 = G135. The sequence
G138 under G135-G138 represents the Matuyama-Brunhes boundary.]
GENOVESA (Tower)
G66
5C177
0.311°N, 270.054°E
Geology: Lowest flow exposed in high cliff section at Darwin Bay.
G67
5C186
0.311°N, 270.054°E
Geology: Overlies G66, separated by thin, scoreous[sic] flow units.
*Mag: G67 = G66 [Confirmed by later lab work.]
G68
5C200
0.316°N, 270.050°E
Geology: Flow exposed above beach at B[ahia] Darwin, in cliff 15 m
thick[sic].
G69
5C212
0.311°N, 270.054°E
Geology: About equiv[alent] to G67 or slightly younger.
*Mag: G69 = G67 [Not supported by later lab work.]
6
G70
5C221
0.311°N, 270.054°E
Geology: Overlies G69. Separated by red scoria zones from overlying and
underlying flows.
*Mag: G70 = G69
G71
5C230
0.311°N, 270.054°E
Geology: Overlies G70
*Mag: G71 = G70 [G71 = G70 = G69 confirmed by later lab work.]
G72
5C238
0.301°N, 270.048°E
Stairway of the Duke {Not designated
on nav. chart, but is located on N. shore of peninsula forming S. side of
Bahia Darwin, E. of entrance.]
Geology: At tide level.
*Mag: G72 = G71 [Not confirmed by later lab work.]
G73
5C247
0.301°N, 270.048°E
Geology: Underlies G72. Petrologically distinct.
4°NE.
Attitude [strike] N60E dip
G74
5C255
0.301°N, 270.048°E
Geology: overlies G72 & G73. May be equivalent to G68, but more likelym is
slightly older. Covered by thin crust of very young, fluid lava.
*Mag: G74  G73  G72 [Confirmed by later lab work.]
G75
5C266
0.323°N, 270.041°E
Geology: South wall of Tower Crater. The lower 1/3 of the walls are covered
with talus, mainly blocks that have spalled off the walls. Yet the present
surfaces are encrusted with fumarolic deposits.
G76
5C274
0.323°N, 270.041°E
Geology: Overlies G75
*Mag G76 = G75 [Not confirmed by later lab work.]
G77
5C283
0.323°N, 270.041°E
Geology: overlies G76, separated by at least one flow.
*Mag: G77  G76
G78
5C292
0.323°N, 270.041°E
Geology: Overlies G77
*Mag: G78  G77 [Not confirmed by later lab work.]
G79
5C300
0.323°N, 270.042°E
Geology: Outer rim of crater, which is set back 50 m from main rim & rise 50
m above it. [This site on S side of crater, N of Bahia Darwin.]
*Mag: G79 = G78 [This identity confirmed by later lab work.]
G80
5C310
0.340°N, 270.038°E
Geology: Flow near vent complex on NW side of island.
G81
5C319
0.340°N, 270.039°E
Geology: 2 to 3 flow units above G80.
*Mag: G80  G81
G82
%c330
No annotations.
0.338°N, 270.031°E
G83
5C339
0.338°N, 270.031°E
Geology: Overlies G82
*Mag: G82  G83
7
G84
5C348
0.338°N, 270.032°E
Geology: Overlies G83
*Mag: G83  G84
ISABELA (Albemarle)
G14
4C119
0.010°S, 268.408°E
Cape Berkeley
Geology: 30 foot cliff cut by surf in this aa flow. No vegetation.
m.y. [Age determination unpublished]
K-Ar .06
G15
4C127
0.240°S, 268.611°E
Tartuja Pt [sp? Punta Tortuga, or
Tortoise Point as shown on chart.]
Geology: Aa flow with “palagonitized” top. Scattered cactus, some large
ones. Mangrove forest probably grows on this flow.
