Trilobites, scolecodonts and fish remains occurrence and the depositional paleoenvironment of the upper Monte Alegre and lower Itaituba formations, Lower – Middle Pennsylvanian of the Amazonas Basin, Brazil

Accepted Manuscript Trilobites, scolecodonts and fish remains occurrence and the depositional palaeoenvironment of the upper Monte Alegre and lower Itaituba formations, lower – Middle pennsylvanian of the Amazonas Basin, Brazil Luciane Profs Moutinho, Sara Nascimento, Ana Karina Scomazzon, Valesca Brasil Lemos PII:

S0895-9811(16)30098-0

DOI:

10.1016/j.jsames.2016.06.011

Reference:

SAMES 1578

To appear in:

Journal of South American Earth Sciences

Received Date: 29 March 2016 Revised Date:

16 June 2016

Accepted Date: 26 June 2016

Please cite this article as: Moutinho, L.P., Nascimento, S., Scomazzon, A.K., Lemos, V.B., Trilobites, scolecodonts and fish remains occurrence and the depositional palaeoenvironment of the upper Monte Alegre and lower Itaituba formations, lower – Middle pennsylvanian of the Amazonas Basin, Brazil, Journal of South American Earth Sciences (2016), doi: 10.1016/j.jsames.2016.06.011. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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TRILOBITES, SCOLECODONTS AND FISH REMAINS OCCURRENCE AND THE DEPOSITIONAL PALAEOENVIRONMENT OF THE UPPER MONTE ALEGRE AND LOWER ITAITUBA FORMATIONS, LOWER – MIDDLE PENNSYLVANIAN OF THE

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AMAZONAS BASIN, BRAZIL

*Luciane Profs Moutinho1, Sara Nascimento1, Ana Karina Scomazzon1, Valesca Brasil Lemos1

43127, Sala 211, 91501-970, Porto Alegre, RS, Brasil.

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*Corresponding author – [email protected]

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1 – Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Prédio

ABSTRACT

This study aims to characterize the scolecodonts, trilobite pygidium fragments and fish remains of an outcropped region in the southern Amazonas Basin, comprising the uppermost section of the Monte Alegre Formation and the basal section of the

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Itaituba Formation. These, correspond to part of the marine portion of the Tapajós Group, related to an intracratonic carbonate platform. The Monte Alegre Formation includes a deposition of fluvial-deltaic and aeolian sandstones, siltstones and shales of interdunes and lakes, intercalated with transgressive carbonates of a shallow restrict nearshore marine environment. The Itaituba Formation comprises a thickest deposit of

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marine carbonates, representing the establishment of widespread marine conditions, and is the richest interval containing organisms of shallow marine environment in the Pennsylvanian of the Amazonas Basin. The associated fauna includes brachiopods,

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bivalves, gastropods, crinoids, echinoids, bryozoans, corals, foraminifers, sponges, ostracods, trilobites, scolecodonts, fish remains and conodonts, mainly in the packstones, and subordinately in the wackestones and mudstones. Conodonts Neognathodus atokaensis, Diplognathodus orphanus, Idiognathodus incurvus, and

foraminifers Millerella extensa, Millerella pressa, Millerella marblensis, Eostaffella ampla, Eostaffella pinguis and Eostaffella advena characterizes a predominant Atokan age to the analyzed profile. The fossil association herein presented is taxonomically diversified and biologically interesting, comprising an important and well preserved, for the first time occurrence of two molds and two fragments of Proetida trilobites. Well preserved Eunicida and Phyllodocida scolecodonts and paleonisciform fish remains.

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These fossils help in the palaeoenvironmental establishment of the studied interval in the Amazonas Basin and as a potential biostratigraphic and paleoecological tool to correlate regionally and globally the Pennsylvanian.

KEYWORDS

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Faunal association, Invertebrates, Pennsylvanian, Amazonas Basin

1. Introduction

Over the last decade, the knowledge about the Brazilian Paleozoic basins has

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been expanded. The Amazonas Basin has been subject of geological interest, mainly for petroleum. Stratigraphic and structural studies were carried out by Petroleo Brasileiro SA (PETROBRAS), based on subsurface date from ca. 200 wells, most of

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them continuously cored, providing the lithostratigraphic subdivisions (Caputo, 1984). On the other hand, due to an extensive rainforest and deep soil cover on this region, outcrops are scarce and confined to marginal areas, including the outcropping section analyzed herein (Figure 1).

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Figure 1 – Location Map

The Pennsylvanian is the most studied Paleozoic interval of the Amazonas Basin, especially the limestones of upper Monte Alegre and lower Itaituba formations, mainly due to paleoenvironmental conditions favorable to the occurrence and preservation of a diverse marine fauna fossil association with U.S. Midcontinent

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affinities (Altiner and Savini, 1991, 1995; Chen et al., 2004, 2005; Scomazzon et al., 2016). This is the richest known fauna of the Amazonas Basin, including corals,

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bryozoans, echinoderms, ostracods, mollusks, brachiopods and diverse microfossils. Shale and siltstone beds often contain crustaceans and plants indicative of episodic freshwater deposition, which are interpreted as shallow marine subtidal to supratidal deposits.

Until present the main studies in the area focused on biostratigraphic aspects

based primarily on conodonts (Scomazzon, 1999, Scomazzon, 2004, Nascimento et al., 2005, 2010, Nascimento, 2008, Scomazzon et al., 2016) and palynomorphs (Nascimento et al, 2009) as tools to biostratigraphic analysis on the refinement concerning to Morrowan/Atokan ages; sedimentary and stratigraphic aspects (Matsuda, 2002; Moutinho, 2002, 2006, Moutinho et al.), taphonomic and paleoecological aspects (Moutinho and Lemos, 2002, Moutinho et al., 2002, 2003a,

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2003b, 2007a, 2007b, 2016), Sr and Nd isotopic signature (Scomazzon et al., 2002, 2005, Scomazzon, 2004) and on stable isotopic chemical stratigraphy (Moutinho, 2006, Moutinho et al., 2007b). Trilobites, scolecodonts and fish remains despite being broadly observed in

have not received proper attention, being characterized herein.

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richness and abundance in the literature of Amazonas Basin undertaken until today,

Trilobites, marine extinct arthropods, have large stratigraphic value, being

useful in paleontological correlations, dating and establishing paleoprovinces. In Brazil,

the Order Phacopida is of great importance to the Devonian, with many characteristic genera of Malvinokaffric province. They are recorded at the lower Devonian of the

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Paraná Basin, Ponta Grossa Formation, Middle Devonian of Maecuru Formation in the

Amazonas Basin, Devonian of Pimenteira Formation in the Parnaíba Basin, and Pennsylvanian of Piauí Formation in the Parnaíba Basin (Carvalho and Fonseca,

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1988). Among the eight orders of Trilobite Class, only the Proetida Order crossed the Devonian / Carboniferous threshold and in Brazil is represented by specimens of the Ameura Genus in Pennsylvanian basins of Amazonas, Itaituba Formation and Parnaíba, Piauí Formation (Carvalho and Fonseca, 1988). In the Pennsylvanian interval of Amazonas Basin, the trilobites are widely represented in stratigraphic record by preserved body parts analyzed in thin sections, but on the macroscopic scale their

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observation and collection is very rare in the outcrop horizons, being found in the studied area and characterized herein for the first time. Scolecodonts, the mouth pieces of jaw-bearing polychaete annelid worms, occur in abundance as microfossils in the fossil record. They are found as discrete elements that remind conodonts, but different of them in composition and structure.

