3 Unicamp, Campinas SP, Brazil

We worked about the field sections at Montevidiu, Alto Garcas, and at Araguainha, along the trail mt100.

The geological and biostratigraphical sequences are similar and well dated; They belong to the Corumbataï - Piramboia or to Terezina formation of upper Permian. At Araguainha the Fe=Si microspherules, fond from the impact breccias with melt matrix, near a shatter cone, are Tatarian, may be Changxingian, when the glassy microspherules at Montevideo are Kazanianto Kougurian and correlable with South Africa sequences.

The extraterrestrial events of the upper Permian are believed diversified in several alternative stages of geological time. Those later would be linked to several warmer steps of climatic changes, and to progressive disappearances of a lot of animal and vegetal species, before the catastrophic final event at the limit upper Permian/upper lower Triassic; at the time appears a new vegetation and the first most primitive dinosaurs, adjusted at a drier and even some desertic areas, according to discoveries at Santa Maria (RS).

The sedimentological and electronically microprobes studies show that evolution, during the geological sequence at Araguainha as at Montevideo; but further thorough studies with isotopes measurements, should be probably necessary, before complete results, that are in progress, with a definitive evidence of a meteoritic event in a complex occurrence.

A.P. Crosta et al. (1981). Revista Brasileira de Geocencias, H3 139 - 146.

W. von Engelhardt et al. (1992). Meteoritics, 27, 442 - 457.

A. Erichsen e J. Miranda (1939) Bol. N° 94 Serv. Geol. e Miner.

A. Erichsen e Loforen (1940) Boll. N° 102 Dito

V.J. Fulfaro (1971) Tese de Livre Docencia IG-USP, Bol. de Eng. Sao Carlos, 14, 112 pp.

V.J. Fulfaro (1972) An. Acad. Brazil; Ciencias 44 suppl., 147, 148.

R.M. Rohn (1994) Tese de Doutouramento; 376 pp., Sao Paulo.

R.M. Rohn (1993) 1 Simposio sobre chronostratigrafia do la bacia de Parana, Rio Claro, SP.

B. Theilen - Willige (1981) Clausthaler Geowissenschaftliiche Dissertation. HH 8 210 S., 116 Abh., 10 Tab. Clausthaler Zellerfeld.

J.M. Thery (1998) Annual Meeting of ICGP 384, Budapest, Hungary

J.M. Thery (1999) 14 Journee thematique des Geologues du Permien, 18 Juin 1999, Paris, Colegio de Espana, abstract 2p., 19-19

___________________________________________________________________________

1 Charles University, Department of Geology, Pøevoznická 14 , 143 00 Prague 4 Czech Republic , e-mail: vetvicka@mail.natur.cuni.cz

Back in 1997 I had the opportunity to study impact craters of Finland and Estonia.

I have obtained a grant for this project from the ZIS Foundation.

I was able to participate at the International Symposium (an IGCP Project Number 384) in Estonia thanks to a generous support from the Organising Committee.

I have collected specimens inside the following impact craters: Kaali, Ilumetsa, Lappajärvi, Kärikkosekä and Lumparn.

There is a total weight of valuable samples of 140 kg. I am examining them and my results are going to be published.

In the Lumparn Crater I have found some shatter cones and breccias.

There is a possibility the breccias could be formed as tectonic breccias = not formed by a collision, impact of a meteorite.

Preliminary results will be presented as a report with figures at the International Workshop Meeting IGCP 384.

___________________________________________________________________________

1Prof. Alessandro Colombetti
University of Milano – Bicocca

14.30 – Departure: Castelnovo ne’Monti

15.00

STOP 1 – The Pietra di Bismantova

Along the way to the place, on the left, there are good outcrops of the Antognola Formation (upper Oligocene – lower Miocene). Here it’s possible to see the shales member. In this member, but in other localities, are found the terrestrial spherules of barium sulphates.

From the Eremo place there is a spectacular view of the cliff of Pietra di Bismantova, made from grainstones and boundstones of upper Burdigalian (?) – Langhian, here with a tickness of over 100 meters.

Here we can see the base of grainstones, with a layer of methamorphic cobbles (Serpentinites, calceschists and slates), in stratigraphical contact with the lowermost marlstones of Antognola Formation [fig. 1].

Starting from the Eremo, along the track for the top of the cliff, we can see, for some hundred of meters, the contact between the basis of grainstones of Bismantova and the Antognola Formation. There are many fossil fragments of Echinoderms, Algae, Corals and Lamellibranchiata, typical of a low sea.

From the top of the Pietra di Bismantova we can see the Apenninic chain with its geological structures.

Leader: Alessandro Montanari^1
1 Dr. Alessandro Montanari
Osservatorio Geologico di Coldigioco
62020 Frontale di Apiro - Italy
Tel./Fax: (++39) 0733-618291
Tel./Mssg. (++39) 0733-618125

9:40
STOP 1 Sedimentology of the K/T interval in the Poggio quarries

The Monte Cònero is the eastermost anticline of the northern Apennine thrust-and-fold belt. The lowermost formation exposed on the nearly vertical eastern limb of the anticline is the Lower Cretaceous Maiolica. The Aptian-Albian Marne a Fucoidi, Cenomanian Scaglia Bianca, and the Senonian Scaglia Rossa are missing in this area due to a hiatus.

