# Geochronological advances in human and proboscideans first arrival date in the Philippines archipelago (Cagayan valley, Luzon Island)

Jean-Baptiste Lambard, Alison Pereira, Pierre Voinchet, Herve Guillou, Marian Reyes, Sébastien Nomade, Xavier Gallet, Maricar Belarmino, Jean-Jacques Bahain, John de Vos, et al.

► To cite this version:

Jean-Baptiste Lambard, Alison Pereira, Pierre Voinchet, Herve Guillou, Marian Reyes, et al. Geochronological advances in human and proboscideans first arrival date in the Philippines archipelago (Cagayan valley, Luzon Island). Quaternary Geochronology, 2024, 84, pp.101597. 10.1016/j.quageo.2024.101597. hal-04675119

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# Geochronological advances in human and proboscideans first arrival date in the Philippines Archipelago (Cagayan Valley, Luzon Island)

Jean-Baptiste LAMBARD<sup>a*</sup>, Alison PEREIRA<sup>b</sup>, Pierre VOINCHET<sup>c</sup>, Hervé GUILLOU<sup>a</sup>, Marian C. REYES<sup>e</sup>,

Sébastien NOMADE<sup>a</sup>, Xavier GALLET<sup>c</sup>, Maricar BELARMINO<sup>d</sup>, Jean-Jacques BAHAIN<sup>c</sup>, John DE VOS<sup>g</sup>,

Christophe FALGUÈRES<sup>c</sup>, Andrea D. COSALAN<sup>f</sup>, Thomas INGICCO<sup>c</sup>.

a: Laboratoire des Sciences du Climat et de l'Environnement, UMR 8212 LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France.

b: UMR 8148 GEOPS, Université Paris-Saclay, Laboratoire GEOPS, F-91400 Orsay.

c: UMR 7194 HNHP, MNHN-CNRS-UPVD, ASU, Département Homme et Environnement, Muséum National d'Histoire

Naturelle, F-75013, Paris, France.

d: National Museum of the Philippines, Padre Burgos St., 1000, Manila, The Philippines.

e: Archaeological Studies Program, Albert Hall, University of the Philippines, Diliman, 1101, Quezon City, The Philippines.

f: University of the Philippines, Quezon Hall, UP Diliman, Quezon City, The Philippines.

g: National Museum of Natural History, Leiden, The Netherlands.

## Abstract :

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The Paleolithic site of Kalinga, in the Cagayan River Basin (Luzon Island), has recorded the oldest known traces of human occupation of the Philippine archipelago (709 ± 68 ka, Ingicco et al., 2018).

The island of Luzon is further known for its endemic Hominin *Homo luzonensis* (Callao cave) recently dated at 134 ± 14 ka, which makes it the oldest human remains in the Philippines.

The present study provides new chronological data on the Kalinga site and surrounding localities on the left bank of the Cagayan Valley and tackles the question over the geochronology of the human settlement of the basin. Following the discovery of some abundant paleontological remains and lithic artefacts on surface, several excavations took place since the 1970s. In 2014, new research in the area by our team on a site named Kalinga led to the recovery of hundreds of undisturbed archaeological remains (lithic tools and butchery marks). Apart from the early Middle Pleistocene ages obtained for the Kalinga site, the geochronology of the area is still largely unknown. Through the use of ESR on bleached quartz and ⁴⁰Ar/³⁹Ar single crystal laser fusion on plagioclase dating methods, the chronology of four archaeological sequences has been here constrained for the first time. Our results highlight a human occupation presence between 796 ± 70 ka and 273 ± 20 ka reducing the
31 chronological gap between Kalinga site and Callao Cave, placing the Cagayan basin as a cornerstone
to better understand the human arrival in insular Asia.
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34 **1. Introduction**

35 The most ancient human remains found on Luzon island in the Philippines, were discovered in 2007 in
36 Callao Cave, located on the eastern bank of the Cagayan River (Mijares et al., 2010) and have been
described as a new Hominin species, *Homo luzonensis* (Détroit et al., 2019). A recent study using the
uranium series concluded on a first appearance date (FAD) for the species of 134 ± 14 ka. (Grün and
39 Stringer, 2023).

40 More recently, archaeological discoveries evidenced that the Cagayan River Basin - one of the largest
41 geomorphological complexes of the island of Luzon - is further home to the earliest indirect evidence
42 of Hominin presence in the Philippine archipelago (Innicco et al., 2018). This basin is wedged between
43 two volcanic arcs, namely the Sierra Madre to the east and the Cordillera Central to the west
44 (Dickinson, 1974; Aurelio et al., 2013). The five anticlines enclosed between these two arcs are
45 coined, from west to east, Dagupan, Pangul, Cabalwan, Barung and Enrile (fig. 1b) (Mathisen and
46 Vondra, 1978; 1983). They are the result of tectonic compression of the Cagayan sedimentary basin.
47 The 900 m thick sedimentary sequence filling the basin up was divided into two formations, the Plio-
48 Pleistocene Ilagan Formation and the Pleistocene Awidon Mesa Formation (fig. 1b) (Corby, 1951;
49 Durkee and Peterson, 1961). The Awidon Mesa Formation, is 400 m thick and made up of three
50 lithofacies of various thicknesses: at the base, meandering alluvial deposits are intercalated with
51 volcanic tuff, then come anastomosing alluvial deposits interbedded with coarser pyroclastic
deposits, and finally lahars and ignimbrite deposits capping the sequence (Durkee and Peterson,
52 1961; Mathisen and Vondra, 1983). Fossils of now-extinct megafauna are common in this formation
53 and contributed to suggest a Pleistocene age for the Awidon Mesa deposits that also display
54 numerous tektites (Durkee and Peterson, 1961) belonging to the Australasian strewn field which has
55 been dated by $^{40}$Ar/$^{39}$Ar to 788 ± 3 ka (Jourdan et al., 2019).
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In the Kalinga area, at the southern tip of the Cabalwan Anticline, within the volcanic cross-bedded sands with intercalated silty layers (Mathisen, 1981; Innicco et al., 2018), the coexistence of this extinct megafauna (mainly proboscideans and rhinoceros) and early Hominins were suspected from surface archaeological findings first made in 1935 (Beyer, 1947; Von Koenigswald, 1958; Tobias, 1999). However, FAD and last appearance date (LAD) for the extinct mammalian taxa are still debated because of the lack of reliable and precise chronological control. Such control is of primary importance, considering reaching the island of Luzon always required crossing open sea straits, even during Quaternary glacial maxima with marine low stands (fig. 1a) (Past Interglacials Working Group of PAGES, 2016).

A butchered rhino carcass associated with a few stone artefacts excavated at the Kalinga site were chronologically constrained to 709 ± 68 ka by several absolute and relative methods applied on different materials sampled along the stratigraphic sequence: Electro-spin resonance (ESR) on optically bleached quartz, ESR/U-series on tooth enamel, $^{40}$Ar/$^{39}$Ar on plagioclase and paleomagnetism.

Additionally to the Kalinga site, three other localities located within a 500 m² area surrounding Kalinga (fig. 1c), have been excavated and delivered stone artefacts and faunal remains: Espinosa site (Fox, 1971; Fox and Peralta, 1974), Tusk site (Bautista and De Vos, 2000) and Clyde site (Jago-on, 2009). The vestiges were found both embedded in sediments at the surface. Unfortunately, unlike for Kalinga site, anthropogenic activity remains and faunal remains were not recovered in the same sedimentary layers.

A first attempt to date the Awidon Mesa Formation was made using $^{40}$K/$^{40}$Ar radioisotopic method in 1981 (Mathisen, 1981). Ages obtained were either too old (8.0 ± 4.1 Ma) or too young (close to modern times) compared to what one could expect on biochronological correlations with other Southeast Asian faunal records. More recently, $^{40}$Ar/$^{39}$Ar on hornblendes and OSL on feldspars methods were applied on sediments sampled along the southern tip of the Enrile anticline and permitted to attribute an age of at least 400 ka to an ignimbrite and a tuff layer (Jensen et al., 2010;
Liscaljet, 2012). The dated outcrop was yet barren of any paleontological and archaeological remains and the results are therefore of little use for constraining the biochronology of the region. The establishment of the chronological context of the Awidon Mesa Formation and more globally of the Cagayan Valley deposits, remains thus very challenging. The objective of the present contribution is to improve the current knowledge regarding the ages of the archaeological and paleontological remains excavated since the 1970s in the Kalinga area and thus to try to better understand and characterize the Hominin and Proboscidean presence during the Pleistocene.

Figure 1: a) Physiographic map of Southeast Asia with a sea level 110 m lower than present, approximating its configuration 790 ka ago (Past Interglacials Working Group of PAGES, 2016). b) Geological map of the central Cagayan basin region from (Mathisen, 1978; Durkee and Peterson, 1961) DTM from the SRTM NASA dataset 30 m resolution). c) Topography (DTM from the PHIL-LiDAR 2 Program 1 m resolution) and location of the Kalinga area sites and samples.