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The Scolecodont systematic classification is difficult and necessarily parataxonomic because of the difficult relation of mandibular pieces found separately from the corresponding animal, and also because of, as in conodonts, the same organism may

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have different elements together, in the same jaw (Távora and Nascimento, 2011). Scolecodonts are registered as fossils from the Lower Ordovician to Recent. Their greatest diversity occurred in the Upper Ordovician to Devonian (Kielan-Jaworowska, 1966). Dental apparatus parts of scolecodonts are potentially useful for establishing biostratigraphic zoning, however, there exist few studies in this context. In Brazil, Lange (1949) conducted a biostratigraphic analysis in scolecodonts from Ponta Grossa Formation, Devonian of the Paraná Basin, with reasonable resolution. This paper is an attempt to characterize for the first time scolecodonts of the outcropped area. This effort can contribute to applied biostratigraphic studies and provides ecological relationships with the associated fauna, mainly consisting of fish fragments and

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conodonts that are abundantly represented in this upper Monte Alegre and lower Itaituba formations. Fish remains are important for the study of paleoecology and evolution of the ichthyofauna. In the brazilian paleozoic basins they are registered to the south, in the Carboniferous and Permian of the Paraná Basin - Irati, Estrada Nova, Teresina, Rio do

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Rastro and Corumbataí formations. Richter (1985) published about Permian

paleoichthyology of Rio Grande do Sul State, Richter (2002) discussed about late

Permian osteichthyes of Santa Catarina State and Würdig-Maciel (1975) published the Permian microvertebrate fauna from the Estrada Nova and Irati formations, in Rio Grande do Sul State. To the north in the Amazonas - Itaituba Formation and Parnaíba -

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Pedra de Fogo and Poti formations, during the Carboniferous and Permian periods.

Few amazonian fossil fishes have been described. Janvier and Melo (1987) published some indeterminate actinopterygian scales from the Late Devonian and also described

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Late Silurian or Early Devonian acanthodian tooth, spines and scales (Janvier and Melo, 1988). Duffin et al. (1996) described the first microvertebrate fauna from South America, coming from the Itaituba Formation. The samples include teeth of Cooleyella amazonenses and ? Denea sp. (Symmoriidade, Euselachii), ? Triodus sp (better interpreted as Bransonella sp. (Richter et al., 1999). (Xenacanthidae) a tricúspide tooth of uncertain affinities, mucous membrane denticules, probably of symmoriidae

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(Stemmatodus sp.) and two types of condrichthyan scales. Previous to that publication, only a single shark tooth had been recorded from the Itaituba Formation, namely Cladodus pirauariensis (Santos, 1967). Richter et al. (1999) described seven morphological types of actinopterigyan teeth, together with one indeterminate (?Actinopterygii) tooth, plus lower actinopterygian and acanthodian dermal scales

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(Acanthodidae).This paper aim to improve the knowledge of the fish remains by characterizing the shark assembly and associated actinopterygian and acanthodian morphology to apply to paleoenvironmental and biostratigraphic of global correlation,

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as observed, especially for Silurian and Devonian strata of different world provinces, as discussed in Blieck and Turner (2000). Thus improving studies of the occurrence of this fossil association herein

characterized by trilobite fragments, scolecodonts and fish remains, are important in the reconstruction of the paleoenvironmental evolution and biostratigraphy during the Pennsylvanian in the Amazonas Basin.

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2. Materials and Methods Were collected one hundred kilograms of sedimentary rocks, mainly siliciclastic (sandstones and shales) evaporitic (anhydrite and gypsum minerals) and carbonatic (dolomites, boundstones, mudstones, wackestones, packstones and grainstones) in four outcrops in chronostratigraphic order: along the margin of the Tapajós River, and

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in three limestone quarries (named quarries I, II and III). These studied deposits comprise a vertical section of approximately 80 m encompassing the upper Monte Alegre and lower Itaituba formations, in the south border of the Amazonas Basin, near Itaituba City, southernmost Pará State (Figure 1).

A total of 2 levels from the Tapajós River section, 21 levels from the quarry I, 42

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level of quarry II and 7 levels of quarry III were sampled for fossil analysis and

approximately 60 kg of sedimentary rock samples, mainly carbonates and shales were processed. Processing techniques were applied at the laboratory of microfossil

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preparation of Universidade Federal do Rio Grande do Sul UFRGS/Porto Alegre, Brazil. The samples were weighed (300 g per sample) and crushed about 2 cm. The carbonate samples were placed in a plastic bucket with a capacity of 1.5 L of water, filled with 90% of water (~1.3 L) and 10% of acetic acid P.A. (~150 ml). The material was allowed to stand, being stirred once a day to the acid ionization. At the end of carbonate dissolution procedure, the samples were washed and sieved (0.85 and

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0.063 mm). Microfauna was picked, classified and photographed in the scanning eléctron microscope (UFRGS/Porto Alegre, Brazil) and were also photographed under binocular microscope (Geo UFRGS/Porto Alegre, Brazil). The collection is deposited in the Departamento de Paleontologia e Estratigrafia/UFRGS/Porto Alegre, Brazil. Among the four studied sections were found fish remains in a total of 44

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horizons and scolecodonts in 28 horizons. Appendix 1 provides the full list of processed samples, identified by depth. For each sampled horizon is presented a quantitative report of fossil obtained and its lithological characterization based on

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previous petrographic studies in Moutinho (2006). Additionally, two molds and two remains of trilobite pygidium were collected in the upper portion of the quarry II (Figure 2).

3. Geologic Setting The Amazonas Basin is a large intracratonic sedimentary basin occupying 500,000 km2 within the northern brazilian Amazonas and Pará states (Figure 1). Three sectors are distinguished trending generally east – west, the north and south borders and the central basin area, Cunha et al. (2007). These tectonogeomorphologic units

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are divided into smaller sub-units, mainly half-grabens and platforms those controls the facies distribution, sediment influx direction, ocean water circulation patterns and the extent of sedimentary accommodation throughout the Paleozoic (Eiras et al., 1998). The Paleozoic sedimentary succession is limited by two Precambrian shields, the Guianas to the north and the Brazilian to the south of the Amazonian Craton (Pereira et

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al., 2012). To the east, it is separated from the Marajó Basin by the Gurupá Arch, and

to the west it is divided from Solimões Basin by a subsurface basement-high, the N-S trending Purus Arch. The basin holds a Proterozoic through Recent sedimentary and

sub-volcanic record up to 6.000 m thick, in the central area. The CarboniferousPermian contribution accounts for more than half of the total deposition (Caputo, 1984;

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Milani and Zálan, 1998).

The Pennsylvanian-Permian deposits correspond to a second order megasequence represented by the Tapajós Group, which comprises in ascending order to

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the Monte Alegre, Itaituba, Nova Olinda and Andirá formations (Cunha et al., 1994). This unit accumulated followed by intense erosion caused by the early Hercynian Orogenic episode and represents a transgressive to regressive cycle from Pennsylvanian through Permian, associated to significant climatic changes from cold to warm and arid (Scotese and Mckerrow, 1990).

The Monte Alegre Formation is a relatively thin rock unit with maximum known

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thickness of 140 m in the subsurface and comprises an extensive sequence of fluvial and eolian sandstones, interbedded with siltstones and shales from inter-dunes and lagoonal environments, with limestones and dolomites toward the top. This formation testifies the first marine ingression of Pennsylvanian age in the Amazonas Basin. The Itaituba Formation, the main focus of this paper, comprises a thick deposit

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of marine carbonates related to the Pennsylvanian marine transgression in the basin. Outcrops on north and south borders, and varies in thickness from 110 meters in the southern outcropping area to 420 meters in the central part of the basin (subsurface),

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being controlled by the east-west basin trend. Its stratotype is located at the southern border and outcrops near of Itaituba City, along the Tapajós River. A second outcrop area corresponds to three limestone quarries located 30 km southwest of Itaituba City. This unit, in subsurface and in the outcrops area, overlies conformably the Monte Alegre Formation. The upper limit of the formation, only observed in subsurface, is conformable with the overlying Nova Olinda Formation. The limestones, mainly due to palaeoenvironmental conditions, are particularly favorable to the occurrence and preservation of a diverse marine fossil fauna association. The studied section of about 80 meters in length includes the 18 meters

Tapajós River section and the three limestone quarry sections, which are about 58,5

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meters long (Figure 2), stratigraphically linked and, due to vegetative recover, not correlated laterally.