The rest of the Campanian to Eocene Scaglia Rossa is well exposed in sea cliffs, and in several abandoned limestone quarries.

The Scaglia Rossa of Monte Cònero has a facies different from the equivalent unit of the classic Gubbio sequence. First of all, the Cretaceous portion of this formation exhibits a whitish-beige colour instead of the typical pink of the Umbrian facies, and secondly, coccolith-foraminiferal pelagic limestones are here interbedded with white calcarenitic and calciruditic turbidites derived from a carbonate platform, which was located not far to the east of the present Cònero area.

The K/T boundary is exposed in the lower Fornaci quarry face (Fornaci West Section), near the village of Poggio di Ancona (Fig. 1).

Approaching the quarry face is dangerous due to rock fall, and therefore it has to be observed from a safe distance.

The K/T boundary is located about 80 cm below a 3 m thick calcirudite marker bed called the Marchesini Level or MegaT, and is marked by a 18 mm greenish clay layer sandwiched between pelagic limestones. A part from their whitish colour, the texture and microfacies of these limestones (i.e. the top Cretaceous mayaroensis limestone, and the basal Tertiary, porcellaneous eugubina limestone) are identical to those in the classic Gubbio sections. The whitish colour is due to a relatively reduced state of the paleoseafloor in comparison with the well oxygenated, abyssal environment in the Gubbio and Furlo areas. Higher planckton productivity and upwelling in this proximal environment may have been the main reasons

for more reduced conditions on the seafloor in respect to other open sea, deeper areas of the paleobasin.

The K/T boundary is well exposed, and easy to reach, in the Fonte d'Olio quarry, which we will visit in Stop 4. For the moment, we will take a closer look at the Cònero Scaglia facies in the upper level of the Fornaci quarry.

10:00

STOP 2 Fornaci Central and East Sections

On the way to the upper level of the Fornaci quarry, we will stop for a minute in front of a small quarry face where the K/T boundary is exposed. In this outcrop, the MegaT is not present, and the K/T boundary falls within a genuinely pelagic interval. On the other hand, a thick calcarenite layer is found in the top part of the outcrop (M. pusilla pusilla Zone). The absence of the MegaT, and the presence of this second massive calcarenite, and viceversa in the Fornaci West outcrop, indicate that these calcareous turbidites are strongly channelled, thus are laterally discontinuous (see stratigraphic correlation in Fig. 2).

In the upper quarry outcrop (Fornaci Central Section), several of these calcarenitic turbidites are exposed below the MegaT. Some of them have clear erosional bottoms and are channelled; others exhibit a flat base, and an upward convex top surface: these represent lobes of calcareous debris interfingered with the abyssal pelagic sediment.

A closer look at these calcareous turbidites reveals a granular texture made of biogenic debris. Orbitoids, rudist fragments, calcareous algae, pieces of corals, and lithoclasts of pre-existing shallow water limestones are the main constituents of these turbidites, and indicate that they were derived from a dismantling carbonate platform. These detritic layers are found below and above the K/T boundary, and my represent excellent material for studying the biofacies evolution of the western Adriatic platform which was completely disrupted after the K/T event.

In simple words, they may function as messengers of an evolving, and eventually killed platform, the incomplete remanence of which is now buried under the Adriatic sea floor.

Large flutes and inclined laminations indicate a preferential paleocurrent flow from East toward West. Some large flutes with different shapes (i.e. bulb, tongue, and curl), are exposed at the base of some MegaT boulders piled up at the edge of the quarry ledge.

The K/T boundary is exposed on a ledge in the upper part of the outcrop, about 80 cm below the MegaT. It is not safe to climb up there to see it. Therefore, we will move on to the next stop, in the Fonte d'Olio section where the K/T boundary is well exposed and easy to reach.

11:00

STOP 3 The K/T boundary at Fonte d'Olio

In the upper part of the Fonte d'Olio valley, in the so-called Quagliotti Quarry, the K/T boundary exhibits the exact same facies as in the Fornaci quarries (Fig. 3). However, the Tertiary Scaglia shows a whitish colour indicating that in this part of the Cònero basin, reduced conditions on the sea floor lasted for several million years after the K/T event.

Here we can observe the K/T boundary from up close (Fig. 4). The clay layer exhibits a green-ochre colour and is therefore different from the same (red) layer observed at Gubbio and Furlo, and anywhere else in the Umbria-Marche basin. Bioturbation in the top layer of the Cretaceous, usually represented by abundant traces of Zoophycos and Planolites burrows in the classic, well oxygenated facies of Gubbio, are very scarce at Monte Cònero, possibly indicating slightly reducing conditions at the water-sediment interface.

Reducing conditions of the paleoseafloor are also indicated by the fact that goethite (i.e., iron oxide) spherules are absent in this K/T boundary layer. Only altered microkrystites made of immature, pale-green glaucony, and K-feldspar are present, along with shocked quartz grains, and well differentiated arenaceous benthonic foraminifers, which are somewhat bigger than those found in other K/T boundary layers in the region. Moreover, the boundary clay contains 10 ppb Ir, the largest anomaly measured in the Umbria-Marche basin (Montanari, 1990). Perhaps the K/T boundary of Monte Cònero is the best preserved in the Apennines despite the fact that its facies is different from the classic Gubbio (or Petriccio) facies.

