A Re-Evaluation of the Cenozoic Stratigraphy and Paleontology
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GEOCON 2019: Geoscience for a resilient and sustainable Philippines R. N. de Lara*, E.Y. Mula**, and M.A. Zepeda, D. Sc.* *General Geology Section and ** Geological Laboratory Services Section, Lands Geological Survey Division, Mines and Geosciences Bureau 1 • Introduction • Statement of the Problem • Significance of the Study • Objectives • Methodology • Conceptual Framework • Results and Discussion • Conclusion and Recommendation GEOCON 2019: Geoscience for a resilient and sustainable 2 Philippines Introduction BACKGROUND OF THE STUDY • Cenozoic Stratigraphy Project of the Philippines (research component of the National Geological Mapping Program) - Stimulated by the demand for precise geologic maps - Highlights the role of paleontology and other basic science researches in enhancing Quadrangle Geological Mapping - Way of addressing popular defects in the existing geologic maps through long-term mapping and rock sample analysis GEOCON 2019: Geoscience for a resilient and sustainable Philippines 3 Introduction • Central Luzon Basin - filled with 8,000 meters thick sedimentary sequence (Saldivar-Sali, 1978) - Structurally controlled by the major branches of the northern segment of the Philippine Fault (Vigan-Aggao Fault) (Maleterre, 1989; Pinet, 1990) GEOCON 2019: Geoscience for a resilient and sustainable Contour interval: 500 m, eliminating valleys less than 2.5 km across; solid lines are major fault trace of Philippines the Philippine fault after Allen (1962). (Retrieved from “A Report on Tectonic Landforms along the Philippine Fault Zone in the Northern Luzon Philippines by Nakata et al., 1977) 6 Introduction • Location of the study area - Sta. Ignacia Quadrangle, Tarlac Province - Covers the municipalities of Santa Ignacia and Mayantoc, and portions of San Jose, Camiling, and San Clemente GEOCON 2019: Geoscience for a resilient and sustainable Philippines 7 N/P DE LEON AND MILITANTE- AGE DIVINO-SANTIAGO (1963) PEÑA (2008) ZONES MATIAS (1992) Statement of the HOLO. N23 PLEISTO. N22 Problem N21 L N20 E N19 Tarlac Formation PLIOCENE N18 Tarlac Formation Previous workers on N17 L Tarlac Formation Malinta Formation the stratigraphic N16 Malinta Formation N15 sequence of western N14 N13 M N12 Central Luzon Basin MIOCENE Malinta Formation N11 Moriones Formation Moriones Formation had conflicting age N10 assignments of four (4) N9 N8 Moriones Formation sedimentary units, N7 E N6 namely, Aksitero, N5 N4 L P22/N3 Moriones, Malinta, and NE P21/N2 Tarlac formations M OLIGOCENE P20/N1 E P18/19 Aksitero Formation P17 GEOCON 2019: Geoscience for a resilient and sustainable Philippines L P16 8 P15 P14 P13 M P12 EOCENE P11 P10 P9 P8 E P7 P6 Significance of the Study The results of this study would serve as a new source of information and refinement of the Cenozoic stratigraphy of Sta. Ignacia Quadrangle. Moreover, this would be of immense help to future researchers in reconstructing and understanding the geologic history of the area. GEOCON 2019: Geoscience for a resilient and sustainable 9 Philippines Objectives This study mainly focuses on the re-evaluation of the age and stratigraphic relationships of these formations based on fossil evidence GEOCON 2019: Geoscience for a resilient and sustainable 10 Philippines Methodology 1. Data Compilation 2. Base Map Generation 3. Field Investigation and Sampling 4. Laboratory Analysis 5. Data Synthesis GEOCON 2019: Geoscience for a resilient and sustainable Philippines 11 Conceptual Framework SAMPLE PALEONTOLOGICAL SAMPLING PREPARATION ANALYSIS • Collection of sedimentary • Samples submitted to the • Picking of fossils samples (logging of laboratory for washing, • Identification of fossils coordinates, description, polished blocks, or thin • Age and Paleoenvironment proper labeling) section DATA FIELD RE-EVALUATION OF THE COMPILATION INVESTIGATION CENOZOIC STRATIGRAPHY OF STA. IGNACIA • Review of Related QUADRANGLE Literature • Base map Generation LITHOLOGIC DATA MAPPING INTEGRATION LITHOLOGIC DESCRIPTION • Integrating the gathered • Lithological characteristics field data into the initial • Megascopic analysis geologic map based on field • Sedimentary structures validation results • Fossils present GEOCON 2019: Geoscience for a resilient and sustainable 12 Philippines GEOCON 2019: Geoscience for a resilient and sustainable 13 Philippines Results and Discussion • Lithology a b AKSITERO FORMATION - Oldest sedimentary formation considered as the carapace of the Zambales Ophiolite - Pale yellow to yellowish-white fine-grained limestone (MYWell--MBbedded,-003).indurated,(a) Highlycalcareous,indurated, wellgreenish-bedded,siltstonefossiliferouswithin thelimestoneBarangaywhichBigbigaextends, Mayontocapproximately. It is probably30 metersalso partwithinof GEOCON 2019: Geoscience for a resilient and sustainable Barangaythe AksiteroBigbigaFormation, Mayontoc(GPS.: TheN15°limestone31’57.7”/Eunit120°striking22’27.6”)NE. and dipping SE is probably the lower Bigbiga Limestone unit Philippines of the Aksitero Formation (GPS: N15°32’8.8”/E120°22’25.4”). (b) Closer view of the fossiliferous limestone of the Aksitero Formation. 