|
Klondyke Formation | |
|
Lithology |
Lower member - Polymictic conglomerates Upper member – Sandstone, mudstone, shale with minor conglomerate, limestone, calcarenite and calcirudite |
|
Stratigraphic relations |
Unconformably overlies the Kennon Limestone in the Baguio District and grades at the top into the Amlang Formation; overlain concordantly by the Mirador Limestone |
|
Distribution |
Baguio District; Itogon, Benguet |
|
Age |
late Middle Miocene to early Late Miocene |
|
Thickness |
2,820 m at the type locality; up to 3,500 for the Marcos Highway section |
|
Previous Name |
Klondyke Series (Leith, 1938) |
|
Renamed by |
Balce and others (1980) |
|
Synonymy |
Suyoc Conglomerate (Gonzales, 1956) |
The Klondyke Formation, previously designated as Klondyke Series by Leith (1938), is a thick sequence of clastic sedimentary rocks consisting mainly of polymictic conglomerates with interbedded sandstones, siltstones, shales and occasional limestone lenses and in places intercalated with flow breccias and pyroclastic rocks. Clasts of the conglomerate consist of volcanic rocks and quartz diorite as well as sedimentary rocks, including limestone fragments. Some of these clasts attain boulder-size dimensions.
The Klondyke Formation rests unconformably over the Kennon Limestone at Bued River and Kennon Road (Km. 225) near the Klondyke Hot Springs, from where the formation obtained its name. The Kennon Road section traverses the formation downdip up to Km. 216, at the La Union-Benguet provincial boundary, where it grades into the Amlang Formation. It is also well exposed along Marcos Highway and Asin road and has been mapped at such high elevations as Mt. Santo Tomas in Baguio City.
The Klondyke Formation is overlain concordantly by the Mirador Limestone along Marcos Highway near Tuba River, at Irisan along Naguilian Road and along Asin Road.
On the basis of their study of the Marcos Highway section of the Klondyke Formation, De Leon and others (1990) subdivide the formation into a lower member consisting mainly of massive to thickly bedded conglomerate with tuffaceous or calcareous matrix and an upper member consisting of mudstone-shale with sandstones and conglomerates as well as occasional thin beds of calcarenites and calcirudites and lenses of limestone.
On the other hand Balce and others (1980) subdivide the unit into tow intertonguing coeval units, distinguished by the predominance of conglomerate in one (Klondyke Conglomerate) and of pyroclastics in the othr (Pico Pyroclastics). The pyroclastics outcrop around Mt. Santo Tomas, in Pico area at Trinidad and other areas around Baguio City.
Estimates of the thickness of the formation vary from a low of 1,798 m (Balce and other, 1980) to a high of 3,500 m for the Marcos Highway section (De Leon and others, 1990).
On the basis of nannofossils obtained from samples along Marcos Highway, De Leon and others (1990) date the formation as Middle Miocene to early Late Miocen.
Polymictic conglomerates in the vicinity of Suyoc are probably correlative with the Klondyke Formation. These conglomerates with interbeds of alternating gray to black siltstones and sandstones were earlier defined as Suyoc Conglomerate overlying the volcaniclastics of the Balili Formation (Gonzales, 1956; Maleterre, 1989). The conglomerate contains well-rounded pebbles and cobbles of chert, epidotized volcanic rocks and intraformational limestone. However, Baker (1983) and Ringenbach (1992) regard the relationship between the conglomerate and volcaniclastics as intertonguing, and therefore the conglomerate is considered part of the Balili Formation. Nevertheless, the Suyoc Conglomerate could still be a distinct unit as indicated by its Middle Miocene dating.
Formation sequence
- Preceeded by - Itogon Quartz Diorite
- Succeeded by - Mirador Limestone