The Terminal Eocene Events: an Introduction

In the years immediately following the publication by Alvarez et al. (1980) of the hypothesis that the impact of a giant extraterrestrial object was the cause of the K/T boundary mass extinction, an obvious question crossed the mind of those researchers who found such a hypothesis at least interesting: are there other mass extinction events throughout Earth's history that could be related to impacts?

It was with this question in mind that Alvarez et al. (1982) undertook a trace element geochemical investigation across two interesting stratigraphical boundaries, namely the Permian-Triassic (P/TR), and the Eocene-Oligocene (E/O). The first records the most severe Phanerozoic mass extinction, whereas near the latter, in some Caribbean and Gulf of Mexico deep sea cores, glassy microspherules were known to exist, and they were already recognised as impactoclastic material (see review in Montanari et al, 1993, and references therein). Moreover, with the first compilation and analysis of a data base and the plotting of marine families extinction rates through the past 250 Ma, Raup and Sepkoski (1982) showed that, in addition to the K/T boundary, there were some other ten statistically significant extinction peaks through this span of Earth history, and one of them was, in fact, at or near the E/O boundary. While the P/TR boundary yielded no Ir anomaly, the samples from the microspherule layer near the E/O boundary contained up to 0.4 ppb Ir. This was one order of magnitude less than the K/T boundary, but undoubtedly a strong indication that an anomalous accretion of extraterrestrial matter occurred at that time (Alvarez et al., 1982). These coincidences (Ir, microspherules, and mass extinction) were rendered even more intriguing by the fact that the largest impact structure in the past 250 Ma record known on Earth in the early 1980s was the 100 km-diameter Popigai crater, in central Arctic Siberia. Early radioisotopic dates were indicating an imprecise age of 39 ± 9 Ma for the Popigai structure, thus, covering the long stratigraphic interval between the Middle Eocene to the Early Oligocene. The whole picture of the terminal Eocene events in the early 1980s was somewhat out of focus compared to the controversial but undoubtedly exciting, emerging story of the K/T boundary. That the Late Eocene was a time of major change in Earth's history was felt by many researchers (see Pomerol and Premoli Silva, 1986). During the Eocene, the separation of Antarctica from the southern continents led to the formation of the circum-Antarctic current and the gradual glaciation of the continent. As the Antarctic polar ice cap spread until reaching the ocean, cold water masses formed along the continent's coasts. Being denser than warmer surface waters, these cold water masses started to sink moving away from the isolated continent for long distances toward North, eventually changing water circulation and temperature in the Earth's oceans. With time, the glaciation and a renewed oceanic circulation affected climate. Climatic cooling began to affect productivity of abyssal organisms as well as the plankton, and eventually altered the equilibrium of the global ecosystem. The global cooling model, so strongly supported by geologic, geochemical, and tectonic evidence, was a classical example of gradualism, which could stand by itself, and explain the observed global changes without having to invoke a catastrophic extraterrestrial event. Moreover, there was neither discrete boundary clay nor a dramatic extinction of dinosaurs (or of anything else) across the E/O boundary that could really attract the attention of the earth science community toward a possible extraterrestrial cause (or con-cause) for these events. And yet, impact evidence near the boundary were already available since the early 1970s. This was enough to encourage a few researchers to investigate further on these impact signatures.

One of the most hampering factors against a prompt development of research on the possible cause-and-effect relationship between impacts and mass extinction near the E/O boundary was, since the very beginning, a somewhat confusing stratigraphic and geochronologic calibration of this time interval. In fact, ages ranging between 36 and 34 Ma for the North American tektites, to which the Caribbean and Gulf of Mexico microtektites are related, were determined by fission track and K/Ar dating by a number of researchers. On the basis of biomarkers, the microtektites in Caribbean and Gulf of Mexico cores were assigned to the upper Eocene NP18 (nannofossil) Zone or to the P15 (foraminiferal) Zone is some cores, and to the NP19 Zone or P16 Zone in others. Further accurate 40Ar/39Ar dating of microtektites and tektite fragments from a land-based section in Barbados yielded an age of 35.4 ± 0.6 (Glass et al., 1986). The confusion was that the chronostratigraphic time scales most used in the early 1980s were assigning an age around 37 Ma to the E/O boundary and, therefore, they were in contrast with an age of 34.7-36 Ma for the microtektites, which were apparently contained in upper Eocene sediments. In other words, on the basis of geochronology the impact that generated the tektites and microtektites occurred in the lower Oligocene but microfossil associated with them indicated an upper Eocene age.

Such stratigraphic and geochronologic uncertainties did not help in searching the needle in the haystack. Precise and accurate means for world wide time correlation are the sine qua non for assessing the uniqueness of a sudden event such as an impact, and locate it within the stratigraphic-paleontologic record. Moreover, the time correlation between marine sediments and an impact crater, upon which any kind of inference on a possible cause-and-effect relationship can be drawn, has to be based on numerical geochronology, and, therefore, on a reliable radioisotopic calibration of the time scale. The problem lies in the fact that marine sediments are rarely dated by radioisotopic means just as impact rocks are rarely dated by biostratigraphic means.