G46
5C002
0.583°S, 269.046°E
Isano [sp?] Perry [in Bahia de
Perry]
Geology: Aa flow with fluid patches. Rough surface of flow slopes into sea
with no wave erosion. Sparsely vegetated, with mangroves along coast.
Otherwise, flow looks very young.
G47
5C010
0.560°S, 269.034E
Geology: Pahoehoe flows, 10% of surface filled with sand. Vegetation
includes grass, prickly pear, and cereus[sp?]. Part of surface removed by
surf, but no nick. Older than G46.
G48
5C019
0.345°S, 268.960°E
Geology: Pahoehoe flow that forms a dark lava beach along miles of coast. [NE
of Volcan Alcedo.]
MARCHENA (Bindloe)
G3
Age:
4C020
0.305°N, 269.492°E
Irregularly eroded.
G4
4C028
0.305°N, 269.492°E
Geology: Near G3, prob[ably] younger.
by scoria. G4 is lowest unit.
3 flow units 1 to 2 m thick, separated
G85
5C357
0.359°N, 269.464°E
Geology: Thin pahoehoe flow overlain & underlain by volcanic sediments.
Dense, green vegetation inland. Broken, and flow dips over schallendomes.
Samples spread over flow units to detect tilting. [Note: The term
schallendome is not in the 4th edition (1997) of the AGI Glossary of Geology.]
*Mag[netics]: No tilting.
PINTA (Abingdon)
G1
4C004
0.547°N, 269.263°E
Age: Surface of flow well preserved. Locally several meters of flow removed
by surf. Large stand of cactus on top.
G2
Age:
4C013
0.547°N, 269.265°E
Extremely young. Very little vegetation.
8
Young beach line.
G86
5C367
0.581°N, 269.218°E
Geology. High cliff on W side of Pinta, exposing cross section of an ancient
volcano. Flows slope down & [?] to the north & south.
G86 is the lowest flow in the section.
Outcrop is glassy & crumbly & contains patches of chalcedony (?). Overlying
flow has a pillowy bottom. G86 is >2.5 m th[ick].
G87
5C376
0.581°N, 269.218°E
Geology: About 40 to 50 m above G86.
flow is fresh
Rock appears oxidized, yet overlying
G88
5C384
0.581°N, 269.218°E
Geology: 100 to 120 m up in section above G86.
First few samples are less oxidized.
Massive flow 5 m th[ick].
G89
5C393
0.554°N, 269.228°E
Cabo Chalmers
Geology: Several flows face the graben which forms a small bay here.
G89 is the third down from the top of a series of three flow units.
G90
5C402
0.555°N, 269.221°E
Geology: Thick flow at the cape.
Cabo Chalmers
G91
5C411
0.557°N, 269.221°E
Cabo Chalmers
Geology: Flow in cove NW of Chalmers. Prob[ably] strat[igraphically] below
G90, but petr[ographically] similar. Exc[ellent] O.C. [outcrop].
G92
5C420
0.593°N, 269.466°E
Geology: Great cliff on W side of Pinta.
dip N about 9°. Lowest flow in section.
From N flank of cliff, where flows
G93
5C429
0.593°N, 269.466°E
Geology: 10 to 15 m above G92.
G94
5C437
Geology: 10 to 15 m strat[] above G73, separated by a fine layer of beach
sand. Incrustation of salt or bicarbonate(?) appears in fine cracks.
G95
5C447
0.593°N, 269.466°E
Geology: 3 flows up from G94, with 2 intervening ash layers.
PINZON (Duncan)
G18
4C150 0.598°S, 269.325°E
Geology: Flow forming capping rock on the N side of the rim of the central
crater. Flows have slight dip to NE  initial dip. Flow 7 m thick.
G19
4C160
0.598°S, 269.326°E
Geology: Below G18 on crater rim of Duncan.
RABIDA (Jervis)
G16
4C135
0.400°S, 269.292°E
Geol: Dike about 1 to 1.5 m thick, cuts and may feed upper part of red
agglomerate ridge.
