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In-situ soft sediment deformation structures (SSDS) are commonly used as paleoseismic indicators in marine and lacustrine sedimentary records. Earthquake-related shear can deform sediment in the shallow subsurface through Kelvin-Helmholtz instability. The SSDS related to Kelvin-Helmholtz instability have been used to quan-tify shaking strength of past earthquakes. However, the relative importance of i) lithology and physical proper-ties, ii) potential basal shear surfaces (e.g. clastic deposits), iii) slope angle, and iv) seismic shaking strength (e.g. peak ground acceleration) for deformation related to Kelvin-Helmholtz instability remains poorly studied. Lake Rinihue (south-central Chile) is chosen as a natural laboratory for disentangling the effect of the aforemen-tioned factors because i) the sediment composition of background sediment varies downcore and ii) volcanogenic clastic deposits are abundant within the sedimentary sequence. A previous study at lake Rinihue identified 25 SSDS intervals induced by historical earthquakes of varying rupture extent in 17 sediment cores taken at slope angles ranging from-0.2 degrees to-4.9 degrees (i.e. 16 slope sites and 1 basin site). Our study shows that defor-mation mostly occurs directly above volcanogenic deposits (i.e. 72 % of SSDS intervals), suggesting that volcanogenic deposits promote earthquake-induced deformation by strain softening, liquefaction or water film formation. Deformation thickness of SSDS increases with higher slope angles (i.e. strong positive correlation). Ad-ditionally, deformation thickness commonly corresponds to the stratigraphic depth of the youngest preceding volcanogenic deposit, but for steeper slope angles stratigraphically older volcanogenic deposits can function as basal shear surface. Therefore, we suggest that deformation thickness is primarily regulated by gravitational stress (i.e. slope angle) and secondarily by the stratigraphic depth of volcanogenic deposits. The earthquakes related to strongest shaking caused almost exclusively SSDS with highest deformation degrees (i.e. folds and intraclast breccia) as well as largest spatial extent of SSDS, resulting in highest numbers of related SSDS in the investigated cores. Thinner SSDS have higher deformation degrees at a given shaking strength, as seismically -induced shear energy acts more effectively on thinner deforming sequences. Therefore, we suggest that deforma-tion degree is primarily controlled by shaking strength and secondarily modulated by the thickness of the deforming sequences. We infer that deformation thickness is not a reliable indicator of paleoseismic shaking strength as this relies on many preconditioning factors independent of shaking strength. On the other hand, deformation degree can be a good proxy for shaking strength also in settings with varying lithotypes and intercalated clastic event deposits, provided multiple cores are studied to avoid under-or overestimation of paleoseismic shaking strength. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

This study was supported by Projects PID2019- 104625RB-I00 and PGC2018-098272-B-I00 (Secretaría de Estado de I+D+I, Spain), B-RNM-072-UGR18 (FEDER Andalucía), P18-RT-4074, and RNM-208 (Junta de Andalucía). Thanks to C. Sanz de Galdeano for his support in the field at the Alfarnate outcrop. We gratefully acknowledge the constructive comments of two anonymous reviewers., This paper describes various soft-sediment deformation structures present in the Triassic deposits of the Betic External Zone (Southern Iberian). These structures, together with variations in deposit thicknesses, internal angular unconformities, and synsedimentary faults, point to intense tectonic activity from the Middle to Late Triassic related to a stage of rifting. The Middle–Late Triassic in the Betic External Zone shows a sedimentary record represented by Muschelkalk and Keuper facies. In the Ladinian Muschelkalk, carbonates appear slumps, breccias, load casts, slide and parallel shear sur faces, and tsunamites. In the sandstones of the Carnian Keuper facies, different seismite beds and ball and pillow structures can be discerned. Above these deposits, the carbonate Zamoranos Formation of the Rhaetian displays volcaniclastic rocks with conglomerates, slumps and synsedimentary faults. All these features and magmatism suggest some tectonic activity, possibly related to the breakup of Pangaea, especially at the end Triassic. We highlight the features that indicate this tectonic activity over time and discuss the factors that triggered the development of these structures, along with the conditions that made this possible., Secretaría de Estado de I+D+I B-RNM-072-UGR18, European Regional Development Fund P18-RT-4074, RNM-208, Junta de Andalucía

