Comparison of Tidalites in Siliciclastic, Carbonate, and Mixed Siliciclastic-Carbonate Systems: Examples from Cambrian and Devonian Deposits of East-Central Iran

For the comparison of lithofacies in siliciclastic, carbonate, and mixed siliciclastic-carbonate tidal systems, three successions including Top Quartzite (Lower-Middle Cambrian), Deranjal Formation (Upper Cambrian), and Padeha Formation (LowerMiddle Devonian) in the north of Kerman and Tabas regions (SE and E central Iran) were selected and described, respectively. Lithofacies analysis led to identification of 14 lithofacies (Gcm, Gms, Gt, Sp, St, Sh, Sl, Sr, Sm, Se, Sr(Fl), Sr/Fl, Fl(Sr), and Fl) and 4 architectural elements (CH, LA, SB, and FF) in the Top Quartzite, 7 lithofacies (Dim, Dp, Dr, Ds, Dl, Dr/Dl, and Fcl) and 2 architectural elements (CH, CB) in the Deranjal Formation, and 17 lithofacies (Sp, St, Sh, Sl, Sr, Se, Sr(Fl), Sr/Fl, Fl(Sr), Fl, Dr, Ds, Sr/Dl, El, Efm, Efl, and Edl) and 5 architectural elements (CH, LA, SB, FF, and EF) in the Padeha Formation that have been deposited under the influence of tides. The most diagnostic features for comparison of the three tidalite systems are sedimentary structures, textures, and fabrics as well as architectural elements (lithofacies association). The CH element in siliciclastics has the highest vertical thickness and the least lateral extension, while in the carbonate tidalites, it has the least vertical thickness and the most lateral extension compared to in other systems.


Introduction
The term Tidalites was introduced by Klein [2,3] to designate a new process for sedimentary facies, deposited by tidal currents [4]. It is now applied to all sediments and sedimentary structures that have accumulated under the influence of tides [5]. Three subenvironments, including subtidal, intertidal, and supratidal, can be distinguished on the basis of sedimentary structures, textures, lithologies, and vertical successions of such facies. Tidalites are somewhat synonymous with peritidal sediments, formed near the tidal zone [6][7][8]. Although tidalites are common in passive margins, they also occur in failed rifts, intracratonic, foreland, backarc/fore-arc, and pull-apart basins (e.g., [9][10][11]). Sedimentary structures are the most diagnostic features used in analyzing and describing tidal flat deposits. These sedimentary lines of evidence reflect different types of physical, chemical, and biochemical conditions in tidal facies. In another word, each different sedimentary structure is representative of one particular subenvironment within the tidal zone [5,11]. Although sedimentary structures in both siliciclastic and carbonate tidal zones are similar, they differ in their abundance. The mixed siliciclastic-carbonate deposits in the ancient shallow and coastal marine environments contain the most sedimentary structures. The aim of this paper is to discuss and compare the petrography and lithofacies characteristics of tidalites in three siliciclastic, carbonate, and mixed siliciclastic-carbonate depositional systems in order to have a better understanding of tidal facies in such sedimentary systems. In this research, in central Iran, the Lower-Middle Cambrian (Top Quartzite) sediments east of Zarand in Kerman area were analyzed to study tidalite from a siliciclastic depositional system (Figures 1 and 2).   Formation) in the same area were also studied for facies interpretations of tidalites in carbonate systems ( Figures  1 and 3). In northern Tabas and northwestern Kerman, three stratigraphy sections of the Padeha Formation were selected and described for analyzing facies characteristics of tidalites in a mixed siliciclastic-carbonate depositional system (Figures 1 and 4). Evaporates are also present in these systems.