G17
4C143
0.403°S, 269.295°E
Geology: Lava flow on coast.
9
SAN CRISTOBAL (Chatham)
G96
5C500
0.867°S, 270.423°E
SW of I. Lobos
Geology: Flow 6 m th[ick] covered with dense vegetation. Several meters
removed by waves. Dense veg.  trees. Streams cut to a higher sea level.
G97
5C509
0.856°S, 270.433°E
Geology: Dense vegetation, cut by surf.
*Mag: G97  G96 [Confirmed by later lab work.]
G98
5C519
0.841°S, 270.458°E
Geology: Terrain smoother than for G97, less rock shows through the
vegetation, non-vegetated patches are “streaked’. Wave-cut. Older than G97.
*Mag: G98  G97 [Confirmed by later lab work.]
G99
5C528
0.816°S, 270.460°E
Pta. Bassa
Geology: Dense vegetation, wave cut several meters, beaches, beach rock.
*Mag: G99  G98 [Not borne out by later lab work.]
G100 5C537
0.822°S, 270.478°E
N. of C. [Pta.] Bassa
Geology: Well developed vegetation, but rock shows through. Wave-cut cliff 1
to 2 m high, beach, [lagoon].
*Mag: G100  G99 [Confirmed by later lab work.]
G101 5C546
0.818°S, 270.499°E
Geology: Dense vegetation. Wave-cut front, windrows of boulders.
than [G]100.
*Mag: G101  G100 [Confirmed by later lab work.]
Younger
G102 5C555
0.810°S, 270.522°E
Geology: Pahoehoe flow with schallendomes, other recognizable flow features
only partly removed by surf. Wave-cut fron of [approx.] 1 meter. Beaches &
poles of boulders. Vegetated. Prob[ably] younger than G101. Faulting, older
than [G]104
*Mag: G102  G101 [Confirmed by later lab work.]
G103 5C565
0.768°S, 270.541°E
[S. of] Cerro Brujo
Geology: Very young flows of C. Brujo. Scanty veg[etation], but beach & row
of trees. Sea has done litle to shape the flow. Air photo: More veg. inland
than [G]108.
G104 5C574
0.778°S, 270.537°E
[SW. of] Cerro Brujo
Geology: Flow features clearly recognizable  only a moderate amount of surf
erosion. Moderate amount of vegetation.
*Mag: G104  G103 [Not borne out by later lab work.]
G105 5C583
0.744°S, 270.560°E
Geology: Thin pahoehoe flow. Moderate veg[etation]. Flow features may be
seen. Surface of flow is brown. Cut from [1/2 to] 1 m high. No faulting,
may be younger than [G]102.
G106 5C592
0.743°S, 270.561°E
Geology: Very young flow, little veg[etation] other than lone cactus.
little modified by waves. Sand beaches - no veg.
10
Front
G107 5C601
0.717°S, 270.610°E
Geology: Dense veg[etation], only a small fraction (1/5) exposed. Sea has
removed about 1 m. Fossiliferous [limey] layer [about 15 cm thick] above
beveled part of flow.
G108 5C611
0.717°S, 270.609°E
Geology: Thin flow immediately SW og G107. little vegetation other than
cereus[sp?] cactus inland. Along coast, mangroves and beaches. Almost no
surf erosion. Prob[ably] same as [G]106 on air photos.
*Mag: G108  G107 [Confirmed, and G108 same as G106 from later lab work.]
G109 5C620
0.715°S, 270.610°E
Geology: Aa flow just NE of G107. Flow is brownish & has lichen and a few
bushes and small trees.
*Mag: G109  G108 ]Confirmed by later lab work.]
G110 5C629
0.700°S, 270.639°E
Caleta [de la] Tortuga [(Bahia
Terrapin)]
Geology: Dense vegetation, eroded surface, red soil or silt cover. Beach
along front.
