We report a detailed paleomagnetic study on two Plio‐Pleistocene lava flow sequences from the Djavakheti Highland, Lesser Caucasus. The Korkhi sequence is composed of two volcanic successions of distinct age (1.9 and 3.1 Ma), while the Apnia sequence was emplaced between 3.8 and 3.1 Ma according to available radiometric datings. Normal, reverse and intermediate polarities have been determined from both sequences. Mean directions of the normal and reverse polarity groups for each section do not match the expected field direction, but the possibility of tectonic rotations has been dismissed. A composite analysis of paleomagnetic directions, of virtual geomagnetic pole (VGP) scatter and available paleointensity results from a previous study, allow the interpretation of the observed paleomagnetic results. In the Apnia sequence, both a short recording time unable to average paleosecular variation (PSV) and an anomalous Earth magnetic field (EMF) record are responsible for the observed paleomagnetic directions. According to paleomagnetic results and radiometric ages, this sequence most probably records the reverse to normal polarity transition C2Ar to C2An‐3n. The upper Korkhi subsequence yields an anomalous EMF record, reflecting a transitional time interval. Paleomagnetic results and available absolute ages suggest that this subsequence either records transition C2r‐1r to Olduvai or Olduvai to C1r‐2r. The lower Korkhi subsequence registers a normal polarity interval within the Gauss chron, reflecting a stable stage of the EMF.

1 Introduction The Earth possesses a magnetic field which varies in direction and intensity. It is generated mainly, by a process that resembles a dynamo, and takes place in the liquid outer core. To gain a better knowledge of this process, it is essential to understand both the short and long‐term behavior of the Earth's Magnetic Field (EMF). The temporal variation of the EMF can be described by longer periods of stability characterized by relatively small and smooth variations of direction and intensity (secular variation) while shorter unstable periods are characterized by more pronounced directional and intensity fluctuations (polarity transitions and excursions) (Johnson & McFadden, 2007; Laj & Channell, 2007). Stable periods may be generally described by the geocentric axial dipole (GAD) model of the EMF for both normal and reverse polarities. These stable periods present a certain dispersion of the magnetic pole position which is called secular variation. During the unstable periods the non‐dipolar fluctuations become more important and can even dominate the EMF geometry. The study of the EMF during the unstable periods may largely contribute to unravel the non‐dipolar processes of the geodynamo. This also includes the study of the paths recording directional changes during instability periods (see, for instance, the detailed reviews about geomagnetic reversals of Merrill and McFadden (1999) and Valet and Fournier (2016) and references therein). Information about EMF variations can be obtained from the thermal remanent magnetization (TRM) recorded by volcanic rocks. Specifically, lava flow sequences can be particularly helpful in revealing the behavior of the EMF during an extended time. This type of records can be found in sequences characterized by sequential image lava flow eruptions (e.g., Caccavari et al., 2015; Camps et al., 2011; Chauvin et al., 1990; Herrero‐Bervera & Valet, 1999; Jarboe et al., 2011; Kissel et al., 2014; Leonhardt et al., 2002; Mankinen et al., 1985; Moulin et al., 2012; Prévot et al., 2003). The aim of the present work is to describe the record of three different periods of the EMF records an apparent full reversal, a transitional stage and a stable normal polarity period in two Plio‐Pleistocene basaltic sequences from the volcanic region of the Djavakheti Highland (sometimes also spelled Javakheti or Dzhavakheti), in the central sector of the Lesser Caucasus. In addition, new, high standard paleomagnetic data are provided in order to contribute to the database of the time averaged geomagnetic field. Since the 1990s, several new paleomagnetic and paleointensity studies have been carried out in the Djavakheti region, using modern methodology applying strict reliability and quality criteria. Many of them were carried out on Pliocene and Pleistocene lava flow sequences (Caccavari et al., 2014; Calvo‐Rathert et al., 2011, 2013; Camps et al., 1996; Goguitchaichvili & Pares, 2000; Goguitchaichvili et al., 1997, 2000, 2001a, 2009, 2016). In these previous studies, several episodes of unstable field behavior could be observed. Calvo‐Rathert et al. (2013) performed a reconnaissance paleomagnetic and paleointensity study on specimens from 14 basaltic lava flows from the Korkhi (sometimes also spelled Korxi) and Apnia sequences, but without knowledge about which specific lava flows from each sequence had been sampled. Analysis of the angular scatter of virtual geomagnetic poles yielded higher values than expected in both sequences and 19 paleointensity determinations from specimens belonging to 8 different flows provided successful determinations showing a large scatter. Directional and some paleointensity data pointed toward a possible transitional field record. For this reason, we sampled again both sequences systematically in order to find a record of geomagnetic excursions or reversals recorded in these lavas.

