Calcare di Sogno
| Calcare di Sogno | |
|---|---|
| Stratigraphic range: Lower Toarcian-Late Bajocian ~ | |
 The transition (Tsg) between Sogno Formation (SOG) and Rosso Ammonitico Lombardo (RAL) at Cesana Brianza | |
| Type | Geological formation |
| Sub-units | Livello a Pesci |
| Underlies | Formazione delle Radiolariti |
| Overlies | Calcare di Domaro, Calcare di Morbio, Unnamed limestones[note 1] |
| Thickness | Typically 120–140 m (390–460 ft) East and west 70–100 m (230–330 ft) |
| Lithology | |
| Primary | Marl, marly limestone & abundance of clay Secondary: Alternation of marly limestones and marls, presence of graded Chalcudites |
| Other | Limestones with nodules of flint & subordinate marls |
| Location | |
| Coordinates | 45°48′N 9°18′E / 45.8°N 9.3°E |
| Approximate paleocoordinates | 33°24′N 18°54′E / 33.4°N 18.9°E |
| Region | Lecco Province |
| Country | Italy |
| Type section | |
| Named for | Sogno |
| Named by | Gaetani & Poliani |
  Calcare di Sogno (Italy)  Calcare di Sogno (Lombardy) | |
The Calcare di Sogno ("Sogno Limestone"; also known as the Sogno Formation) is a geological formation that crops out with typical characteristics in the western Bergamo Prealps, near the border with the Province of Lecco. It outcrops along a northwest–southeast trend running approximately between the municipality of Erve (on the left hydrographic bank of the Adda River) and the municipality of Palazzago (on the right hydrographic bank of the Brembo River).[2] The formation was proposed by Gaetani and Poliani (1978) and formalized by Delfrati et al. (2000).[1] It comprises a rather composite succession of grey and reddish calcareous-marl alternations, generally non-nodular, occasionally with chert nodules and lenses, and subordinate dark claystones. This unit was previously referred to the Rosso Ammonitico Lombardo and represents a lateral equivalent of it.In addition to the type area, the formation is present west of the Adda River in outcrops of limited stratigraphic thickness (areas of Canzo and Cesana Brianza, Alpe del Viceré, and Monte Olimpino near Como).[3] In this context the unit consists of grey-greenish or grey-bluish clayey-marl lithotypes equivalent to the basal part of the formation in the type area, and passes upward into the Rosso Ammonitico Lombardo. On the basis of its paleontological content, the unit is assignable — in its most complete expression — to the Toarcian–lower Bajocian.[1] Thalattosuchian remains are known from the formation, as well as fish and other taxa.[4]
Description
[edit]During the Early Jurassic, concretely towards the Toarcian, the Lombardy Basin became a relatively deep, fully pelagic area, located between the so-called Lugano High, at the west, and the Trento Plateau to the east, with several troughs and palaeohighs (West to east: Monte Nudo Trough, Lugano High, Generoso Trough, Corni di Canzo High, Albenza Plateau, Monte Cavallo High, Sebino Trough and Botticino High).[5] The formation is characterized by a disposition of regional deposition equivalent to the German Posidonia Shale, with a benthic setting and deposition trends, mostly populated by marine fauna.[2] The formation is traditionally subdivided into three informal lithozones, from base to top:[2][1]
- Lithozone 1: thickness between 20 and 40 m; prevailing grey marly limestones and reddish marls, with laminated grey-blackish argillites in the middle part, fossiliferous with fish remains;[6]
- Lithozone 2: thickness between 50 and 70 m; rhythmic alternations of marly limestones in beds around 30–40 cm thick (chert-bearing upward), and marly interbeds ranging from centimetric to decimetric, rich in pelagic bivalves (Bositra), locally forming shell beds (lumachelles); coarse-grained graded clastic beds occur at the western margin of the type area.
- Lithozone 3: thickness between 30 and 40 m; grey and reddish marly limestones in thin undulated beds with centimetric marly-pelitic partings, sometimes passing upward into red marls, containing Bositra and radiolaria, with the latter becoming increasingly abundant toward the top.