Geological Setting
The study area is located in the central part of the Central-East Iranian Microcontinent (CEIM; [12]). The CEIM, together with central Iran and the Alborz Mountains, forms the Iran Plate, which occupies a structural key position in the Middle-Eastern Tethysides [13]. The CEIM consists of three northsouth-oriented structural units, called the Lut, Tabas, and Yazd Blocks (Figure 1), which are now aligned from east to west, respectively [14]. The study area is located in the north and south parts of Tabas Block. The rock succession exposed in this area includes all systems from the Pre-Cambrian up to recent. This Block is bounded by the Great Kavir Fault in the north, the Naini Fault (Nain-Baft Fault) in the west and southwest, and the Nayband Fault in the east (Figure 1). An important characteristic of the Tabas Block is that it bears a complete succession of Paleozoic rocks that is incomplete in other parts of Iran [14,15].
This study focuses on the Cambrian and Early-Middle Devonian rocks in the south and north of Tabas Block (Figure 1(c)). The basement of the Tabas Block consists of metamorphic complexes which contain volcanic, volcaniclastic, and pyroclastic rocks with marbles. This basement is similar to the Arabian Proterozoic basement (Pan-African basement) [18,19]. The Late Precambrian-Lower Cambrian successions of this block include successions of basic lavas, sandstone, and evaporite-dolomite (Rizu and Dezu series) which is attributed to a rifting system by Aghanabati [19]. From a regional point of view, Paleozoic deposits are widespread throughout the Arabian and Iranian terrains. Facies analysis for Cambrian to Devonian rocks in the Tabas Block indicates that they were mostly deposited in shallow marine environments (e.g., [18,20]). The paleogeographic map of the Cambrian to Devonian of Arabia and Iran shows that its adjoining plates formed a broad continental shelf on the northern margin of the Gondwana supercontinent, which bordered on the Paleo-Tethys Ocean (e.g., [19][20][21][22][23]). It should be noted, however, that Lasemi [24] argues that  the Precambrian-Cambrian sedimentary facies indicate the existence of an ocean older than the Paleo-Tethys in Iran, which is named the Proto Paleo-Tethys.
Several formations were introduced from the Cambrian succession in central Iran. The Dahu Formation (Lower Cambrian), Top Quartzite Unit (Lower-Middle Cambrian), Kuhbanan Formation (Middle Cambrian), and Deranjal Formation (Upper Cambrian) are the most widespread in Iran, especially at northern Kerman. Cambrian sedimentary rocks are exposed in most parts of Iran except in the north-east (Kopeh-Dagh region). The Padeha Formation (Lower-Middle Devonian) is part of Devonian succession that has an extensive lateral expansion in Iran. Wendt et al. [25] believed that the Padeha Formation is mainly deposited in a siliciclastic shelf, especially shallow marine environment.

Materials and Methods
This study is based on petrography and facies descriptions from nine stratigraphic sections selected from the Cambrian 6 ISRN Geology and Devonian deposits in eastern and southeastern parts of central Iran. A total number of 780 thin sections were prepared from approximately 980 rock samples for the lab analysis. For carbonates, thin sections were stained with red alizarin solution in order to differentiate calcite and dolomite minerals [26]. The identified facies were classified into siliciclastic and carbonate lithofacies on the basis of field observations, microscopic, and lab analysis. The description of the facies is based on facies codes presented by Miall [1]. New facies codes are also determined and added. The siliciclastic petrofacies and carbonate microfacies are classified and described on the basis of Folk's [27] and Dunham's [28] classifications, respectively. The petrography features and the mineralogical composition of microstructures were analyzed using SEM-EDX in the central laboratory of Ferdowsi University of Mashhad. 180 oriented sedimentary structures were measured from the siliciclastic sediments for paleocurrents analysis.  Table 1). The most diagnostic sedimentary structures in these lithofacies include wave, current, and interference ripples ( Table 2; Figures 5(a) and 5(b)), planar and trough cross-beds, herringbone cross-beds with bimodal pattern of paleocurrent ( Figure 6(a)), reactivation surfaces, flaser and wavy bedding (Figure 7(c)), polygonal mud cracks, and some trace fossils (dominated by Cruziana).

