Table 2. Phenocryst minerals, whole-rock SiO2 content, and notes for samples from pre-1991 eruptive periods.
[Abbreviations: pl, plagioclase; qz, quartz; hb, hornblende; cm, cummingtonite; bt, biotite; ol, olivine; ag, augite; hy, hypersthene. X, essential (>5%); x, varietal (<5%); t, trace; R, thick rims (>30 um); r, thin rims; c, cores of hornblende crystals; S, resorbed essential; s, resorbed varietal; B or b, broken crystal fragments; h, with hornblende rims. SiO2 in wt% (volatile free). Samples are of the dominant juvenile material in dated deposits except for those samples that have a dash in the "Associated 14C sample" column. Ages for dated deposits given in 14C years; other ages are estimates based on stratigraphic relations or weathering]
|
Period |
Age |
Field |
Location |
Associated 14C sample (figs. 6, 7, table 1) |
Notes |
N. latitude |
E. longitude |
Phenocryst minerals |
%SiO2 |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
pl |
qz |
hb |
cm |
bt |
ol |
ag |
hy |
|||||||||
|
Buag |
~400 |
N600B |
Marella River |
-- |
Essential clast in lithic pyroclastic flow from summit dome |
1508'00'' |
12022'00'' |
X |
x |
X |
|
x |
|
|
|
62.0 |
|
Buag |
570+-70 |
P17D |
Clark A.B., |
8 |
Phenocryst-rich dacite pumice from terrace deposit |
1508'42'' |
12033'24'' |
X |
x |
X |
r |
x |
|
|
|
65.7 |
|
Buag |
950+-70 |
P22592-2A |
Pasig River |
15 |
Dacite pumice in dated "gray lahar" |
1507'56'' |
12028'59'' |
X |
S |
X |
r |
X |
|
|
|
65.5 |
|
Buag |
950+-70 |
P22592-2B |
Pasig River |
15 |
Dacite pumice in dated "gray lahar" |
1507'56'' |
12028'59'' |
X |
S |
X |
r |
x |
|
|
|
65.2 |
|
Buag |
950+-70 |
P22592-1 |
Pasig River |
15 |
Banded pumice from dated "gray lahar" |
1507'56'' |
12028'59'' |
X |
x |
X |
r |
x |
x |
x |
|
|
|
Buag |
950+-70 |
P22592-3 |
Pasig River |
15 |
Banded pumice from dated "gray lahar" |
1507'56'' |
12028'59'' |
X |
S |
X |
r |
x |
x |
x |
|
63.6 |
|
Buag? |
|
P22592-3- |
Pasig River |
-- |
Mafic inclusion in pumice. Not in place, possibly from "gray lahar." |
1507'56'' |
12028'59'' |
S |
s |
s |
|
|
s |
s |
|
52.0 |
|
Buag? |
|
P5C |
Marella River |
-- |
Pumice from deposit beneath summit dome pyroclastic flow? |
1505'00'' |
12020'00'' |
X |
s |
X |
r |
X |
|
|
|
65.8 |
|
Buag? |
|
P40-ii |
Marella River |
-- |
Mafic inclusion in dacite block. Deposit forms fluvial |
1508'00'' |
12030'00'' |
no thin section |
53.8 |
|||||||
|
Buag? |
|
P40-i |
Marella River |
-- |
Dense dacite, host for inclusion |
1515'00'' |
12022'00'' |
X |
S |
X |
|
x |
h |
t |
|
63.6 |
|
Maraunot |
2,660+-70 |
P3792-3 |
Clark A.B., near TV tower. |
18 |
Pumice lapilli in dated terrace deposit |
1511'18'' |
12030'20'' |
X |
s |
X |
R |
c |
|
|
|
65.8 |
|
Maraunot |
2,870+-100 |
P3592-1A |
O'Donnell River |
22 |
Phenocryst-rich dacite pumice from upper of 3 pyroclastic-flow deposits. |
1516'00'' |
12022'00'' |
X |
s |
X |
R |
x |
|
|
|
62.5 |
|
Maraunot |
2,870+-100 |
P3592-1B |
O'Donnell River |
22 |
Phenocryst-poor dacite pumice from upper of 3 pyroclastic-flow deposits. |
1516'00'' |
12022'00'' |
B |
b |
b |
r |
|
|
|
|
62.5 |
|
Maraunot |
2,870+-100 |
P3592-1C |
O'Donnell River |
22 |
Darker, fine-grained pumice from upper of 3 pyroclastic-flow deposits. |
1516'00'' |
12022'00'' |
X |
s |
X |
R |
x |
|
|
|
63.4 |
|
Maraunot |
2,990+-80 |
P2Bi |
Sacobia River |
29 |
Phenocryst-rich dacite pumice from dated pyroclastic-flow deposit. |
1511'00'' |
12030'00'' |
X |
s |
X |
Rx |
X |
|
|
|
65.6 |
|
Maraunot |
2,990+-80 |
P2Bii |
Sacobia River |
29 |
Phenocryst-poor dacite pumice from dated pyroclastic-flow deposit. |
1511'00'' |
12030'00'' |
B |
b |
b |
t |
t |
|
|
|
64.2 |
|
Maraunot |
3,260+-70 |
P3592-2A |
O'Donnell River |
31 |
Phenocryst-rich dacite pumice from middle of 3 pyroclastic-flow deposits. |
1516'00'' |
12022'00'' |
X |
s |
X |
t |
t |
|
|
|
65.5 |
|
Maraunot |
3,260+-70 |
P3592-2B |
O'Donnell River |