The U-M sequence, once again, offered the unique opportunity to untangle the apparent geochronologic paradox of the E/O boundary. In fact, Lowrie et al. (1982) reported the presence of several biotite-rich layers interbedded with the pelagic marly limestones of the Scaglia Variegata-Scaglia Cinerea sequence in the Contessa Quarry (CQ) section. These discrete layers represented the fallout of material erupted from distant volcanoes and, thus, they could have been used to date directly, by radioisotopic means, the sediments covering the biostratigraphically and magnetostratigraphically calibrated Eocene-Oligocene interval (Lowrie et al., 1982).

Early K/Ar dates from two biotite layers bracketing the E/O boundary at Contessa yielded an interpolated age for the boundary youngerthan 35 Ma (Montanari, 1983). Further K/Ar, Rb/Sr, and 40Ar/39Ar dating on other biotite layers from the sections of Contessa, the Monte Cagnéro (near Piobbico), and the Massignano (at Monte Cònero near Ancona (see below), finally lead to a precise and accurate interpolated radioisotopic age for the E/O boundary of 33.7 ± 0.4 Ma. This new age determination lowered the dates in use in the 1980s by as much as 3 Ma, and undoubtedly placed the North American tektite strewnfield in the Late Eocene.

While a great effort was made by a number of researchers to resolve the integrated stratigraphy of the E/O boundary in the Apennines (e.g., Premoli Silva et al., 1988), investigations focused on impact spherules and Ir anomalies in deep sea cores revealed that not one, but several impactoclastic layers were present in upper Eocene sediments throughout the world. First of all, it soon became clear that in Caribbean and Gulf of Mexico cores there were not one but two closely spaced microspherule layers: the older one contained clinopyroxene-bearing microkrystites, and the younger one only the crystal-free microtektites. Iridium was foundassociated with the microkrystite layer in several sections in the Caribbean-Gulf of Mexico area, as well as in the Pacific and Indian oceans, whereas the microtektite strewn field, with little or no Ir, was seemingly confined within the Caribbean, Gulf of Mexico, and northwestern Atlantic areas. Shocked quartz and coesite were found to be associated with this Ir-free, microtektite layer (see discussion in Montanari et al., 1993, and references therein).

In addition to the closely spaced spherule layers (about 20 ka apart) in the Globorotalia cerroazulensis Zone (i.e., the P16 Zone), Keller et al. (1987) reported an older microkrystite layer, also associated with Ir, in the upper part of the Globigerinateka semiinvoluta Zone (i.e., the P15 Zone) in equatorial Pacific and Indian Ocean sites. This finding was questioned by Glass and Burns (1987), who argued that the biostratigraphic determination by Keller and co-workers was faulty due to reworking of critical index fossils.

Hazel (1989) used the graphic correlation technique on available biostratigraphic data to determine the stratigraphic position of iridium anomalies and microspherule layers in sections from the North Atlantic, Barbados, Venezuela Basin, Gulf of Mexico, central and western equatorial Pacific, and eastern equatorial Indian Ocean. He proposed at least six microspherule layers in the upper Eocene, three of which were restricted to the eastern American region, and the other three in the equatorial Indo-Pacific region. According to Hazel (1989), all of the Late Eocene microspherule layers studied occur in the G. semiinvoluta Zone.

In contrast, Glass (1990) argued that petrographic and compositional data indicate at least two, or at most four upper Eocene microspherule layers: two closely spaced layers with microkrystites and microtektites in the G. cerroazulensis Zone, and possibly two similar layers in the G. semiinvoluta Zone (as represented in DSDP Site 612).However, the conclusion of only two layers was reinforced by Glass and Koeberl (1999) in their study of ODP 689B core samples. Late Eocene sediments in Core 21-5 of DSDP 612, in the northAtlantic off New Jersey, contain two spherule-bearing layers separated by ~5 cm. The lower layer is represented mainly by microkrystites, although it contains also tektite fragments, whereas the upper layer contains only microtektites and tektite fragments. These microspherule layers were belong to the G. semiinvoluta Zone (Miller et al., 1991) rather than the G. cerroazulensis Zone, in which microtektites and tektite fragments are found at Barbados (Saunders et al., 1984). However, the chemistry of tektite glass in DSDP 612 is almost identical to that of the Barbados section. Moreover, a 40Ar/39Ar plateau age of 35.5 ± 0.3 Ma for the tektitic glass in DSDP 612 (Obradovich et al., 1989) is comparable to a 40Ar/39Ar age of 35.4 ± 0.6 Ma obtained from tektite fragments and microtektites from the Bath Cliff section in Barbados (Glass et al., 1986). Nevertheless, the analytical uncertainty of these dates does not permit to discern whether they are the same impactoclastic material or rather different impactoclastic events closely spaced in time.