## 2. Material and Methods

The sedimentary filling of the Cagayan Basin is supposed to have come to a halt in the kalinga area as a consequence of tectonism leading to the folding of the basin (Mathisen, 1981). The chronological framework of the various sites of the Kalinga area is unclear giving the impossibility to correlate sites using common specific layer comparison between the lithic and faunal assemblages found within the alluvial sequence. To date these archaeological sites and relate them one to the others, we have used, whenever possible on the same layers, two distinct absolute dating methods, ESR on bleached quartz and ⁴⁰Ar/³⁹Ar on plagioclase. ESR on bleached quartz dates the last sunlight exposure of the alluvial quartz (i.e. depositions), while single crystal laser ⁴⁰Ar/³⁹Ar of volcanic feldspars could help grasp the youngest volcanic event recorded in the sediments. Such approach is complex in this sedimentological environment and required the specific sampling strategy detailed below.

### 2.1. Description of the sites and sampling strategy
We sampled four sequences that are: Espinosa, Tusk, Clyde, and Kalinga (fig. 1c). The stratigraphy of the four sequences is detailed in fig.3 and results from our own field observations and excavation reports archived at the National Museum of the Philippines. Sample locations (longitude, latitude and altitude) were then positioned on a Digital Terrain Model (DTM) generated from the PHIL-LiDAR 2 Program with a 1 m resolution. Overall, eleven samples were collected for ESR dating and three for ⁴⁰Ar/³⁹Ar age determination. The labelling of the samples refers to every site name, followed by the dating method and the number of the sample. As an example, sample ES-AR-1, come from Espinosa site (ES), has been dated by ⁴⁰Ar/³⁹Ar (AR) and was the first (1) sample collected at this site. Regarding the Kalinga site where various trenches were studied, the number of the sample is preceded by the Trench label (TH, TY, TJ).

2.1.1. Espinosa site (17°33'45.75"N, 121°33'20.12"E):

Espinosa site is located at about 400 m on the north-west from the Kalinga site (4 km west from Rizal municipality) (fig. 1b and c) and corresponds to the Espinosa Locality 4 site of Bondoc (1979), Fox (1971) and Fox and Peralta (1974).

The deposits that form a 12 m thick sequence (from 88 to 100 m a.s.l.) are mainly made of an alternance of silty and sandy layers (fig. 3). Six main sedimentary units were individualized from the base to the top of the sequence. Unit 1 corresponds to a 3 m thick layer of fine sand containing a silty lens; Unit 2 is a 70 cm thick layer of clays; Unit 3 corresponds to 1 m thick layer of fine to medium sands with alternating dark and light beds; Unit 4 is a 1.5 m thick level of intrusive sandy silt (seismite) (Fox and Peralta, 1974) ; Unit 5 corresponds to a 70 cm thick level of sands ; Unit 6 is a 5 m succession of thick lenses of fine sands constrained in between white silt layers.

Remains of a proboscidean were recovered from Unit 4 and two lithic artefacts interpreted as scrapers were recovered from Unit 6 during the 1970s excavations (Fox and Peralta, 1974).

Unpublished, the proboscidean remains correspond to several bones (ribs, vertebrae, femur). Based on the criteria listed by Wibowo (2016), the weak third trochanter as well as the straight lateral
margin of the femur's shaft would tentatively classify the specimen as *Elephas*. The specimen fits within the lower margin of the normal sized elephants (Inticco, in prep). Furthermore, we identified three potential striations on the anterior aspect of the distal diaphysis that could be interpreted as cutting marks based on their straight delineation and V-shaped profile. We suspect these marks were potentially intentionally made by some Hominins (fig. 2).

Figure 2: Elephas femur displaying cutmarks from the Espinosa site Unit 4 (Fox and Peralta, 1974).

Two samples of sediments were collected, one from Unit 1 (ES-ESR-1) with an auger, therefore preventing the in-situ measure of gamma spectrometry and, one from unit 6 (ES-ESR-2) were stored immediately in UV resisting bags. Additionally, one sample was collected for $^{40}$Ar/$^{39}$Ar from Unit 3 (ES-AR-1) (fig. 3). For $^{40}$Ar/$^{39}$Ar samples, sediments and a few felspar rich pebbles were collected whenever possible.

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145 **2.1.2. Tusk site (17°33'38.14"N, 121°33'33.20"E):**

The site is located 370 m southeast from Espinosa (fig. 1c). In April-May 2001, a Dutch-Filipino team opened two 4 m² excavation squares which delivered 11 proboscidean remains including a tusk, a rib, a vertebra along with seven carpal and metacarpal bones of what probably was a single individual of pygmoid size (Bautista and De Vos, 2000; Liscaljet, 2012), along with three stone flakes and a pebble.

Because these findings were excavated from the topsoil, the authors suggested that the contemporaneity of the fossils and artefacts could not be demonstrated (Bautista and De Vos, 2000).

Based on our observations, the Tusk site is a 3.2 m thick sequence from 91.0 to 94.2 m a.s.l., where we identified three distinct units that are from base to top (fig. 3): Unit 1, a 1.7 m thick of dull yellowish silts. We consider that this layer is the one described by the excavators as dull yellowish clay and underlying the topsoil from where the fossils were recovered (Bautista and De Vos, 2000). Unit 2 is a 80 cm thick layer of brown silty sands. We identify this layer as the same which further compose the topsoil described during the excavation and where the remains were found. Unit 3 is a 70 cm
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thick layer of fining upward coarse sand. One sample was collected with an auger for ESR at 93.0 m a.s.l in the Unit 2 (TU-ESR-1).

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### 2.1.3. Kalinga site (17°33′44.59″N, 121°33′35.20″E):

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Discovered in 2013, the Kalinga site is located 200 m north of Tusk site (fig. 1c). Since 2014, the Kalinga site has been yearly excavated by our international team. The site is divided into three trenches (H, J and Y) and one main excavation area. The sediments are volcanoclastic deposits reworked in a fluvial environment (Innicco et al., 2020). Sediments from Trench H and from the main excavation have been described by Innicco et al., (2018). They form a 7.5 m thick sequence. Unit A, the lowest, corresponds to an approximately 1 m thick layer showing a positive grading of sandy cross-bedded fluvial sediments with silty lenses. It has been dated at 727 ± 30 ka (Innicco et al., 2018). This layer is cut down by an erosive channel filled by a 3.25 m thick layer (Unit F). It corresponds to a mudflow that transported the remains of an almost complete (75 %) rhinoceros carcass bearing cutmarks. 57 stone artefacts and a few additional faunal remains were found in the same layer. On six taxa, four were described as endemic (*Cuora amboinensis* (Claude et al., in review), *Varanus cf. salvator*, *Cervus cf. mariannus*, *Nesorhinus philippensis* (Antoine et al., 2022), *Stegodon cf. luzonensis*). Unit F has been dated by ESR/U-series on rhino tooth at 709 ± 68 ka (Innicco et al., 2018).

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One australasian tektite suggesting a maximum age of 788 ± 3 ka (Jourdan et al., 2019) for this unit was also found. Moreover, Unit F is conformably overlaid by a 1 m thick horizontal coarse sandy to silty layer (Unit G). This layer has been dated by ESR at 701 ± 70 ka (Innicco et al., 2018). Lastly, the sequence is overtopped by a 2.5 m thick silty layer which includes a few sand lenses (Unit H). Another layer of sands was exposed on top of this one but only preserved in another Trench named Y and described herein after. On the Kalinga site a total of six new samples for ESR and two for ⁴⁰Ar/³⁹Ar were collected. The stratigraphic position of the ESR and ⁴⁰Ar/³⁹Ar samples are detailed below.

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**Borehole:** Two new layers were sampled with a borehole at the bottom of trench H (fig. 3). The first sample is a sandy deposit, made within the unit A but at a lower depth and with an absolute a.s.l. of 78 m (KA-ESR-U01). We could not calculate the in-situ gamma dose for this sample. This is linked to

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the impossibility of access to the environment of the sample for the detector. A second sample
suitable for $^{40}$Ar/$^{39}$Ar dating (KA-Ar-U01) was collected at 80 m a.s.l. at the top of unit A (see fig. 3).

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Lastly a third sample (KA-ESR-TH1) was collected for the ESR in the Unit H at 86.5 m a.s.l. inside a very
fine lens of sand within whitish silts bearing hydromorphic figures and ferruginous oxidations.

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**Trench J:** The 3.5m thick (from 80.5 and 84 m a.s.l.) trench J is divided into two main stratigraphic units. Unit 1 is composed of a 1.75 m thick grey clay layer undifferentiable from Unit F of the Trench H (see fig. 3 for correlations); Unit 2 is a 1.75 m thick deposit of fine to coarse cross-bedded sands. Two ESR samples (KA-ESR-TJ1 and KA-ESR-TJ1, see fig. 3) were collected from Unit 2.

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**Trench Y:** It is a 2.7 m thick sequence, from 84.0 to 86.7 m a.s.l. It is on the same bank of the actual gully next to Trench J and is divided into two units. Unit 1 is a 1.0 m thick silty layer similar to the ones observed in Trenches J and H; Unit 2 corresponds to a 1.7 m layer of coarse white sands with oblique sedimentation features. Faunal remains as well as a few stone artefacts were recovered from this unit (Inginco et al. 2020). ESR samples KA-ESR-TY1 and KA-ESR-TY2 were respectively collected at 85.5 m and 86.3 m a.s.l., (Unit 2). KA-Ar-TY1 was collected at 86.3 m next to KA-ESR-TY2 (fig. 3).