2 Geological Setting and Sampling The studied Plio‐Pleistocene sequences are located in the Djavakheti Highland, in the central sector of the Lesser Caucasus, which is one of the largest neovolcanic areas of the Caucasus and one the most seismically active regions of Georgia (Avagyan et al., 2005; Kachakhidze et al., 2003; Philip et al., 1989). The Caucasus mountain system belongs to the Caucasian‐Arabian belt (Sharkov et al., 2015), formed by the still active convergence of the Arabian and Eurasian lithospheric plates within the late alpine tectonic cycle (Adamia et al., 2011). Sharkov et al. (2015) distinguish three stages for the formation of the present structure of the Lesser Caucasus: precollisional (Late Paleozoic‐Early Mesozoic), syn‐collisional (Middle Jurassic‐Middle Miocene), and postcollisional (Late Miocene‐Quaternary). The compressional regime established in the postcollisional stage is responsible for the recent kinematics in the Lesser Caucasus and adjacent areas (Rolland, 2017). These recent kinematics are characterized by a strike‐slip regime, with both trans‐tensional and trans‐pressional characteristics, generated by the still active compression in the zone. Four types of structures can be distinguished: (1) W‐E trending folds and thrusts, (2) N‐S normal faults, (3) NE‐SW trending sinistral strike‐slip faults and (4) NW‐SE trending dextral strike‐slip faults (Avagyan et al., 2010). These structures control the most recent kinematics and act as conduits through which the magma ascends, giving rise to most subaerial neovolcanic activity, with at least three different magmatic stages. The rocks from the present study belong to the second (Pliocene – Early Quaternary) stage of young volcanic activity in the Djavakheti highland and the adjacent Armenian block (Lebedev et al., 2011). Five phases of Pliocene volcanism separated by quiet periods of less than 300 000 years are recognized based on K‐Ar dating: I, 3.75–3.55 Ma; II, 3.30–3.05 Ma; III, 2.85–2.45 Ma; IV, 2.25–1.95 Ma; and V, 1.75–1.55 Ma. Impulses of moderately acid and acid volcanism either preceded the major magmatism (phases III and IV) or were synchronous to it (phase II) or at the end of it (phase III) (Lebedev et al., 2011). Two different sequences belonging to the Akhalkalaki Formation (Figure 1), Apnia (41°21'40"N, 43°16'02"E) and Korkhi (41°27'31"N, 43°27'55"E), have been studied for the present work. The Apnia volcanic sequence is located near the Kura River (Mtkvari in Georgian), and the sequences were sampled from top to base. The sequence consists of 20 consecutive basalt and basaltic andesite lava flows with variable thickness between 0.10 to 8 m (supporting information Figure S1a). Flow boundaries are in general perfectly visible and identifiable. According to Lebedev et al. (2008), the upper lavas have the following K‐Ar ages: the uppermost flow AP01 (YUG‐21 in Lebedev et al., 2008) yields 3.09 ± 0.10 Ma and the 5th flow from the top AP03 (YUG‐26), 3.28 ± 0.10 Ma. In the lower part of this sequence there are two dated lava flows: AP08 (YUG‐28) with 3.75 ± 0.25 Ma and AP12 (YUG‐30) with 3.70 ± 0.20 Ma. Specimens for the K‐Ar datings are taken in the same succession that the paleomagnetic specimens, approximately 300 m toward the west in the same hillside. The lava flows from both samplings have been certain correlated during the paleomagnetic field work. It should be noted that the lower flows are relatively more altered and could have been subject of tectonic stress because multiple micro‐faults and cracks can be observed. In addition, highly explosive volcanism, especially in AP17 and AP18, was observed. Figure 1 Open in figure viewer PowerPoint Schematic geological map of the Plio‐Pleistocene magmatism in the Djavakheti Highland (Lesser Caucasus) showing lava flow sequences sampled in the present study (Calvo‐Rathert et al., 2013; Lebedev, 2015; Lebedev et al., 2008). 1 ‐ Quaternary volcanic rocks (andesites and dacites) of the Samsari ridge (800 – <30 ka); 2–10 Pliocene – Early Quaternary volcanic rocks of Akhalkalaki formation: 2 ‐ Basic lavas (1.75 – 1.40 Ma), 3 ‐ Basic lavas (2.15 – 1.95 Ma), 4 ‐ Later dacites and rhyolites of the Djavakheti ridge (2.25 Ma), 5 ‐ Hyalodacite (2.5 Ma), 6 ‐ Basic lavas (2.65 – 2.45 Ma), 7 ‐ Earlier rhyolites and dacites of the Djavakheti ridge (2.85 – 2.6 Ma), 8 ‐ Dacites of the SW part of Djavakheti highland (3.15 – 3.11 Ma), 9 ‐ Basic lavas (3.22 – 3.04 Ma), 10 ‐ Basic lavas (3.75 – 3.55 Ma); 11 ‐ Sampled lava flow sequences, (1) Korkhi, (2) Apnia; 12 ‐ Lakes. Location map from Google Earth: Image Landsat/Copernicus © 2018 Basarsoft, US Dept. of State Geographer. The Korkhi volcanic sequence (41°27'31"N, 43°27'55"E) consists of two horizons of basalts with different ages separated by an erosional surface covered by a layer of lacustrine sediments. The first subsequence, Lower‐Korkhi, comprises 17 lava flows with thicknesses varying between 0.5 and 5 m (supporting information Figure S1b). In the same way as in Apnia, for this sequence, it was possible to visually verify the breaks between each flow. The second one, Upper‐Korkhi, consists of 10 flows with thickness between 1.5 and 4 m (supporting information Figure S1b). Two of these flows were not found in situ (KR21 and KR23), but were sampled for future paleointensity determination studies and are shown in Table 1, since it is useful to know its paleomagnetic properties. According to K‐Ar datings performed in the present study, over the same paleomagnetic specimens, (supporting information Table S1), the Lower‐Korkhi subsequence yields an age of 3.08 ± 0.09 Ma in flow KR05 (YUG‐332) and 3.11 ± 0.20 Ma in flow KR17 (YUG‐331). Regarding the upper subsequence, it yields an age of 1.85 ± 0.08 Ma in flow KR27 (YUG‐330). Table 1. Paleomagnetic Results K‐Ar ages ChRM VGP Site (Ma) N (n + p) Dec Inc k α 95 φ (°N) λ (°E) P Dp Dm AP01 3.09 ± 0.10 8 + 0 335.7 57.8 250.1 3.5 71.2 312.4 N 4.0 4.9 AP02 6 + 2 337.2 57.4 427.6 2.7 72.2 309.9 N 3.1 3.8 AP04 7 + 0 345.1 61.1 413.1 3.0 78.9 322.3 N 3.5 4.7 AP05 6 + 0 332.6 58.4 215.2 4.6 69.0 316.1 N 5.3 6.6 AP03 3.28 ± 0.10 7 + 0 331.6 63.7 227.5 4.0 69.1 333.8 N 4.6 6.8 AP06 0 + 9 181.4 55.6 40.0 9.7 12.5 222.1 R‐I 11.2 12.9 AP07 7 + 0 200.7 −65.2 127.6 5.4 74.1 104.5 R 6.2 9.7 AP08 3.75 ± 0.25 8 + 0 198.8 −62.4 314.7 3.1 76.0 117.3 R 3.6 5.0 AP09 8 + 0 203.5 −64.8 236.7 3.6 72.4 107.6 R 4.2 6.3 AP10 7 + 0 204.6 −60.2 115.9 5.6 71.6 125.8 R 6.5 8.5 AP12 3.70 ± 0.20 7 + 0 199.1 −58.4 