West of the Adda River, in the areas surrounding the paleo-high of the Corni di Canzo, the formation consists of micaceous blue-green marls and laminated claystones passing upward into the Rosso Ammonitico Lombardo. The environment of the formation was related to a marginal marine deposit, with probably epicontinental deposition from near land environments, being connected to the central European seas and the North African currents of the Toarcian.[7] The formation is linked with the Toarcian Anoxic Event, that is measured in the "Fish Level", that is also the most fossiliferous section.[8]
Environment
[edit]
Two cores, the Colle di Sogno and Gajum are among the best sections that recovered the ecological changes in the Pliensbachian-Toarcian Lombardy Basin.[9] Carbon-and oxygen-isotope data calibrated against nannofossil biostratigraphy has shown that the palaeobathymetry of the deposits was about 1000 and 1500 m, being the deepest records of the T-OAE in the western Tethyan region.[10] As the Sogno Formation was deposited mostly in a pelagic setting, influenced by both the European and African bioregions, taxa of several provenances mix in this layer. The Nannofosil assemblage, that ranges from moderate/poor to good decreasing in the Toarcian AOE (drastic decrease in total abundance is observed in the Fish Level), includes the taxa Lotharingius (L. hauffii, L. sigillatus, L. crucicentralis, L. velatus), Discorhabdus ignotus, Diductius constans, Carinolithus (C. poulnabronei, C. superbus), Mitrolithus jansae and Watznaueria sp.1 in the Gajum Core, while the Sogno Core shows abundance of the genera Biscutum, Calyculus, Carinolithus and Crepidolithus, whereas Bussonius, Diductius, Similiscutum, Parhabdolithus and Tubirhabdus are extremely rare.[11] The overall structure of this microtaxa assemblage trends to suggest a correlation with the biohorizon seen in coeval layers in the Lusitanian Basin, where a common trend is observed in the Western Tethys of north–south migration pathway for several organisms, including calcareous nannoplankton and ammonites.[11]
A local index genus for environment evolution is Schizosphaerella spp. (specially S. punctulata), showing a lower valve size than in coeval layers on connected basins (Lusitanian and Paris Basins), as local result of the Lower Toarcian Jenkyns Event, indicating changes in ocean acidification and fertility rather than temperature.[12]
Fossil content
[edit]Ichnofossils
[edit]| Genus | Species | Location | Material | Type | Origin | Notes | Images |
|---|---|---|---|---|---|---|---|
|
|
Cylindrical burrows |
Pascichnia |
|
Burrow-like ichnofossils referred to vermiform deposit-feeders. Sometimes considered a junior synonym of Palaeophycus.[13] |
 |
Molluscs
[edit]| Genus | Species | Stratigraphic position | Material | Notes | Images |
|---|---|---|---|---|---|
|
|
Shells |
 | ||
|
C. gemma |
|
Shells |
A Dactylioceratidae ammonite. Present and abundant on the Mediterranean Toarcian realm. |
||
|
C. lythensis |
|
Shells |
An indeterminate ammonite. Some of the specimens found are very fragmentary, making its identification complex.[2] |
 | |
|
D. polymorphus |
|
Shells |
Type member Dactylioceratinae family of Ammonites. A common Mediterranean genus, found in deposits across all of Europe. |
 | |
|
H. sp. |
|
Shells |
Type genus of the Harpoceratinae ammonite family |
 | |
|
H. sp. |
|
Shells |  | ||
|
|
Shells |
Echinoderms
[edit]| Genus | Species | Stratigraphic position | Material | Notes | Images |
|---|---|---|---|---|---|
|
|
Ossicles |
Arthropods
[edit]| Genus | Species | Stratigraphic position | Material | Notes | Images |
|---|---|---|---|---|---|
|
?A. sp. |
|
1 complete specimen, MSNM i10852 |
 | ||
|
A. cfr. A. levis |
|
Various specimens |
A Palinuroidean Decapodan. |
 | |
|
C. cf.banzensis |
|
15 specimens, complete and incomplete |
An Erymidae Decapodan. |
 | |
|
?E. sp. |
|
Single Isolated chelae, MSNM i10855 |
 | ||
|
G. garassinoi |
|
Various specimens |
A Coleiidae Decapodan. Was confused with Proeryon hartmanni specimens. |