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**2.1.4. Clyde site (17°34′1.05″N, 121°33′44.04″E):**

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Clyde site was excavated during one single season in 2008 and is located 400 m north from Kalinga site. The excavation consisted of a small test pit and a 36 m trench down the hill (Jago-on, 2009). Although several stone artefacts were found on the surface, no archaeological finding came out of the excavation back then. After surveying the locality in 2020, our team identified fragments of a tusk eroding from that very same hill which encouraged us to open a new excavation 13 x 2 m trench in 2022 which led to the discovery of two stone artefacts at a depth of 3.2 m and several fragments of a *Stegodon* tusk at a depth of 4.3 m within a distinct sedimentary layer.

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This site is composed of three units: Unit 1 is a 2.40 m thick yellowish silty paleosoil, containing silty-sand lenses, clay lenses, root ichnofossils filled in with clay and iron and manganese oxidation sometimes as patches and some other times as concretions; Unit 2 is a 3.1 m thick layer characterized

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210 sands beds. Unit 3, is the topsoil and is up to 50 cm thick.

211 Two ESR samples were collected prior to the 2020 trench: the first one from Unit 1 (CL-ESR-1) using
212 an auger and therefore preventing us to obtain for this sample the *in-situ* gamma dose with the
213 portable spectrometer. The second sample was levied within Unit 2 (CL-ESR-2) and the gamma dose
214 was recorded *in-situ* (fig. 3).

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216 Figure 3: Simplified lithostratigraphic sections of Espinosa site modified from Fox, 1971, Tusk site
217 modified from Bautista and De Vos, 2000, Kalinga site modified and Clyde site modified from Jago-on,
218 2009 positioning the paleontological and archaeological findings. Samples collected for ESR based on
219 the Ti-Li centre only and $^{40}$Ar/$^{39}$Ar are evidenced as well as the analytical results (at 1 sigma of
220 uncertainties).

221 **3. Methods and protocols**

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223 **3.1. ESR on bleached quartz**
224

225 The ESR is a palaeodosimetric method relying on the capacity of quartz grains to store electrons set
226 in motion by natural irradiation. Elements such as uranium (U), thorium (Th), potassium (K), radon
227 (Rn), radium (Ra) emit ionizing radiations (alpha, beta and gamma rays) that delocalize electrons,
228 some of which being trapped within the quartz lattice defects also referred to as paramagnetic
229 centres. The quantity of electrons trapped will depend on the intensity and duration of the
230 irradiation (Ikeya, 1993). For geochronological purpose we use the centres created by the
231 substitution of atoms in the crystal lattice: Aluminum and Titanium atoms. These centres can be
232 reset by different physical processes: heating, pressure, and UV light exposure(Tanaka et al., 1995;
233 Toyoda et al., 1995; Yokoyama et al., 1985). For quaternary geology and prehistory quartz, resetting
234 by the latter process is the most used when dealing with alluvial terraces and fluvial deposits in
general. Indeed, when exposed to sunlight during transport either by a river or the wind, electrons 235 which have been trapped within quartz lattice defects are released. This natural resetting therefore 236 allows to date the deposition of the sediments. Samples were collected from freshly cleaned sections 237 to avoid any recently bleached quartz. 238

The three centres have different responses relative to natural irradiation. For instance, the Al centre 239 records the dose effect more slowly than the Ti-Li centre which itself acquires a dose in a slower way 240 than the Ti-H centre does. However, the latter is usually very feeble and quickly saturated, which 241 make its use irrelevant for Middle Pleistocene sites as it leads to underestimate their age (Tissoux et 242 al., 2007; Voinchet et al., 2020). 243

Here we focused on the lone ESR signals of Titanium (Ti-Li) centre. The aluminum centre of quartz 244 from this region of the Philippines is not exploitable for its high range of angular dependance (e.g. 245 different ESR intensities for the same aliquot depending on its position inside the spectrometer's 246 cavity). Based on our own observations, this high range of angular dependance is due to the inclusion 247 of feldspar grains within the quartz lattice generating both, a heterogeneity of the sample (fig. S1 248 supplementary material), and a superimposition of quartz and feldspar signals on ESR spectra. The 249 analysis of the Al centre is therefore too variable to be measured (fig. S2 supplementary material). 250

ESR paramagnetic centres are not as sensitive to light exposure as optically stimulated luminescence 251 (OSL) centers are. Between 72 et 168 h are needed for the Ti-Li centre to be bleached and around 252 300 h for the Al centre to be considered has bleached (Tissoux et al., 2012, 2007; Toyoda et al., 253 2000; Voinchet et al., 2003). Unlike for OSL method, there is no means for ESR to ensure the 254 completion of bleaching. The efficiency of the zeroing of the signal is therefore achieved by 255 comparing aluminium to titanium bleaching. Some studies on modern analogs of the Cagayan River 256 system shown that for this kind of multiphased transportation of sediment, the cumulated time of 257 light exposure per grain exceeds more than 1600 h, therefore allowing a nearly complete zeroing of 258 both Al and Ti centres (Voinchet et al., 2015). 259
For paleodosimetric method, two parameters are to be determined: the *dose rate* or *annual dose-D*<sub>a</sub>, which corresponds to the annual amount of radiation emitted by the environment surrounding the sample, and the *equivalent dose-D*<sub>e</sub>, which is the total dose or radiation received by the sample since its last burial (Yokoyama et al., 1985).

To determine the D<sub>a</sub>, we have cumulated the gamma, beta, alpha and cosmic contributions. Whenever possible, the gamma activity was measured *in situ*, which accounts for most of the samples. We sampled 100g of sediments that were measured by gamma spectrometry to determine the precise concentrations of radioelements (U, Th, K, Ra, Rn). These concentrations are used to calculate the contribution of beta radiation to the annual dose. The dose associated with alphas is not taken into account because the grains are etched (10 µm) with hydrofluoric acid.

The gamma dose rates were obtained by using the threshold technique (Mercier and Falguères, 2007). We have determined the U, Th and K concentrations in the laboratory by low background and high-resolution gamma-spectrometry (ORTEC© GMX30-70-LB-C). The external beta contributions were calculated from the obtained concentration content. The low content of the radionuclides usually found in quartz grains have led us to consider the internal dose rate as negligible (Murray and Roberts, 1997; Vandenberghe et al., 2008). The external α emission is negligible after the etching (around 10 µm removed) of the grain during preparation (Grün and Stringer, 1991; Toyoda and Ikeya, 1991). The water content (W%) was estimated by weighting every sample before and after a week-long drying at 40 °C (313.15 K). Water attenuation was determined with the formula of (Grün, 1994). Dose rates were determined using the dose rate conversion factor of Guérin et al., 2011. Alpha and beta attenuations were estimated using the tables of Brennan et al., 1991 and Brennan, 2003, depending on each sample grain size, and with a k-value of 0.15 ± 0.1 (Yokoyama et al., 1985). The annual cosmic dose is impacted by the thickness of sediments above every sample and this latter value was therefore measured on the field. The cosmic dose rate was calculated using the equations of Prescott and Hutton, 1994. During the sampling, an *in-situ* gamma-ray measurement was also performed with an ORTEC© portable gamma
spectrometer directly after the sediment sampling made at a horizontal depth of at least 20 cm from the freshly cleaned profile.

This measure, which takes into account the environment surrounding the sample, was used whenever possible in the calculation. Whenever impossible, between 1 and 2 grams of quartz ranging between 100 and 200 µm in size were extracted from the samples (Yokoyama et al., 1981).

Quartz extraction was made according to recommendations (Bahain et al., 2002; Grün, 1989; Ikeya, 1993; Rink, 1997). We retrieved the desired grain size (100-200 µm) by water sieving. This fraction was first treated with a solution of HCL concentrated at 35% as to remove any potential carbonates and therefore to reduce the amount of material before sorting with heavy liquid. Physical separation of minerals was made with a FRANZ© magnetic device. Then, the residuals were soaked into heavy liquid sodium-polytungstate (SPT) at two densities, one at 2.72 g/cm3 for recovering heavy minerals such as apatite, zircon and hornblende, second at 2.58 g/cm3 as to discriminate most of the feldspars from the quartz. As to remove any left-out feldspar the residuals were treated with HF. The use of HF further etches the outer surface of quartz, limiting so the alpha rays influence over the equivalent dose. Due to the high proportion of felspars in our samples, the HF acid attack was longer than commonly done. At least four hours of treatment with a 37% concentration was necessary to eliminate all the felspars. After etching, the residuals were rinsed with 35 % HCL in order to eliminate fluorides. Optical observation of the fully treated quartz grains was conducted with a Leica© binocular S8APO X8 coupled with Leica© LASX software. Measurment of the grains shown that it etching did not concern more than 15 to 20 micrometers of the outersurface of the quartz. The smallest grains were therefore less than 100 µm wide but larger than 60 µm.

