ABSTRACT In this paper, we present old and new data about our integrated interdisciplinary stratigraphic study of sedimentary deposits preserved in the Grotta dei Baffoni Cave of the Frasassi hypogenic cave complex, including sedimentological, paleontological, archaeometric, and radiometric analyses. This research work allowed us to reconstruct the geologic, environmental, and human history of this part of the northeastern Apennines of Italy for the past 200,000 years, from the late Middle Pleistocene to the Present. Accumulation of alluvial sediment began in this cave ~200,000 years ago, when an entrance was breached by the Sentino River during its process of incision and deepening of the Frasassi Gorge coupled with regional tectonic uplift. Flooding of the cave went on until the entrance sill of the cave was lifted up to an elevation that could no longer be reached by the river, sometime in the mid–Late Pleistocene. After this, windblown dust (i.e., loess) and coarser carbonate clasts derived from the disintegration of the vaults due to cryogenic processes and/or seismically induced collapses of the limestone vaults, accumulated on this now-dry underground environment. The stratigraphy of an ~4-m-thick sedimentary deposit accumulated in the vast atrium room of the cave was measured, sampled, and documented in two excavation trenches in 1952 by archaeologist Anton Mario Radmilli. By collecting a dozen stratigraphically located osteological finds for 14 C dating, and revisiting artifacts collected by Radmilli, which are archived respectively in the Museum of Natural History of Verona and in the National Museum of Archaeology of Ancona, we assessed that the cave was frequented by wild animals, such as cave bear and ibex, starting in the mid–Late Pleistocene. Dating of charcoal particles from subsurface sediments in the inner part of the cave suggested that fires were lit in this cave by Epigravettian visitors during the Younger Dryas cold period. Scarce archaeological evidence nevertheless suggests that man began using this underground environment for worship practices probably in the early Neolithic. Human bones in the lower part of one of Radmilli's excavations yielded early Eneolithic ages. No other human bones were found in overlying levels of this excavation, but the typology of animal bones and associated ceramic artifacts, corroborated by our 14 C dates, suggest that this cave was utilized as a worship or ritual place until the early Middle Bronze Age. After that, the cave was sporadically used as a shelter for herders until recent times.

ABSTRACT In this study, we discuss the results from different luminescence dating methods applied to four samples of Pleistocene slack-water sediments from the Frasassi hypogenic cave system, in the northeastern Apennines of Italy. Two samples came from a well-sorted, fine sand deposit in the Grotta Grande del Vento cave (SDS site), while two others were taken from a borehole through a clayey deposit in the adjacent Caverna del Carbone cave (CDC site). Both sites are located at an elevation of ~235 m above sea level (asl), which corresponds to ~30 m above the thalweg of the Sentino River flowing through the Frasassi Gorge outside the cave. In the Frasassi multistory cave system, the elevation of 235 ± 5 m asl corresponds to the third karst level or “floor,” the minimum age of which from speleothem U-Th dating is ca. 130 ± 15 ka. The luminescence ages for the two samples from the SDS site are in good agreement with each other within error, just like the two samples from the CDC profile. Different luminescence dating protocols were used to determine the ages for each individual sample. By applying this comparative approach, and taking the luminescence characteristics of the samples into consideration (quartz optically stimulated luminescence, different feldspar luminescence signals), the ages could be based on the most robust measurement protocol. The ages presented here were all derived from measurements using the post-infrared infrared signal of potassium-rich feldspar stimulated at a temperature of 225 °C (pIRIR225). Incomplete bleaching of the luminescence signal prior to deposition, leading to age overestimation when not detected and corrected for, was not a significant factor for the samples under investigation, because ages calculated for luminescence signals with different bleachability yielded results in agreement within error. Bleaching can therefore be assumed to have been sufficient before the samples entered the cave system. The ages determined for both sites are reliable from a methodological standpoint. The pIRIR225 luminescence dates from the SDS sand range between 129 and 101 ka and are consistent with the minimum age for the third cave floor (~235 m asl) as obtained from previous U-Th dating. In contrast, the pIRIR225 luminescence dates obtained from the clay-rich CDC deposit range from 217 to 158 ka, which is consistent with the minimum age for the fifth subhorizontal cave level when measured from the modern water table, found at ~65 m above the present river thalweg. This apparent discrepancy may be due to the fact that the present entrance of the CDC cave was incised by the river on the south side of Frasassi Gorge sometime during the Eemian interglacial period (marine isotope stage [MIS] 5e), but, being part of a hypogenic karst system in an uplifting tectonic structure, the actual third floor was preexisting, thus anteceding the river incision. On the other hand, the fifth floor of the cave system, some 30 m above the third floor, was incised sometime during the interglacial MIS 7 at around 200 ka, at a time when the saturated phreatic third floor had already been formed and thus was capable of collecting the fine suspension sediment settling from muddy river water flooding the cave.