50.7 8.6 75.3 135.8 R 9.9 12.3 AP11 8 + 0 205.6 −56.6 66.4 6.8 69.8 136.8 R 7.9 9.3 AP13 5 + 0 201.4 −63.2 161.4 6.0 74.1 114.0 R 6.9 10.0 AP14 8 + 0 211.0 −66.7 88.7 5.9 67.0 102.7 R 6.8 11.2 AP15 7 + 0 216.5 −68.1 59.3 7.9 63.3 99.2 R 9.1 15.9 AP16 8 + 0 199.6 −57.1 54.4 7.6 74.5 140.5 R 8.8 10.5 AP17 7 + 0 191.2 −58.2 148.4 5.0 81.1 145.8 R 5.8 7.1 AP18 12 + 0 189.6 −56.8 83.9 4.8 81.6 158.4 R 5.5 6.6 AP20 9 + 0 196.2 −53.3 240.9 3.3 75.2 158.5 R 3.8 4.1 AP19 7 + 0 199.8 −53.6 180.8 4.5 72.8 151.7 R 5.2 5.7 Mean Normal 5 336.5 59.8 467.2 3.5 72.3 318.8 4.0 5.2 Mean Reverse 14 200.6 −60.5 194.1 2.9 74.6 126.1 3.4 4.4 KR27 1.85 ± 0.08 9 + 0 212.5 −50.3 81.2 5.7 62.0 144.7 R 6.6 6.7 KR26 10 + 0 203.0 −52.5 72.7 5.7 70.0 150.7 R 6.6 7.0 KR25 11 + 0 212.0 −61.0 166.2 3.6 66.2 121.2 R 4.2 5.6 KR24 9 + 0 219.2 −25.0 141.2 4.3 45.7 161.6 R 5.0 3.6 KR23 2 + 0 14.1 33.6 185.1 18.5 64.0 191.7 N 21.4 16.6 KR22 9 + 0 218.4 −41.1 107.8 5.0 53.4 150.6 R 5.8 5.0 KR21 2 + 0 77.7 45.4 765.6 9.0 26.2 119.7 N 10.4 9.6 KR20 9 + 0 102.5 −74.3 116.7 4.8 41.0 4.1 R 5.6 13.3 KR19 8 + 0 114.6 −71.8 223.4 3.7 46.5 357.0 R 4.3 8.9 KR18 9 + 0 136.8 −70.1 107.4 5.0 56.1 352.4 R 5.8 11.0 KR17 3.11 ± 0.20 10 + 0 352.6 51.0 442.0 2.3 78.7 257.1 N 2.7 2.7 KR16 10 + 0 358.1 54.0 379.6 2.5 83.1 236.3 N 2.9 3.2 KR15 9 + 0 353.4 51.2 1219.8 1.5 79.2 254.4 N 1.7 1.8 KR14 10 + 0 354.4 51.9 84.5 5.3 80.1 251.8 N 6.1 6.4 KR13 9 + 0 354.8 53.5 688.1 2.0 82.0 254.1 N 2.3 2.5 KR12 10 + 0 357.7 51.8 166.0 3.8 80.9 235.7 N 4.4 4.6 KR11 9 + 0 355.3 53.2 316.4 2.9 81.5 250.8 N 3.4 3.6 KR10 10 + 0 0.6 54.6 99.1 4.9 83.7 219.0 N 5.7 6.3 KR09 10 + 0 2.5 58.9 151.4 3.9 87.5 176.0 N 4.5 5.7 KR08 9 + 0 3.1 52.1 94.4 5.3 82.2 206.7 N 6.1 6.5 KR07 9 + 0 356.7 52.8 243.8 3.3 81.6 242.5 N 3.8 4.1 KR06 10 + 0 2.4 52.7 209.2 3.3 81.7 209.6 N 3.8 4.1 KR05 3.08 ± 0.09 9 + 0 353.6 50.0 61.1 6.6 78.2 251.3 N 7.6 7.7 KR04 10 + 0 348.5 53.8 71.0 5.8 78.5 279.0 N 6.7 7.4 KR03 11 + 0 353.9 53.8 226.1 3.0 81.4 259.5 N 3.5 3.8 KR02 9 + 0 355.5 55.1 196.5 3.7 83.2 256.1 N 4.3 4.8 KR01 9 + 0 346.3 50.5 108.8 5.0 75.0 274.9 N 5.8 5.9 Mean Normal 17 355.7 53.1 538.5 1.5 81.5 248.4 1.7 1.9 Mean Reverse 8 198.7 −61.8 9.1 19.4 76.1 120.8 22.5 30.8

3 Methods The sequences were sampled with a portable water‐cooled drill and directly oriented in the field with both a solar and a magnetic compass and an inclinometer, with an average of 8 cores per lava flow. Standard paleomagnetic specimens were cut from each core. All laboratory paleomagnetic experiments were carried out at the paleomagnetic laboratory at the University of Burgos (Spain). Remanent magnetization was measured using a 2G cryogenic magnetometer, a TD48‐DC (ASC) oven and a LDA3 (Agico) alternating field demagnetizer. In each of the 47 studied flows two pilot specimens were chosen, one to perform 16 steps thermal demagnetization (TH)up to 585°C, and one for 22 steps alternating field demagnetization (AF up to 100 mT. Finally, according to the results obtained from the pilot study, 6 to 10 specimens from each flow were subjected to 9 steps TH demagnetization up to 580°C and 3 were demagnetized in 12 AF demagnetization steps up to 100 mT. Including pilot specimens, 222 specimens belonging to Apnia (156 TH and 66 AF) and 323 to Korkhi (241 TH and 82 AF) were measured. Principal component analysis (PCA) and great circle analysis (GCA) were performed with the Remasoft 3.0 software (Agico) (Chadima & Hrouda, 2006). The isotope‐geochronological study of the basalts from Korkhi section was conducted using special modification of the K–Ar method developed in the Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry – Russian Academy of Sciences (IGEM RAS) for the dating of young magmatic rocks. Its methodology and main analytical characteristics are reported in the paper (Chernyshev et al., 2006). The content of radiogenic Ar was determined on a highly sensitive low‐blank mass spectrometer MI‐1201 IG (SELMI) at the IGEM RAS using the isotope dilution technique with 38Ar monoisotope as a spike. The potassium content was measured by the flame photometry method on an FPA‐01 spectrometer (ELAM‐Center, Russia). In order to avoid a possible distortion of K–Ar dates due to the presence of excess 40Ar in phenocrysts of volcanics, we analyzed only groundmass of basalts. Total errors in the determination of K–Ar age (±2σ) depend on the content of radiogenic argon in specimens and 40Ar*/40Ar tot in the analyzed material. Their absolute values for certain specimens are given in supporting information Table S1 together with age datings. Obtained isotope data were recalculated using decay constants recommended by the International Subcommission on Geochronology (Steiger & Jäger, 1977). Rock‐magnetic measurements were carried out with a variable field translation balance (VFTB). Whole‐rock powdered specimens (between 300 and 400 mg) from 59 specimens of Apnia and 82 of Korkhi were used for these experiments, with the following measurement sequence: (i) IRM acquisition and backfield curves, (ii) hysteresis loops and (iii) strong field magnetization versus temperature (Ms‐T) curves. In the remaining specimens only Ms‐T curves were measured. Measurements of Ms‐T curves were performed in air, heating whole‐rock powdered specimens up to different temperatures and cooling them down to room temperature. Most experiments were performed at a heating rate of 20°C/min, but some specimens were heated up to 700°C using a 10°C/min heating rate. Curie temperatures (T C ) were determined using the two‐tangent method (Grommé et al., 1969). Hysteresis parameters M S (saturation magnetization), M RS (saturation remanence), B C (coercivity) and B CR (coercivity of remanence) were obtained from hysteresis and backfield curves. Isothermal remanent magnetization (IRM) acquisition curves were recorded in a maximum applied field near to 1T. Analysis of these measurements was performed with the RockMagAnalyzer 1.0 software (Leonhardt, 2006).