The resulting fraction was separated into 11 portions of equal weight, referred to as aliquots. One aliquot was left as it is, and nine others were irradiated via a γ⁶⁰Co source, respectively to 150, 300, 600, 1200, 2400, 4000, 6000, 8000, and 12,000 Gy at CENIEH (Burgos, Spain). The last aliquot was
placed under a UV lamp for a minimum of 1600 h, reproducing so natural insolation, as to determine
the ratio of Al non-optically bleachable paramagnetic centres (Voinchet et al., 2003).

The ESR spectra measurement of the 11 aliquots was made with a Brüker EMX spectrometer at a
temperature of 87 K. Each set of 11 aliquots was measured at least three times after rotating the
tube by approximately 120 degrees to consider the signal's angular dependence due to grains
heterogeneity. For the Ti centres, the acquisition parameters included a microwave power of 10 mW,
1024 points resolution, 20 mT sweep width, 100 kHz modulation frequency, 0.1 mT modulation
amplitude, 40 ms conversion time, 20 ms time constant, and 1 scan. The measured value
corresponds to the ESR intensity of the Ti-Li centre. It equals the difference between the top of the
ESR signal's peak at 1.913 g and the baseline (Toyoda et al 2006, Tissoux et al 2007, Duval et al,
2015). This acquisition allowed building a growth curve (ESR intensity/gamma dose). From this, the
De was extrapolated using an exponential + linear mathematical function (Cordier et al., 2012; Duval
et al., 2009).

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**3.2. Single grain <sup>40</sup>Ar/<sup>39</sup>Ar dating**

The <sup>40</sup>Ar/<sup>39</sup>Ar method (McDougall et al., 1999 and references therein) is a radioisotopic dating
method based on the radioactive decay of <sup>40</sup>K in <sup>40</sup>Ar* (* for radiogenic). This method is commonly
used to date materials of volcanic origin (rocks and minerals). Applied to feldspars of volcanic origin
remobilized within alluvial deposits, it can be used to assign a probable maximum age to these
deposits (Pereira et al., 2017).

The samples were crushed and sieved with different mesh size from 2 mm to 250 µm. The selected
fractions were cleaned by ultrasonic bath in distilled water at 20°C. The most pristine and unfractured
plagioclase crystals ranging between 2 mm and 500 µm were handpicked from each sample, with at
least 50 crystals selected. Crystals were then cleaned with a 7% dilute hydrofluoric acid (HF) solution
to remove every particle attached to their surface. The selected minerals were irradiated for 120 min

332

333
in the Cadmium-coated CLICIT facility at Oregon State (USA). Prior to the analysis, the crystals were
place in an ultra-high vacuum chamber, each crystal was swept at about 0.2 W (laser power) for 30
seconds to remove any potential particle and pollutant gases still agglomerated on the surface of the
minerals. Crystals were fused using a Teledyne Cetac CO₂ laser (100 W) at a power of 2.5 W for 15
seconds. Then, the extracted gas was purified for 90 seconds by a GP50 getter ran at room
temperature and for 210 seconds by two hot GP50 SAES getters (300°C) (Florindo et al., 2021). Then
the gas was introduced into a NGX-600 Noble Gass Mass Spectrometer (ISOTOPX). The spectrometer
is equipped with a Nier source and 9 ATONA Faraday cups and an electron multiplier. ⁴⁰Ar, ³⁹Ar,
³⁸Ar,³⁷Ar were measured simultaneously on 4 ATONA while ³⁶Ar was measured by the ion counter
equipped with an electron multiplier. All technical details and performances of the NGX are detailed
in Cox et al. (2020). The neutron J fluence for each sample was calculated using the co-irradiated
Alder Creek Sanidine (ACs-2) standard with an age of 1.1891 Ma (Niespolo et al., 2017) according to
the ⁴⁰K total decay constant of Renne et al., (2011). The calculated J value of the three samples was
(5.66x10⁻⁴ ± 3.40x10⁻⁷). Procedural blank measurements were performed after every two or three
unknowns. Mass discrimination correction was monitored by measuring air argon of various beam
sizes and calculated relative to a ⁴⁰Ar/³⁶Ar ratio of 298.56 (Lee et al., 2006). Analytical data were then
processed with the ArArCALC software (Koppers, 2002). For the identified crystal populations, the
weighted mean ages and the full external uncertainties were calculated using the Excel add-ons
isoplot 3.0 (Ludwig, 2000).

## 4. Results

### 4.1. Geochronological results

ESR ages account for the deposition period of sedimentary layers. All the ages are reported at 1σ of
uncertainties. Results obtained for Clyde, Kalinga, Tusk and Espinosa sites are summarized in Table. 1.
One of the specificities observed in the Kalinga area is a very low radioelement content in the
sediments (see Table 1).
359

360

361

362

363

364

Table 1: ESR analysis. Ages and analytical uncertainties are reported at $1\sigma$. The water content (W%) was estimated by comparing the mass of the natural sample before and after a week-long drying in an oven at 40 °C (313.15 K). We therefore estimate the percentage of wet weight. Dose rates were determined using the dose rate conversion factor updated by Guérin et al. (2011). The alpha and beta attenuations for the selected grain sizes were estimated using the tables of Brennan (2003) with a k-value of 0.15 (Yokoyama et al., 1985). The cosmic dose rate was calculated using the equations of Prescott and Hutton (1994). The Ti-Li ages and $D_e$ were calculated using the expolin function (exponential and linear).

365

366

367

368

In the following, uncertainties of all ages are given at $1\sigma$. $^{40}$Ar/$^{39}$Ar results are presented as probability diagrams in figure 4 (a, b, c) and as tables in supplementary materials S4. The most likely $^{40}$Ar/$^{39}$Ar age we defined for each site was the one of the most recent crystal population whose ages were consistent with each other. The ESR results gave a deposition age for the layer.

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371

Figure 4: $^{40}$Ar/$^{39}$Ar results obtained for the Espinosa and Kalinga sites. $^{40}$Ar/$^{39}$Ar ages are presented as relative probability diagram (each crystal is represented with its error at $\pm 1\sigma$, the youngest crystals/population are evidenced in blue for each dated level).

372

### 4.1.1. Tusk site

373

374

At the Tusk site, the lone sample TU-ESR-1 has been dated to 796 $\pm$ 70 ka which gives an age to the fossil layer discovered at the base of the Unit 2 (figs. 3 and 4).

375

### 4.1.2. Espinosa site

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377

378

379

The ages of ES-ESR-1 and ES-ESR-2 bracketed the entire section between 834 $\pm$ 80 ka and 623 $\pm$ 45 ka. The $^{40}$Ar/$^{39}$Ar ages of ten plagioclases from ES-AR-1 range between 2971 $\pm$ 149 ka and 1166 $\pm$ 89 ka (see Supplementary dataset S4). The two youngest crystals of these ten provided statistically equivalent age of 1189 $\pm$ 79 ka (fig. 4).

380

### 4.1.3. Kalinga site

381

382

383

384

The $^{40}$Ar/$^{39}$Ar ages of KA-Ar-U01, were ranging between 2502 $\pm$ 110 ka and 1047 $\pm$ 185 ka (fig. 4). The ages of the five youngest crystals were statistically equivalent and thus may be related to a single eruption event or several eruptions close in time. Their weighted mean age was 1096 $\pm$ 54 ka (MSWD = 0.47, Probability = 1.0). The $^{40}$Ar/$^{39}$Ar ages of sample KA-Ar-TY1 range from 1962 $\pm$ 279 ka to 825 $\pm$
385

96. The six youngest crystals correspond to a statistically homogeneous population with a calculated weighted mean age of 909 ± 30 ka (MSWD = 0.26, Probability = 0.9). We consider this age as a maximum one for the stone artefacts and fossils found in a layer above.

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388

**Trench H:** KA-ESR-U01 (Unit 0 in fig. 3) was dated to 994 ± 45 ka and KA-ESR-TH1 to 554 ± 30 ka. These results allow us to further extend the chronological timescale of this section that is directly above the fossil bearing strata Unit F.

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**Trench J:** The J trench was stratigraphically equivalent to Units F and G of the trench H. Samples KA-ESR-TJ1 and KA-ESR-TJ2 were respectively dated to 678 ± 50 ka and 695 ± 65 ka by ESR.

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**Trench Y:** A preliminary dating in our lab of trench Y samples KA-ESR-TY1 and KA-ESR-TY2 (uppermost sands) returned ages of 895 ± 45 ka and 833 ± 50 ka respectively. These ages were inconsistent with the stratigraphic framework. A residual Ti signal observed on the bleached aliquot (done for Al investigation) have leaded us to a new approach. As for aluminum measurement dating protocol, we subtract the Ti residual intensity to all the Ti ESR intensity on the aliquots of these two samples. The new measurements provide then ages of 365 ± 30 ka (KA-ESR-TY1) and 273 ± 20 ka (KA-ESR-TY2) (See table. 1).

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396

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398

399

400

### 4.1.4. Clyde site

401

On Clyde site, CL-ESR-1 at the base of the section (see fig. 3) was dated to 516 ± 45 ka, thus providing a maximum age for the *Stegodon* tusk fragments and stone artefacts found above in Unit 1. CL-ESR-2 at the top of the section was dated to 399 ± 40 ka. This sample provides a minimum age for the archaeological and paleontological remains found in Unit 1.