Miller et al. (1991) advanced the hypothesis that the Barbados and DSDP 612 tektites represent different impact events separated by ~ 0.5-1.0 Ma, in the upper G. semiinvoluta Zone, and the middle of G. cerroazulensis Zone. As an alternative hypothesis, Miller et al. (1991) proposed that tektite glass in the two sites was produced by the same impact event within the G. cerroazulensis Zone, and that very high sedimentation rates at DSDP 612, and diachroneity of biomarkers defining zonal boundaries in the Late Eocene, would make them appear as two different events. With this background of confusing information on how many impacts, and of which age, occurred in the Late Eocene, Montanari et al. (1993) undertook a systematic search for Ir in 5 cm-spaced samples from the Massignano section, near Ancona, which was at the time the best exposure of the Eocene-Oligocene transition known in the U-M region. A prominent ir anomaly was found in a level dated at 35.7 ± 0.4 Ma, and another peak in a sample higher in the section. This encouraged further high-resolution impact stratigraphic investigations of this section, the exciting results of which are summarised and referenced below.

11:45

STOP 4 The Global Stratotype Section and Point for the Eocene/Oligocene Boundary at Massignano

With the meeting of the IUGS-Subcommission on Paleogene Stratigraphy at Monte Cònero (Ancona, October 1-3, 1987), a period of prolific interdisciplinary stratigraphic research begun in the abandoned quarry of Massignano, carried out by a number of international research teams. The quarry face exposes a 23 m thick continuous, and complete sequence of pelagic marly limestones and calcareous marls, rich in well preserved benthic and planktonic microfossils, and interbedded with several biotite-rich volcanosedimentary layers spanning the Upper Eocene and the lowermost Oligocene. This can be regarded as an ideal situation for the application of an integrated stratigraphic approach aimed at the precise and accurate calibration of the litho-, bio-, magneto-, and chemostratstratigraphic records with direct radioisotopic datings. An IUGS-SPS special publication (Premoli Silva et al., 1988) containing several technical, interdisciplinary papers first discussed at the Monte Cònero meeting (Coccioni et al., 1988; Coccioni, 1988; Parisi and Coccioni, 1988; Bice and Montanari; 1988; Odin et al., 1988; Asaro et al., 1988; Capo and DePaolo, 1988; Montanari et al., 1988; Montanari, 1988a-b; Deino et al., 1988; Odin Montanari, 1988) was presented at the 1989 IGC in Washington, along with formal proposals for promoting the Massignano quarry as Global Stratotype Section and Point (GSSP) for the Eocene-Oligocene boundary (Premoli Silva and Montanari, 1989: Montanari and Odin, 1989). The Massignano GSSP was formally established by the IUGS-SPS at the 1993 IGC in Kyoto (Premoli Silva and Jenkins, 1983).

A number of studies further refining the mineralogic and lithostratigraphic (Mattias et al., 1992; Montanari et al., 1994), biostratigraphic and paleontologic (Gonzalvo and Molina, 1992a-b; Molina et al., 1993; Brinkhuis and Coccioni, 1995), magneto-stratigraphic (Lowrie and Lanci, 1994; Lanci et al., 1996), chemostratigraphic (Montanari et al., 1993; Vonhof et al., 1998), and geochronologic (Odin and Montanari, 1989; Oberli and Meier, 1991; Odin et al., 1991) attributes of this section were published independently in various international journals (see integrated stratigraphic summary in Fig. 5).

In particular, recent high-resolution stratigraphic studies lead to the discovery, at 5.6 m in the GSSP section, of an impactoclastic layer, possibly of world-wide occurrence and probably related to the Popigai impact event. This 5 cm thick layer contains an iridium anomaly (Montanari et al., 1993), shocked quartz (Clymer et al., 1996; Langenhorst, 1993), impact spinel and altered microkrystites (Pierrard et al., 1998), and a prominent anomaly of 3He (Farley et al., 1998). This 3He anomaly, which peaks at the impactoclastic layer, but extends above and below it for some 12 m, indicates that the Earth experienced a 2.2 million years long comet shower, accompanied by multiple impacts, which could have had an important role in the global environmental and biologic crises of the Late Eocene. These new discoveries encouraged further detailed studies especially on the paleontologic and paleobiologic records of the Massignano GSSP aimed at the verification of the effects that the inferred cosmic crisis may have had on the terminal Eocene marine biota (Gardin et al., 1999; Huber et al., 1999).

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Lowrie, W.., Napoleone, G, Perch-Nielsen, K., Premoli Silva, I., and
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update. In: Sharpton VL and Ward PD (eds.) Global Catastrophes in Earth
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anomalies of Late Eocene age at Massignano (Italy), and in ODP Site 689B
(Maud Rise, Antarctica): Palaios, 8: 420-437.

Montanari, A., Deino, A., Drake, R., Turrin, B. D., De Paolo, D. J., Odin,
S. G., Curtis, G. H., Alvarez, W., and Bice, D. M., 1988, Radioisotopic
dating of the Eocene-Oligocene boundary in the pelagic sequence of the
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Impacts accelerated global cooling? in "The strontium Stratigraphic record
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1Prof. Alessandro Colombetti
University of Milano – Bicocca

8.00 – Departure: Castelnovo ne’Monti

11.00

STOP 1 – Sassorosso Town: Panoramic view of Pania di Corfino and its geological setting.

From this point we can see the complete stratigraphical sequence of Tuscany Basin, from Macigno to Pania di Corfino Formation.

On the right side, at the background, you can see the highest heights (Mt. Cella, 1946 mt; Mt. Vecchio, 1982 mt; Mt. Prado, 2054 mt) of the area, made of the turbiditic sediments of Macigno.