It consists of a diverse range of carbonate rocks, including

limestones, mudstones, wackestones, packstones and grainstones with marine fauna, intercalated with less abundant dolomites, sandstones and siltstones and represents the establishment of widespread marine conditions in the Amazonas Basin. Dolomitic

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and clastic beds often contain physical and biogenic structures indicative of episodic freshwater deposition, being interpreted as shallow supratidal deposits.

Figure 2 - Profile

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4. Upper Monte Alegre and Lower Itaituba Formations Bioestratigraphy Age estimations of upper Monte Alegre and lower Itaituba formations have been

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based on microfossil assemblages, including spores and pollens (Playford and Dino, 2000), fusulinids (Altiner and Savini, 1991, 1995) and conodonts (Lemos, 1990, 1992a, 1992b; Nascimento et al., 2005; 2009; 2010; Neis, 1996; Scomazzon, 1999, 2005, Scomazzon et al., 2016), but they are controversial.

The latest and most well calibrated chronostratigraphic framework (Figure 3) for the Pennsylvanian of the Amazonas basin is based on foraminifera (Altiner and Savini, 1991, 1995) and conodonts (Nascimento et al., 2010; Scomazzon et al., 2016).

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According to biostratigraphic estimations based on these microfossils, the uppermost Monte Alegre /lower Itaituba formations interval is considered to be upper Morrowan/Atokan in age. Further information concerning to the Tapajós Group biostratigraphy, including detailed data on the studied area, is found in Altiner and Savini (1991, 1995); Lemos (1990), Nascimento et al. (2005, 2009, 2010) and

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Scomazzon et al. (2005, 2016).

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Figure 3 - Chronostratigraphyc chart

5. The outcrops – Lithology, Sedimentology and Depositional Model A short introduction to the lithology, sedimentology and palaeoenvironmental

depositional model assumed for the Monte Alegre and Itaituba formations during the upper Morrowan and Atokan ages is given here, whereas further details may be found in Moutinho (2006), Scomazzon et al. (2016) and Moutinho (2006). The lowermost Tapajós river section corresponds to the stratigraphic boundary

between the Monte Alegre and Itaituba formations, Morrowan and Atokan in ages, respectively. The section is mostly formed by eolic and fluvial-deltaic siliciclastics,

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dolostones and subordinated fossiliferous carbonates (Figure 2). The basal lithology is the uppermost Monte Alegre eolic sandstones, overlaid by a succession of deltaic siliciclastics and dolostones, which represent deposition in a restricted intertidal and supratidal environment and consists of the basal strata of Itaituba Formation. A thin fossiliferous limestone occurs in the middle of the section and contains a diverse

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benthic fossil association (brachiopods, crinoids, bryozoans, foraminifera, ostracodes,

and cephalopods, among others) and represents, on the whole, deposition in a carbonate platform setting and the establishment of shallow marine conditions.

The limestone quarries are mostly composed by mudstones, wackestones, packstones, grainstones, and subordinate shales with a large amount of evaporitic,

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siliciclastic and fossil content (Figure 2). These horizons represent, on the whole,

deposition in shallow marine depositional conditions, mostly in the subtidal, intertidal and supratidal environmental contexts. In quarry III, the basal lithology is a thick

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siliciclastic horizon 9 m meters thick, beginning with sandstones overlapping siltic facies, rich in organic matter, with levels containing coal and fossils of plants, representing a deltaic front prograding into the carbonatic platform (Figure 2). Upwards, it is comprised mostly of carbonate and siliciclastic rocks, often containing physical and biogenic structures indicative of episodic freshwater deposition interpreted as shallow supratidal deposits, overlaid by a succession of marine limestones similar from those of

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quarries I and II.

The sandstone deposit in the basal strata of quarry III was considered by Matsuda (2002) as stratigraphically equivalent to the Mark 65 of Carozzi et al. (1972), a lithostratigraphic standard attributed to the Morrowan – Atokan limit. However, Scomazzon (2004) provided evidence by means of conodonts and lithostratigraphic

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correlation that the Carozzi’s Mark 65 would actually be correlated with the siliciclastic deposits of the lower strata of the Tapajos section, corroborated by Nascimento et al.

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(2005) and Nascimento et al. (2010).

6. Paleoenvironment and Biota Moutinho et al. (2006) proposed that an intracratonic carbonate platform was

developed in the basin during the Pennsylvanian. This platform was located in low to medium latitudes, between 30° and 35º S. The ideali zed depositional profile suggested for the Atokan age in this basin characterizes a carbonate ramp with carbonate sedimentation predominately controlled by tides. It consists in an integrated system, composed by three basic sub-environments: supratidal, above the normal waves base and constantly exposed to subaerial conditions, as it is flooded only by winter or storm

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tides; (2) intertidal, exposed once or twice a day, according to tidal regimen and local wind conditions; and (3) subtidal, which is rarely exposed to subaerial conditions (Figure 4). It is important to emphasize that within these environmental contexts there are a number of sub-environments, mainly characterized by variations in energy conditions and sedimentation rates, controlled by water depth.

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These microenvironments are laterally distributed over the tidal plain,

suggested as the depositional environment for the studied carbonates, with their

vertical distribution being an important tool in the interpretation of the oscillations in the relative sea level. Due to the variety of microenvironments formed in the context of

intermediate ramp, the facies wackestones, packstones and grainstones might occur

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intercalated. This way, besides faciological descriptions, it is also important to verify faunal composition, their preservation state and the presence of diagenetic features in

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the analyzed facies, aiming for the adequate understanding of their lateral distribution.

Figure 4 - depositional profile

In subtidal/lower intertidal sediments, the condensates black shales of open water may occur, often bioturbated and increasing towards the basin (Figure 4). Grainstones, packstones and wackestones of marine fauna are the most common

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facies and occur near the bioclastic bars, decreasing into the basin. Here occur predominantly Faunal Rich Packstones associated to Bioclastic Wackestones. Migrating into the basin, the most distal facies are predominantly Packstones and Wackestones composed of large bryozoan fragments associated with shell fragments of fibrous, punctuated and crenulated brachiopods and skeletal elements of

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echinoderms.

The bioclastic bar of lower intertidal separates the open sea area (lower

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intertidal/subtidal) from the protected intertidal lagoon (Figure 4). The bioclastic bar is considered the local of maximum production and the oolitic and bioclastic grainstones are the dominant facies. Organic remains are often subjected to waves and currents, including storm waves and tidal currents that also rework them, affecting the biological communities and forming stratified deposits of oolitic and bioclastic packstones and grainstones. Oolitic Grainstones are the dominant facies while Bioclastic Grainstones appear to be formed preferably within the lower intertidal. Restricted carbonates are formed in the subenvironment represented by the protected intertidal lagoon (Figure 4). There, low energy is dominant and salinity, temperature and circulation patterns fluctuate. In this environmental context the dominant facies correspond to low energy Recrystallized and Rare Biota Mudstones

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and less frequent Bioclastic Wackestones, often organic matter rich and bioturbated. In lagoons, salinity fluctuations are periodic, resulting in the precipitation of evaporites, such as gypsum and anhydrite, and consequently the formation of dissolution evaporite molds. Also, the variations in salinity and temperature rates, associated with low energy conditions favor the development of opportunistic organisms such as

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gastropods and ostracods, more adapted to unstable environmental conditions.

The supratidal sabkha comprises a very shallow and narrow marginal zone,

located behind the tidal flat and is subjected to extreme conditions of hypersalinity (Figure 4). This condition is ideal for the formation of dolomite and evaporite deposits,

resulting in the precipitation of gypsum and anhydrite. Thus, the presence of organisms

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is rare, summarized by microbial mats intercalated with organic matter. Terrigenous

grains such as quartz, feldspar and clay are commonly found associated with dolomites and evaporites.

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The tidal flat is a muddy environment, subjected to siliciclastic sedimentation with dominant facies corresponding to sandstones with sigmoidal stratification, siltstones with mud cracks and finely laminated silty sandstones associated to siliciclastic and carbonate intraclasts within microbial mats (Figure 4). Additionally, evaporite and dolomitic deposits were formed when high tides and storms introduce seawater within this context.

