Field Report

FIELD REPORT IN ILOCOS SUR

Submitted by: Angelika C. Mandig 201312449 Submitted to: Ms. Karla Navarro Professor

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TABLE OF CONTENTS TITLE PAGE TITLE PAGE

1

TABLE OF CONTENTS ABSTRACT

2

3

INTRODUCTION

4

REVIEW OF RELATED LITERATURE A. B.

REGIONAL GEOGRAPHY

6

REGIONAL GEOLOGY AND TECTONIC SETTING 7

DISCUSSION AND INTERPRETATION 8 CONCLUSION

10

REFERRENCE

11

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ABSTRACT This field report aims and main purpose is to familiarize students with the basic technique in Field Methodology and be able to apply knowledge in basic principles of Historical Geology. The province of Sulvec, Narcavan falls within latitudes 16° 40’ to 17° 54’ north and longitudes 120° 20’ to 120° 56’ east. The participants were divided into groups and were assigned to each designated area to observe and study. With this, students were able to perform task more efficiently and fast. Upon correlating results gathered, the following geologic events took up the whole outcrop: deposition of different sedimentary rocks, intrusion of igneous rocks, tilting of the rock layes, attaching of corals to the deposition area, uplifting and lastly the formation of corals into carbonates.

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INTRODUCTION The fieldwork was conducted as a part of requirement in the subject Field Methodology. The main purpose of this is to expose the students with different properties of different rocks and apply knowledge on certain historical geology principles and aims to familiarize the students with the basics of field observations and field methodology. The fieldwork was conducted in Ilocos Sur, in Ilocos Region, Philippines from the day of 26 to 28 of February in the year 2016. Students of BS Geology who are participant in the said fieldwork were divided into 13 groups having 5 members each. The groups were then assigned into their own outcrop designation and were instructed to observe and study it. Each group has different vicinity and has a task needed to accomplish. The participants observed their area and was able to gather rock samples and information. Topics from historical geology covers and can be apply in the work of the students such as; the law of superposition, which was applied when determining which of the rock sequence is older or younger; the law of intrusion, which was used in determining the relative age of an intrusive body between rock layers; and the law of intrusion which was used when determining to which rock body is older in a strata given that there is an intrusion happened. The main outcrop is located Narvacan, province of Ilocos, Sur in the Philippines and bears the coordinates: 17.450759, 120.433355. It is located beside the highway and exactly on the seashore facing the sea. The four hundred and five km distance of Manila to Ilocos Sur can reach by either land travel or air travel. There is an extensive road network that leads to the province from various parts of Luzon. There are 4 | Page

several bus lines that ply the Manila to Ilocos route. These are: The Philippine Rabbit us Line, Partas Co., GV Florida Transit, Farinas Transit and Dominion. When travelling by plane, you can take a flight from Manila to Laoag via Cebu Pacific or Philippine Airlines. Travel time by air is about an hour and 1011 hours by land via public transport and 8 hours by private car along Manila to Ilocos Highway. Paraiso Ni Juan is located in Narcavan, Ilocos Sur. When travelling by land, take a bus that is Laoag-bound then inform the conductor to drop you off to Sulvec Point (Paraiso Ni Juan). Accompanied by their professor geologist Ms. Karla Navarro and Mr. JV Umali and other instructor, the main goal of the fieldwork was successfully accomplished. Students were able to learn and correlate possible succession of events due to evidences found.

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REVIEW OF RELATED LITERATURE A. REGIONAL GEOGRAPHY The Philippines is an archipelago that consist 7,107 islands with a total land area of 300,000 square kilometers (115,831 sq mi). The islands are divided into three groups: Luzon, Visayas, and Mindanao.

The largest of these islands is

Luzon at about 105,000

square kilometers (40,541 sq mi). The next largest island is Mindanao at about 95,000 square kilometers (36,680 sq mi). The Philippines has a tropical wet climate dominated by a rainy season and a dry season. Philippines is divided into 18 regions (17 administrative and 1 autonomous). Region I, otherwise known as the Ilocos Region, is composed of four (4) provinces – Ilocos Norte, Ilocos Sur, La Union and Pangasinan – and nine (9) cities – Laoag, Batac, Candon, Vigan, San Fernando,

Dagupan,

San

Carlos,

Alaminos,

and

Urdaneta.