The (Plio)-Pleistocene Zarzal Formation was deposited in the Cauca Depression and Quindío-Risaralda Basin between the Western and Central Cordilleras (Northern Andes). This area is structurally located on the transcurrent Romeral Fault System (RFS). Because of the interaction between the Nazca plate and the Chocó-Panamá block (an active indenter), the RFS strike-slip component changes direction around the study zone (dextral in the south, senestral in the north). Zarzal sediments are the oldest ones not to have been affected by the Pliocene Andean tectonic phase. Their study aims at better understanding the subsidence of these two interandean sedimentary basins within a regional compressional regime. The two basins are separated by the the Serrania de Santa Barbara (SSB), made of Tertiary sediments thrusted during the Pliocene tectonic phase. Zarzal sediments are fluvio-lacustrine: diatomites are encountered on both sides of the SSB and are alternating with braided stream or alluvial deposits. Sedimentation was strongly influenced by volcanic processes which led to the deposition of the Quindío-Risaralda and Cartago volcaniclastic fans sourced from the Central Cordillera. These volcaniclastic mass flows mixed with the Zarzal sediments, and even dammed and infilled a lake in the Quindío-Risaralda Basin (east of the SSB). Numerous extensional features affect Zarzal sediments with a mean extensional trend subparallel to the SSW-NNE trending cordilleras. The syndepositional tectonic activity is demonstrated by numerous seismites. In the Cauca Depression, sediments are infilling the basin more rapidly than it subsides or than the relief lifts up, thereby drowning the topography. This might be related to the tectonically- induced, downstream damming of the Cauca River valley to the north by the Chocó-Panamá block.

Middle Triassic deposits in the Velebit Mts. of the External Dinarides in Croatia show strong differentiation of sedimentary environments and facies. In the area of Donje Pazarište, a 90 metre thick section includes six different facies, each with its specific genetic characteristics (Flysch-like Facies ; Carbonate Shale Facies ; Pyroclastic Density Current Facies ; Platy Limestone with Pyroclastics Facies ; Limestone Breccia Facies and Slumped Limestones with Pyroclastics and Chert Facies). In the same area, in the nearby Top of Donje Pazarište section, a Pyroclastic Flow Facies was defined, and this was also recognized ~15 km to south-east, in the area of Brušane village, in the foothills of Vinac. Throughout the area and section investigated, the effects of intense tectonic and volcanic activity can be traced. The pronounced differences in the facies determined facies are interpreted as consequences of syntectonic and volcanically influenced sedimentation in a graben/half- graben depositional system.

International audience; Two sedimentary basins are identified in the Turkana Depression (East African Rift System, Kenya). One of them, the Ekitale Basin, is presented in detail. Located on the western rift shoulder of the northern Turkana Depression, the preserved portion of the Ekitale Basin is 3–5‐km wide and bordered by N40°–50° normal faults. These normal faults were inherited from the reactivation of pre‐existing basement structures. The Ekitale Basin is filled by the ~75‐m‐thick Topernawi Formation. The lower portion of the formation provides evidence that the basin was occupied by a lake, bordered by alluvial fans, and into which river‐derived turbiditic complexes were deposited. The upper portion is comprised of pyroclastic deposits, originating from volcanic activity, and interbedded with fluvial deposits emplaced during periods of volcanic quiescence. The Ekitale Basin opened just after 28 Ma and was abandoned prior to 25 Ma, placing it after the deposition of the Oligocene Traps (ca. 33.9–27 Ma) and prior to the rift climax (after 14 Ma). This syn‐rift basin largely impacts our understanding of the Cenozoic rift evolution in the Turkana Depression. It helps to identify, for the first time, the first pulse of extension of the Cenozoic rifting, revealing a two‐step rifting scenario for the northern Turkana Depression. The Ekitale Basin, and analogous syn‐rift basins, is believed to have developed from the reactivation of pre‐existing structures during a period of extension marked by low differential stress and a low amount of extension.