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Finally, the open continental area, dominated by fluvial and eolic environments (Figure 4). The dominant facies are laminated sandstones, siltstones and mudstones. These microenvironments are laterally distributed over the tidal plain, suggested as the depositional environment for the studied carbonates, with their vertical distribution being an important tool in the interpretation of the oscillations in the relative

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sea level. Due to the variety of microenvironments formed in the context of intermediate ramp, the facies wackestones, packstones and grainstones might occur intercalated. This way, besides faciological descriptions, it is also important to verify

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faunal composition, their preservation state and the presence of diagenetic features in the analyzed facies, aiming for the adequate understanding of their lateral distribution.

6.1 Invertebrate Communities Previous studies based on invertebrate’s composition allowed the definition of

three distinct communities characterized by specifically adaptations and tolerances to environmental conditions (Moutinho, 2006; Moutinho et al., 2016). Intertidal lagoon community is composed by eurihaline organisms well adapted to muddy substrates and major oscillations in water salinity, oxygenation and salinity. This community is composed by productid brachiopods, mollusks such as gastropods

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and bivalves, ostracods and simple tubiform and sphaerical foraminifera, such as Diplosphaerina spp. and Earlandids. In this context, fragments of echinodermal skeletons may be wave and bottom currents transported from neighboring environmental contexts. Among the conodonta genera Diplognathodus, Adetognathus, Ellissonia and Hindeodus seems to be locally abundant.

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Low intertidal community is dominated by prismatic, crenulated and fibrous brachiopods and echinoderms. Bryozoans, thin shelled bivalves, gastropods,

ostracodes, trilobites, scolecodonts and fish remains although not abundant can be

always considered diagnostic of this environmental context. Among the conodontes genera, Idiognathodus and Neognathodus highlights, associated to the foraminifera

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genera Globivalvulina supporting the offshore character of the deposition. Brachiopods

seems to be organisms adapted for living in more turbulent settings, above the normal wave base and here represented by quasi-infaunal productides, that have developed

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tubular spines on ventral valves which probably rooted the shell in the substrate providing some stability on these turbulent setting and spiriferids that process a greatly extended hinge line which possibly served to stabilize the shell on a soft substrate. Among the echinoderms, most fossil crinoids were habitants of relatively shallow current-swept waters and make use of the currents in feeding. Crinoids process an attachment structure responsible for their settlement on the substrate, affixing the

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column to the sea floor or to a hard substrate.

Subtidal community is dominated by prismatic, crenulated and fibrous brachiopods and echinoderms associated to quite abundant and diverse bryozoans and rarely found rugose corals. Rugose corals are scarce and seem to be confined to this environmental context. Bryozoans and rugose coral are organisms morphologically

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more sensitive to the destructive effects of turbulence, inhabiting less turbulent settings below the normal wave base, but still susceptible to be affected by storm waves. The very delicate bryozoan branched forms, represented by Synocladia genus, prefer a

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habitat of weak or absent current action. Solitary rugose corals had no really effective means of anchorage on the sea floor; they did not normally cement themselves to the substrate and seem to have preferred soft substrates. The horn-like shape would give a reasonable degree of support if the coral were to be half sunken in mud, convex side down, suggesting an adaptation for fixation in soft substrates. Sponges, thin shelled bivalves, gastropods, ostracodes, trilobites, scolecodonts and fish remains although not abundant can be always considered diagnostic of this environmental context. Among the foraminifera genera present, it is noteworthy the occurrence of small forms, such as Palaeonubecularia

spp.,

Monotaxinoides

spp.,

Globivalvulina

spp.

and

Pseudoglomospira spp. and fusulines (Millerellids and Eostaffellids), confined to and

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diagnostic of Subtidal environments. Planoendothyra spp. and Tetrataxis spp. are common small foraminifera genera present and also confined to the Subtidal environment that also shows a diverse conodont fauna mainly composed by open marine forms such as Idiognathodus spp. and Neognathodus spp. and more restrictive

spp. and Hindeodus spp..

7. Trilobites, scolecodonts and fish remains occurrence

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forms such as Adetognathus spp., Diplognathodus spp., Gondolella pp., Idioprioniodus

The figure 2 provides an overview of the vertical distribution of trilobites,

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scolecodonts and fish remains along the four studied stratigraphic sections (Tapajós river section, quarries I, II and III) while the figure 5 and appendix 1 demonstrate the

trilobites occurrences.

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relation between carbonatic facies and the proportion of fish remains, scolecodonts and

In the Figure 5, the X axis represents the observed carbonate facies and the Y axis represents the number of horizons in which fish remains, scolecodonts and trilobites are observed respectively.

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Figure 5

In almost all occurrences, trilobites are registered in thin sections (Figure 6) and preferable occur in facies associated to open marine contexts, being very common in bioclastic packstones and subordinated wackestones of normal marine fauna (appendix 1), where shallow water below normal wave base conditions prevailed

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(Figure 6). In the top horizon of quarry II trilobites exoskeletons are registered for the first time as molds and remains mainly incomplete (pygidium) and poorly preserved

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(Figure 7).

Figure 6

Figure 7

A great number of ways of trilobite occurrence can be found in the Pennsylvanian and the relative abundance of particular preservational types may be used to characterize separate taphofacies (Speyer and Brett, 1988). In taphonomic

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terms, the studied trilobite’s exoskeletons are registered in totality as molds and incomplete remains composed by articulated pygidium. As with modern arthropods, trilobite exoskeletons, whether exuvial or carcass remains, presumably dissociated very rapidly during decomposition, yielding cephala, pygidia and thoracic segments (Schäfer, 1972; Plotnick, 1984). Such sclerites were supposed to remain in close

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proximity unless disturbed by deep burrowers, surface scavengers or current agitation.

The monotonous occurrences of the studied trilobites do not allow the

establishment of distinct taphofacies. In the other hand, the modes of trilobite occurrence in the Pennsylvanian of the Amazonas basin can be related to depositional,

biogenic and behavioral phenomena. I.e., considering the degree of taphonomic

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attribute of fragmentation and the inferred environmental conditions preconized as

persistent current agitation, multiply reworked lag accumulation, surface disintegration and biogenic disturbance, among others (Driscoll, 1967; Speyer and Brett, 1988).

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The bioclastic wackestone horizon which trilobites were obtained corresponds to an environmental context typical of lower intertidal and composed of marine fauna, mainly

sparse

brachiopods,

abundant

echinoderms,

ostracods,

conodonts

(Neognathodus spp. and Idiognathodus spp.) and foraminifera (Globivalvulina spp.) (appendix 1). Moutinho et al. (2016) provided the taphonomic investigation of the invertebrates observed on the same level where trilobite remains were obtained.

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According to them, the bioclastic packstone indicates that skeletal organism remains that inhabited neighboring environmental context are found in the same stratigraphic horizon. They were preserved in the same stratigraphic horizon culminating in the formation of a within-habitat time-averaged assemblage. In this case, parauthoctonous skeletal remains, derived from nearby environmental contexts would have been buried

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in the same stratigraphic level of elements composing the biocenosis and associated skeletal remains.

Considering the preservational condition observed in trilobites from the top of

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quarry II and the information concerning to the shallow water and associated fauna environmental context we believe that these organisms were authoctonous elements of the assemblage. The main mode of occurrence, illustrated by partially articulated remains is due to the high degree of bioturbation observed in the hosting rock associated to the exposure time before the final burial of the tanatocenosis. The observations above are in accordance with the data of Silva and Fonseca

(2005) and Carvalho et al. (2011). Both authors noticed that during the Carboniferous, Proetida trilobites were very abundant in shallow marine, carbonatic subtidal to intertidal deposits, and are associated with bioclastic concentrations that were generated in shallow water conditions (between the normal and the storm wave base).

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The majority of the scolecodonts obtained were interpreted as belonging to polychaetes from Eunicida Order (Dales, 1963) (Figure 8), although the Phyllodocida Order (Dales, 1963) has also been identified (Figure 9). Almost all samples prolific to polychaete disarticulated jaw elements produced a high number of identifiable scolecodonts, mainly maxillae from the first (MI) and the second (MII) pair (Figures 8

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and 9). The degree of morphological variations is great, and varies from totally undenticulated MI specimens (Figure 8 A - D) to ones with pronounced curvature

(Figure 8 E - I) and well developed denticles (Figure 9 A - D). The MII specimens

Figure 8

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Figure 9

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commonly show denticles anteriormost larger with broken tips (Figure 9 E - J).