These sediments testify the first arrival of turbidites, due to the apenninic orogenetic belt.

The contact between Scisti Policromi and Macigno occur at Foce di Terrarossa (1141 mt).

Here the outcropping area is not in good exposure, nevertheless the contact is sharp between the two different litotypes, because of the suddenly arrival of the turbidite currents in to the pelagic basin of the Scisti Policromi.

Along the SS. 24 route, near Casina Rossa, you can see the Scisti Policromi Formation, composed by argillitic, massive reddish layers, with greenish interbedded marly layers.

The exterior morphology of such layers is due probably to the deeply reworking operated by dwelling organism in the sediments.

Witnesses of such activity are the ramified structures of centimeters dimentions, which represents the old house tunnels and food traces.

The entire outcrop present a secondary cleavage and deeps towards the east.

On the left side you can see the top of the hill were lies the little town of Sassorosso.

The name of this town derived from the presence of the red rocks of the Rosso Ammonitico Formation (at the top of the hill), while beneath it lies the Calcare Massiccio Formation, dipping towards E – ESE.

A series of antiappenninic faults separes the Rosso Ammonitico Formation to the Calcare Selcifero di Limano one, and this latter from Scisti Policromi.

In front of you, on the other side of the Il Fiume Stream Gorge [Fig. 1], there is a good exposure of Retic – Hettangian sediments (Pania di Corfino Formation), which present a low anticline tectonical structure, with the axial dipping toward the east.

It’s notable the good stratification in thin layers and megabeds of Pania di Corfino Formation, in opposition of the deeply fracturation of the sub-vertical and massive formation of Calcare Massiccio, which has produced a very huge accumulation of detritus slope.

At the top of Pania di Corfino lays a little layer of Rosso Ammonitico Formation.

In the outcrop the Pania di Corfino Formation presents two different litologies, recognised by different morphologies and kind of vegetation.

The lower a middle part of the formation is composed by about 180 meters of dolomitic limestones, till 5 meters thicked. The higher one, sicked about 80 meters, is composed by calcareous layers, thicken no more than one meter, with interbedded marlstones, more frequent toward the top of the formation. The layers are rich enough of Retic fossils.

At the passage of the overlaying Calcare Massiccio, the rise a 1.50 meters thicken marlstones, in which some quartzose granules, of silt dimensions have been found (Bice et al., 1992).

They present a crystalline deformed structure, due to the very high pressure. Such deformation are referred to a great meteoric impact at the end of Triassic age, which had produced the so-called "Shocked Quartz", on the quartzose crystals present in the rocks involved in the impact event.

The incredible explosion should have produced also a long serie of meteorological phenomena so strong to modify the original climatic condition, and bring out the extinction of some groups of animals, that really happened at the Triassic / Jurassic boundary.

11.50

STOP 2: Triassic / Jurassic boundary near Il Colle.

The Triassic / Jurassic (T/J) boundary represents one of the five most severe marine extintions in Phanerozoic history and is a time of important terrestrial extintions.

The most important T/J sections in the world are the Kendelbach (Austria), New York Canyon (Nevada, United States) and the Pania di Corfino (Italy).

Recent developments supporting one or more asteroid or comet impacts as the primary cause of the K/T mass extintions, Permo/Trias and T/J.

Traces of ejecta were found by Bice et al. (1992) in the Il Fiume Stream Gorge, near the town of Corfino (Tuscany, Italy).

Another good exposure of the T/J boundary is in the outcrop of Il Colle, near the town of Sassorosso [Fig. 2].

In the Il Colle outcrop we can see the last 2 meters of the Pania di Corfino formation.

This formation consist in limestones, with two principal facies: about 80% of skeletal packstone and wackestone; the remaining 20% is biomicrite and sparsed biomicrite.

Calcareous shale is interbedded with the limestone.The first facies contains bivalves, benthic foraminifera, echinoderms, gasteropods and rare serpulids. Bice et al. (1992) interprets this facies as rapresenting a fully marine, shallow subtidal habitat.

The second facies contains rare uniserial foraminifera and anomuran micropellets. The boundary shale is an unfossiliferous micritic shale.

Immediately above the boundary shale, the first 26 cm of the Calcare Massiccio is unfossiliferous, laminated micrite.

If we see the Il Fiume section [fig. 3], the shocked quartz occur in 3 differents layers: the lower half of the boundary shale (A), and in two shale beds located at 1.2 (B) and 2.4 m (C) below the boundary. The same there is at Il Colle outcrop.

The shocked quartz grains are the 20% of the total amount of detrital minerals found in the shales. These grains are very thin (1 to 2 microns), with closely spaced planar zones that are optically discontinuous with the rest of the grains. In some grains the lamellae are decorated by small inclusions of bubbles. This type of quartz is very similar to the K/T boundary one.

Other levels with a minor concentration of quartz grains with single set of lamellae was found in a shale layer 0.7 m (D) below the boundary, 3.7 m (F) below and 2.6 m (E) above the boundary.

The resulting average rate of accumulation suggests that the beds A to C may span about 150,000 years (Bice et al., 1992), well within the expected time of a comet shower, like proposed by Hut et al. (1987).