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406

## 5. Discussion

407

### 5.1. Geochronology

408

ESR results obtained in this study allow us to refine the chronological framework of the western bank of the Cagayan valley at the latitude of Tuguegarao with a coherent constraint of each sequence. Yet, this method was applied using the lone Ti-Li centre which is unusual. All the ESR dates are nevertheless

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coherent with the stratigraphy and defined a chronological framework between 796 ± 70 ka and 273 ± 20 ka (fig. 5). It is worth noticing that the ⁴⁰Ar/³⁹Ar ages on plagioclase single grains (for three layers) were matching the ESR ages. The most recent volcanic activities of these three samples fall in between 1189 ± 79 ka and 909 ± 30 ka. We will not go further in the interpretation of these volcanic events for which little is known still. Without an exhaustive database listing all volcanic activities in and around the Cagayan basin, it is impossible to define the source and origin of the feldspars we have dated here.

### 5.1.1. Tusk site

Taken alone, the description of Bautista and De Vos, (2000), would not allow us to establish with certainty that the remains were in a primary position. Yet, a more recent study of the same fossils (Liscaljet, 2012), including seven carpal bones from the same limb, suggests that these remains were in anatomical connection and therefore endured little movement. Therefore, with this in mind and based on our dating of sample TU-ESR-1, we consider the bonebed to have an age of 796 ± 70 ka.

### 5.1.2. Espinosa site

The ages obtained for the two layers, at the bottom and on top of the section, bound the *Elephas sp.* remains between 834 ± 80 ka and 623 ± 45 ka. This interval is comparable to the one of the Kalinga site Trench H, Unit F (Ingicco et al., 2018). Also, contra the conclusions made by Fox et Peralta, (1974) that the contemporaneity of humans and this extirpated proboscidean could not be demonstrated at Espinosa site, we believe that these unseen before cutting marks (fig. 2) prove otherwise, even though the two lithic scrappers were not recovered from the same sedimentary layer and are younger than 623 ± 45 ka (fig. 3 and 5).

### 5.1.3. Kalinga site

At Kalinga the geochronological data are in adequation with the succession of stratigraphic layers. The silty layer KA-ESR-TH1 was dated to 554 ± 30 ka, while the uppermost sands were dated to 365 ± 30 ka for KA-ESR-TY1 and to 273 ± 20 ka for KA-ESR-TY2. All the ⁴⁰Ar/³⁹Ar ages match the Ti-li ages as shown in fig. 4. These results allow us to date the upper stratigraphic part of the site where stone
437

artefacts and faunal remains were recovered. It therefore suggests a human occupation of the valley
around 300 ka (see fig. 4), maybe without interruption since 709 ka.

438

439

**5.1.4. Clyde site**

440

All the remains are bound between 516 ± 45 ka and 399 ± 40 ka making of this site the LAD of *Stegodon* sp. in the valley so far.

441

442

**5.2. Faunal Assemblage**

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

All the studied sites delivered proboscidean remains. Proboscideans have been central in setting up the biochronological frame of several Southeast Asian islands (van den Bergh, 1999). Regarding the Philippines, our new chronological constraints constitute the very first ones for the endemic proboscideans of Luzon Island. While attempting to decipher the diversity of the Philippines megafauna, Bautista et De Vos in 2000, already noted the presence of *Stegodon* and of *Elephas* remains on the island of Luzon but they were not able to conclude on their respective age or on their potential contemporaneity. In the Kalinga area, two proboscidean species also known in Asia for the Pleistocene period were evidenced (*Elephas* sp. and *Stegodon* sp.). The *Elephas* remains with cutting marks from Espinosa site (dating back to between 834 ± 80 ka and 623 ± 45 ka) (figs. 2 and 5) overlap in age with the *Stegodon* remains from Kalinga site (709 ka ± 68 ka). The duration of the contemporaneity of *Stegodon* and *Elephas* on the Southeast Asian continental island of Java is still debated (see Brasseur, 2009). *Elephas* were supposed to be absent in the Trinil HK biozone and appear first in the Kedung Brubus biozone, meaning after the Jaramillo reverse Event, within the Brunhes Epoch (De Vos et al., 1982; Leinders et al., 1985). In counterparts, *Stegodon* appeared in Java synchronously with earlier stages of colonization of the island by mammals and disappeared with the Ngandong fauna, being swiped out by the arrival of modern taxa by the MIS 5 (Rizal et al., 2020; van den Bergh, 1999; Westaway et al., 2007). In summary, and although not all the Javanese biozones have been dated so far, it seems, according to the geochronological data we have, that the two genera may have coexisted in Java between ca. 800 ka and ca. 100 ka. The existence of *Elephas* as early as 1Ma (Grenzbank sedimentary unit within the Sangiran dome) was proposed by Brasseur,
463 (2009). All in all, this coexistence range for the two taxa is comparable with our results for the
464 Philippines. The genus *Elephas*, unlike *Stegodon*, is absent from the whole fossil record of the oceanic
465 islands of Flores and Sulawesi (van den Bergh, 1999), although the species *Stegoloxodon celebensis*
466 (Markov and Saegusa, 2008) of the latter island has been tentatively attributed for a while the genus
467 *Elephas*.

468 Moreover, our results further contribute to constrain the geochronological framework for FAD and
469 LAD of *Stegodon* on the island of Luzon. The Tusk site *Stegodon* remains were dated to 796 ± 70 ka
470 which we consider to this day to be the FAD for this taxon which were analogous to the Kalinga site
471 remains of this taxon. The LAD for this taxon in the area was estimated between 516 ± 45 ka and 399
472 ± 40 ka based on Clyde site findings.

473 **5.3. Hominin occupation range**

474 Our results further allow us to extend the chronological constraints on the Middle Pleistocene
475 Hominins occupation of the western bank of the Cagayan Valley. We have dated the Hominins FAD to
476 at least 796 ± 70 ka based on the stone artefacts recovered at Tusk Site (Bautista and De Vos, 2000).
477 This occupation overlap with the error marges of Kalinga Unit F occupation date. We also dated a
478 human presence at 399 ± 40 ka based on a few stone artefacts recovered from Unit 2 of Clyde Site.
479 Nevertheless, caution must be taken with regard to the hypothesis of the presence of Hominins
480 during this long period. Indeed, this scheme remains speculative for several reasons. First, in the
481 absence of any Hominin remains, there is no evidence that these dates define an occupation range
482 for one single human species. Second, the age of 796 ± 70 ka obtained at Tusk site was based on two
483 distinct stratigraphic profiles we hypothesized to be a unique sedimentary sequence. A final
484 demonstration of this can only be achieved through a rejuvenated excavation at the site. Third, for
485 the human occupation, a younger age has been obtained at Kalinga layer Y of 273 ± 20 ka which also
486 delivered some stone artefacts. This age is yet questionable for the methodological reasons exposed
487 above. Yet, one cannot entirely reject that this Trench Y corresponds to the actual maximum
488 occupation range so far for Hominins in the Kalinga area. Despite these uncertainties, our results
489

contribute to fill part of the gap between the Kalinga toolmakers and butchers and the Callao Cave

*Homo luzonensis* (Détroit et al., 2019) recently dated to 134 ± 14 ka, further questioning the

continuity of the occupation of the Cagayan River Basin by Hominins and their endemic evolution.

490

491

492

493

Figure 5: synthesis of the occupation ranges for Human and Proboscidean from Tusk, Espinosa, Kalinga and Clyde sites. The hexagonal shape represents the past studies whereas the square shape represents this study. The color code represents the uranium series ages in green, the ESR ages in red and the $^{40}$Ar/$^{39}$Ar ages in blue. All ages are expressed at 1σ. The precise proboscidean remains found in sections are sown on the anatomical representations in grey.

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495

496

497

# 6. Conclusion

498

499

Our coupled ESR - $^{40}$Ar/$^{39}$Ar dating study carried out on quartz and feldspars from Middle Pleistocene

fluviovolcanic deposits in the central Cagayan Valley allows the following proposals:

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501

1. On the basis of the dating of faunal and lithic remains from Kalinga and three other sites (Espinosa, Tusk and Clyde) we conclude that archaic Hominins presence on the western bank of the Cagayan Valley would have been effective from at least 796 ± 70 ka and would have lasted until 273 ± 20 ka, yet maybe with no continuity between the two.

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505

2. We brought some new and significant temporal arguments regarding the contemporaneity of *Stegodon* sp. and *Elephas* sp. in this part of Island Southeast Asia.

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3. While these new chronological constraints open up new questions about the continuity of human occupation in the basin, they also represent a new step towards bridging the gap between the occupations of the Kalinga region and the Hominin species endemic to Luzon Island *Homo luzonensis*, therefore questioning its geographic, temporal and phylogenetic origin all at once.

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512

# Acknowledgements
513 The Kalinga excavation project was funded by the French Department for Foreign Affairs (Project MARCHE, to T.I.), The National Museum of The Philippines (to C.J-o and M.C.R.). T.I. also received funding from Sorbonne Université (Projet Emergence Tropemin with Valéry Zeitoun).