4 Rock Magnetic Results Rock magnetic experiments were performed to determine the carriers of remanent magnetization and to obtain information about their thermal stability and their grain size. Magnetic properties may vary along the same outcrop due to its thickness or differences in cooling rate. Because of this, the results obtained from a single specimen are not representative of the magnetic characteristics of the whole lava flow, and thus, in this work several specimens per flow have been analyzed. Specimens were grouped by proximity in the outcrop and one specimen was selected from each group to carry out rock‐magnetic experiments. From each of the 47 studied flows three specimens were selected for the measurement of magnetization versus temperature (Ms‐T) curves and one to three specimens from each lava flow were used for isothermal remanent magnetization (IRM) acquisition and hysteresis curves. Strong field magnetization versus temperature (Ms–T curves) were measured to find out the carriers of remanence and to detect at what temperatures possible alterations occur in the specimens. Among all measurements four different types of behavior could be distinguished (supporting information Figure S2): Type H: 23 specimens out of 59 on the Apnia and 24 specimens out of 82 analyzed on the Korkhi sequence are characterized by reversible curves and a single high Curie temperature (T C ) mineral phase near 580°C, corresponding to low‐Ti titanomagnetite/magnetite (supporting information Figure S2a). In one case, a small stable hematite phase was also observed. We considered a curve to be reversible if the heating and cooling branches displayed the same magnetic phases and the difference between initial magnetization before heating and the final magnetization after cooling had been completed was less than ± 15%. It should be mentioned that Curie temperatures determined from heating curves, with a mean of T CH1 = 570°C, were higher than those determined from cooling curves (mean T CC1 = 552°C). This disagreement could be due to a lack of thermal equilibrium between the inner and outer part of the specimens, due to fast heating/cooling, causing a difference between the recorded and the real temperature. However, the same behavior is observed in slowly heated specimens. Changes in Curie temperature could also arise from cation reordering during heating in thermomagnetic experiments (Bowles et al., 2013). Type H*: 25 specimens out of 59 from the Apnia and 26 specimens out of 82 analyzed from the Korkhi sequence showed a similar behavior to type‐H specimens, with the same low‐Ti titanomagnetite phase both in the heating and cooling curves. However, initial and final magnetization differed by more than ± 15%. In addition, two specimens with a somewhat different behavior were also included in the H*‐group. In both specimens low‐Ti titanomagnetite/magnetite was not the only carrier of remanence, as another very weak phase with a higher Curie temperature both in the heating (T CH2 = 617°C) and the cooling curves (T CC2 = 610°C) was observed (supporting information Figure S2b). This high Curie temperature might be ascribed to the presence of low‐Ti titanohematite, but the effect of a possibly relatively high fraction of an antiferromagnetic phase should be also observed in the values of its hysteresis parameters and IRM‐acquisition curves. However, all these values do not display significant differences with those from other specimens. On the other hand, the high Curie temperatures might be attributed to the presence of partially oxidized magnetite, i.e., to the maghemitization of magnetite. The Curie temperature of this phase would be related to the degree of oxidation and lies between magnetite and maghemite Curie temperatures (Gehring et al., 2009; Liu et al., 2001). Usually in this type of basalts a high temperature oxidation is observed in which ilmenite and magnetite exsolution is produced. This oxidation can occur during rock formation above Curie temperature, indicating that the recorded magnetization is an original TRM. In addition, the magnetization loss observed between the heating and cooling curves also can be attributed to the thermally unstable magnetic component maghemite inverting to hematite. Type L: 3 specimens out of 59 from the Apnia and 17 out of 82 from the Korkhi sequence belong to this group. They display irreversible behavior and two phases (supporting information Figure S2c). The first phase appearing in the heating curve with Curie temperatures between T CH1 = 190°C and T CH2 = 280°C (supporting information Table S2.), matching those of high‐Ti titanomagnetite. The second is a high Curie temperature phase observed in both heating and cooling curves. It is considered to be low‐Ti titanomagnetite and represents small fraction of the initial magnetization. Type M: 8 out of 59 specimens from the Apnia and 15 out of 82 from the Korkhi sequences belong to this group. They also show an irreversible behavior and two phases can be distinguished (supporting information Figure S2d). The first one is low‐Ti titanomagnetite/magnetite and appears both in the heating and cooling curves. The second weaker phase is observed only in the heating curve and displays an intermediate Curie temperature phase within the 320°C to 440°C range (supporting information Table S2), likely high‐Ti titanomagnetite. On other hand, the inflection at about 320°C could be titanomaghemite, generated by the oxidation of the titanomagnetite. On other hand, also could be primary maghemite. At 350°C maghemite converts into hematite with a significant loss of magnetization which is reflected in the cooling curve. The reason why the hematite Curie temperature is not observed is that about 20% of the initial magnetization has been transformed into a 200 times more weakly magnetized mineral, which accounts for only 1/1,000 of initial magnetization and is therefore not detectable. A Day‐plot of hysteresis parameter ratios (Day et al., 1977, as modified by Dunlop, 2002) shows that all studied specimens can be found in the pseudo‐single‐domain (PSD) area, except specimen KR23‐01AII, which plots on the boundary between the PSD and the single‐domain (SD) area (supporting information Figure S4 and Table S2.). This specimen shows a Ms‐T curve combining type M and L behaviors. The PSD behavior of the remaining specimens might also be explained by a mixture of SD and MD (multidomain) particles. If the data from the present study are compared with theoretical Day plot curves calculated for magnetite (Dunlop, 2002), the relative amount of MD particles in the mixture would vary in most cases between approximately 10% and 80%. In the case of the Korkhi sequence, different domain structures can be distinguished between both subsequences. In Upper‐Korkhi, a trend toward SD is observed, whereas in Lower‐Korkhi a trend is toward a higher percentage of MD in the mixture (supporting information Figures S4 and S5). Isothermal remanent magnetization (IRM) acquisition curves indicated that 86–99% of saturation isothermal remanent magnetization (SIRM) had been acquired by all specimens at 200 mT (supporting information Table S2 and Figure S3), thus pointing to low coercivity ferrimagnetic phases as main carriers of remanence.