ABSTRACT The massive Jurassic limestone making up the core of the Frasassi-Valmontagnana blind thrust anticline hosts a large sulfidic cave complex, which, due to Pleistocene tectonic uplift, has been incised by the Sentino River, forming the deep Frasassi Gorge. The Frasassi cave complex is organized into seven horizontal levels, with the youngest and presently active one at river level, and the oldest (ca. 1.2 Ma) one some 200 m above the Sentino River. Therefore, the Frasassi cave complex records the river incision history of this still-active Apennine mountain belt. In addition to an uplift rate of ~0.55 mm/yr for the Holocene, previous radioisotopic dating and surveying of phreatic calcite deposits revealed an overall tilting of the Frasassi anticline of ~0.2° toward N60E for the past 9000 or so years. Our study adds to this history of tectonic tilting by focusing on a group of 30 tilted stalagmites found at the bottom of the Abisso Ancona of the Grotta Grande del Vento (the largest room in the Frasassi complex). These stalagmites have a fairly uniform plunge of ~81° trending toward N30W, and we interpret this to record a tilt of the cave toward S30E during the formation of the stalagmites. From U-Th dating of these paleotiltmeters, we deduce that the Frasassi anticline was tilted by ~0.3° from 32 to 7 k.y. B.P., and the tilt rate gradually increased during this period. The 60° (NE) direction of oblique-slip faults in this area and the local focal mechanisms of recent seismic activity suggest that the tilting is caused by movement along a listric oblique strike-slip zone south of the Frasassi anticline. Our findings also demonstrate that given the right conditions, stalagmites can be used as paleotiltmeters that provide insight into recent crustal deformation.

ABSTRACT In this study, we present a composite δ 18 O and δ 13 C record obtained from four speleothems from the Grotta Grande del Vento Cave, located within the Frasassi karst system, northeastern Apennines of central Italy. The ages were determined by U-series analysis, employing thermal ionization mass spectrometry (TIMS), and the composite isotopic profile covers most of the time period from ca. 95,000 yr B.P. until ca. 10,000 yr B.P., including the last part of marine isotope stage (MIS) 5, most of the last glacial (MIS 4–2), and the earliest Holocene (MIS 1), with a hiatus lasting from ca. 65,000 to ca. 55,000 yr B.P. We compared this record with other speleothem records from the Eastern Mediterranean, with caves from western Portugal, with two marine records from the Eastern Mediterranean and the Aegean Sea, and with the North Greenland Ice Core Project (NGRIP) ice-core record. The Frasassi speleothem record provides further insight for a wider regional understanding of the paleoclimate record through the discrepancies and similarities between the northeastern Apennines of central Italy and the Western, Eastern, and northeastern Mediterranean regions. The time interval between ca. 86,000 and 83,000 yr B.P. shows low δ 18 O values in the Western and Eastern Mediterranean speleothems and the marine records. This period coincides with sapropel (S3) and is associated with increased hydrological activity and warming. On the other hand, Frasassi speleothem δ 18 O data do not show a similar low trend, suggesting that increased hydrological activity either did not reach the Frasassi region and/or the region received rainfall from other sources and/or the proportion of winter-summer rainfall was different. Another interval in which different conditions prevailed in the Frasassi region is during the transition from MIS 5 to glacial MIS 4, from ca. 83,000 to 65,000 yr B.P., when Frasassi speleothem δ 18 O values decreased, whereas all other records show a clear increase in δ 18 O. Comparison with the NGRIP record suggests that Northern Hemisphere temperature changes are reflected in Frasassi speleothem δ 18 O fluctuations during this interval. A major pronounced isotopic event associated with warming and pluvial conditions during the last glacial evident in the entire Mediterranean region between ca. 54,500 and 52,500 yr B.P. is recorded also in the Frasassi speleothem isotopic profile. This event is followed by a transition from wet and warm climatic conditions to cold conditions. The end of the last glacial is associated with climate instability, evident mainly from the very large oscillations in the Frasassi δ 13 C record. The transition from the last glacial to early Holocene is characterized by a decreasing trend in δ 18 O and a sharp increase in δ 13 C values.