The

provinces have a combined number of one hundred twenty five (125) cities and municipalities and three thousand two hundred sixty five (3,265) barangays. Region I is situated in the northwestern part of Luzon with its provinces stretching along the blue waters of West Philippine Sea. Bounded on the North by the Babuyan Islands, on the East by the Cordillera Provinces, on the west by the West Philippine Sea, and on the south by the provinces of Tarlac, Nueva Ecija and Zambales. It falls 6 | Page

within 15°00’40” to 18°00’40” North Latitude and 119°00’45” to 120°00’55” East Longitude. The region’s territorial jurisdiction occupies an aggregate area of 1,284,019 hectares with the Province of Pangasinan having the largest land area of 536,818 hectares followed by the Province of Ilocos Norte with 339,934 hectares, the Province of Ilocos Sur with 257,958 hectares and the Province of La Union with 149,309 hectares.

B. REGIONAL GEOLOGY AND TECTONIC SETTING Ilocos Sur contains many geological formations including the Suyo Schist, Ilocos Peridotite,

Bangui Formation, Magabbobo

Limestones, Bojeador Formation, Dagot Limestone, Pasaleng Quartz Diorite, Batac Formation, Pasuquin Limestone, Laoag Formation, and Uplifted Coral Reefs. Ilocos Basin is characterized with a thick (8,000 m) sedimentary sequence (Saldivar-Sali, 1978), the Ilocos- Central Basin flanks western Luzon Island along a generally N-S axis. The northern part of the basin (Ilocos) is filled with Upper Oligocene - Middle Miocene

marine

detrital

sediments

(mostly

conglomerates

and

sandstones) derived from the Luzon Central Cordillera Range located to the east. These sediments are overlain by an Upper Miocene - Pliocene sedimentary sequence dominated by sandstones, shales and shallow water carbonates and tuffaceous deposits. On the southern part, the eastern

and

western

flanks

of

the

central

Luzon

Basin

are

stratigraphically distinguished from each other. Sediments on the east are characterized by a significant amount of volcanic sources (volcanic sandstones and shales, tuffs) and by a shallow marine depositional environment (carbonates). To the west, Neogene sediments dominated by Middle Miocene Turbities ovelie directly the Eocene ophiolites of 7 | Page

Zambales. The Ilocos - Central Luzon Basin is structurally controlled by main branches of the northern segment of the Philippine Fault, notably the Vigan- Aggao Fault (Maleterre, 1989; Pinet, 1990)

METHODOLOGY Ilocos Sur province a province of the Philippines located in the Ilocos Region in Luzon. It is bordered by Ilocos Norte and Abra to the north, Mountain Province to the east, La Union and Benguet to the south, and the South China Sea to the west. The province falls within latitudes 16° 40’ to 17° 54’ north and

longitudes

20’ to 120° 56’

east.

120°

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Figure 1.Ilocos Sur Map

Travel time by air is about an hour, 10-11 hours by land via public transport and 8 hours by private car along Manila to Ilocos Highway. Paraiso Ni Juan is located in Narcavan, Ilocos Sur. The climate is generally dry as defined by the Hernandez climate classification - the dry months are from October to May. However, the southernmost portion, Cervantes, is humid and rain is evenly distributed throughout the year while the eastern part of Sugpon is drier. August has the most rainfall while January and February have the least. The mean temperature in the province is 27 degrees C. January is the coldest. Upon reaching the outcrop in Paraiso Ni Juan near Sulver Point, the students were then started studying and observing each designated area. Students collected samples/evidences that would help them identify which body of rock deposited and which comes next and so on. After collecting samples, the students then now started comparing and describing each samples with their physical appearance. Identifying wheater the rock is an igneous or sedimentary rock follows respectively. After completing the task of observing and gathering data in each respective area. The students were gathered again as a class to finally put a depth analysis and have a discussion in the historical geology of the area.