G111 5C638
0.696°S, 270.639°E
Geology: Immediately E of G110. Dense vegetation including trees, but some
bare rock. Surf erosion of 2 m and boulders, but shape of flow not changed.
Younger than G110.
*Mag: G111 = G110 [Confirmed by later lab work.]
G112 5C647
0.686°S, 270.665°E
Geology: Fairly heavy vegetation, abou 10% exposed rock. Sea has removed 7 m
to expose columnar joints. Flow features visible on photos.
*Mag: G112  G111 [Confirmed by later lab work.]
G113 5C656
0.690°S, 270.697°E
B[ahia] Hobbs
Geology: Abundant veg[etation] including small trees but about 10% exposed
rock. Not much erosion by surf. Air photos, G113 is lighter, lower, & older.
G114 5C665
0.693°S, 270.700°E
Geology: East of beach of G113. Vegetated. Extensive surf erosion, with
cemented beach boulders inland, some exfoliated.
*Mag: G114  G113 [Not borne out by later lab work.]
G115 5C674
0.702°S, 270.723°E
Geology: Thin pahoehoe flow (from C[erro] Pitt) which outcrops beneath the
sand all along east end of B[ahia] Hobbs. Only 30 to 50 cm of flow eroded by
surf. Dense vegetation. Prob[ably] comes from same cone as G113 & G114.
*Mag: G115  G114, but close [Confirmed by later lab work.]
G116 5C683, 5C692
0.712°S, 270.753°E
Cerro Pitt
[5C683 is the site in lava, 5C692 is the site in tuff baked by the lava.]
Geology: Lava flow resting in a crater on Cerro Pitt. Flow is 2 m thick & is
scoreaceous basalt. Over- and underlain by tuff, the latter baked.
*Mag: Excellent agreement between flow and tuff.
G117 5C698
0.711°S, 270.759°E
[Pta. Pitt]
Geology: Flow NE from Cerro Pitt. Overlain and underlain by tuff deposits.
May or may not be the same as G116.
*Mag: Yes, it is the same. G117 = G116 [Confirmed by later lab work.]
11
G118 5C711
0.759°S, 270.543°E
Cerro Brujo
Geology: Flow is in the crater of Cerro Brujo. Uppermost of several flow
units. Considerable erosion since the cone was formed. Arroyos and an
alluvial flat. Sea cliffs and tunnels.
G119 5C721
0.886°S, 270.393°E
Cerro Chivo
Geology: Cone, eroded by surf to expose agglomerate layer and an old beach.
G119 on the flank of cone and prob[ably] came from it.
G120 5C730
0.881°S, 270.402°E
Geology: Vent about 1 km N of Cerro Chivos[sic]. Lower agglomerate sequence
with shells, dipping away from G120troward G119, indicating a local source.
G121 5C739
0.881°S, 270.402°E
Geology: Underlies G120, separated by bed of red scoria and cobbles, possibly
weathered.
*Mag: G121  G120 [Confirmed by later lab work.]
G122 5C747
0.903°S, 270.377°E
Pta. Chacabuco
Geology: Much denser vegetation than north of Wreck Bay. Surf erosion to
form outcrop.
[Cox conluded that this was the oldest lava he collected on San Cristobal.]
SANTA CRUZ (Indefatigable)
G23
4C192
0.758°S, 269.690°E
Academy Bay - Cove
Geology: Abundant vegetation on flow, wave erosion 5 1/2 m thick.
same as flows at Darwin Station.
May be
G24
4C200
0.717°S, 269.517°E
Tortuga Bay
Geology: Young flow between surf and bay on SE corner of bay. Large
Opuntia[sp?] cactus grove on top. 6’[foot] scarp due to faulting. Top of
flow sampled.
G25
4C207
0.741°S, 269.696°E
Academy Bay
Geology: Flow underlying Darwin Foundation grounds. 300 yds E of Station
dock. 1 to 2 m of flow removed by surf.