Scolecodonts add little to the Pennsylvanian biostratigraphy because the insufficient present knowledge of polychaete development. Another significant problem is that publications dealing with Pennsylvanian collections are rare and most of them have rudimentary fossils hand-drawings that do not allow good identifications. Based on the investigated scolecodont assemblage no biostratigraphic data is available. The

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scolecodonts can, however, be used as depositional environment indicators especially because numerous eunicemorph polychaetes like the ones described herein usually occur in shallow water mudstones and carbonates. The majority of recent Eunicida live in shallow-water sediments, especially nearshore, (Szaniawski, 1996).

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Although showing a preference for muddy substrates (Figure 5), scolecodonts are registered in almost all lithologies, being equally common in wackestones and packstones of normal marine fauna (appendix 1), where shallow water below normal

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wave base conditions prevailed. Commonly the scolecodonts are retrieved in association with fish remains, brachiopods and conodonts belonging to the genera Idiognathoides (appendix 1). According to Driese et al. (1984), the genera Idiognathoides is typical of marine low energy environments, normal salinity and muddy

substrate. Nascimento et al. (2010) considered the combined occurrence of

Idiognathodus, Idiognathoides and Neognathodus as characteristic of deposits of low

energy marine environments, with normal salinity and muddy substrate as is observed in the lower intertidal/subtidal environments. These observations are in agreement with data of (Bergman, 1979, 1989, 1995; Eriksson, 1997, 2001; Hints, 2000, Eriksson and Bergman, 2003; Paxton, 1986) who noticed that fossil jawed polychaetes were facies

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controlled in their distribution, where the abundance and taxonomic scolecodonts diversity increases with decreasing depositional depth, because shallow-water environments provided more suitable living conditions than deeper ones. Although water deep was presumably the primary influence on polychaete distribution, other controlling factors, such as temperature, light salinity, turbidity and access of nutrients,

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which are commonly correlated to water depth, may have been important (Eriksson and Bergman, 2003). In fact, most described scolecodont collections were extracted from carbonate rocks deposited in shallow water (between the normal and the storm

wave base). According to these authors, faunas of deep water, below the storm wave base are poorly known.

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The microvertebrate fauna is recorded in almost all lithologies (Figure 5),

showing a slight preference for packstones of normal marine fauna, where shallow water below normal wave base conditions prevailed (appendix 1). It is represented by of

Cooleyela

amazonensis

(Neoselachii,

Anachronistidae) (Figure

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teeth

10),

Condrichtyan teeth of undetermined affinities (Figures 11 A – H, 13 A and B, 14 F - H and L), Condrichtyan scales of undetermined affinities (Figures 11 I and J, 12 and 14 D, F and K), Actinopterygian teeth (Palaeonisciformes) (Figures 13 C – F and 14 I), dermal scales (Figure 14 J, M, O and Q) and teeth (Figures 14 N and P) of undetermined affinities, Acanthodian spines of undetermined affinities (Figure 14 A - C)

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and fragmentary plates that could correspond to pharyngeal tooth plates of undetermined affinities (Figure 13 G and H). Cooleyella amazonensis was first described by Duffin et al. (1996) and considered a part of the first confidently dated microvertebrate fauna recorded from South America. The importance of this specie is in the fact that Cooleylla amazonensis

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helps to fill in a gap in the anachronistid neoselachian lineage, until the publication of

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Duffin et al. (1996) recorded only inside Great Britain and the USA (Figure 10).

Figure 10

In the studied material there is a great variety of condrichtyan teeth of

undetermined affinities, mainly represented by isolated fragmentary tooth. There are specimens of multicuspid crown surmounting a lingually expanded root with the central cusp as the highest in the crown (Figures 11 G and H). There are more fragmentary specimens comprising the base or a part of the base, usually robust and elongated, surmounted by a number of 2 or 3 cusps, which had commonly lost the apexes (Figure 11 C). In some cases the cusps are circular in cross-section and strongly ornamented by a series of vertical ridges arising from the base (Figure 11 A). The most fragmentary

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specimens are preserving the root and the cusp bases only. The number of cusp bases varies according to the specimen and the bulk of theirs length having been lost due to postmortem damage (Figure 14 L). There are, additionally, tricuspid tooth very well represent in the microvertebrate record. The specimens are nearly complete showing worn symmetrical tooth. It has a tricuspid crown which lacks ornamentations. The

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central cusp is the highest one and flanked by one pair of lateral cusplets, each of

which is more or less equivalent to the central cusp in height (Figures 11 D - F). Thus,

there are specimens comprising a subcircular base or a part of the base, surmounted

by 1 cusp, which had commonly keeping the apexes (Figure 11 B). In this case, due to the degree of alteration experienced by the teeth is hard to measure whether these

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monocuspides correspond to rightful teeth or others, formed by more than one cusp and changed by the excessive wear processes suffered prior to the final burial. Additionally there are specimens comprising a quadratic base or a part of the base,

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surmounted by 1 cusp, which had commonly lost the apexes (Figure 13 B). Is some cases, in the other hand, less fragmentary tooth are keeping the apexes (Figure 13 A). Finally it is possible to identify some specimens composed only by the isolated cusps and lacking the base. Here again, is difficult to evaluate if the isolated cusps are rightful teeth or only the result of wearing processes (Figures14 F - H).

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Figures 11, 12, 13, 14

Concerning to wearing processes, it is possible to say that in almost all the cases the apexes of the cusps are missing due to postmortem damage however, we cannot dismiss the injurious processes suffered during physical and chemical

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preparation of the samples.

The condrichtyan scales observed are classified as type 2 scales of Duffin et al.

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(1996) (Figures 12 A – C and 14 K). A second type of scales of undetermined affinities is identified (Figures 12 D and E, 14 D and E). These scales have an expanded, subcircular basal plate surmounted by a single, posteriorly directed pointed cusp. 3 pairs of coarse lateral ridges descend the cusp flanks on either side. Except for the absence of a large vertical foramen perforating the anterior part of the cusp, these scales resemble the type 1 of Duffin et al. (1996) (Figures 12 D and E, 14D and E).

Type 2 scales are isolated crows. The posteriorly directed crown is ornamented by a central ridge that reaches the crown apex and has two orders of bifurcation anteriorly. The central ridge is flanked by at least two pairs of lateral ridges wich terminate well before the crown apex and bifurcate anteriorly (Figures 12 A – C and 14 K).

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The actinopterygian teeth are represented in 2 assemblages. The ones assigned to the Palaeonisciformes, easily recognizable due the presence of the acrodin cap (Figures 13 C – F and 14 I) and a very fragmentary collection of teeth of uncertain affinities (Figure 14 N and P). All the teeth reported in this section that are overall conical in shape and bear

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an acrodin cap, belongs to fishes traditionally classified as Palaeonisciformes, a paraphyletic group of lower actinopterygians (Gardiner and Schaeffer, 1989). Herein,

we are using the scheme of classifications proposed by Richter et al. (1999), which includes 7 types of Palaeonisciformes tooth, which 3 are present in the studied

collection. These are the types C, D and F. Type C is shaft slightly curved, 1.5 times as

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high as broad, acrodin cap is short, shaft ornamented with long and narrow microtubercules which merge into one another (Figure 13 F). Type D are tooth sigmoidal in shape, about 2.3 times as high as broad at the base, shaft bearing

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longitudinal microtubercules, most of them about 20 µm long (Figures 13 C and D). Type F are tooth slim, needle-like, slightly curved, 4.6 times as high as broad at the base. Shaft ornamented with longitudinal tubercules most of them about 20 µm long, acrodin cap sharp (Figure 13 E). The teeth described above presumably had a marginal position in the jaws, but these tooth types do not necessarily represent distinct biological species. There is a high variety of dental shapes within single actinopetygian

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species, even today, and morphological differences can be attributed to the slightly different functions they perform in acquiring and processing the food depending on the region of the mouth they come from (Richter et al, 1999). Fish dermal scales of

undetermined affinities are represented in 2

assemblages: a very fragmentary collection of teeth of uncertain affinities (Figure 14 O

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and Q) and a second type of dermal scales possessing a smooth surface (lacking ornamental tubercules or other types of ornamentation) and quasi triangular in external

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view (Figure 14 J).