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DISCUSSION AND INTERPRETATION The outcrop is mainly composed of sedimentary rocks which are siltstones, mudstones, and sandstones that is theorized from a section in Ilocos- Basin stating that sediments present in some sedimentary layer and for the whole area are derived from the Luzon Central Cordillera that is located to the east. Also, intrusion of igneous bodies which are andesite, basalts, and diorites was seen in the outcrop. The intrusion was continuous into the different areas of the outcrop that is why some groups were able to see it. With this, we can conclude that there was a volcanic and magmatic activity undergone in the vicinity causing the intrusion of igneous body to the sedimentary sequence happen. Students specifically from Groups I and II were able to observe the presence and deposition of mudstones, sandstones and later siltstones

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which was followed by geologic processes such as tilting, intrusion, erosion and formation of corals. On the part where Group I where assigned they were able to observe that a basaltic rocks are at the bottom and were overlain by andesite that is overlain by another basaltic body, overlain by formation of reefal limestones and finally a layer of diorite on top of the sequence. A possible explanation for this is that the Basaltic rocks were the first one to form and it was intruded by an andesite at its center part which explains the basaltic rocks beneath and above it, after the intrusion, reefal limestones formed and was overlain by a layer of dioritic rocks. Group II has also the same observation.

Figure 1.Body Unit ABC, a part of the outcrop from Group II

Figure 2. Body Unit C,D, a part of the outcrop from Group II

Figure 3. Body Unit D,E, a part of the outcrop from Group II

The following groups were able to observed and seen evidence of the following series of events: deposition of siltstone, deposition of sandstones and intrusion of andesite, and lastly the formation of carbonates. The body of the igneous rocks is an intrusion, proving this is the contact between the two beds of sedimentary rock and the charred part present on the upper part and lower part of the contact. Also, a contact with carbonates with an igneous rock was also seen, seeing that carbonates filled the outer spaces and holes of the igneous rock proves that carbonates formed last.

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Figure 4. Contact of carbonates and igneous rock

Student in Group

V and VII follows the same trend with previous groups. According to observations of this group in their designated area, the siltstone was at the bottom of the rock layering and then followed by sandstones, and was then intruded

by

andesites

the formation of

and

carbonate rocks.

.

Observations

Figure 5. Intrusion of Andesite

from

the

succeeding

groups observed and showed a body of sedimentary rock which is sandstone at the base of the outcrop first to deposit followed by andesite which is igneous rock and finally followed by a sedimentary rock limestone on top of it all.

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Figure 6. Sequence of sedimentary rock (sandstone), igneous rock (andesite) followed by sedimentary rock again (limestones).

CONCLUSION The outcrop is a part of the Ilocos Basin in Ilocos Region, Philippines with sediments originated from Luzon Central Cordillera range. Upon correlating the data and information gathered by the 13 groups of BS Geology and with the help of readings in book Geology of the Philippines it is therefore concluded that the deposition of outcrop in Paraiso Ni Juan, Brngy. Sulvec, Narvacan Ilocos Sur was the deposition of sediments in Ilocos Basin. The outcrop also undergone geologic processes such as tilting and the layers are reversed, coarser sedimentary rock layers are on top of the outcrop and 13 | P a g e

finer ones are on the bottom. After the deposition of sedimentary rocks, an intrusion of magma took up next. The intrusion are very visible in some parts of the area, because of the different cooling it formed two different igneous rocks which are andesite and diorite. Another sedimentary rock was formed when the coral reefs started to attach itself to the deposition and then when the outcrop was uplifted the coral reefs were then started to form as a carbonates and then into limestones.

REFERENCES: Websites http://denr-mgb1.org/pdf/2014/NARRATIVE%20REPORT.pdf http://www.ilocossur.gov.ph/index.php? option=com_content&view=article&id=82&Itemid=248 http://www.islandsproperties.com/maps/ilocossur.htm http://onlinelibrary.wiley.com/doi/10.1029/2006JB004506/full https://www.researchgate.net/profile/Nicolas_Pinet/publication/239730442_Pi net_N_Stephan_JF_The_Ilocos_Foothills_and_western_Central_Cordillera_a_key _region_for_the_understanding_of_the_geodynamic_evolution_of_the_eastern 14 | P a g e

_eurasian_margin_in_Luzon_area_Philippines_In_Tecton/links/00b7d51c205ac 74f3f000000.pdf http://geology.utah.gov/map-pub/survey-notes/glad-you-asked/igneoussedimentary-metamorphic-rocks/ https://www.msnucleus.org/membership/html/k-6/rc/rocks/3/rcr3_1a.html

PDF Files Geology of the Philippines http://dhsprogram.com/pubs/pdf/fr01/01chapter01.pdf

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