Pimenteira Formation
| Pimenteira Formation | |
|---|---|
| Stratigraphic range: Late Eifelian-Famennian ~ | |
| Type | Geological formation |
| Unit of | Canindé Group |
| Sub-units | Picos Member Passagem Member |
| Underlies | Cabeças Formation |
| Overlies | Itaim Formation |
| Thickness | 20 m (66 ft) |
| Location | |
| Region | Piauí Tocantins |
| Country | Brazil |
| Extent | Parnaíba Basin |
| Type section | |
| Named for | Pimenteiras, Piauí |
The Pimenteira Formation, also known as Pimenteiras Formation,[1] is an Mid to Late Devonian geological formation of the Parnaíba Basin, northeastern Brazil. It mainly outcrops in the states of Piauí and Tocantins.[2] It is was deposited in a shallow sea, under the influence of currents and storm waves, as well as fluvio-deltaic influences.[3]
Being part of the Malvinokaffric Realm, it haboured a diverse fauna of invertebrates such as trilobites, brachiopods, bivalves, gastropods, and tentaculids, as well as elamobranches and plant remains.[3]
History
[edit | edit source]The name 'Pimenteira' was first proposed by Small (1914) to ascribe a shale sequence 20 m in thickness close to the municipality of Pimenteiras, Piauí.[2] Caster (1948), reported on the occurrence of several fossils in the area, like trilobites[1] and shark fin bones,[1] and Kegel (1953) later visited the region between Picos and Pimenteiras, collecting specimens and later describing them.[4][1]
Initially, Kegel (1952) divided the formation into the Itaim and Picos members. Blankennagel (1952) later considered that only the Picos Member is part of the formation, with the Itaim Member being the upper part of the Serra Grande Formation.[5]
Description
[edit | edit source]Geology
[edit | edit source]The Pimenteiro Formation is made up of dense dark-grey shale sections interlayered with thick to thin sandstone, commonly found are also hummocky cross-stratification. The formation is interpreted as a transgressive system, deposited under a shallow marine environment with the influence of storm waves.[3] It possesses two sub-units, the lower Picos Member and the upper Passagem Member.[2]
The Picos Member is composed by sandstone and intercalated siltstone and shale, with common hummocky cross-stratification, representing the first great Devonian transgression into the Parnaíba Basin. The sandstone is well defined in the old strata, of Middle Devonian origin, but it gradually fizzles out as it approaches the upper layers, of Late Devonian origin. The Passagem Member is composed by thin and micaceous sandstone, with asymptotic and hummocky stratification. This unit represents a system of fluvio-deltaic floods, in which turbulent, episodic flows went beyond the coastal limit.[2]
The formation has outcrops on the states of Piauí and Tocantins. Sediments on the eastern border of the formation are dated be from the Late Eifelian to the Early Givetian, while the central and western portions were dated to be from the Late Eifelian to the Early Famennian.[2]
Paleoenvironment
[edit | edit source]When it was deposited, the Pimenteiro Formation was a shallow marine environment under the influence of currents and storm waves, as well as fluvio-deltaic influences.[3] The Passagem Member has been proposed to be influenced by episodic floods.[6] During the Mid to Late Devonian, the formation was situated below the antarctic circle, its fauna being part of the endemic Malvinokaffric Realm.[3]
It haboured a diverse fauna of invertebrates such as trilobites, brachiopods, ostracods, bivalves, gastropods, hyolithids, and tentaculids, as well as fish, like elamobranches and acanthodians. Plant remains are also found, as well as ichnofossils.[3]
Fossil Content
[edit | edit source]Flora
[edit | edit source]Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | Presence | Description | Images |
|---|---|---|---|---|
| Archaeosigillaria[2] | A. picosensis | Picos Member. | A lepidodendrale lycophyte. | |
| Haplostigma[2] | H. furquei | Passagem Member. | A lycophyte. | |
| Paleostigma[2] | P. sewardii | Passagem Member. | A lepidodendrale lycophyte. | |
| Protolepidodendron[2] | P. kegeli | Picos Member. | A protolepidodendrale lycophyte. | |
| Sigillaria[2] | S. sp. | Picos Member. | A lepidodendrale lycophyte. | |
| Spongiophyton[2] | S. sp. | Picos Member. | A spongiophytace. |
_2_(15335065127).jpg){kind=link}
_p165_Protolepidodendron.png){kind=link}
Arthropods
[edit | edit source]| Genus | Species | Presence | Description | Images |
|---|---|---|---|---|
| Burmeisteria[1] | B. notica | Picos Member. | A homalonotid trilobite. | |
| Eldredgeia[2] | cf. E. venusta | Picos Member. | A calmoniid trilobite. | |
| Metacryphaeus[1] | M. cf. australis[1]
M. kegeli[2] M. meloi[2] M. turbeculatus[2] |
Picos Member.
Passagem Member. |
A calmoniid trilobite. |
Echinoderms
[edit | edit source]| Genus | Species | Presence | Description | Images |
|---|---|---|---|---|
| Exaesiodiscus[3] | E. dimerocrinosus
E. sp. |
Picos Member,[2] mid-upper Eifelian.[3] | A crinoid. Possibly related to Dimerocrinites. | |
| Laudonomphalus[3] | L. aff. L. tuberosus
L. sp. A L. sp. B L. sp. C L. sp. D |
Picos Member. | A flucticharacid crinoid. | |
| Marettocrinus[2] | M. sp. | Picos Member. | ||
| Monstrocrinus[3] | M. incognitus | Picos Member,[2] mid-upper Eifelian.[3] | A rhodocrinitid crinoid. |
Brachipod
[edit | edit source]| Genus | Species | Presence | Description | Images |
|---|---|---|---|---|
| Amphigenia[2] | A. cf. A. elongata | Picos Member. | A brachiopod. | |
| Australocoelia[2] | A. palmata | Picos Member. | A brachiopod. | |
| Australospirifer[2] | A. iheringi | Picos Member. | A brachiopod. | |
| Chonetoidea indet.[2] | Passagem Member. | A brachiopod. | ||
| Lingula[2] | L. sp.