5 Paleomagnetic Results In most flows, paleomagnetic measurements yielded a single main paleomagnetic component (Figures 2a and 2b), although all of them yielded a viscous present‐day normal‐polarity overprint, which was easily removed with weak alternating fields (less than 10 mT) or low temperatures (up to 200 to 250°C). However, in some specimens belonging to flows AP02, AP06, KR18, KR22, KR23, KR25 and KR27 a second component was observed which could be isolated from the main component (Figures 2c and 2d). Median destructive fields (MDF) are variable within each flow, ranging between 30 and 90 mT. A relationship between the behavior of the Ms‐T curves and the capacity to obtain paleomagnetic directions has not been observed. In two flows, AP02 and AP06, paleomagnetic analysis of some specimens had to be performed by means of great circle analysis (GCA) (Table 1). In such cases, mean flow directions were calculated combining directly determined directions and remagnetization circles (McFadden & McElhinny, 1988). Paleomagnetic directions showed a low scatter in all sites. Between 7 and 12 ChRM directions/remagnetization circles were used to calculate the mean paleomagnetic direction of each lava flow (Table 1). Figure 2 Open in figure viewer PowerPoint Orthogonal demagnetization vector plots obtained with the Remasoft software (Chadima & Hrouda, 2006). Solid symbols are for the horizontal projection (Declination) and open symbols for the vertical projection (Inclination). Projection in geographic coordinates. (a) Thermal‐demagnetization of AP01–03AII and KR01–02BII and AF‐demagnetization of AP03–07C and KR06–07D. (b) Thermal‐demagnetization of AP15‐03CI and KR26‐01AI and AF‐demagnetization of AP12‐05BI and KR24‐07C. (c) Thermal‐demagnetization of AP02‐02C and AF‐demagnetization of AP02–03C. d) Thermal‐demagnetization of KR27‐02BII and AF‐demagnetization of KR27‐04BII. Virtual geomagnetic poles (VGPs) were determined from all previously determined flow mean paleomagnetic directions. Subsequently, the optimum cutoff angle (Vandamme, 1994) was deduced from the VGP angular scatter of the complete Apnia sequence and separately for the two subsequences of Korkhi, considered independent due their K‐Ar ages. The directions corresponding to a stable field regime, with either normal or reverse polarity, as well as those corresponding to an anomalous regime (called henceforth intermediate polarities) could be distinguished. The intermediate directions have been excluded from the group mean direction and group mean pole calculations of both normal and reverse polarity groups (Table 1). Apnia shows a cutoff angle of 36.5° with respect to the reference pole used (i. e. latitude 53.51°), above which the VGPs are considered intermediate. Therefore, the pole obtained in lava flow AP06 is taken to reflect an intermediate geomagnetic regime. Lower‐Korkhi shows a cutoff angle of 34.6° and consequently all directions record a normal polarity of the magnetic field. The situation in Upper‐Korkhi is more complicated. The VGPs obtained in these 8 flows are all close to intermediate latitudes (Figure 4 and Table 1). Hence, the application of the Vandamme method might be unsuitable in this case, as it would include all poles in a reverse polarity stable regime (cutoff angle of 74.9°), despite the relatively anomalous values observed. In fact, Upper‐Korkhi directions possibly do not correspond to a Fisherian distribution. In several studies, arbitrary cutoff angles have been used (e.g., Biggin et al., 2008). If a cutoff angle of 45° like in this latter study is applied, a strict interpretation would exclude only sites KR20 and KR22 as having intermediate polarity directions. However, two more flows, KR19 and KR24 yield VGP latitude around λ=46°, which, if confidence limits Dp and Dm are taken into account, fall clearly below the 45° threshold. Although flow KR19 yields a latitude λ= 58.9°, it has not been taken into account for an analysis of possible tectonic rotations (see below), as this flow lies below four flows with anomalous directions. Thus, only the three uppermost flows of the Upper‐Korkhi subsequence have been used to determine possible tectonic rotations of this unit. For all the above, VGPs obtained in the Upper‐Korkhi subsequence are considered as a record of an anomalous magnetic field and these directions will be treated as a separate group of reverse‐intermediate polarities in order to estimate their paleosecular variation parameters. After these calculations, the Apnia sequence shows 14 reverse, 1 intermediate and 5 normal polarity flows (Figure 3 and Table 1). The reverse polarity flows lie in the lower part, above flow AP06, which displays an intermediate polarity and the following flows in the upper part of the sequence all display normal polarity. The Lower‐Korkhi sequence shows 17 normal polarity flows and Upper‐Korkhi 8 reverse‐intermediate polarity flows (Figure 4 and Table 1). This latter subsequence could display an anomalous EMF regime. Figure 3 Open in figure viewer PowerPoint Paleomagnetic results of the Apnia sequence. (a) Stereographic projection of mean paleomagnetic directions (ChRMs) of each lava flow, with normal and reverse directional groups averages (pink), with their corresponding α 95 , and the expected direction (Besse & Courtillot, 2002) (purple). Solid symbols and open symbols show directions with positive and negative inclinations, respectively (reverse average is projected in both north and south hemispheres). (b) Stereographic projection of Virtual Geomagnetic Poles (equal‐area projection) together with paths linking VGPs by stratigraphic order. Normal and reverse polarity group averages (pink) and the expected pole for the last 5 Ma in Eurasia (Besse & Courtillot, 2002) (purple). Positive/negative VGP latitudes are shown with solid and open symbols respectively. Projection created using the GMAP2012 for Windows 7 software (Torsvik & Cocks, 2012; Torsvik & Smethurst, 1998, 1999) (http://www.earthdynamics.org/Bugs/GMAP_2012.htm). (c) Declination and inclination of paleomagnetic directions, and latitude of VGPs, stratigraphically ordered. Note that AP06 has a reverse declination whereas that its inclination is normal, which demonstrates that is a recorded unusual orientation resulting in a transitional‐reverse VGP latitude. Figure 4 Open in figure viewer PowerPoint Paleomagnetic results of the Korkhi sequence. (a) Stereographic projection of mean paleomagnetic directions (ChRMs) of each lava flow, with normal and reverse directional group averages (pink), with their corresponding α 95 , and the expected direction (Besse & Courtillot, 2002) (purple). Solid symbols and open symbols show directions with positive and negative inclinations, respectively (reverse average is projected in both north and south hemispheres). (b) Stereographic projection of Virtual Geomagnetic Poles (equal‐area projection) together with paths linking VGPs by stratigraphical order. Normal and reverse polarity groups averages (pink) and the expected pole for 0–5 Ma in Eurasia (Besse & Courtillot, 2002) (purple). Positive/negative VGP latitudes are shown with solid and open symbols respectively. Projection created using the GMAP2012 for Windows 7 software (Torsvik & Cocks, 2012; Torsvik & Smethurst, 1998, 1999) (http://www.earthdynamics.org/Bugs/GMAP_2012.htm). (c) Declination and inclination of paleomagnetic directions, and latitude of VGPs, stratigraphically ordered. The brown zig‐zag line represents the erosional surface between Lower‐Korkhi and Upper‐Korkhi subsequences.

6 Analysis of Tectonic Rotations It is interesting to note that α 95 confidence ellipses from normal and reverse group mean directions of the Apnia sequence and both Korkhi subsequences do not overlap. In addition, in both cases normal and reverse populations are not antipodal. Application of the reversal‐test (McFadden & McElhinny, 1990) to the mean directions of upper and lower subsequences of both units yields a negative result. In particular, Apnia normal and reverse mean directions give γ C (angle between data set means) = 21.7° and γ crit (critical angle after M&M1990) = 4.6°, and therefore a positive‐indeterminate classification which points to two different populations. Korkhi subsequences yield a negative‐C classification, with an observed angle γ C = 15.2° and γ crit = 19.5°. Even so, it must be taken into account that the last two subsequences have different ages and cannot be compared. Thus, both directional populations from both sequences can be considered non‐antipodal. Taking into account that the Apnia sequence and the Lower‐Korkhi subsequence erupted between 3.1 ± 0.1 Ma and 3.75 ± 0.25 Ma and Upper‐Korkhi presents an age of 1.85 ± 0.08 Ma, mean paleomagnetic directions of all polarity