ABSTRACT The objective of this research was to determine the age relationships between Early Jurassic sedimentary units in the Umbria-Marche Apennines using strontium isotope stratigraphy. These age relations are critical for evaluating the mechanism by which the small platforms in the region formed. I present an alternative model for carbonate platform differentiation and evolution based on the strontium isotope data; this model relies primarily on growth of individual small platforms through differential sediment accumulation rather than the generally accepted model of extensive late-stage faulting. Strontium isotope stratigraphy provides a high-resolution correlation tool for the region. Because 87 Sr/ 86 Sr values steadily decrease in the Hettangian–Pliensbachian section of the Early Jurassic, they illuminate relationships in different carbonate facies very well. This is particularly valuable where physical and/or biostratigraphic correlation is difficult, such as in the Umbria-Marche carbonate platforms. Strontium isotopic ratios from measured basinal stratigraphic sections along the Burano and Bosso Rivers indicate that at least a 100 m section of the Corniola Formation was deposited while adjacent platforms continued to grow. The small Umbria-Marche platforms drowned synchronously in the late Sinemurian, based on 87 Sr/ 86 Sr values from several platforms at the end of Calcare Massiccio Formation deposition. Measured 87 Sr/ 86 Sr values for all platforms are the same within error. These stratigraphic relationships indicate that differentiation into shallow- and deep-water facies occurred in the latest Triassic/earliest Jurassic, early in the development of the margin. Current models explain the differentiation of platforms and basins by late-stage extensive normal faulting, requiring hundreds of meters of stratigraphic throw. Large-displacement faults are not consistent with the age relations determined by strontium isotope stratigraphy in the region. Minor faulting in the Late Triassic coupled with growth by differential sediment accumulation of small, shallow-water carbonate platforms continuing for several million years would produce the exposed platform/basin relationships. Inferred accumulation rates for the platform and basin sequences suggest that the observed relief of the platform escarpments was generated in less than 7 m.y., a time period consistent with the documented stratigraphy in the region.

ABSTRACT Discoveries in the 1980s greatly expanded speleologists’ understanding of the role that hypogenic groundwater flow can play in developing caves at depth. Ascending groundwater charged with carbon dioxide and, especially, hydrogen sulfide can readily dissolve carbonate bedrock just below and above the water table. Sulfuric acid speleogenesis, in which anoxic, rising, sulfidic groundwater mixes with oxygenated cave atmosphere to form aggressive sulfuric acid (H 2 SO 4 ) formed spectacular caves in Carlsbad Caverns National Park, USA. Cueva de Villa Luz in Mexico provides an aggressively active example of sulfuric acid speleogenesis processes, and the Frasassi Caves in Italy preserve the results of sulfuric acid speleogenesis in its upper levels while sulfidic groundwater currently enlarges cave passages in the lower levels. Many caves in east-central Nevada and western Utah (USA) are products of hypogenic speleogenesis and formed before the current topography fully developed. Wet climate during the late Neogene and Pleistocene brought extensive meteoric infiltration into the caves, and calcite speleothems (e.g., stalactites, stalagmites, shields) coat the walls and floors of the caves, concealing evidence of the earlier hypogenic stage. However, by studying the speleogenetic features in well-established sulfuric acid speleogenesis caves, evidence of hypogenic, probably sulfidic, speleogenesis in many Great Basin caves can be teased out. Compelling evidence of hypogenic speleogenesis in these caves include folia, mammillaries, bubble trails, cupolas, and metatyuyamunite. Sulfuric acid speleogenesis signs include hollow coralloid stalagmites, trays, gypsum crust, pseudoscallops, rills, and acid pool notches. Lehman Caves in Great Basin National Park is particularly informative because a low-permeability capstone protected about half of the cave from significant meteoric infiltration, preserving early speleogenetic features.

A handful of investigative teams in several parts of the world are studying abundant biological communities in caves formed by sulfuric-acid speleogenesis. These caves are atypical in terms of origin, chemistry, and ecosystem properties. They prominently display sulfur minerals, characteristic cavity topologies, and notable biological diversity and biological productivity resulting directly from the conditions that produce the caves. Even long-inactive systems still harbor some of these indicators. The microbial and macroscopic ecosystems within sulfuric-acid speleogenetic caves are geologically mediated and maintained. This geological mediation is a theme connecting them with other sulfur-driven ecosystems on Earth, including deep-sea hydrothermal vents, sulfurous near-surface hydrothermal systems, and solfataras. Evidence exists for potentially significant microbial participation in the process of speleogenesis itself. Recent results confirming the high relative abundance of sulfur on Mars, an apparent sedimentary basin with high sulfate concentration, near-surface indicators of ice and water, and trace detection of reduced gases (especially methane) in the Martian atmosphere, possibly deriving from subsurface microbial sources, set the stage for suggesting that sulfuric-acid speleogenetic systems may be useful as astrobiological analogs for hypothetical Mars ecosystems. Unique speleogenetic mechanisms may occur on Mars and could provide subsurface void space suitable for habitation by such hypothetical microbial systems.