||
|
P. hartmanni |
|
Various specimens |
An Erymidae Decapodan Crustacean, common in Mediterranean formations. |
 | |
| U. cf.posidoniae
U. alpina |
|
Isolated chelae, MSNM i10851, il0863, i10864 |
An Astacidean Decapodan of the family Uncinidae. A large decapodan, with sizes up to 40 cm. |
 |
Fish
[edit]| Genus | Species | Stratigraphic position | Material | Notes | Images |
|---|---|---|---|---|---|
|
Monte Cornizzolo |
+100 specimens |
Type member of the family Leptolepidae inside Leptolepiformes. It is the most abundant fish found in the formation. |
 | |
|
Monte Cornizzolo |
Several specimens |
The main member of the family Pachycormidae inside Pachycormiformes. Large sized fish, able to reach near 1.4 m long. |
 | |
|
Monte Cornizzolo |
Several specimens |
Type member of the family Pholidophoridae inside Pachycormiformes. |
 |
Crocodyliformes
[edit]| Genus | Species | Location | Material | Notes | Images |
|---|---|---|---|---|---|
|
cf. P. sp. |
|
Various specimens MSNM V4012, MSNM V4013. |
A Thalattosuchian marine crocodylomorph of the family Teleosauridae.The specimens found were of small size, with several characters that show a possible juvenile or subadult status. |
 |
Flora
[edit]Several plant leaves and fragments of wood were not identified.[6]
| Genus | Species | Stratigraphic position | Material | Notes | Images |
|---|---|---|---|---|---|
|
|
Leaves |
Affinities with the Ginkgoaceae. Arboreal plants related to the modern Ginkgo species. |
 | |
|
|
Leaves |
Affinities with the Cheirolepidiaceae and Araucariaceae. Arbustive to arboreal plants with several leaf morphotypes, probably from nearshore environments. |
 |
See also
[edit]- List of fossiliferous stratigraphic units in Italy
- Toarcian turnover
- Toarcian formations
- Marne di Monte Serrone, Italy
- Podpeč Limestone, Slovenia
- El Pedregal Formation, Spain
- Mizur Formation, North Caucasus
- Sachrang Formation, Austria
- Posidonia Shale, Lagerstätte in Germany
- Irlbach Sandstone, Germany
- Ciechocinek Formation, Germany and Poland
- Krempachy Marl Formation, Poland and Slovakia
- Djupadal Formation, Central Skane
- Lava Formation, Lithuania
- Azilal Group, North Africa
- Whitby Mudstone, England
- Fernie Formation, Alberta and British Columbia
- Whiteaves Formation, British Columbia
- Navajo Sandstone, Utah
- Los Molles Formation, Argentina
- Mawson Formation, Antarctica
- Kandreho Formation, Madagascar
- Kota Formation, India
- Cattamarra Coal Measures, Australia
Notes and references
[edit]Notes
[edit]References
[edit]- ^ a b c d e f g h i j k l SGN (2000). "Carta Geologica d'Italia 1:50.000 – Catalogo delle Formazioni (Fascicolo I)". Quaderni, Serie III, del SGI. 7 (1): 22–31. Retrieved 10 May 2022.
- ^ a b c d e f g h i j k Gaetani, Maurizio; Poliani, Giuseppe (1978). Il Toarciano ed il Giurassico medio in Albenza (Bergamo) (84 ed.). Milan: Riv. It. Pal. Strat. pp. 349–382. Retrieved 10 May 2022.
- ^ Michetti, A.M.; Livio, F.; Pasquarè, F.A.; Vezzoli, L.; Bini, A.; Bernoulli., D.; Sciunnach, D. (2012). "Note illustrative della carta geologica d'Italia - foglio 075 - Como" (PDF). Servizio Geologico D'Italia: 72.
- ^ a b c d e Delfino, M.; Dal Sasso, C. (2006). "Marine reptiles (Thalattosuchia) from the Early Jurassic of Lombardy (northern Italy)". Geobios. 39 (2): 346–354. Bibcode:2006Geobi..39..346D. doi:10.1016/j.geobios.2005.01.001. hdl:2318/79280. S2CID 128423512. Retrieved 10 May 2022.
- ^ Gaetani, M. (2010). "From Permian to Cretaceous: Adria as pivotal between extensions and rotations of Tethys and Atlantic Oceans" (PDF). Journal of the Virtual Explorer. 36 (5): 13–24. doi:10.3809/jvirtex.2010.00235. Retrieved 10 May 2022.
- ^ a b c d e f g Tintori, A. (1977). "Toarcian fishes from the Lombardian basin". Bolletino della Società Paleontologica Italiana. 16 (4): 143–152. Retrieved 10 May 2022.
- ^ Gaetani Escursione, M.; Erba, E. (1990). "Il Bacino Lombardo: un sistema paleo alto/fossa in un margine continentale passivo durante il Giurassico" (PDF). Congr. Naz. Soc. Geol. It. 75 (2): 1–23. Retrieved 10 May 2022.