groups have been compared with the expected direction obtained from the 0 Ma pole of the synthetic apparent polar wander path (APWP) for Europe (Besse & Courtillot, 2002), as the difference between the expected directions for 0 and 5 Ma are negligible (Figures 3a and 4a; Table 2). The reference pole of the European plate has been taken because it is not possible to obtain a stable reference in the Djavakheti region due to its tectonic activity. The mean normal‐direction of the Apnia sequence yields an angular distance of Δ = 14.0° with the expected direction, while the mean reverse‐direction shows a significantly lower angular difference of Δ = 8.7°. If the same comparison is performed with the normal‐polarity Lower‐Korkhi subsequence, the angular difference with the expected direction is Δ = 7.1°. The mean reverse‐intermediate‐direction of the whole Upper‐Korkhi subsequence yields an angular distance of Δ = 8.5°, but the large α 95 confidence angle of this last subsequence statistically overlaps with the expected direction. Therefore, mean paleomagnetic directions from both Apnia polarity groups and Lower‐Korkhi do not agree with the expected direction for the sequences age. Note that the normal‐polarity upper Apnia stretch shows the largest angular distance. These results allow the following possible explanations: Either both sequences have experienced tectonic rotations or they have recorded an anomalous behavior of the EMF. Also, an incomplete averaging of secular variation due to an extremely fast emission of lava flows could also account for the observed behavior. Table 2. Rotation Analysis Polarity group N Dec Inc α95 Δ R ± ΔR F ± ΔF Apnia‐normal 5 336.5 59.8 3.5 14.0 −27.3 ± 6.7 −1.3 ± 3.4 Apnia‐reverse 14 20.6 60.5 2.9 8.7 16.8 ± 6.1 −2.0 ± 3.1 Lower‐Korkhi 17 355.7 53.1 1.5 7.1 −8.1 ± 4.4 5.4 ± 2.4 Upper‐Korkhi 8 18.7 61.8 19.4 8.5 15.7 ± 32.4 −3.3 ± 15.3 Upper‐Korkhi (φ > 60°) 3 29.0 54.7 9.9 14.7 26.0 ± 13.6 3.8 ± 7.8 B&C 2002 – 0 Ma 25 3.0 58.5 3.0 B&C 2002 – 5 Ma 30 3.8 58.5 2.6 Tectonic motion of the studied sequences can be analyzed directly by comparing the declination and inclination of the mean direction of the four polarity groups (Dm and I m ) with the expected values (D e and I e ). Possible vertical axis rotations are determined with the difference in declination or “rotation” R = Dm – D e and horizontal axis rotations with the difference in inclination or “flattening” F = I e – I m . However, analysis of possible tectonic rotations with results from the Upper‐Korkhi subsequence is not straightforward, as the data are not time‐averaged directions and they, initially, cannot be used to estimate vertical axis rotation. Tentatively, we have compared the expected direction with the mean direction obtained from the three uppermost Upper‐Korkhi flows, as explained above. If applied to the results obtained in the upper and lower parts of both sequences, and after calculation of confidence limits (Demarest, 1983) it can be observed that inclination values agree well with the expected directions (Table 2). Only in the Lower‐Korkhi normal‐polarity flows a significant but minor flattening F = 5.4 ± 2.4° can be observed. It might be concluded that the sequences have not undergone horizontal axis rotations. Vertical axis rotations, however, show larger values. In the lower reverse‐polarity part of the Apnia sequence, a clockwise vertical axis rotation R = 16.8 ± 6.1° is observed while the upper normal‐polarity part shows a counter‐clockwise rotation R = −27.3 ± 6.7° (Table 2). If these results are regarded as a product of tectonics in the Lesser Caucasus area, two considerable rotations in opposite direction must have occurred. If the available K‐Ar ages are considered (Lebedev et al., 2008), the following sequence of rotations would be needed to explain the observed paleomagnetic results: First a ≈ 44.1° clockwise rotation of the lower part of the sequence in a very short time period, between 3.75 ± 0.25 Ma and 3.1 ± 0.1 Ma (approximately 500 ka), and subsequently, after the emission of the upper part a ≈ 27.3° counter‐clockwise rotation of the whole sequence. Thus, the possibility of two consecutive rotations in opposite directions in Apnia sequence seems rather unlikely. Since, the kinematics does not work for a fault to show counter‐clockwise rotation followed by clockwise rotation unless you change the stress field significantly or new structures develop to facilitate the reversal of rotation on the same structural block. In the normal‐polarity Lower‐Korkhi subsequence a small counter‐clockwise rotation R = −8.1 ± 4.4° is observed. The reverse‐polarity Upper‐Korkhi three upper most flows, on the other hand, display a larger clockwise rotation R = 26.0 ± 13.6°, (Table 2). Like in the Apnia sequence, two successive rotations in opposite directions would be needed to explain the results. However, in this case an initial 24° counterclockwise rotation of the lower part would have been followed by a 16° clockwise rotation of the whole sequence, just the opposite sequence as in Apnia. This latter fact also makes the possibility of two consecutive rotations in opposite directions in Korkhi rather unlikely. Note that the occurrence of tectonic rotation is only one of several different possibilities to explain deviations from expected directions. Anomalous field behaviour and/or not time‐averaged field direction could also account for the observed data.

7 Paleosecular Variation Analysis In this section, the time averaged field of the records of the Apnia and Korkhi sequences will be analyzed. In order to evaluate the behavior of paleosecular variation (PSV), an analysis of the angular standard deviation (ASD) of VGPs scatter has been carried out. Total angular scatter can be estimated by (Cox, 1969), where N is the number of analyzed sites and δ i is the angular distance of the i‐th VGP from the expected pole position or from the mean VGP. It is also necessary to apply a correction for the within‐site angular scatter S W (McElhinny & McFadden, 1997). The corrected total angular scatter S B is given by , with n being the average number of specimens measured in each lava flow. Setting aside that some doubt has been cast on this method (Linder & Gilder, 2012), it may help identify sections that likely do not average PSV. However, a ‘positive ASD test’ (where observed dispersion matches the expected one) is not a sufficient condition to ensure an adequate time average field direction. When this analysis is performed with respect to the mean VGP for the Apnia sequence, both the reverse and normal polarity data sets yield very low scatter, displaying clearly lower values (Table 4) than expected from Model G of paleosecular variation of lavas (PSVL) (McFadden et al., 1988) fits to data from the last 5 Ma from McElhinny and McFadden (1997) and Johnson et al. (2008) at 41° latitude. On the other hand, when angular scatter with respect to the reference pole (Besse & Courtillot, 2002) is calculated for both polarity groups in the Apnia sequence, the reverse‐polarity group displays an angular scatter matching the expected field (Table 4 and supporting information Figure S6a) while the normal‐polarity group shows a higher angular scatter, although its confidence interval spans the expected field. The following different although not incompatible explanations can be put forward: A short recording time in the normal polarity section of the sequence unable to average PSV. Absence of tectonic rotations, as scatter with respect to the mean VGP is negligible, but is as expected with respect to the GAD, especially for the reverse polarity group. An anomalous EMF in the normal polarity group. Scatter with respect both to the reference pole (Besse & Courtillot, 2002) and the mean VGP is much lower than expected in Model G in Lower‐Korkhi, suggesting that a short time is recorded and PSV is not averaged (Table 4 and supporting information Figure S6b). If tentatively the same calculations are performed for all flows of the anomalous