G26
4C224
0.579°S, 269.833°E
Plazzas Is. [Islas Plaza]
Geology: Large flow forming west end of Plazzas Island. Flow dips ca. 4° to
the N.
G27
4C241
0.486°S, 269.741°E
Channel [Canal de Itabaca]
Geology: Baranca at W end of South Channel near small cove.
(1) Black vesicular lava at tide level is R.
G27
(2) Thick, massive flow overlying (1) and separ[ate]d thin rubble zone
is G27, also R.
(3) Different flow at top of cliff is N.
G28
4C248
0.486°S, 269.741°E
South Channel [south side of Canal
de Itabaca]
Geology: Overlies G27, separated by a poorly exposed rubbly zone from G27.
G29
4C254
0.486°S, 269.741°E
South Channel
Overlies G28, separated by red rubbly zone. G29 is massive, about 8 m thick.
Overlain by thinner flow (not sampled)
12
G31
4C271
0.530°S, 269.610°E
Geology: Tide-level flow. 2 to 3 m of surface removed by surf.
developed vegetation similar to Acad. Bay
Well
G152 5V020
0.701°S, 269.778°E
Puerto Nunez
Geology: Thin pahoehoe from vent near head of bay. Not completely vegetated.
Front only slightly thinned by surf.
G153 5V029
0.582°S, 269.829°E
Geology: Thin pahoehoe flow east of Cerro Colorado. [Cerro Colorado not on
nav. charts. Site on main shore SW of Islas Plaza.] Surface bare and
brownish, but a few scattered Opuntias[sp?] and bushes or trees. Only a
little surf erosion.
G154 5V038
0.566°S, 269.827°E
Geology: Flow which spills over the cliff. Sampled where it extends into
sea. Only half of flow is vegetated with cactus and trees. On air photo,
this does not appear to be youngest flow. May not spill over cliff [Opinion
revised from field observation; Cox evidently acquired aerial photographs
after his expeditions.]
G155 5V047
0.547°S, 269.801°E
Geology: Flow in graben. Surface is brownish and 1/3 bare of vegetation,
especially on schallen domes. Sea has removed several meters of surface.
Appears much older than G154.
G156 5V056
0.508°S, 269.760°E
Geology: Lava flow at tide level. Top beveled by sea. Overlain by scoria
and red ash, in turn overlain by a (N) flow that cascades over the cliff.
[G156 has R polarity; the overlying R flow has no site number or data.]
G176 5V237
0.519°S, 269.520°E
Geology: Lava flow which forms irregular coast and small islands. Top
densely vegetated, but flow form can be seen under the trees. Sea has removed
1/2 to 1 m of basalt to reveal columnar joints.
G177 5V246
0.528°S, 269.507°E
Geology: Massive flows with columnar joints. Deeply weathered cavernous
surfaces on vertical faces. Densely overgrown upper surface.
[Later lab work shows that G177 and G176 have the same magnetization
direction.]
G178 5V255
0.528°S, 269.506°E
Geology: 100 m west of G177, separated by a boulder beach. Flow consists of
numerous flow units. Heavily vegetated upper surface (trees) with red soil.
Sea has stripped several meters of upper surface, but irregular flow outline
is preserved. Prob[ably] from nearby volcano.
*Mag: Large [magnetic compass] corrections. Scatter in NRM [natural remanent
magnetization], but cleans up well [with alternating-field partial
demagnetization]. Apparently lightning.
[This is one of the few sites for which Cox explicitly noted remagnetization
by probable lightning. Judging by strength of natural remament magnetization,
a few other sites also were partially remagnetized by lightning. As
represented by the comprehensive Cox collection, paleomagnetic evidence for
lightning strikes is rare in the Galapagos Islands.]
G179 5V264
0.531°S, 269.484°E
“Bowditch Island” [Small unnamed
island close to shore west of Pta. Bowditch]
Geology: Small cone with series of thin discontinuous flows. Some
veg[etation] including Opuntia. Sea has removed several meters of basalt.