516 The ESR and mobile gamma-ray spectrometers of the French National Museum of Natural History were bought with the financial support of the 'Sesame Île-de-France' program and the 'Région Centre' respectively. The sampling and in situ gamma spectrometer measurements were conducted by Alluyn, A. and Voinchet, P. in November 2019.

520

521 References :

522 Antoine, P.-O., Reyes, M.C., Amano, N., Bautista, A.P., Chang, C.-H., Claude, J., De Vos, J., Ingicco, T., 2022. A new rhinoceros clade from the Pleistocene of Asia sheds light on mammal dispersals to the Philippines. Zoological Journal of the Linnean Society 194, 416–430.

525 Aurelio, M.A., Peña, R.E., Taguibao, K.J.L., 2013. Sculpting the Philippine archipelago since the Cretaceous through rifting, oceanic spreading, subduction, obduction, collision and strike-slip faulting: Contribution to IGMA5000. Journal of Asian Earth Sciences, Geological Evolution of Asia 72, 102–107.

529 Bahain, J.-J., Laurent, M., Falguères, C., Voinchet, P., Farkh, S., Tissoux, H., 2002. Datation par résonnance paramagnétique électronique (RPE) des formations fluviatiles pléistocènes et des gisements archéologiques ou paléontologiques associés. Quaternaire 13, 91–103.

532 Bautista, A.P., De Vos, J., 2000. Archaeological exploration and excavation at Solana - Cagayan (No. 4), Litho-, Bio and chronostratigraphy of the fossil mammal bearing deposits of the Philippines.

534 Beyer, O., 1947. Outline review of philippine archeology by islands and provinces. The Philippine Journal of Science 231.

536 Bondoc, N.H., 1979. A re-investigation of the Espinosa archaeological sites : Cagayan & Kalinga- Apayao Anthropological papers (National Museum (Philippines)), 32.

538 Brasseur, B., 2009. Dynamique et histoire des dépôts du Pleistocène inférieur et moyen ancien du dôme de Sangiran (Java central, Indonésie) : caractérisation des surfaces d'occupation à Homo erectus (These de doctorat). Paris, Muséum national d'histoire naturelle.

541 Brennan, B.J., 2003. Beta doses to spherical grains. Radiation Measurements 37, 299–303.

542 Brennan, B.J., Lyons, R.G., Phillips, S.W., 1991. Attenuation of alpha particle track dose for spherical grains. International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements 18, 249–253.

545 Corby, W., 1951. Geology and oil possibilities of the Philippines. Department of Agriculture and Natural Resources Technical Bulletin, Philippines 21, 362.

547 Cox, S.E., Hemming, S.R., Tootell, D., 2020. The Isotopx NGX and ATONA Faraday amplifiers. Geochronology 2, 231–243.

549 De Vos. J., Sartono, S., & PY, S. 1982. The fauna from trinil, type locality of homo erectus: a reinterpretation.

551 Détroit, F., Mijares, A.S., Corny, J., Daver, G., Zanolli, C., Dizon, E., Robles, E., Grün, R., Piper, P.J., 2019. A new species of Homo from the Late Pleistocene of the Philippines. Nature 568, 181–186.

553 Dickinson, W.R., 1974. Tectonics and Sedimentation. SEPM (Society for Sedimentary Geology).

554 Durkee, E.F., Peterson, S.L., 1961. Geology of Northern Luzon, Philippines. Bulletin 45.
555 Florindo, Fabio, Marra, F., Angelucci, D.E., Biddittu, I., Bruni, L., Florindo, Federico, Gaeta, M., Guillou, H., Jicha, B., Macrì, P., Morigi, C., Nomade, S., Parenti, F., Pereira, A., Grimaldi, S., 2021.

557 Environmental evolution, faunal and human occupation since 2 Ma in the Anagni basin, central Italy. Sci Rep 11, 7056.

559 Fox, R.B., 1971. Ancient man and Pleistocene fauna in Cagayan Valley, Northern Luzon, Philippines. A Progress Report of the Philippine National Museum, Manila 32.

561 Fox, R.B., Peralta, J.T., 1974. Preliminary report on the paleolithic archaeology of Cagayan Valley, Philippines and the Calalwanian Industry. Proceedings of the First Regional Seminar on Southeast Asian Prehistory and archaeology, Philippine National Museum, Manila 100-147.

564 G. Guérin, Mercier, N., Adamiec, G., 2011. Dose-rate conversion factors: update. Ancient TI 5-8.

565 Grün, R., 1994. A cautionary note: use of water content and depth for cosmic ray dose rate in AGE and DATA programs. Ancient TL 12, 50-51.

567 Grün, R., 1989. Electron spin resonance (ESR) dating. Quaternary International 1, 65-109.

568 Grün, R., Stringer, C., 2023. Direct dating of human fossils and the ever-changing story of human evolution. Quaternary Science Reviews 322, 108379.

570 Grün, R., Stringer, C.B., 1991. Electron spin resonance dating and the evolution of modern humans. Archaeometry 33, 153-199.

572 Ikeya, M., 1993. New Applications of Electron Spin Resonance: Dating, Dosimetry and Microscopy. World Scientific.

574 Ingicco, T., Reyes, M.C., de Vos, J., Belarmino, M., Albers, P.C.H., Lipardo, I., Gallet, X., Amano, N., van den Bergh, G.D., Cosalan, A.D., Bautista, A., 2020. Taphonomy and chronosequence of the 709 ka Kalinga site formation (Luzon Island, Philippines). Sci Rep 10, 11081.

577 Ingicco, T., van den Bergh, G.D., Jago-on, C., Bahain, J.-J., Chacón, M.G., Amano, N., Forestier, H., King, C., Manalo, K., Nomade, S., Pereira, A., Reyes, M.C., Sémah, A.-M., Shao, Q., Voinchet, P., Falguères, C., Albers, P.C.H., Lising, M., Lyras, G., Yurnaldi, D., Rochette, P., Bautista, A., de Vos, J., 2018. Earliest known hominin activity in the Philippines by 709 thousand years ago. Nature 557, 233-237.

582 Jago-on, S.C.B., 2009. Report on the archaeological excavation and exploration in Cagayan Valley. Proceedings of the Society of Philippine Archaeologists 7, 24.

584 Jensen, G.M., Storey, M., Roberts, R.G., Lachlan, T.J., Thomsen, K.J., Murray, A., 2010. Combined 40Ar/39Ar and OSL dating of Pleistocene pyroclastic and fluvial deposits in the Cagayan Valley Basin, Northern Luzon, The Philippines.

587 Jourdan, F., Nomade, S., Wingate, M.T.D., Eroglu, E., Deino, A., 2019. Ultraprecise age and formation temperature of the Australasian tektites constrained by ⁴⁰Ar/ ³⁹Ar analyses. Meteorit Planet Sci 54, 2573-2591.

590 Koppers, A.A.P., 2002. ArArCALC—software for 40Ar/39Ar age calculations. Computers & Geosciences 28, 605-619.

592 Lee, J.-Y., Marti, K., Severinghaus, J.P., Kawamura, K., Yoo, H.-S., Lee, J.B., Kim, J.S., 2006. A redetermination of the isotopic abundances of atmospheric Ar. Geochimica et Cosmochimica Acta 70, 4507-4512.

595 Liscaljet, N., 2012. Napakaliit trompa: New pygmy proboscidean remains from the Cagayan Valley (Philippines). Quaternary International, Mammoths and their Relatives 2: Biotopes, Evolution and Human Impact V International Conference, Le Puy-en-Velay, 2010 276-277, 278-286.

598 Ludwig, K., 2000. Users manual for Isoplot/Ex: a geochronological toolkit for Microsoft Excel. Berkeley Geochronology Center Spec. Publ. 1a, 53.

600 Leinders, J. J. M, 1985. The age of the hominid-bearing deposits of Java: state of the art. Geologie en Mijnbouw 64, 167-173.

602 Markov, G.N., Saegusa, H., 2008. On the validity of Stegoloxodon Kretzoi, 1950 (Mammalia: Proboscidea). Zootaxa 1861, 55-56.

604 Mathisen, M.E., 1981. Plio-Pleistocene geology of the Central Cagayan Valley, Northern Luzon, Philippines (Doctor of Philosophy). Iowa State University, Digital Repository, Ames.
606 Mathisen, M.E., Vondra, C.F., 1983. The fluvial and pyroclastic deposits of the Cagayan Basin,
607 Northern Luzon, Philippines-an example of non-marine volcaniclastic sedimentation in an
608 interarc basin. Sedimentology 30, 369-392.

609 Mathisen, M.E., Vondra, C.F., 1978. Pleistocene geology fauna and early man in the Cagayan Valley.
610 Northern Luzon, Philippines. Geological Society of America Abstract 10, 451.

611 McDougall, I., Dougall, I.M., Harrison, T.M., McDougall, P. of G.I., Harrison, P. of G.D. of E. and S.S.T.M.,
612 Harrison, C. in E.M.M., 1999. Geochronology and Thermochronology by the 40Ar/39Ar
613 Method. Oxford University Press.