Upper‐Korkhi record, a much higher than expected scatter value, together with very high confidence limits is obtained in both cases (Table 4 and supporting information Figure S6b). These results seem to point to an anomalous EMF record in Upper‐Korkhi although a non‐adequately averaged PSV cannot be discarded. Nevertheless, it should be noted that results in Upper‐Korkhi are far away from the model values, probably showing a truly unstable EMF behavior, which could be already expected from the anomalous near to intermediate latitudes shown by the VGPs. In some cases, consecutive lava flows can show statistically identical paleomagnetic directions, and such overlapping directions are considered to form directional groups (DG). In the present study DGs have been detected with the method proposed by Chenet et al., 2008, and their mean paleomagnetic directions are shown on Table 3. Each individual DG formed by more than one flow is a robust indication of rapid emplacement, implying very short eruptive periods. Thus, each DG represents a single snap‐shot of the magnetic field, and has the same weight iASD calculations. Seven different DGs were detected in the Apnia sequence, three in the reverse polarity stretch and three in the normal one. These few DGs are consistent with the interpretation of a non‐adequately averaged PSV. In the Korkhi sequence, six DG were defined in the lower section and six in upper‐one (note that some of them only include a single flow) (Table 3). The same kind of angular scatter analysis performed on DGs both with respect to the expected pole and the mean VGP, yields very similar results than with individual lava flows (Table 4). Table 3. Directional Groups Directional Groups Flows N Dec Inc α 95 k φ (°N) λ (°E) Dp Dm Apnia‐normal DG1 AP02‐01 2 336.5 57.6 2.0 8,146.5 71.7 311.1 2.3 2.8 DG2 AP04 1 345.1 61.1 3.0 413.1 78.9 322.3 3.5 4.7 DG3 AP03–05 2 332.1 61.1 11.6 231.9 69.3 324.8 13.4 18.0 mean 3 337.8 60.0 5.8 298.5 73.3 319.0 6.7 8.7 Apnia‐intermediate DG4 AP06 1 181.4 55.6 9.7 40.0 −12.5 42.1 11.2 12.9 Apnia‐reverse DG5 AP15‐07 9 204.2 −62.9 2.9 274.7 −72.1 295.6 3.4 4.8 DG6 AP17‐16 2 195.5 −57.7 10.1 307.1 −77.7 322.5 11.7 14.2 DG7 AP19‐18 3 195.4 −54.6 5.4 349.4 −76.4 335.6 6.2 7.0 mean 3 198.0 −58.5 7.5 181.9 −76.1 316.3 8.7 10.8 Upper‐Korkhi DG1 KR26–27 2 207.9 −51.5 13.8 164.6 −66.0 326.8 15.9 16.6 DG2 KR25 1 212.0 −61.0 3.6 166.2 −66.3 301.2 4.2 5.6 DG3 KR24 1 219.2 −25.0 4.3 141.2 −45.7 341.6 5.0 3.6 DG4 KR22 1 218.4 −41.1 5.0 107.8 −53.4 330.6 5.8 5.0 DG5 KR19–20 2 109.0 −73.1 9.4 353.3 −43.8 180.6 10.9 24.2 DG6 KR18 1 136.8 −70.1 5.0 107.4 −58.9 172.4 5.8 11.0 mean 6 202.6 −58.7 24.2 7.2 −72.7 312.7 28.0 34.9 Lower‐Korkhi DG1 KR17 1 352.6 51.0 2.3 442.0 78.6 257.1 2.7 2.7 DG2 KR16 1 358.1 54.0 2.5 379.6 82.9 236.3 2.9 3.2 DG3 KR10–15 6 356.0 52.7 1.7 1,307.5 81.2 246.0 2.0 2.1 DG4 KR09 1 2.5 58.9 3.9 151.4 87.4 176.0 4.5 5.7 DG5 KR02–08 7 356.3 53.0 2.6 462.6 81.6 245.0 3.0 3.2 DG6 KR01 1 346.3 50.5 5.0 108.8 75.0 274.9 5.8 5.9 mean 6 355.0 53.5 3.7 279.6 81.6 253.1 4.3 4.7 Table 4. VGPs Angular Scatter Comparison Mean VGP Expected pole Individual flows Directional groups Individual flows Directional groups Analyzed data sets S B S U S L S B S U S L S B S U S L S B S U S L Apnia‐normal 3.6 7.0 1.3 21.3 41.4 7.8 Apnia‐reverse 5.0 7.8 2.8 14.7 23.1 8.2 Upper‐Korkhi 35.0 61.2 16.0 34.0 63.5 13.7 35.8 62.6 16.4 35.0 65.3 14.1 Lower‐Korkhi 1.2 2.0 0.6 4.0 7.5 1.6 8.0 13.2 4.1 9.0 16.7 3.6

8 Discussion Paleomagnetic results in the Apnia sequence yield from bottom to top a record of reverse and normal polarity directions separated by a single transitional lava flow. Mean normal and reverse directions do not match the expected field direction and are non‐antipodal. Tectonic rotations have been discarded. In the lower reverse polarity stretch of the section, a directional group (DG) with 9 lava flows toward the upper end of the stretch, has been defined, indicating a fast emission of the lava flows, implying that PSV might not be well averaged in this stretch and displaying only a short image of the EMF record. Analysis of secular variation scatter with respect to the mean VGP of both normal and reverse intervals yields very low values (Table 4 and supporting information Figure S6). The same analysis performed with respect to the reference pole yields an angular scatter matching the expected scatter for the reverse‐polarity group and a high angular scatter for the normal‐polarity group. From this analysis, PSV could be averaged in the lower Apnia subsection although S B with respect to the mean VGP is very low, apparently reflecting a short recording time. In contrast, results of the upper Apnia subsection would allow different, and not mutually exclusive interpretations. As tectonic rotations have been discarded, a short recording time unable to average PSV and an anomalous EMF record are both possible. Uncertainties of available K‐Ar data do not allow to characterize the periodicity of the volcanic emissions with accuracy. The eruptions in this region occurred from numerous fissures and monogenic cones. They have a pulsating character such that the periods of intense eruptions could be followed by pauses of different duration. I If regular eruption intervals are considered, K‐Ar data in the Apnia sequence (Lebedev et al., 2008) might be used to perform a rough estimation of the duration of volcanic activity in each subsequence. If the maximum and minimum times intervals given by the dating uncertainty is considered, each flow would have been emitted approximately between 30 to 80 ka. A time interval of 104 years has commonly been thought to be sufficient to characterize PSV (Carlut et al., 1999; Johnson & Constable, 1996; Merrill et al., 1996), although other studies (Merrill and Mcfadden, 2003) suggest that at least 105 years are necessary. While these maximum emission intervals would allow PSV averaging in both subsequences, very low eruption intervals are also possible, producing records with non‐averaged PSV. A different estimation might be performed considering the duration of a polarity transition being of the order of magnitude of 1 to 10 ka. If we take the length of the transition as the time elapsed between AP07 to AP03, these three lava flows would then have been erupted in 1 to 10 ka (300–3,000 years per lava flow roughly). Through extrapolation, the entire sequence would have been generated in more than 6 ka to 60 ka, a sufficient time to average PSV. Absolute intensity values can supply critical information about the unstable character of the recorded EMF. Calvo‐Rathert et al. (2013), performed a paleointensity study on specimens from both the Apnia and Korkhi sequences, in which no information about the specific stratigraphic order of each lava flow was available. Paleomagnetic information, however, may be used to correlate results from Calvo‐Rathert et al. (2013) (CR13 in the following specimen description) and the present study. Most determinations were performed on specimens from the reverse polarity subsection. Flow AP5 (CR13) can be correlated with DG7 (AP18, AP20 and AP19) and yields a reliable mean paleointensity F = 17.3 ± 1.6 μT based on five determinations: Flow AP6 (CR13) yields an also very reliable mean paleointensity 39.8 ± 7.8 μT, obtained from six determinations. Although its paleomagnetic direction does not exactly agree with the ones obtained in the present study, it is very near to the direction between DG5 and DG6. Flow AP10 (CR13) coincides with AP11. Rejection of one differing and clearly lower quality determination of the three performed, yields a mean paleointensity value F = 27.9 ± 4 μT. Flow AP1 (CR13) matches AP18, and yields a single rather anomalous paleointensity determination F = 76.1 ± 7.7 μT. Only a single determination from flow AP7 (CR13) which matches AP04 from the present work is available in the normal polarity stretch, yielding F = 54.3 ± 2.2 μT. Calvo‐Rathert et al. (2013) detect a single flow in the Apnia sequence with a transitional