13
G180 5V273
0.602°S, 269.463°E
"Whale Bay" [Not named on nav.
chart; 5 km S of I. Eden. Incorrect reference by Cox.]
Geology: Pahoehoe flow. Considerable trimming by the sea to form cliff
several meters high.
14
G181 5V282
0.602°S, 269.463°E
"Whale Bay" [Incorrect reference by
Cox.]
Geology: Overlies G180 directly.
Mag: 3 samples hit by lightning, 2 not completely recovered on [magnetic]
cleaning. These omitted in final stat[istics]. G181 = G180. [Later lab work
showed that not only G181 = G180, but G181 = G180 = G31, the latter being 22
km to the northeast on the north coast of Santa Cruz. Sites G181 and G178 are
the only ones noted by Cox to have been struck by lightning, and perhaps
coincidentally, both are on the north and west coasts of Santa Cruz. G31 was
also likely struck by lightning, though Cox did not note it.]
SANTA FE (Barrington)
G182 5V292
0.804°S, 269.965°E
Geology: Flow that is exposed along fault block.
Str[ike] EW, dip 0 to 4° N.
Uncertainty in dip of 4° 
G183 5V301
0.798°S, 269.937°E
Geology: 10 m thick flow exposed in cliff.
G184 5V310
0.802°S, 269.962°E
Geology: Flow at NW end of island west of lagoon.
*Mag: One R specimen. No obvious explanation. [The flow has N polarity. No
explanation has subsequently been found, but inadvertent inversion of the core
is most likely. One such error out of more than a thousand opportunities is
not bad, and may equally as well be laid to a laboratory technician as to Cox
in the field.]
G185 5V319
0.798°S, 269.948°E
Geology: Flow 30 to 40 m thick, large vertical joints with “skins” 1 to 2 cm
th[ick] along joints.
G186 5V328
0.798°S, 269.948°E
Geology: Underlies G187 and separated from it by another flow and by two
zones containing rubble and some sediments.
*Mag: G186  G185, but the two are similar.
SANTIAGO (James)
G5
4C036
0.230°S, 269.155°E
Geology: Small cove N of James Bay, several hundred meters from coast.
Bedded tuff, variegated. Large trees on top.
G6
4C044
0.227°S, 269.155°E
James Bay
Geology: Very young. Sparse cactus, low brush along edge.
cut a cliff 20{feet] high.
Active surf has
G7
4C052
0.283°S, 269.437°E
Sullivan Bay
Geology: Broken pahoehoe surface with patches of brush, surface generally
barren. Several meters of surface removed by surf.
G20
4C168
0.163°S, 269.175°E
Geology: Thin flow near base of agglomerate and cinder conethat had its
center in a small bay. More than half of cone removed by sea.
G21
4C178
0.163°S, 269.175E
Geology: 100 m east of G20, may or may not be contemporaneous.
Petrologically different.
*Mag: G20 & G21 have different directions.
15
G22
4C185
0.158°S,269.179°E
Geology: 1 mile E of G21. Abundant vegetation on top.
meters of surface.
Sea has removed 4
G32
4C279
0.287°S, 269.440°E
Bartholomew Is.
Geology: Puddle of lava filling small cone, half of which has been removed by
erosion. Cavernous weathering.
G33
4C287
0.286°S, 269.443°E
Bartholomew Is.
Geology: Cone similar to G32.
*Mag: Mag[netic] directions similar to G32.
G49
5C027
0.197°S, 269.171°E
Geology: N end of beach with flamingo lagoon. Pahoehoe flow, apparently from
cone to the N. Wave-eroded cliff 3 to 4 meters high. Source cone also
dissected. Red soil on flow, vegetation including trees.
G157 5V066
0.220°S, 269.395°E
Geology: Young flow. Surface weathered light brown. About 10% vegetated,
including a few trees. Only a few cm of surface stripped where it meets sea
in a bay.