614 Mercier, N., Falguères, C., 2007. Field gamma dose-rate measurement with a NaI (TI) detector: re-evaluation of the “threshold” technique. Ancient TL 25(1).

616 Mijares, A.S., Détroit, F., Piper, P., Grün, R., Bellwood, P., Aubert, M., Champion, G., Cuevas, N., De
617 Leon, A., Dizon, E., 2010. New evidence for a 67,000-year-old human presence at Callao Cave,
618 Luzon, Philippines. Journal of Human Evolution 59, 123-132.

619 Murray, A.S., Roberts, R.G., 1997. Determining the burial time of single grains of quartz using optically
620 stimulated luminescence. Earth and Planetary Science Letters 152, 163-180.

621 Niespolo, E.M., Rutte, D., Deino, A.L., Renne, P.R., 2017. Intercalibration and age of the Alder Creek
622 sanidine 40Ar/39Ar standard. Quaternary Geochronology 39, 205-213.

623 Past Interglacials Working Group of PAGES, 2016. Interglacials of the last 800,000 years. Rev. Geophys.
624 54, 162-219.

625 Prescott, J.R., Hutton, J.T., 1994. Cosmic ray contributions to dose rates for luminescence and ESR
dating: Large depths and long-term time variations. Radiation Measurements 23, 497-500.

627 Renne, P.R., Balco, G., Ludwig, K.R., Mundil, R., Min, K., 2011. Response to the comment by W.H.
628 Schwarz et al. on "Joint determination of 40K decay constants and 40Ar*/40K for the Fish
629 Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geochronology" by P.R.
630 Renne et al. (2010). Geochimica et Cosmochimica Acta 75, 5097-5100.

631 Rink, W.J., 1997. Electron spin resonance (ESR) dating and ESR applications in quaternary science and
632 archaeometry. Radiation Measurements 27, 975-1025.

633 Rizal, Y., Westaway, K.E., Zaim, Y., van den Bergh, G.D., Bettis, E.A., Morwood, M.J., Huffman, O.F.,
634 Grün, R., Joannes-Boyau, R., Bailey, R.M., Sidarto, Westaway, M.C., Kurniawan, I., Moore,
635 M.W., Storey, M., Aziz, F., Suminto, Zhao, J., Aswan, Sipola, M.E., Larick, R., Zonneveld, J.-P.,
636 Scott, R., Putt, S., Ciochon, R.L., 2020. Last appearance of Homo erectus at Ngandong, Java,
637 117,000-108,000 years ago. Nature 577, 381-385.

638 Tanaka, K., Machette, M.N., Crone, A.J., Roger Bowman, J., 1995. ESR dating of aeolian sand near
tenantant creek, Northern territory, Australia. Quaternary Science Reviews 14, 385-393.

640 Tissoux, H., Falguères, C., Voinchet, P., Toyoda, S., Bahain, J.J., Despriée, J., 2007. Potential use of Ti-
center in ESR dating of fluvial sediment. Quaternary Geochronology, LED 2005 2, 367-372.

642 Tissoux, H., Voinchet, P., Lacquement, F., Prognon, F., Moreno, D., Falguères, C., Bahain, J.-J., Toyoda,
643 S., 2012. Investigation on non-optically bleachable components of ESR aluminium signal in
644 quartz. Radiation Measurements 47, 894-899.

645 Tobias, Carol.M., 1999. ARCHAEOLOGICAL HISTORY OF CAGAYAN PROVINCE | Hukay. Bulletin of the
646 university of the Philippines Archeological Studies Program 2, 24.

647 Toyoda, S., Goff, F., Ikeda, S., Ikeya, M., 1995. ESR dating of quartz phenocrysts in the El Cajete and
648 Battleship Rock Members of Valles Rhyolite, Valles Caldera, New Mexico. Journal of
649 Volcanology and Geothermal Research 67, 29-40.

650 Toyoda, S., Ikeya, M., 1991. ESR dating of quartz and plagioclase from volcanic ashes using E'1, A1 and
651 Ti centers. International Journal of Radiation Applications and Instrumentation. Part D.
652 Nuclear Tracks and Radiation Measurements 18, 179-184.

653 Toyoda, S., Voinchet, P., Falguères, C., Dolo, J.M., Laurent, M., 2000. Bleaching of ESR signals by the
sunlight: a laboratory experiment for establishing the ESR dating of sediments. Applied
654 Radiation and Isotopes 52, 1357-1362.

656 van den Bergh, G.D., 1999. The Late Neogene elephantoid-bearing faunas of Indonesia and their
657 palaeozoogeographic implications. Scripta Geologica 117, 1-419.
658
659

Vandenberghe, D., De Corte, F., Buylaert, J.-P., Kučera, J., Van den haute, P., 2008. On the internal radioactivity in quartz. Radiation Measurements 43, 771–775.

660
661
662

Voinchet, P., Falguères, C., Laurent, M., Toyoda, S., Bahain, J.J., Dolo, J.M., 2003. Artificial optical bleaching of the Aluminium center in quartz implications to ESR dating of sediments. Quaternary Science Reviews 22, 1335–1338.

663
664
665
666
667
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669
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671
672
673
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675
676
677
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679
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681

Voinchet, P., Moreno, D., Bahain, J.-J., Tissoux, H., Tombret, O., Falguères, C., Moncel, M.-H., Schreve, D., Candy, I., Antoine, P., Ashton, N., Beamish, M., Cliquet, D., Despriée, J., Lewis, S., Limondin-Lozouet, N., Locht, J.-L., Parfitt, S., Pope, M., 2015. New chronological data (ESR and ESR/U-series) for the earliest Acheulian sites of north-western Europe: NEW chronological data for the earliest acheulean sites of nw europe. J. Quaternary Sci. 30, 610–622.

Voinchet, P., Pereira, A., Nomade, S., Falguères, C., Biddittu, I., Piperno, M., Moncel, M.-H., Bahain, J.-J., 2020. ESR dating applied to optically bleached quartz - A comparison with 40Ar/39Ar chronologies on Italian Middle Pleistocene sequences. Quaternary International, Electron spin resonance (ESR) dating in Quaternary studies: evolution, recent advances and applications 556, 113–123. h

Von Koenigswald, G.H.R., 1958. Preliminary Report on a Newly-Discovered Stone Age Culture from Northern Luzon, Philippine Islands. Asian Perspectives 2, 69–70.

Westaway, K.E., Morwood, M.J., Roberts, R.G., Rokus, A.D., Zhao, J.-x., Storm, P., Aziz, F., van den Bergh, G., Hadi, P., Jatmiko, de Vos, J., 2007. Age and biostratigraphic significance of the Punung Rainforest Fauna, East Java, Indonesia, and implications for Pongo and Homo. Journal of Human Evolution 53, 709–717.

Wibowo, U., 2016. Walking With Indonesian elephants: attribution of isolated proboscidean femurs and tibias to genus based on morphological differences. University of Wollongong Thesis Collection 1954-2016.

Yokoyama, Y., Falgueres, C., Quaegebeur, J.P., 1985. ESR dating of quartz from quaternary sediments: First attempt. Nuclear Tracks and Radiation Measurements (1982) 10, 921–928.

Yokoyama, Y., REYSS, J.-L., Guichard, F., 1981. Production cross sections of Al-26, Na-22, Be-7 from argon and of Be-10, Be-7 from nitrogen- Implications for production rates of Al-26 and Be-10 in the atmosphere. Earth and Planetary Science Letters 53, 203–210.

List of Tables:

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693
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695
696
697

Table 1 - ESR analysis. Ages and analytical uncertainties are reported at 1σ. The water content (W%) was estimated by comparing the mass of the natural sample before and after a weekly drying in an oven at 40 °C (313.15 K). Dose rates were determined using the dose rate conversion factor updated by (Guérin et al., 2011). The alpha and beta attenuations for the selected grain sizes were estimated using the tables of (Brennan, 2003) with a k-value of 0.15 (Yokoyama et al., 1985). The cosmic dose rate was calculated using the equations of (Prescott and Hutton, 1994). The Ti-Li ages and De were calculated using the expolin function (exponential and linear).
698 **List of Figures:**

699 Figure. 1- a) Physiographic map of Southeast Asia with a sea level 110 m lower than present, approximating its configuration 790 ka ago (Past Interglacials Working Group of PAGES, 2016). b) Geological map of the central Cagayan basin region from (Mathisen, 1978; Durkee and Peterson, 1961) DTM from the SRTM NASA dataset 30 m resolution). c) Topography (DTM from the PHIL-LiDAR 2 Program 1 m resolution) and location of the Kalinga area sites and samples.

704 Figure. 2- Elephas femur displaying cutmarks.

705 Figure. 3- Simplified lithostratigraphic sections of Espinosa site modified from Fox, 1971, Tusk site modified from Bautista and De Vos, 2000, Kalinga site modified and Clyde site modified from Jago-on, 2009 positioning the paleontological and archaeological findings. Samples collected for ESR based on the Ti-Li centre only and ⁴⁰Ar/³⁹Ar are evidenced as well as the analytical results (at 1 sigma of uncertainties).