31 |
Phenocryst-poor dacite pumice from middle of 3 pyroclastic-flow deposits. |
1516'00'' |
12022'00'' |
B |
b |
B |
t |
|
|
|
|
64.9 |
|
Maraunot |
3,260+-70 |
P3592-2C |
O'Donnell River |
31 |
Darker, fine-grained pumice from middle of 3 pyroclastic-flow deposits. |
1516'00'' |
12022'00'' |
X |
s |
X |
|
|
t |
|
|
62.1 |
|
Maraunot |
3,260+-70 |
P3592-2Fi |
O'Donnell River |
31 |
Mafic inclusion in phenocryst-rich dacite pumice from |
1516'00'' |
12022'00'' |
X |
|
X |
|
|
h |
|
|
57.2 |
|
Maraunot |
3,390+-90 |
P11 |
Sacobia River |
32 |
Phenocryst-rich pumice from pyroclastic-flow deposit |
1511'00'' |
12029'36'' |
X |
s |
X |
R |
t |
|
|
|
66.1 |
|
Maraunot |
3,590+-90 |
P39A |
Marella River |
33 |
Phenocryst-rich pumice from pyroclastic-flow deposit |
1505'00'' |
12020'00'' |
X |
s |
X |
|
t |
h |
|
|
62.8 |
|
Maraunot |
3,590+-90 |
P39B |
Marella River |
33 |
Dense phenocryst-rich dacite lithic from pyroclastic-flow deposit. |
1505'00'' |
12020'00'' |
X |
s |
X |
R |
c |
|
|
|
66.3 |
|
Maraunot |
>1,000 |
P3792-2a |
Clark A.B., |
-- |
Pumice lapilli from tephra fall deposit, weathering suggests >1,000 yr B.P. |
1511'18'' |
12030'20'' |
X |
s |
X |
R |
|
|
|
|
|
|
Crow Valley |
4,800+-60 |
P12A |
Sacobia River |
35 |
Dacite pumice from terrace deposit |
1511'00'' |
12030'00'' |
X |
S |
X |
R |
t |
|
|
|
64.9 |
|
Crow Valley |
4,800+-60 |
P12B |
Sacobia River |
35 |
Phenocryst-rich dacite pumice from terrace deposit |
1511'00'' |
12030'00'' |
X |
t |
X |
r |
c |
|
|
|
|
|
Crow Valley |
4,890+-70 |
P22392-4 |
Sacobia River |
37 |
Dacite pumice from base of dated pyroclastic-flow deposit |
1510'55'' |
12028'55'' |
X |
s |
X |
R |
|
|
|
|
65.6 |
|
Crow Valley |
4,960+-70 |
P31B |
O'Donnell River |
39 |
Dacite pumice from pyroclastic-flow deposit |
1514'54'' |
12022'00'' |
no thin section |
65.6 |
|||||||
|
Crow Valley |
4,930+-80 |
P3592-3A |
O'Donnell River |
38 |
Phenocryst-rich dacite pumice from lower of 3 pyroclastic-flow deposits. |
1516'00'' |
12022'00'' |
X |
|
X |
R |
|
|
|
|
65.1 |
|
Crow Valley |
4,930+-80 |
P3592-3B |
O'Donnell River |
38 |
Phenocryst-poor dacite pumice from lower of 3 pyroclastic-flow deposits. |
1516'00'' |
12022'00'' |
B |
B |
b |
b |
t |
|
|
|
65.6 |
|
Crow Valley |
5,010+-80 |
P32B |
O'Donnell River |
40 |
Dacite pumice from thick pyroclastic flow on north side of drainage. |
1514'48'' |
12021'48'' |
X |
|
X |
R |
|
|
|
|
65.9 |
|
Crow Valley |
5,100+-70 |
P31A |
O'Donnell River |
42 |
Dacite pumice from pyroclastic-flow deposit |
1514'54'' |
12022'00'' |
X |
s |
X |
r |
t |
|
|
|
65.6 |
|
Crow Valley |
5,130+-80 |
P41B |
Bucao River |
43 |
Dacite pumice from lahar, 14C age on interbedded silt |
1515'42'' |
12010'06'' |
X |
s |
X |
|
t,c |
|
|
|
63.4 |
|
Pasbul |
8,380+-80 |
P42 |
Gumain River |
48 |
Dacite pumice |
1502'03'' |
12027'02'' |
X |
|
X |
t |
c |
|
|
|
63.9 |
|
Inararo |
>35,000 |
P31392-1 |
Abacan River |
51 |
Phenocryst-rich pumice from eroded pyroclastic-flow deposit. |
1510'25'' |
12029'50'' |
X |
S |
X |
|
X |
|
|
|
66.7 |
|
Inararo |
>35,000 |
P-1-16i |
Abacan River |
51 |
Dacite pumice lapilli from matrix of columnar-jointed pyroclastic-flow deposit. |
1511'00'' |
12030'00'' |
X |
Xs |
X |
R |
X |
|
|
|
64.4 |
|
Inararo |
>35,000 |
P-1-16ii |
Abacan River |
51 |
Dacite pumice block from columnar-jointed pyroclastic-flow deposit. |
1511'00'' |
12030'00'' |
X |
Sx |
X |
R |
X |
|
|
|
65.8 |
|
Inararo |
>35,000 |
P24D |
Abacan River |
-- |
Dacite pumice block from basal lahar or pyroclastic-flow deposit in Abacan River. |
1511'00'' |
12030'00'' |
X |
Xs |
X |
|
X |
|
|
|
67.1 |
|
Inararo |
>35,000 |
P44 |
Abacan River |
-- |
Indurated tuff at base of sequence in Abacan River |
1511'00'' |
12030'00'' |
X |
s |
X |
|
x |
t |
|
|
64.4 |
|
Ancestral |
|
P34 |
Pasig River |
-- |
Dominant lithic type from indurated lahar |
1508'00'' |
12030'00'' |
X |
|
X |
|
|
|
|
x |
66.0 |