Volcanic activities provide cataclysmic hazards to surrounding environments and human life by various eruptive and hydrologic processes, e.g., lava flows, pyroclastic flows, pyroclastic fallout, debris avalanches, debris flows, and flood flows. Although there are many studies dealing with the prevention and mitigation of volcanic hazards, these are mostly concentrated on primary eruptive processes occurring in areas proximal to active volcanoes. However, studies from historic and pre-historic eruptions have shown that the remobilization and resedimentation of volcanic debris in the aftermath of an eruption will potentially generate severe hazards in far-distant downstream areas, especially when a large-scale rhyolitic eruption triggers the remobilisation. This paper introduces the research on volcaniclastic remobilisation and resedimentation in the aftermath the 1.8 ka Taupo eruption, Northern Island, New Zealand that have been addressed mainly by groups from the Institute of Geological and Nuclear Sciences and the Department of Geology at the University of Otago, New Zealand. Spatiotemporal variations in volcaniclastic remobilisation and resedimentation occur along the Waikato River in response to the 1.8 ka Taupo large-scale explosive eruption. During the eruption, climactic emplacement of the Taupo ignimbrite (30km^3) caused the destruction of drainage networks and modification of pre-existed topography over an area of 20,000 km^2. This resulted in drastic depositional system changes not only in proximal areas directly affected by ignimbrite deposition but also in far downstream areas, beyond the limit of ignimbrite emplacement, by inundation with large volumes of reworked voIcaniclastic debris. The example from the aftermath of the 1.8 ka Taupo eruption shows two significant points in terms of volcanic hazards. Firstly, the hydrological remobilization of volcaniclastic material and its impact may constitute severe hazards more widespread and persistent than the primary eruptive impacts. Although people living far from volcanoes are usually prone to ignore volcanic hazards because they are less affected by primary volcanic ejecta, they may be vulnerable to the impacts of remobilization and resedimentation of volcaniclastic debris on such distant areas. Secondly, for rhyolitic caldera volcanoes associated with emplacement of a large-ignimbrite, the delivery pattern of volcanic sediment load through river drainages does not match with that of cone type stratovolcanoes, for which models are available. The nature and distribution of ignimbrite relative to topography and drainage patterns enhances the formation of ephemeral and intra-caldera lakes that can impound large amounts of water after the eruption. Such impoundments can potentially cause catastrophic outbursts and floods and complicate predictions of the timing and scale of remobiIisation in the aftermath of the eruption. Thus, volcaniclastic resedimentation by various hydrologic processes can create more serious hazards than actual volcanic eruptions, in terms of variety, persistence, extensiveness, and sudden onset. Hence, studies on the sedimentological features of voIcaniclastic material should be enhanced for further understanding, prevention, and mitigation of post-eruptive volcanic hazards by voIcaniclastic remobilization and resedimentation.

The Rhodope and Evros areas of the Thrace Region in north-eastern Greece and the adjusted areas in Bulgaria are characterized by wide spread volcanic formations of Upper Eocene to Miocene in age. The volcaniclastic materials associated with such formations have, in some cases, undergone inter alia a notable zeolitization process. The mineralogy of the altered volcaniclastics is often dominated by clinoptilolite -heulandite type of minerals. The Winchester and Floyd (1977) plots indicating rhyodacite/dacite to trachyandesite parent materials, while the similar diagram, as modified by Pearce (1986), indicate andesite to trachyandesite precursors. The alkalinity index (Nb/Y ratio) seems to coincide between the two types of diagrams, but, there is a notable difference of the differentiation index, i.e. the Zr/TiO2 ratio. The Th-Co diagram (Hastie et al., 2007) unfolds a clearer picture for the nature of the precursors and reveals a clear progression of a calc-alkaline to a high-K calc alkaline affinity of the parental volcanic materials.

The volcaniclastic Tepoztlán Formation (TF) represents an important rock record to unravel the early evolution of the Transmexican Volcanic Belt (TMVB). Here, a depositional model together with a chronostratigraphy of this Formation is presented, based on detailed field observations together with new geochronological, paleomagnetic, and petrological data. The TF consists predominantly of deposits from pyroclastic density currents and extensive epiclastic products such as tuffaceous sandstones, conglomerates and breccias, originating from fluvial and mass flow processes, respectively. Within these sediments fall deposits and lavas are sparsely intercalated. The clastic material is almost exclusively of volcanic origin, ranging in composition from andesite to rhyolite. Thick gravity-driven deposits and large-scale alluvial fan environments document the buildup of steep volcanic edifices. K-Ar and Ar-Ar dates, in addition to eight magnetostratigraphic sections and lithological correlations served to construct a chronostratigraphy for the entire Tepoztlán Formation. Correlation of the 577 m composite magnetostratigraphic section with the Cande and Kent (1995) Geomagnetic Polarity Time Scale (GPTS) suggests that this section represents the time intervall 22.8–18.8 Ma (6Bn.1n-5Er; Aquitanian-Burdigalian, Lower Miocene). This correlation implies a deposition of the TF predating the extensive effusive activity in the TMVB at 12 Ma and is therefore interpreted to represent its initial phase with predominantly explosive activity. Additionally, three subdivisions of the TF were established, according to the dominant mode of deposition: (1) the fluvial dominated Malinalco Member (22.8–22.2 Ma), (2) the volcanic dominated San Andrés Member (22.2–21.3 Ma) and (3) the mass flow dominated Tepozteco Member (21.3–18.8 Ma). peerReviewed