In the studied collection there are a huge number of acanthodian spines of

undetermined affinities. In general, it appear as fragments of jagged spines, ranging from 1 to 3,5 mm long, with a lateral denticulate surface (Figures 13 G and H). Fragmentary plates that could correspond to pharyngeal tooth plates of

undetermined affinities are fragmentary and tuberculated, wearing round perforated tubercules almost regular in size. It may occur organized in rows (Figure 13 H) or aleatory distributed (Figure 13 G). The features of isolated parts of the exoskeleton of actinopterygian fossil fishes,

especially scales and teeth add little to the biostratigraphy to the Pennsylvanian because they have not been sufficiently considered in stratigraphical correlation.

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Detailed descriptions of such elements are scarce and there is also the widely accepted concept that there is not sufficient morphological interspecific variation of tooth and scale types within the actinopterygians to allow systematic studies based on these potential morphological differences. In fact, the taxonomic value of detached scales of lower actinopterygian has also been questioned (Gardiner, 1969, 1984), since

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the surface ornamentation of the scales in distinct genera may look alike and variation of morphology can occur along the body of the fish.

In addition to shark remains and associated actinopterygian and acanthodian remains, the fish bearing strata also contain relics of undescribed bryozoans,

ostracodes, echinoderms, mollusks and brachiopods, corroborating the open marine

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conditions assumed for the deposits studied. Also, the occurrence of Cooleyella amazonensis supports this environmental model, since the genus Cooleyella is known

form marine deposits both in Britain (Early Carboniferous; Duffin and Ward, 1983) and

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the USA (Late Carboniferous and Permian; Gunnel, 1933; Duffin and Ward, 1983).

8. Conclusions

Macroscopic fragments and molds of trilobites were obtained for the first time in the Itaituba Formation, corresponding to an environmental context of lower intertidal characterized by typical bioclastic wackestones of marine fauna.

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Pennsylvanian scolecodonts are still not well known and the collection described here, although taxonomically diversified and biologically interesting, adds little to our knowledge of the biostratigraphy. Concerning to the depositional environment, on the other hand, scolecodonts can be useful, helping to characterize the environmental context where the scolecodonts bearing rocks were formed.

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Although articulated skeletons of actinopterygian fishes are relatively rare in South American deposits of Paleozoic age, isolated teeth and dermal scales are quite common. For this reason, the tooth types and dermal scales identified here are

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therefore of potential biostratigraphical use both in the Amazonas Basin and outside. Thus, it is needed detailed descriptions of such elements and the understanding of morphological

interespecific

variation

of

tooth

and

scale

types

within

the

actinopterygians to allow systematic studies based on these potential morphological differences. Therefore, the microstructural features of the actinopterygian tooth and dermal scales should be used in conjunction with macroanatomical and morphological information of the whole fish to establish systematic interrelationships. On the other hand, there has been little work on the histology and microstructure of scales and teeth of these fishes. That is the reason why the most useful studies would be those which combine the detailed description of macroscopic features and the histology in normal

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light and under the scanning electron microscopy in order to provide morphological details of the fossil to facilitate their use in biostratigraphical correlation.

Acknowledgments We are grateful to José Emidio and Paulo Rubens (CAIMA cement industries)

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for allowing us access to quarry localities. We are also glad to the Geologist Dr. Nilo

Siguehiko Matsuda for the assistance in collecting the samples and relevant field

discussions and to the Geologist Dra. Cristiane Pakulski da Silva for the support with the photographs and plates. The research was supported by CNPq-CTPETRO grant

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461082/2000-4, CNPq-DS grant 308397/2004-5 and CNPq-PDI grant 308853/2005-9.

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NASCIMENTO, S., 2008. Conodontes e a Cronoestratigrafia da Base da Seção Pensilvaniana, na Região de Itaituba, Porção Sul da Bacia do Amazonas, Brasil. Tese de Doutorado em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul. Porto Alegre. 246p. NASCIMENTO, S., PALUDO, L.S., SOUZA, P.A., LEMOS, V.B., SCOMAZZON, A.K., 2009. Biochronostratigraphy (conodonts and palynology) from a selected strata of the Itaituba Formation (Pennsylvanian of the Amazonas Basin) at Itaituba locality, Pará State, Brazil. Pesquisas em Geociências (UFRGS. Impresso). 1, 37-47

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NASCIMENTO, S., SCOMAZZON, A.K., MOUTINHO, L.P., LEMOS, V.B., MATSUDA, N.S., 2005. Conodont biostratigraphy of the lower Itaituba Formation (Atokan, Pennsylvanian), Amazonas Basin, Brazil. Revista Brasileira de Paleontologia. 8,3, 193202.

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NASCIMENTO, S., SCOMAZZON, A.K., LEMOS, V.B., MOUTINHO, L.P., MATSUDA, N.S., 2010. Bioestratigrafia e Paleoecologia com base em conodontes em uma seção de carbonatos marinhos do Pensilvaniano inferior, Formação Itaituba, borda sul da Bacia do Amazonas, Brasil. Pesquisas em Geociências (UFRGS. Impresso). 3, 243256.

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NEIS, P.A., 1996. Resultados Biocronoestratigráficos das Associações de Conodontes da Formação Itaituba, Carbonífero Superior (Pensilvaniano), da Bacia do Amazonas. 1996. 138f. Dissertação (Mestrado em Geociências), Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre. PAXTON, H. 1986. Generic revision and relationships of the Family Onuphidae (Annelida: Polychaeta). Records of the Auatralian Museum, 38: 1 – 74. PLAYFORD, G.B., DINO, R., 2000. Palynostratigraphy of upper Palaeozoic strata (Tapajós Group), Amazonas Basin, Brazil: Part one. Palaeontographica Abt. B. Bd., 255, 1-46. PEREIRA, E., CARNEIRO, C.D.R.; BERGAMASCHI, S.; ALMEIDA, F.F.M. de. 2012. Evolução das Sinéclises Paleozoicas: Províncias Solimões, Amazonas, Parnaíba e

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Paraná. In: Hasui, Y.; Carneiro, C.D.R.; Almeida, F.F.M. de; Bartorelli, A. Geologia do Brasil, p. 374-394. PLOTNICK, R. E. 1984, Biostratinomy and early diagenesis of modern arthropods (abstr.): Geological Society of America Abstracts with Programs, 16, p. 186 – 187.

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RICHTER, M. 2002. A ray-finned fish (Osteichthyes) from the Late Permian of the State of Santa Catarina (Paraná Basin), southern Brazil. Revista Brasileira de Paleontologia, 56 – 61 p.

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RICHTER, M., NEIS, P. A., SMITH, M. M. 1999. Acabthodian and Actinopterygian fish remains from the Itaituba Formation, late Carboniferous of the Amazon Basin, Brazil, with a note on acanthodian ganoin. Jb. Geol. Paläont. Mh., 12 p.728 – 744. SANTOS, R. S. 1967. Sobre um Cladodontídeo do Carbonífero do Rio Paraueri, Amazonas. Simpósio sobre a Biota Amazônica, Atas (Geociências), 1: 425 – 430. SCHÄFER, W.1972. Ecology and Palaecology of Marine Environments: Edinburgh, Oliver & Boyd, 568 p.

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SCOMAZZON, A.K., 1999. Refinamento bioestratigráfico com base em conodontes, no Pensilvaniano da Bacia do Amazonas – Região do Tapajós. Dissertação de Mestrado em Geociências, Instituto de Geociências, Universidade Federal do Rio Grande do Sul. Porto Alegre, 142p.