14.00 – Lunch

17.30

STOP 3: The Romanoro outcrop.

In order to understand the problem of dating the Romanoro event, it’s important to know the geological and structural setting of this area of the Apenninic chain.

The Romanoro Flysch is a tectonic scale, part of the Sestola Vidiciatico Tectonic Unit.

This unit is a tectonic belt interbedded between the Ligurain Unit, at the top, and the Tuscany one, at the bottom. Shales with scales of calcareous formations and ophiolites mainly compose the Sestola Vidiciatico. The oversthrusting of the Ligurian nappes and the underthrusting of the Tuscany ones had erased the original relationships between the rocks now enclosed in the intermediate tectonic unit.

Moreover the folding of the Tuscany units in two large anticlines, as we can see in the tectonic windows of Gazzano and Gova, have complicated the geological situation [fig. 4].

Starting from the top to the bottom of Monte Modino Mt. (1410 meters) we can see:

- The Ligurian Units, with the Venano Stratigraphic Sequence: the Poggio Castellina Sandstones and the Poggio Mezzature Shales. This sequence is the upside down part of a regional scale anticline. A regional thrust line divides this unit to the one below.

- The Sestola Vidiciatico unit, with its scales. In the Romanoro area we can see: the Calcareous Shale Complex, that envelope tectonically the Castellaccio "Black" Shales and the Romanoro Flysch.

- The Tuscany Units, not outcropping in this place, but that are visible in the nearest window of Gazzano. In this area there is the Cervarola Stratigraphic Sequence: the Poggi di Fontanaluccia Siltstones, the Civago Marlstones and the Cervarola Sandstones.

Calcareous siltstones, marlstones and shales of turbiditic origin mainly form the Romanoro Flysch.

The stratigraphic sequence near the route outcrop is normal. The analysis of the sedimentologic structures show a little part of the Bouma Sequence with only the Td and Te intervals, and this demostrate a sedimetation under a diluite turbidite currents, with low energy deposition. The strata are horizontal or have a little (10°) dip towards south – southeast [fig. 5].

In the ancient quarry on the left side, ten - twenty meters up from the route outcrop, the sequence is upside down, with the presence of megabeds. This tectonic passage is covered, but we can suppose the presence of an isoclinal fold-fault structure, due to the rapid changing of the deposition polarity.

On the bottom of the calcareous siltsones it’s easy to find traces of paleocurrents and/or dwelling organisms.

At the top of the Romanoro Flysch, the transition to the uppermost Castellaccio Shales is marked by a thin thrusting surface, covered by a calcite vein; however we formulate the hypotesis that originally these two formations was in stratigraphic contact.

All the formation is deeply affected by faults, joints and a secondary cleavage due to the formation of Gazzano and Gova anticlines.

In the "route" outcrop we can see a sequence of little faults, with calcite veins, and a large boudinage of the calcareous siltstone beds.

The metallic microspherules were found in the levels FR 1 and 2. The SEM, mineralogical and metallographical analyses have confirmed the iron meteorite origin.

During new sampling, were found glassy microspherules, now under analyses; the presence of impact materials will be sure if it was confirmed their origin.

The datation of the sediments and of the meteoritic event is an open question.

New data (see in this volume) have partially clarified the original age of the Romanoro Flysch.

In consequence of the large abundance of Tertiary foraminifera (mainly we can observe an Eocene – Oligocene fauna), the age of the sediments is younger than the K/T event.

This hypotesis has been confirmed by the presence of Miocenic planctonic foraminifera, in bad conservation, and the results of the ⁸⁶Sr/⁸⁷Sr datation.

The ageis: Lower Miocene.

The analyses of calcareous nannoplancton show a unique Cretaceous age.

Due to the tectonic situation it’s very hard to collocate this formation into a sure sedimentary basin; probably the original basin was the Epiligurian one. This type of basin was joined to the thrusting of Ligurian units, that during their movement created this ensialic basin in a close little ocean.

AA. VV., 1992, L’Appennino Tosco – Emiliano, in Guide Geologiche Regionali. Ed. BE-MA, 329 p.

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Bice D.M., Newton C.R., McCauley S., Reiners P.W. and McRoberts C.A., 1992, Shocked quartz at the Triassic – Jurassic Boundary in Italy. Science, 255, 443 – 446.

Colombetti A., Ferrari G. e Nicolodi F., 1997, Su alcune microsferule metalliche ritrovate all’interno di uno strato calcareo marnoso, appartenente al Flysch di Romanoro (Unità Sestola - Vidiciatico), nell’Alto Appennino modenese. Ateneo Parmense Acta Naturalia, 33.

Colombetti A., Ferrari G., Nicolodi F. and Panini F., 1998, Some metallic spherules in calcareous marly sediments of the Romanoro Flysch, Sestola - Vidiciatico tectonic unit (Modena district, Northern Apenines, Italy). Planetary and Space Sciences, 46, Special Paper, Parigi.

Colombetti A. and Nicolodi F., 1998, La Sorgente Sulfurea di Farneta nella valle del T. Dolo (Prov. Di Modena). Ateneo Parmense Acta Naturalia, 34.