710 Figure. 4- ⁴⁰Ar/³⁹Ar results obtained for the Espinosa and Kalinga sites. ⁴⁰Ar/³⁹Ar ages are presented as relative probability diagram (each crystal is represented with its error at ± 1σ, the youngest crystals/population are evidenced in blue for each dated level).

713 Figure. 5- synthesis of the occupation ranges for Human and Proboscidean from Tusk, Espinosa, Kalinga and Clyde sites. The hexagonal shape represents the past studies whereas the square shape represents this study. The color code represents the uranium series ages in green, the ESR ages in red and the ⁴⁰Ar/³⁹Ar ages in blue. All ages are expressed at 1σ. The precise proboscidean remains found in sections are sown on the anatomical representations in grey.

718
<figure><img src="image_2.png" /></figure>
<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>
## Espinosa

<figure><img src="image_5.png" /></figure>

ES-ESR-2
623 ± 45 ka

## Tusk

<figure><img src="image_6.png" /></figure>

ES-Ar-1
< 1189 ± 79 ka

TU-ESR-1
796 ± 70 ka

ES-ESR-1
834 ± 80 ka

Altitude m a.s.l

Altitude m a.s.l

## Legend

<figure><img src="image_7.png" /></figure>

Coarse sand

<figure><img src="image_8.png" /></figure>

Medium-coarse sand

<figure><img src="image_9.png" /></figure>

Medium sand

<figure><img src="image_10.png" /></figure>

Sand

<figure><img src="image_11.png" /></figure>

Fine sand

<figure><img src="image_12.png" /></figure>

Fine cross-bedded sand

<figure><img src="image_13.png" /></figure>

Very fine sand

<figure><img src="image_14.png" /></figure>

Silts

<figure><img src="image_15.png" /></figure>

Clay

<figure><img src="image_16.png" /></figure>

Geological correlation

<figure><img src="image_17.png" /></figure>

Lithic tools

<figure><img src="image_18.png" /></figure>

Paleontological remains

<figure><img src="image_19.png" /></figure>

ESR age (ka)

<figure><img src="image_20.png" /></figure>

$^{40}$Ar/$^{39}$Ar age (ka)

<figure><img src="image_21.png" /></figure>

ESR/U series age (ka)

## Kalinga

<figure><img src="image_22.png" /></figure>

KA-ESR-TH1
554 ± 30 ka

<figure><img src="image_23.png" /></figure>

Bore hole

<figure><img src="image_24.png" /></figure>

KA-Ar-U01
< 1096 ± 54 ka

KA-ESR-U01
994 ± 45 ka

## Trench Y

<figure><img src="image_25.png" /></figure>

KA-ESR-TY2
273 ± 20 ka

KA-Ar-TY1
< 909 ± 30 ka

KA-ESR-TY1
365 ± 30 ka

## Clyde

<figure><img src="image_26.png" /></figure>

CL-ESR-2
399 ± 40 ka

CL-ESR-1
516 ± 45 ka

Altitude m a.s.l

## Trench H

Altitude m a.s.l
<figure><img src="image_27.png" /></figure>

<figure><img src="image_28.png" /></figure>

<figure><img src="image_29.png" /></figure>

Weighted mean Age = 1189 ± 79 ka
n/N = 2/10

Weighted mean Age = 909 ± 30 ka
Intercept = 40°Ar/3°Ar = 314 ± 24

MSWD = 0,26 P = 0,90
n/N = 6/10

Weighted mean Age = 1096 ± 54 ka
Intercept = 40°Ar/3°Ar = 298 ± 10

MSWD = 0,47 P = 0,99
n/N = 5/10

20

160

120

80

0

240

200

160

260

2800 ka
134 ± 14 ka

Callao

<figure><img src="image_30.png" /></figure>

709 ± 68 ka

<figure><img src="image_31.png" /></figure>

Kalinga site

<figure><img src="image_32.png" /></figure>

<figure><img src="image_33.png" /></figure>

<figure><img src="image_34.png" /></figure>

<figure><img src="image_35.png" /></figure>

Tusk site

<figure><img src="image_36.png" /></figure>

<figure><img src="image_37.png" /></figure>

Espinosa site

<figure><img src="image_38.png" /></figure>

<figure><img src="image_39.png" /></figure>

Clyde site

<figure><img src="image_40.png" /></figure>

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

Ma

1.0

1.1

1.2

Ma

Late Pleistocene

Middle Pleistocene

Early Pleistocene

BRUHNES

MAT

UY

AMA

<figure><img src="image_41.png" /></figure>

Nesorhinus
philippensis

<figure><img src="image_42.png" /></figure>

Elephas sp.

<figure><img src="image_43.png" /></figure>

Stegodon sp.

Jaramillo
Cobb
Mountain

Shape code

Color code

<figure><img src="image_44.png" /></figure>

ESR U/Th age ± 1σ

<figure><img src="image_45.png" /></figure>

ESR age ± 1σ

30

$^{40}$Ar/$^{39}$Ar age ± 1σ

<figure><img src="image_46.png" /></figure>

Artefacts
<figure><img src="image_47.png" /></figure>
<table><thead><tr><th></th><th>Sample</th><th>D<sub>a</sub><br>(µGy/y)</th><th>D<sub>β</sub><br>(µGy/y)</th><th>D<sub>γ</sub><br>(µGy/y)</th><th>D<sub>γ</sub> in situ<br>(µGy/y)</th><th>D<sub>cos</sub><br>(µGy/y)</th><th>D<sub>a</sub><br>(µGy/y)</th><th>W %</th><th>D<sub>e</sub></th><th>R<sup>2</sup></th><th>Age (ka)</th><th>BI<br>(%)</th></tr></thead><tbody><tr><td rowspan="2">Espinosa</td><td>ES-ESR-1</td><td>4±1</td><td>297±10</td><td>128±7</td><td></td><td>166±8</td><td>467±12</td><td>13.4</td><td>507±70</td><td>0.994</td><td>834±80</td><td></td></tr><tr><td>ES-ESR-2</td><td>5±1</td><td>491±17</td><td>204±12</td><td>152±8</td><td>166±8</td><td>814±22</td><td>22.5</td><td>425±81</td><td>0.989</td><td>623±45</td><td></td></tr><tr><td>Tusk</td><td>TU-ESR-1</td><td>4±1</td><td>411±16</td><td>169±12</td><td></td><td>166±8</td><td>581±20</td><td>13.2</td><td>462±78</td><td>0.983</td><td>796±70</td><td></td></tr><tr><td rowspan="8">Kalinga</td><td>KA-ESR-U01</td><td>5±1</td><td>273±10</td><td>127±8</td><td></td><td>130±8</td><td>408±13</td><td>10.5</td><td>405±38</td><td>0.992</td><td>994±45</td><td></td></tr><tr><td>KA-ESR-TJ1</td><td>5±1</td><td>375±11</td><td>159±8</td><td>230±12</td><td>171±9</td><td>781±18</td><td>17</td><td>563±83</td><td>0.991</td><td>678±50</td><td></td></tr><tr><td>KA-ESR-TJ2</td><td>5±1</td><td>358±13</td><td>155±10</td><td>223±11</td><td>163±8</td><td>750±20</td><td>17</td><td>478±91</td><td>0.985</td><td>695±65</td><td></td></tr><tr><td>KA-ESR-TY1</td><td>5±1</td><td>358±13</td><td>155±10</td><td>223±11</td><td>171±9</td><td>758±20</td><td>17</td><td>277±26</td><td>0.990</td><td>365±30</td><td>39</td></tr><tr><td>KA-ESR-TY2</td><td>5±1</td><td>375±11</td><td>159±8</td><td>230±12</td><td>163±8</td><td>772±18</td><td>17</td><td>211±16</td><td>0.982</td><td>273±20</td><td>35</td></tr><tr><td>KA-ESR-TY1</td><td>5±1</td><td>358±13</td><td>155±10</td><td>223±11</td><td>171±9</td><td>758±20</td><td>17</td><td>671±68</td><td>0.998</td><td>895±45</td><td></td></tr><tr><td>KA-ESR-TY2</td><td>5±1</td><td>375±11</td><td>159±8</td><td>230±12</td><td>163±8</td><td>772±18</td><td>17</td><td>650±79</td><td>0.993</td><td>833±50</td><td></td></tr><tr><td>KA-ESR-TH1</td><td>9±1</td><td>543±12</td><td>247±9</td><td>261±14</td><td>160±8</td><td>973±20</td><td>26.4</td><td>539±62</td><td>0.998</td><td>554±30</td><td></td></tr><tr><td rowspan="2">Clyde</td><td>CL-ESR-1</td><td>10±1</td><td>501±12</td><td>236±9</td><td>248±12</td><td>166±8</td><td>925±19</td><td>26.1</td><td>476±82</td><td>0.993</td><td>516±45</td><td></td></tr><tr><td>CL-ESR-2</td><td>10±1</td><td>551±12</td><td>253±9</td><td>283±14</td><td>160±8</td><td>1005±21</td><td>22.8</td><td>401±62</td><td>0.996</td><td>399±40</td><td></td></tr></tbody></table>