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SCOMAZZON, A.K., KAWASHITA, K., KOESTER, E., MATSUDA, N., LEMOS, V.B., SOLIANI Jr., E., COSTA, K.B., MIZUSAKI, A.M. 2002. 87Sr/86Sr and 143Nd/144Nd isotopic signature from Carboniferous conodonts of Amazonas Basin, Brazil. In: XLI Congresso Brasileiro de Geologia, João Pessoa, PB, 15 a 20 de setembro de 2002. Resumos, p. 508. SCOMAZZON, A .K.,; KOESTER, E., MOUTINHO, L.P., MATSUDA, N.S., NASCIMENTO, S., LEMOS, V.B. Sr and Nd isotopic analysis in fossils and carbonatic rocks of Itaituba and Nova Olinda Formations, Pennsylvanian of Amazonas Basin. Gondwana 12 Conference, Mendoza, Argentina, 6 – 11 de Novembro de 2005. Abstract , p. 328. SCOMAZZON, A.K., MOUTINHO, L.P., NASCIMENTO, S., LEMOS, V.B., MATSUDA, N.S., 2016. Conodont biostratigraphy and paleoecology of the marine sequence of the Tapajós Group, Early-Middle Pennsylvanian of Amazonas Basin, Brazil. Journal of South American Earth Science, 65, 25-42.

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TUCKER, M.E., 1992. Sedimentary Petrology - an introduction to the origin of sedimentary rocks:, J. Wiley. 252 p. 1992. (Geoscience Texts v.3)

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WÜRDIG-MACIEL , N.1975. Ichtiodontes e ichtiodorulitos do Grupo Passa Dois. Pesquisas, Porto Alegre, 85 p.

FIGURE CAPTIONS:

Figure 1. Location map of Amazonas Basin showing north and south platforms and the central basin area. In detail showing sampled outcrop localities of Monte Alegre and Itaituba formations. Modified after Eiras et al., (1998) and Scomazzon, (2004).

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Figure 2. Reference section of the studied profile, showing the vertical stacking of the sections corresponding to the outcrops described and sampled in the Tapajós River section, quarries I, II and III and in section of core # BOR-14. The segment of BOR # 14, which stratigraphically connects the sections corresponding to the quarries I and II, has been described based on a drill core ceded by CAIMA and subsequently through

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outcrops, located on top of the quarry I. The physical structures and biogenic,

diagenetic features and fossil content observed are shown in columns to the left of the lithological profile. Ages based on conodonts, foraminifera and palynomorphs data. The fossil content here studied is represented along the right side of the profile.

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Figure 3. A. Chronostratigraphic chart of the Tapajós Group, Pennsylvanian-Permian

Unit of the Amazonas Basin (Modified after Cunha et al., 2007); B. Chronostratigraphy for the Pennsylvanian (after Menning et al., 2006), ages and geochronologic

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correspondence according to the international stages (after Cohen et al., 2013; updated).

Figure 4. Idealized depositional profile model assumed for the Monte Alegre and Itaituba formations during the late Morrowan - Atokan age and its subdivisions three basic sub-environments (Moutinho, 2006 a; Modified after Selley (1970); Anstey and

figure 2).

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Chase (1974); Shinn (1983); Tucker (1992) and Moutinho (2002). (Legend according to

Figure 5. 5 the relation between carbonatic facies and the proportion of fish remains, scolecodonts and trilobites occurrences. The X axis represents the observed carbonate

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facies and the Y axis represents the number of horizons in which fish remains, scolecodonts and trilobites are observed respectively.

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Figure 6. A. Thin section microphotograph of Faunal Rich Packstone microfacies of

lower intertidal/subtidal environment showing a hardly fragmented non-identified bioclasts associated to abundant spines of Trilobites (Tri), foraminifera Tetrataxis spp. (For) and ostracod (Ost) Observe the geopetal calcite cement partially filling the ostracod and the bioturbation on the center of the section (Biot) (Quarry II); B. Thin section

microphotograph

of

Bioclastic

wackestone

microfacies

of

lower

intertidal/subtidal environment with trilobites (Tri). Notice the large fragment of the distal portion of a thoracic trilobite segment (Tri). Note the uniform structure of the bioclast and the extinction bands characteristics of this group when observed in polarized light (Quarry I); C. Thin section microphotograph of Bioclastic wackestone microfacies of

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lower intertidal/subtidal environment showing trilobites (Tri), foraminifers (For), and brachiopods (Brach). Note an entire thoracic segment of trilobite showing their typical aspect of "hook" and the form of hook in the distal portions of the segment, characteristic of this arthropod group. (Quarry II); D. Thin section microphotograph of Bioclastic wackestone microfacies of lower intertidal/subtidal environment. Among

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many brachiopods fragments include a trilobite spine in cross-section (Spin), which clearly shows the extinction bands characteristics of the group; and a distal fragment of

a trilobite thoracic segment (Tri), where we can observe the convoluted structure and distal features. Crinoids (Crin), Bryozoans (Bry), brachiopods (Brach) and foraminifera

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Tetrataxis spp. (For) are also present (Quarry II).

Figure 7. Trilobites Order Proetida Fortey and Owens (1975), obtained at the top of

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Quarry II. Itaituba Formation.

Figure 8. Scolecodonts. Order Eunicida (Dales, 1963) and Phyllodocida (Dales, 1963). A – C. MI maxilar elements of eunicid undenticulated specimens; E – I. MI maxilar elements of phyllocid specimens with pronounced curvature and denticules. Monte Alegre and Itaituba formations.

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Figure 9. Scolecodonts. Order Eunicida (Dales, 1963). A – D. MI maxilar elements of phyllocid denticulated specimens; E – J. MII maxilar elements of phyllocid denticulated specimens. Monte Alegre and Itaituba formations. 10. Fish teeth of Cooleyella amazonensis Duffin et al. (1996).

Formation.

Itaituba

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Figure

Figure 11. Usual shark remains (Condrichtyes) of Itaituba Formation. A – H. Shark

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teeth (Condrichtyes); I and J. Shark scales (Condrichtyes).

Figure 12. Usual shark scales (Condrichtyes) of Itaituba Formation. A – C. Type 2 of Duffin et al.(1996) scales; D and E. Type 1 of Duffin et al.(1996) resembling scales.

Figure 13. Usual fish remains of Itaituba Formation. A and B. Shark teeth showing quadratic bases (Condrichtyes); C – F. Fish teeth (Paleonisciformes) and G and H. Fragmentary plates resembling to pharyngeal tooth plates of undetermined affinities.

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Figure 14. Usual fish remains of Itaituba Formation. A – C. Acanthodian spines (Acanthodiformis); D and E. Type 1 of Duffin et al.(1996) resembling scales; F – H. Shark teeth (Condrichtyes); I. Fish teeth (Paleonisciformes); J, M, O, P. Fish scales of uncertain affinities; L. Shark teeth (Condrichtyes) and N and P. Fish teeth of uncertain

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affinities.

Appendix 1. Samples of sedimentary rocks collected in the Tapajós River section and

quarries I, II and III, petrographic descriptions and quantification of fossils obtained by picking.

Colored cells correspond to levels where fish remains, scolecodonts and

trilobites were obtained. Fish Teeth (ft), fish scales (sc), fish pharyngeal plates (php).

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The symbol * correspond to the levels where fragments of trilobite pygidium’s were

obtained. The other horizons of trilobite occurrence were provided by petrographic

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analysis.