direction, AP2 (CR13). This flow should match AP06 from the present study, which is the only one yielding transitional results. Mean directions of both flows, however, are different and also their paleomagnetic behavior differs. An orientation error during block sub‐sampling in 1984–1986 of the specimens studied by Calvo‐Rathert et al. (2013) might be possible, but is difficult to confirm, as recovery of some information regarding the sampling and sample preparation more than thirty years ago might be impossible. In this flow two paleointensity determinations with very different values were obtained, but rejection of one lower‐quality determination (f = 0.35), yields F = 26.0 ± 1.4 μT. The general trend in the reverse polarity section seems to correspond to rather low paleointensity values, and even the more intense specimens from flow AP6 (CR13) are somewhat lower than the current field value of 49 μT in Georgia. Thus, results obtained in the Apnia sequence are somewhat ambiguous, allowing multiple, but not exclusive interpretations. As tectonic rotations have been discarded, a short recording time unable to average PSV and an anomalous EMF record are both possible. Specifically, in the reverse polarity section the presence of a DG formed by 9 flows supports the first interpretation, while a VGP scatter matching expected values together with low paleointensities tends to support the second one. The presence of a lava flow recording a transitional direction overlying reverse polarity and underlying normal polarity flows, both with somewhat anomalous directions points to the fact that the Apnia sequence records a reverse to normal transition. Taking into account K‐Ar ages (Lebedev et al., 2008), the polarity change recorded would correspond to the Gilbert‐Gauss reversal (C2Ar to C2An‐3n), If, however, the sequence is a composite transition record (e.g., Coe et al., 2004), its reverse lower part would correspond to chron C2Ar and the upper part to C2An‐2n. Lower‐Korkhi shows 17 normal‐polarity lava flows, whose mean direction does not agree with the expected field direction (Besse & Courtillot, 2002). No transitional directions are observed and tectonic rotations have been discarded. Paleomagnetic directions have been grouped into 6 different DGs, from which two include 6 and 7 lava flows. Several single flows appear interlayered between DGs, pointing toward two intervals with a higher eruption rate separated by discrete eruptions more disconnected in time. The subsequence shows a very low S B both with respect to the expected pole and the mean VGP. Thus, it appears to be a record of a very short eruption interval and PSV is not averaged. A rough eruption rate estimation in the Lower‐Korkhi subsequence using the available K‐Ar ages, provides an approximate ratio of 20 ka/flow using the upper and lowermost values given by the uncertainty interval which adds up 340 ka for the complete subsequence. The minimum eruption time interval yields a zero value due to overlapping of K‐Ar age uncertainties. Using the average of 300–3,000 years/flow, obtained from the transition period in Apnia, Lower‐Korkhi was formed between 5 to 51 ka. The maximum eruption intervals would allow PSV averaging, but very low eruption intervals would also be possible, yielding non‐averaged PSV record. Regarding paleointensities in Calvo‐Rathert et al. (2013), only two determinations from Lower‐Korkhi are available (22.7 ± 1.2 μT and 40.5 ± 4.4 μT), each of them performed on a single specimen, and thus not providing enough information. Therefore, paleomagnetic results and K‐Ar data reveal that the Lower‐Korkhi subsequence is recording a normal polarity interval in the Gauss chron, and reflecting a stable stage. Upper‐Korkhi is formed by eight reverse‐intermediate polarity lava flows recording anomalous field directions with values near to intermediate/transitional ones. As expected, its VGP mean does not match the expected field direction and the occurrence of significant tectonic rotations has been excluded. In addition, 6 DG have been defined among a total of eight lava flows, pointing toward discrete eruptions rate more disconnected in time or a rapidly varying directional pattern. A single K‐Ar date is available in the Upper‐Korkhi subsequence not allowing an estimation of the duration of its emplacement. VGP scatter both with respect to the expected pole and the mean VGP is fairly high and with very wide uncertainty values, also suggesting that this subsequence displays an anomalous EMF record, reflecting a transitional time interval. No paleointensity data from Upper‐Korkhi are available in Calvo‐Rathert et al. (2013), and paleomagnetic results and K‐Ar data suggest that this subsequence records either transition C2r‐1r to Olduvai or Olduvai to C1r‐2r.

9 Conclusions A detailed paleomagnetic study has been carried out on two lava flow sequences, Korkhi and Apnia, from the Djavakheti Highland in Lesser Caucasus. The Korkhi sequence is composed of two volcanic successions of distinct age (1.85 ± 0.08 Ma and 3.1 ± 0.1 Ma), while the Apnia sequence was emplaced between 3.75 ± 0.25 Ma and 3.1 ± 0.1 Ma. Mean paleomagnetic directions of the normal and reverse polarity groups for each section do not match the expected field direction and they are not antipodal in any of the sequences. An analysis of possible tectonic rotations discarded this possibility. Paleomagnetic results and radiometric ages show that the Apnia sequence most likely records the reverse to normal polarity transition C2Ar to C2An‐3n (Gilbert‐Gauss). The fact that the sequence consists of a stacked sequence of flows recording from bottom to top reverse and normal polarity directions separated by a flow yielding a transitional direction, both with somewhat anomalous directions, points to the fact that the Apnia sequence records a reverse to normal transition. A record of a composite transition, however, cannot be discarded, given that the hiatus described by Lebedev et al. (2011) coincides in age with the transitional lava flow, the previous one next to it, can justify that more than one transitions are spanned, so that its reverse lower part would correspond to chron C2Ar and the upper part to C2An‐2n. Analysis of paleomagnetic directions from flows and directional groups, VGP scatter and available paleointensity results (Calvo‐Rathert et al., 2013) allows, on the other hand, differing though not mutually exclusive interpretations: As tectonic rotations have been discarded, a short recording time unable to average PSV and an anomalous EMF record are both possible. The Lower‐Korkhi subsequence records 17 normal polarities with very similar directions. Analysis of paleomagnetic directions and VGP scatter points toward a record of a short eruption interval in which PSV is not averaged. Paleomagnetic results and K‐Ar data reveal that this subsequence records a normal polarity interval inside the Gauss chron reflecting a stable stage of the EMF. Upper‐Korkhi shows a more unstable EMF behavior. Its 8 lava flows display a reverse to transitional polarity with intermediate latitude VGPs. This directional behavior as well as significantly large VGP scatter suggest that this subsequence displays an anomalous EMF record, reflecting a transitional time interval. According to paleomagnetic results and K‐Ar data this subsequence records either transition C2r‐1r to Olduvai or Olduvai to C1r‐2r.

Acknowledgments This work was supported by Project CGL2012–32149 (Ministerio de Economía y Competitividad, Spain), Project BU066U16 (Junta de Castilla y León, Spain) and pre‐doctoral grant BES‐2013–064060 (Ministerio de Economía y Competitividad, Spain). The data used in this work are listed in the tables and references. Jonathan Glen, Michael S. Petronis and anonymous reviewers are acknowledged for their constructive comments and suggestions which have helped to improve this manuscript. AG is grateful to the financial support given by DGAPA‐PAPIIT IN101717.

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