- ^ Channell, J. E. T.; Casellato, C. E.; Muttoni, G.; Erba, E. (2010). "Magnetostratigraphy, nannofossil stratigraphy and apparent polar wander for Adria-Africa in the Jurassic–Cretaceous boundary interval". Palaeogeography, Palaeoclimatology, Palaeoecology. 293 (1): 51–75. Bibcode:2010PPP...293...51C. doi:10.1016/j.palaeo.2010.04.030. Retrieved 10 May 2022.
- ^ a b Erba, E.; Gambacorta, G.; Visentin, S.; Cavalheiro, L.; Reolon, D.; Faucher, G.; Pegoraro, M. (2019). "Coring the sedimentary expression of the early Toarcian Oceanic Anoxic Event: new stratigraphic records from the Tethys Ocean". Scientific Drilling. 26 (4): 17–27. Bibcode:2019SciDr..26...17E. doi:10.5194/sd-26-17-2019. hdl:2434/698406. S2CID 210961368. Retrieved 10 May 2022.
- ^ Erba, E.; Cavalheiro, L.; Dickson, A. J.; Faucher, G.; Gambacorta, G.; Jenkyns, H. C.; Wagner, T. (2022). "Carbon-and oxygen-isotope signature of the Toarcian Oceanic Anoxic Event: insights from two Tethyan pelagic sequences (Gajum and Sogno Cores-Lombardy Basin, northern Italy)". Newsletters on Stratigraphy. 321 (2): 451–477. doi:10.1127/nos/2022/0690. hdl:2434/923620. S2CID 246990063. Retrieved 10 May 2022.
- ^ a b Visentin, S.; Erba, E. (2021). "High-resolution calcareous nannofossil biostratigraphy across the Toarcian Oceanic Anoxic Event in Northern Italy: clues from the Sogno and Gajum Cores (Lombardy Basin, Southern Alps)". Rivista Italiana di Paleontologia e Stratigrafia (Research in Paleontology and Stratigraphy). 127 (3): 539–556. Retrieved 10 May 2022.
- ^ Faucher, G.; Visentin, S.; Gambacorta, G.; Erba, E. (2022). "Schizosphaerella size and abundance variations across the Toarcian Oceanic Anoxic Event in the Sogno Core (Lombardy Basin, Southern Alps)". Palaeogeography, Palaeoclimatology, Palaeoecology. 595 (3) 110969. Bibcode:2022PPP...59510969F. doi:10.1016/j.palaeo.2022.110969. hdl:2434/969201. S2CID 247983702. Retrieved 10 May 2022.
- ^ Keighley, D. G.; Pickerill, R. K (1995). "The ichnotaxa Palaeophycus and Planolites_ historical perspectives and recommendations". Ichnos. 3 (4). doi:10.1080/10420949509386400.
- ^ Jaselli, L. (2021). "Reappraisal of the Lower Jurassic crinoid fauna of Lombardy (Italy): insights on regional museum collections". Bollettino della Società Paleontologica Italiana. 60 (2): 112. Retrieved 19 October 2023.
- ^ a b c d e f Garassino, A. (2001). "I crostacei decapodi del Toarciano (Giurassico inferiore) di Sogno (Bergamo, N Italia)". Atti della Società italiana di scienze naturali e del museo civico di storia naturale di Milano. 141 (3): 187–197. Retrieved 10 May 2022.
- ^ a b c Audo, D.; Williams, M.; Charbonnier, S.; Schweigert, G. (2017). "Gabaleryon, a new genus of widespread early Toarcian polychelidan lobsters". Journal of Systematic Palaeontology. 15 (3): 205–222. Bibcode:2017JSPal..15..205A. doi:10.1080/14772019.2016.1167786. S2CID 87613086. Retrieved 10 May 2022.
- ^ a b Garassino, A.; Gironi, B. (2005). "Proeryon hartmanni (v. Meyer, 1835)(Crustacea, Decapoda, Eryonoidea) and Archaeopalinurus cfr. A. levis Pinna, 1974 (Crustacea, Decapoda, Palinuroidea) from the Lower Jurassic (Toarcian) of Cesana Brianza-Suello (Lecco, N Italy)". Atti della Società italiana di Scienze naturali e del Museo civico di Storia naturale in Milano. 146 (1): 53–68. Retrieved 10 May 2022.
- ^ Schweigert, G. (2003). "The lobster genus Uncina Quenstedt, 1851 (Crustacea: Decapoda: Astacidea: Uncinidae) form the Lower Jurassic". Stuttgarter Beiträge zur Naturkunde. 332 (4): 1–43.