G158 5V075
0.231°S, 269.412°E
Geology: Pahoehoe flow, surface weathered brown. A few shrubs and trees, ca.
5% of surface. Well developed mangroves along coast. <5 m surf erosion.
G159 5V084
0.252°S, 269.422°E
Geology: Pahoehoe flow, surface weathered light brown, about 5% vegetation.
3 to 4 m surf erosion in this protected bay.
G160 5V093
0.207°S, 269.379°E
Geology: Thin paahoehoe flow, about 10% vegetated. Older than G157.
weathered to light brown. Only a litle surf erosion.
G161 5V102
0.192°S, 269.337°E
Geology: Thin pahoehoe flow, rather jumbled top.
parts of flow.
Surface
Sea erosion exposes deeper
G162 5V111
0.195°S, 269.335°E
Geology: Pahoehoe flow, surface weathered brown. about 1/2 surface covered
wit cactus, trees, and shrubs. In bay, little surf erosion.
G163 5V120
0.160°S, 269.324°E
Geology: Flow, well preserved pahoehoe surface, weathered brown. Surface
less broken than that of G162, but slightly more vegetated. Irregular seaward
edge preserved, but surf erosion of 1 1/4 to 2 m.
*Mag: Very unusual direction. Low intensity.
G164 5V129
0.182°S, 269.302°E
Geology: Thin pahoehoe flow that forms a peninsula in bay off photos. Thin,
unbroken flow with no evidence of age other than stripping by surf. Dense
mangroves.
G165 5V138
0.160°S, 269.301°E
Geology: Thin pahoehoe flow indistinguishable from G164 and G163.
little trimming by the sea.
*Mag: Low intensity. G165 = G163.
16
Mangroves,
G166 5V147
0.162°S, 269.263°E
Geology: Flow from small cone. Surface weathered brown and about 1/2 covered
with cactus, shrubs, and grass. 3 1/2 m cliff cut by surf.
G167 5V156
0.148°S, 269.251°E
Geology: Thick pahoehoe flow. Sea cliff about 7 m high. However top is
fresh, with well-preserved flow features. Scanty veg[etation] near sea, but
denser cover inland.
G168 5V165
0.147°S, 269.225°E
Geology: Thick flow. Upper few meters eroded by surf.
Surface well vegetated and cut by stream gulleys [sic].
Large beach boulders.
Near a vent.
G169 5V174
0.144°S, 269.210E
Geology: Series of thin pahoehoe flows make up local point.
12m high.
Sea cliff 10mto
G170 5V183
0.144°S, 269.211°E
Geology: 300 m E of G169. One of a series of alternating scoria and
agglomerate layers.
G171 5V192
0.147°S, 269.203°E
Geology: Thick lens of lava about 200 m across and 8 to 10 m thick in the
middle, apparently filling a local crater. Top heavily vegetated. Sea cliff
15 m high.
G172 5V201
0.148°S, 269.197°E
Geology: Lowest of three flows esposed in cliff section.
the west.
G173 5V210
0.148°S, 269.197°E
Geology: Overlies G172, separated by thin pahoehoe flows.
From vent 300 m to
G173 = G172.
G174 5V219
0.148°S, 269.197°E
Geology: Overlies G173, separated by a 20 cm thick zone of red ash and
rubble.
*Mag: G174  G173
G175 5V228
0.367°S, 269.415°E
Isla Sombrero
Geology: Thin pahoehoe flows. Surface weathered light brown. Sparse
vegetation, mainly small shrubs. Only slight modification of flow by waves.
WOLF (Weniman)
G9
4C069
1.390°N, 267.183°E
Geology: Flow at head of cliff at N end of island.
*Mag: NRM very scattered. 400 oe AC needed for cleaning.
G10
4C079
1.388°N, 267.182°E
Geology: 50 to 100 ft higher in the same section as G9.
17