Colombetti A. and Nicolodi F., (in press), Evidences of meteorite impact in a turbidite sequence of northern Apennines (Modena district - Italy). IGCP384 Annual Meeting, Budapest, Hungary, 26 Sept. - 3 Oct. 1998.

Daniele G., Mochi E. and Plesi G., 1996, L’insieme ligure – emiliano dell’Appennino modenese: unità tettoniche e successioni stratigrafiche nella zona di Frassinoro. Atti Soc. Tosc. Sci. Nat. Mem., serie A, 102, 147 – 158.

Rentz K., 1971, Zur Geologie der Zone zwischen der Secchia und dem Apennin Hauptkamm. Diss. Freie Univ., Berlin.

Reutter K.J., 1969, La Geologia dell’alto Appennino Modenese tra Civago e Fanano, e considerazioni geotettoniche sull’unità M. Modino – M. Cervarola. Ateneo Parmense Acta Naturalia, 5 , 1 – 88.

- Introduction, by Prof. Alessandro Colombetti

Chair of the session: Prof. Francois Marini

G. A. ALBERTÃO and A. A. GRASSI

Cs. H. Detre, I. Tóth, Gy. Don, A.Z. Kiss, I. Uzonyi, P. Bodó, Zs. Schléder

Coffee Break

Gy. Don , Cs. H. Detre , P. Solt

J. Hoxha

Lunch

Chair of the session : Prof. Gilberto Albertao

Sz. Bérczi, Cs. H. Detre, Gy. Don, P. Solt, I. Uzonyi

• Discovery of glassy microspherules at the top of Irati shales (Upper Permian) at Montevidiu (Goias, Brazil) comparison with the microspherules found at the impact cratering of Araguainha (Mt, Go, Brazil).

J.M. Thery, P. Solt, P. Crosta

Coffee Break

A. SIEGL-FARKAS

Y.W Isachsen

F. MARINI ¹ , A. RAUKAS ² and R. TIIRMAA

Welcome Party

Chair of the session: Prof. Csaba Detre

A. Colombetti, G. Ferrari and F. Nicolodi

Raukas, A.

Coffe break

I. Vetvicka

A. Colombetti and F. Nicolodi

• Bismantova field trip (September, 8)
• K/T and Eoc./Olig. Boundaries field trip (September, 9)
• T/J boundary and Romanoro field trip (September, 10)

Albertao G.A. – Petrobras/EPBC/GERET/GEREV –C – Av. E. Agostinho 665, 27913, Macaé, RJ, Brazil

Biggioggero B. - University of Milano, Mineralogy and Petrology Section , via Botticelli 23, 20133 Milano, Italy

Cara F. - Albanian Geological Survey, Institute of Geological Research. Blloku "Vasil Shanto" Tirane, Albania

Colombetti A. - University of Milano-Bicocca, Dept. Of Geological Sciences and Geotechnologies, via Mangiagalli 34, 20133 Milano, Italy

Detre Cs. - Geological Institute of Hungary, H-1143 Budapest, Stefánia út 14, Hungary

Don Gy. - Geological Institute of Hungary, H-1143 Budapest, Stefánia út 14, Hungary

Ferrari G. - University of Milano, Dept. Of Earth Sciences, via Mangiagalli 34, 20133 Milano, Italy

Fioretti A. - CNR, Centro Studi Geodinamica Alpina, C.so Garibaldi, 37 - 35137 Padova Italy

Gardi A. - University of Milano, Dept. Of Geophysics, via Cicognara 7 , 20100 Milano, Italy

Glikson A. - Research School of Earth Science Australian National University, Canberra, ACT 0200, Australia

Hoxha J. - Albanian Geological Survey, Institute of Geological Research. Blloku "Vasil Shanto" Tirane, Albania

Iaccarino S. – University of Parma, Parco Area delle Scienze 157a – 43100 Parma, Italy

Isachsen Y.W. - New York State Geological Survey/State Museum, Albany, NY 12230 (USA); or HANLEY, Kristy, Dept. of Earth and Atmospheric Sciences, University at Albany, Albany, NY 12222 (USA)

Jobstraibizer P. - Dip.to di Mineralogia e Petrologia dell’Università, C.so Garibaldi, 37 – 35137 Padova - Italy

Marini F. – E.N.S.G., Rue du Doyen Roubault, EP40, 54501 Vandoeuvre les Nancy Cedex, France

Montanari A. - Osservatorio Geologico di Coldigioco 62020 Frontale di Apiro - Italy

Nicolodi F. – University of Milano, Dept. Of Earth Sciences, via Mangiagalli 34, 20133 Milano, Italy

Panini F. – University of Modena, Dept. of Earth Sciences, P.le S. Eufemia 19, 41100 Modena, Italy

Pohl H. - Institute of Geology at Tallinn Technical University, 7 Estonia Avenue, Tallinn 10143, Estonia

Solt P. - Geological Institute of Hungary, H-1143 Budapest, Stefánia út 14, Hungary

Siegl - Farkas A. - Geological Institute of Hungary, H-1143 Budapest, Stefánia út 14, Hungary

Thery J.M. - 9 Jardin Gabrieli, Tours, France

Vetvicka I. - Charles University, Department of Geology, Pøevoznická 14 , 143 00 Prague 4 Czech Republic