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middle Atokan

80

P3C20

Quarry III

C19 P3C18 C17

P3C15 P3C14 C13 P3C12 C11

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70

P3C16

C6 C3 C2 C1

60

C56/57 C55 C54 C53

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FOSSIL CONTENT PLANT REMAINS

C50/51

BIVALVES

C49

C43

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BRYOZOA

C42 C40 C26 34/37

C24/25 C23 C21/22 C19/20 C13/14/17 C10/11/12

Fe

C8 C7

P2C3/6

C2 C1 C0

CORALS FORAMINIFERS

ECHINOIDS

CRINOIDS ECHINODERMA GASTROPODS

OSTRACODS

TRILOBITES

SCOLECODONTS

FISH REMAINS

CONODONTS

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B#14

S

ALGAL MATS

C33

PHYSICAL STRUCTURES

S

WAVE MARKS

C31 C30 C29 C28 C27

LAMINATION LENTICULAR BEDDING CROSS-LAMINATION MICRO-SIGMOIDAL

INDISTINCT CROSS-LAMINATION

C26

BASAL TANGENTIALCROSS STRATIFICATION ARGILLACEOUS FILM

C25

MICRO-HUMMOCKY

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S

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20

Quarry I

30

ITAITUBA FORMATION

40

BOR 14

50

PRODUCTIDAE BRACHIOPODS

C45/46

lower Atokan - 2.5 Ma

Quarry II

BRACHIOPODS

C47/48

C22 C21 C20 C19 C16 C15 C14 C13 C11/12 C11

DISSECATION-CRACK FINNING-UP ORIENTED FRACTURE

S

FRACTURE STYLOLITE SHARP CONTACT GRADATIONAL CONTACT

?

UNDEFINED CONTACT

DIAGENETIC FEATURES EVAPORITIC MOLD

C10 C9b C9 C8

EVAPORITIC NODULE GYPSUM MOLD

S

C7 C6 C4 C2 C1

Fe

MICRO-CRYSTALINE SILICA FERRUGINOUS PELOIDS

-HG-

“HARDGROUND” COMPACTION DISSECATION CRACK SPHEROIDAL FOLIATION

BIOGENIC STRUCTURES

WEAKLY BIOTURBATED MODERATELY BIOTURBATED INTENSELY BIOTURBATED

LITHOLOGY BIOCLASTIC GRAINSTONE OOLITIC GRAINSTONE PACKSTONE

P 04

WACKESTONE MUDSTONE CRYSTALINE MATRIX LAMINATED DOLOMITE

P 03

DOLOMITE SANDSTONE

TCX 3.3/3.4/3.5

FINE SANDSTONE/SILTSTONE

TCX 3.1 TCX 3.1.1

SILTSTONE SHALE

TCX 3.0

PMW P G F MC

Morrowan

0

Height(m)

Tapajós River Section

10

Monte Alegre Formation

MICROBIAL LAMINATIONS

P 12

Age

COARSE SAND MEDIUM SAND FINE SAND GRAINSTONE PACKSTONE WACKESTONE MUDSTONE PELITE

PTO-10 MALOQ

Fossil content

PMWPG FMC

Fossil content this paper

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Figure 8. Scolecodonts. Order Eunicida (Dales, 1963) and Phyllodocida (Dales, 1963). A – D. MI maxilar elements of eunicid undenticulated specimens; E – I. MI maxilar elements of phyllocid specimens with pronounced curvature and denticules. Monte Alegre and Itaituba formations.

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Figure 11. Usual shark scales (Condrichtyes) of Itaituba Formation. A – C. Type 2 of Duffin et al.(1996) scales; D and E. Type 1 of Duffin et al.(1996) resembling scales.

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Figure 12. Usual shark remains (Condrichtyes) of Itaituba Formation. A – H. Shark teeth (Condrichtyes); I and J. Shark scales (Condrichtyes).

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ACCEPTED MANUSCRIPT Shallow marine and faunal rich carbonate deposits of Monte Alegre and Itaituba Formations, Pennsylvanian of the Amazonas Basin. First recovering of macroscopic fragments and molds of trilobites. Taxonomically diversified scolecodonts fauna still not well known. Isolated fish teeth and dermal scales quite common. Faunal association of biostratigraphic potential and paleoecological use both in the

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Amazonas Basin and outside.

Rare Biota Mudstone

C19 74,00

Faunal Rich Packstone

RI PT

C20 76,00

Trilobites

Faunal Rich Packstone

Scolecodonts

Lithology

C21 77,50

Fish remains

Depth (meters) Quarry III

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8 ft 9 sc

Bioclastic wackestone

26 ft 10 sc 3 php

C 15 71,00

Collapsed

2 ft

C14 70,00

Laminated siliciclastics

6 ft

4*

C40 50,00

3

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C41 50,00

Rare Biota Mudstone

1

C39 50,00

Rare Biota Mudstone Rare Biota Mudstone

C38 48,50

Rare biota Mudstone

5 sc

C33 48,00

Rare Biota Mudstone

1 ft

C31 47,800

Rare Biota Mudstone

C30 47,60

Rare Biota Mudstone

C29 47,40

Rare Biota Mudstone

C28 47,20

Rare Biota Mudstone

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Quarry II

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C57 Bioclastic 60,00 wackestone C55 Faunal Rich 1 ft 58,50 Packstone 1 sc C53/ Faunal Rich C54 2 sc Packstone 57,70 C50/ Bioclastic C51 1 ft wackestone 56,00 C49 Faunal Rich 5 ft 55,80 Packstone C48 1 ft Microbial mat 3 sc 55,00 C47 Microbial mat 54,500 C46 Faunal Rich 54,00 Packstone C44 Grainstone 52,00 C42 Recrystallized 50,00 calcareous

1

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C16 72,00

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C18 Recrystallized 6 ft 73,50 Mudstone 2 sc

1

1

1

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Faunal Rich Packstone

C20 46,20

Rare biota Mudstone

Quarry I

1 5 ft

5

1 sc 1

2

1

1

5 4

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Rare biota 1 ft Mudstone Bioclastic Wackestone Bioclastic 1 ft Wackestone 1 sc Faunal Rich Packstone Bioclastic 1 ft Wackestone 1 sc Bioclastic Wackestone Faunal Rich Packstone Faunal Rich 1ft Packstone Faunal Rich 4 ft Packstone Faunal Rich 20 sc Packstone 1 php Bioclastic 1 ft Wackestone Bioclastic 20 ft Wackestone 26 sc Faunal Rich Packstone Faunal Rich 100 ft Packstone 5 sc Microbial mat

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Recrystallized 2 ft Mudstone 1 sc Recrystallized 7 ft Mudstone 1 sc

3

Recrystallized 2 ft Mudstone 1 sc

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C19 46,10 C17 46,00 C16 45,90 C15 45,80 C14 45,70 C13 45,60 C12 45,50 C11 45,40 C10 45,30 C9 45,20 C8 45,10 C3/6 45,00 C2 40,00 C1 40,00 C0 40,00 C35 41,00 C34 40,50 C33/ 32 40,00 C31 38,00 C30 37,00 C29 36,50 C26 36,00 C25 35,00 C24 34,00

3

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C21 46,30

1 ft

SC

Rare Biota Mudstone Rare Biota Mudstone Faunal Rich Packstone Faunal Rich Packstone Bioclastic grainstone Faunal Rich Packstone

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C27 47,00 C26 46,90 C25 46,70 C24 46,60 C23 46,50 C22 46,40

Recrystallized Calcareous Bioclastic Wackestone Faunal Rich Packstone Bioclastic Wackestone Bioclastic Wackestone Recrystallized Mudstone

11 ft 10 ft 2 sc

1 1 ft 1 sc

7

10 ft

8

3 ft C22 Recrystallized 5 sc 15 33,00 Mudstone 1 ph p C21 Recrystallized 5 ft 1 31,80 Mudstone

4

C19 30,00

Microbial Mat

20 ft 8 sc

15

C16 28,80

Packstone/ Wackestone

1 sc

3

C15 28,50

Faunal Rich Packstone

17 ft 2 sc

14

C14 28,30

Oolitic grainstone

C13 28,00

Bioclastic Grainstone

C10 26,50 C9 26,00 C8 25,00 C7 24,00

Wackestone/ Mudstone Bioclastic Wackestone Faunal Rich Packstone Bioclastic Wackestone Faunal Rich Packstone Faunal Rich Packstone

3 ft 1 ft 25 ft 8 sc 4 ft 3 sc 1 ft 1 sc 12 ft 3 sc 10 ft 4 sc

7 13

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TCX 3.4 8,00

1

2 3

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TCX 3.5 8,00

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C20 Recrystallized 6 ft Mudstone 18 sc 31,00

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Tapajós River section

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