Lingula cf. L. manni |
Picos Member.
Passagem Member. |
A lingulid brachipod. | |
| Monsenetes[2] | M. cf. M. boliviensis | Picos Member.
Passagem Member. |
A brachiopod. | |
| Montsenetes[2] | M. carolinae | Picos Member. | ||
| Mucrospirifer[2] | M. cf. M. pedroanus | Picos Member.
Passagem Member. |
A mucrospiriferid brachiopod | |
| Orbiculoidea[2] | O. sp. | Picos Member. | A discinid brachiopod. | |
| Pleurochonetes[2] | P. comstocki | Passagem Member. | A brachiopod. | |
| Pustulatia[2] | P. ? curupira | Passagem Member. | A brachiopod. | |
| Spiriferida indet.[2] | Passagem Member. | A spiriferida brachipod. | ||
| Terebratulida indet. | Picos Member.
Passagem Member. |
A terebratulida brachiopod. | ||
| Tropidoleptus[4] | T. carinatus | Picos Member.
Passagem Member. |
A tropidoleptid brachiopod. |
_1_(48318642651).jpg){kind=link}
_4.jpg){kind=link}
Conulariids
[edit | edit source]| Genus | Species | Presence | Description | Images |
|---|---|---|---|---|
| Conularia[2] | C. sp.
?C. cf. C. africana |
Picos Member.
Passagem Member. |
A conulariid. | |
| Ctenoconularia[2] | C. cf. C. undulata | Picos Member. | A conulariid. |
Tentaculites
[edit | edit source]| Genus | Species | Presence | Description | Images |
|---|---|---|---|---|
| Styolina[2] | S. clavulus | Passagem Member. | A tentaculite. | |
| Tentaculites[2] | T. cf. T. eldregianus
T. oseryi |
Passagem Member. | A tentaculitid tentaculite. |
.jpg){kind=link}
Annelids
[edit | edit source]| Genus | Species | Presence | Description | Images |
|---|---|---|---|---|
| Annulitubus[7] | A. fernandesi | Uppermost Pimenteira Formation. | A polychaete annelid. |
Molluscs
[edit | edit source]| Genus | Species | Presence | Description | Images |
|---|---|---|---|---|
| Bucanella[2] | B. sp.
B aff. B. deiremsi B. laticarinata B. quadrilobata |
Picos Member.
Passagem Member. |
A bucanellid bivalve. | |
| Cucullella[2] | C. triquetra | Picos Member.
Passagem Member. |
A cucullellid bivalve. | |
| Grammysioidea[2] | G. lundi | Passagem Member. | A grammysiid bivalve. | |
| Palaeoneilo[2] | P. sp.
P. sp. A P. sp. B |
Picos Member.
Passagem Member. |
A malletiid bivalve. | |
| Platyceras[2] | P. (Platystoma) baini | Passagem Member. | A platyceratid gastropod. | |
| Plectonotus[2] | P. (Plectonotus) derbyi | Picos Member.
Passagem Member. |
A plectonotine gastropod. | |
| Nuculites[2] | N. sp.
N. aff. N. oblongatus |
Picos Member.
Passagem Member. |
A cucullellid bivalve. | |
| Spathella[2] | S. pimentana | Passagem Member. | A modiomorphid bivalve. | |
| Tropidodiscus[2] | T. sp. | Picos Member. | A tropidodiscid gastropod. |
.jpg){kind=link}
.jpg){kind=link}
Fishes
[edit | edit source]
_(Silica_Formation,_Middle_Devonian;_quarry_northwest_of_Paulding,_Ohio,_USA)_2_(48327478132).jpg){kind=link}
Ichnofossils
[edit | edit source]| Genus | Species | Presence | Description | Images |
|---|---|---|---|---|
| Arenicolites[2] | Picos Member. | Burrow made by some kind of worm. | ||
| Asteriacites[2] | A. isp.
A. stelliforme |
Picos Member. | Burrow of sea stars on the sea floor. | |
| Bifungites[2] | B. munizi
B. piauiensis |
Picos Member.
Passagem Member. |
Possible Annulitubus burrow. | |
| Conichnus[2] | Picos Member. | |||
| Cruziana[2] | Picos Member.
Passagem Member. |
Trilobite burrows. | ||
| Diplichnites[2] | Picos Member. | Arthropod trackways. | ||
| Gyrophylites[2] | Passagem Member. | |||
| Merostomichnites[2] | M. piauiensis | Picos Member. | Eurypterid traces. | |
| Neoskolithos[2] | N. picosensis | Picos Member. | ||
| Palaeophycus[2] | P. tubularis | Picos Member. | Open burrows, probably made by polychaetes. | |
| Phicosiphon[2] | P. incertum | Picos Member. | ||
| Planolites[2] | P. beverleyensis | Picos Member. | Traces left by the feeding process of worm-like animals. | |
| Rusophycus[2] | Picos Member.
Passagem Member. |
A trilobite resting trace. | ||
| Scolicia[2] | Picos Member. | Traces assigned to various groups. | ||
| Skolithos[2] | Picos Member. | A burrow. | ||
| Zoophycus[2] | Picos Member | Trace produced by moving and feeding polychaete worms. |
References
[edit | edit source]- ^ a b c d e f g Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd be bf bg Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g h i j k Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).