14 Results and Discussion • Lithology MORIONES FORMATION - Unconformably overlying Aksitero Formation - Interbedded sandstone, shale, Sandstone and conglomerate with minor limestone (CM-KBCA-001). An outcrop of thick conglomerate cropping out within the rough road of Barangay Maasin, San (TAR(SI-BIG-KA--17003B)).ASedimentarynewly exposedsequenceexcavatedobservedpotion innearSansoterothe piggeryshowingBrgy.alternatingBigbiga, Mayantocthin to medium, Tarlac consistingbeds of of (TARClemente-BIG-22. ItB)consistsAn interlayeringchiefly ofofgrayish,sandstone,pebblesiltstone,to cobble,and angularshale intoansuboutcroproundedseenclastsalongofthewellriverbankinduratedof fineBayating- graytuffaceous-colored fossiliferoussiltstone andshalesandstone. (GPS N 15topped° 30' 37by.879a "conglomerateE 120° 23' 5.506bed").. The conglomerate is composed of GEOCON 2019: Geoscience for a resilient and sustainable Rivergrainedsandstonein Brgysandstone. Bigbigamatrixin, Mayantocaandbrownish,limestone, Tarlacsilty,clasts.sheared(GPS. TheNmatrix15beds° 31strike(GPS' 22.789:NN40"15EW°39120and’28° .23dip5”/E' 2611120.NE904°19.")(GPS’.53.9”)N. 15⁰ 31’ 37.20” E 120⁰ Philippines 24’ 28.80”) 15 Results and Discussion • Lithology MALINTA FORMATION - Conformably overlies the Moriones Formation - Interbedded sequence of well-bedded, fine- to coarse- grained lapilli tuff, shale, sandstone, and minor tuffaceous conglomerate An outcrop located in Purok 1 of Barangay Maminyog in the Municipality of Mayantoc. The upper portion consists (TARThin -bedBR-of13siltstone) Thin bedinterbeddedof siltstonebetweeninterbeddedtwo sandstonebetweenbedstwo. Thesandstonebeddingbedsplanes. ThearebeddinggenerallyplanesstrikingareN15generallyE and of friable tuffaceous sandstone while the lower portion is made up of highly indurated tuffaceous sandstone. (GPS dippingstriking 50N15NWE .and(GPSdippingN 15⁰5033NW’ 50. .(GPS40” EN12015⁰⁰2633’’ 2050..4040”)” E 120⁰ 26’ 20.40”) GEOCON 2019: Geoscience for a resilient and sustainable N 15⁰ 35’ 38.40” E 120⁰ 21’ 7.20”). Philippines 16 Results and Discussion a • Lithology b TARLAC FORMATION - Conformably overlies the Malinta Formation - Thinly stratified, calcareous, light gray to greenish gray shale and sandstone - Most widespread sedimentary rock in the study area (a) An(a) 3Bed-m highof granule outcrop- to locatedpebble-sized in Brgytuffaceous. Timmaguabsandstone, Sta.approximately Ignacia, Tarlac50 meters (GPSaway N 15from° 34'Piglos 28.288"River .E GEOCON 2019: Geoscience for a resilient and sustainable (b) Closer view of the sandstone sample (GPS N 15⁰ 34’ 13.394” E 120⁰ 27’ 27.678”) 120° 26' 16.009"). Philippines (b) Closer view of the outcrop: 1- fine-grained sandstone; 2- shale; 3 - coarse-grained sandstone 17 N/P AGE Fossil Assemblage ZONES MY-MB-003 Globorotalia opima nana opima Globorotalia tripartita Globigerina HOLO. N23 • PLEISTO. Aksitero Formation N22 N21 Sample MY-MB-003 L N20 E N19 PLIOCENE N18 N17 - Highly indurated, well- L N16 bedded, fossiliferous limestone N15 N14 (striking NE and dipping SE) N13 M N12 MIOCENE extending approximately 30 N11 N10 meters in Brgy. Bigbiga, N9 N8 1 mm Mayantoc, Tarlac Globorotalia opima nana N7 E N6 N5 Globogerina tripartita Globogerina tripartita Presence of: N4 L NE P22/N3 ✓ Globorotalia opima nana P21/N2 M ✓ Globogerina tripartita OLIGOCENE P20/N1 E P18/19 P17 L P16 GEOCON 2019: Geoscience for a resilient and sustainable 1 mm P15 0.5 mm Philippines P14 18 P13 M P12 EOCENE P11 P10 P9 P8 E P7 P6 Fossil Assemblage N/P AGE ZONES SI-KA-003 Orbulina universa Orbulina trilobus Globigerinoides globosa Globoquadrina dehiscens Globoquadrina HOLO. N23 PLEISTO. • Moriones Formation N22 N21 Sample SI-KA-003 L N20 E N19 PLIOCENE N18 - Alternating thin to medium N17 L N16 beds of tuffaceous siltstone and N15 sandstone (striking N40W and N14 N13 M N12 dipping 11NE) overlain by a MIOCENE N11 N10 conglomerate bed (limestone N9 clasts set in a sandy matrix) N8 N7 Orbulina universa Globoquadrina sp. E N6 N5 Presence of: N4 L NE P22/N3 ✓ Orbulina universa P21/N2 M ✓ Globogerinoides trilobus OLIGOCENE P20/N1 ✓ Globoquadrina globosa E P18/19 GEOCON 2019: Geoscience for a resilient and sustainable P17 20 Philippines ✓ Globoquadrina dehiscens L P16 P15 P14 P13 M P12 EOCENE P11 P10 P9 P8 E P7 P6 Fossil Assemblage N/P AGE ZONES CM-KBCA-001 Globigerinoides trilobus Globigerinoides globosa Globoquadrina • Moriones Formation universa Orbulina HOLO. N23 PLEISTO. Sample CM-KBCA-001