ABSTRACT Numerous examples of transverse drainages in the Apennines inspired early, forward-thinking models to describe how rivers established and maintained their courses as mountains were being raised beneath them. We assemble the rate of base-level fall (τ- U ) and associated channel χ-z data of ten transverse rivers draining the Apennine pro-wedge using a channel stream power linear inverse approach. We apply the results to evaluate competing models of transverse drainage development as well as the underlying dynamic and tectonic processes responsible for Apennine topography. The channel inversion approach employs the simplifying assumption of uniform uplift and erosion at the catchment scale, but accounts for variable rock erodibility as the first-order determinant of regional, mean channel steepness. Accordingly, local deviations in channel steepness are interpreted by the model as transient upstream-propagating waves of base-level fall originating at the catchment mouth. Modeled timing, rate, and unsteadiness of these base-level falls are broadly consistent with geomorphic, geologic, thermochronologic, and paleo-elevation isotopic data, indicating that the Apennines emerged impulsively at ~2.5 Ma at rates ranging from ~0.2–0.3 mm/yr for the central Apennines to rates of ~0.7 mm/yr for the southern Apennines. Syn-deformation and foreland-propagating superposition dominate transverse drainage development for the northern and north-central Apennines, which are underlain by an intact Adriatic slab. In contrast, further south where a slab window separates the Adriatic slab from the base of the Apennine wedge, dynamic uplift prevails and the transverse drainages have developed in response to regional superposition and integration of catchments through spillover and headwater capture processes.

Abstract Geological studies of the Sibillini Mountains carried out mainly during the last century, provided evidence of a hypogeal karst characterized by a small number of caves of limited extent. The only one mentioned by numerous ancient authors is the ‘Grotta della Sibilla’, on account of its legendary references. This cave is the keeper of one of the most fascinating secrets of the Apennines, having been both a place of mountain cult as far back as pre-historical times and the home of the fortune-telling prophetess ‘Sibilla’. Historical sources tell of the presence of someone mysterious at the site from the time of the Romans but amongst the historical descriptions, the testimony of Antoine de la Sale is most notable: he visited the cave in 1420 and described it as a good-sized cavity within the bowels of the mountain. Nothing about this setting is mentioned in the geological literature or in topographic descriptions, made for the first time at the beginning of the 1940s, when a regular but small cave was revealed. Today rockfall deposits completely obstruct the entrance. On the basis of the above-mentioned legendary references, geomorphological and geophysical studies started helping to define the real extent of the cave. The planimetric trend of the electromagnetic anomalies surveyed allow us to make hypotheses about the presence of a vast hypogeal system.

ABSTRACT The Cretaceous and Paleogene pelagic limestone and marl formations of the Umbria-Marche Apennines of north-central Italy have proven to be exceptional recorders of the history of Earth and of life on Earth, and they have been the subject of numerous geological and paleontological studies over the last several decades. Founded a quarter century ago, in 1992, the Geological Observatory of Coldigioco is a research and teaching center focused on these exceptional rocks. This chapter is a historical introduction that briefly reviews the highlights of the lithologic, biostratigraphic, sedimentologic, magnetostratigraphic, impact-stratigraphic, geochemical, geochronological, time-scale, and cyclostratigraphical research done on the Umbria-Marche stratigraphic sequence, much of it facilitated by the Geological Observatory of Coldigioco. This review covers work up to the Coldigioco 25th anniversary Penrose conference in September 2017; it does not treat work presented at that conference or done since then. A remarkable irony is that a century ago, the Umbria-Marche Cretaceous–Paleogene sequence was so difficult to date that early work contained an error of ~35 m.y., but now there is a reasonable hope that this entire section may eventually be dated to an accuracy and precision of ~10,000 yr. This review begins with an homage to the little medieval city of Gubbio, its wild Festa dei Ceri, and its Bottaccione Gorge, where much of the research described here has been done. The review ends with three points of perspective. The first is the notion that sometimes geology can be done by looking up at the sky, and astronomy can be done by looking down at Earth, with much of the Coldigioco-based research being of this latter kind. The second is the observation that geology and paleontology are contributing far more new information to Big History—to our integrated knowledge of the past—than any other historical field in the humanities or sciences. The third is that three of the major scientific revolutions of geology in the twentieth century have direct connections to the Umbria-Marche stratigraphic sequence—the turbidite revolution, the development of plate tectonics, and the downfall of strict uniformitarianism.