Results
On the basis of the identified lithofacies, three CH, LA, and SB elements, representative of tidal channel deposits and sand body macroforms, were recognized (Table 3, Figures 10  and 11). These elements were deposited in subtidal and intertidal subenvironments. The dominant petrofacies are mature-supermature quartzarenite and chertarenite. Also, textural inversion was identified in some of the lithofacies.  The field studies resulted in identification of dominant carbonate lithofacies such as Ds, Dl, Dr, and Dp. The Dl lithofacies completely consists of primary dolomites (Table 1) The microscopic analysis led to recognition of several carbonate microfacies such as dolomudstone, sandy dolomudstone, dolomitic lime mudstone, dolomitic stromatolitic boundstone, dolomitic peloidal packstone, and dolomitic intraclast-ooidal grainstone. Sparse sandstone (Sp, Sr, and Sh) lithofacies with low lateral distribution were also intercalated with the carbonate facies. The quartzarenite is the only siliciclastic petrofacies observed in the sandstone lithofacies.
The lithofacies analysis reflects the dominant role of tidal currents in deposition of the studied facies. Under this sedimentary condition, the dolomudstone, sandy dolomudstone (consisting of Dl lithofacies), and the boundstone    (Dsp lithofacies) were deposited in the upper intertidal and supratidal subenvironment. The carbonate lithofacies (Dsd, Dr, and Dp) as well as sparse sandstone lithofacies (Sh, Sr, and Sp) were deposited in the intertidal zone and tidal channels reflecting CH and CB elements ( Table 3). The fine-grained marl lithofacies (Flc) indicated that deposition may have taken place in subtidal lagoon [31].

Mixed Siliciclastic-Carbonate Tidalites.
Based on the lithological diversity and the presence of different flow regimes in this depositional system, the mixed siliciclasticcarbonate tidalites contain the most diagnostic sedimentary signature. In the siliciclastic-carbonate systems, in addition to tidal influences, environments such as fluvial, estuaries, deltas, and wave current are effective in the type of sediments (e.g., [32]). However, the intensity of the tidal currents is the main factor in controlling the deposition of tidalites. In some of the studied sections, the sediments of the Padeha Formation were deposited by tidal currents [33]. For example, in the type section (the Ozbak-Kuh section), the Dahane-Kalot in north of Tabas, and the Sarashk sections in northeast Kerman (Figure 1), the sediments of this formation consist of tidalites, reflecting tidal subenvironments and conditions. The Padeha Formation was first measured and introduced by Ruttner et al. [34] in Ozbak-Kuh Mountain, north of Tabas, and was described as the second formation within the Goshkamar Group (Niur and Padeha Formation). The sedimentary succession of the Padeha Formation comprises siliciclasts, dolomites, and evaporites. The formation overlies the carbonate settings of the Niur Formation and is overlain by the carbonate deposits of the Sibzar and Bahram Formations. The Padeha Formation has been assigned to Lower-Middle Devonian based on its stratigraphic position [25,35,36] and can be considered as an equivalent of the Lower Devonian red siliciclastic sediments that are extended widely in other regions in the world. Due to different deposition conditions and the distances between the studied sections

Discussion
The identified tidalites in three depositional systems are compared, based on structural, textural, and architectural elements, through the following sections.
In contrast to the ancient paleoenvironments, in the recent coastal sediments, tidal facies and other sedimentary facies formed by currents can easily be reconstructed and observed. Sedimentary textures and structures of tidalites are the most important factors in interpretation of tidal deposits. Siliciclastic sediments contain more preserved sedimentary structures than carbonates; therefore, it is easier to identify subenvironments.
The high diversity of ripple marks in the Sr lithofacies indicates the presence of different flow regimes in the environment ( Figure 5). Such sedimentary conditions are well represented by the Top Quartzite siliciclasts. In these sediments, the changes from wavy to current ripples with sinusoidal, straight, and complex crests in the short distance reflect dominance of wave currents in a tidal flat environment. These types of ripple marks were rarely recognized within the sediments of the Padeha Formation. Instead, symmetrical ripples with sinusoidal and straight crests were observed ( Table 2). In the carbonate sediments of the Deranjal Formation, ripple marks were commonly identified as wavy and climbing ripples (Dr lithofacies). The ripple lithofacies are common in intertidal and partially common in the lower parts of supratidal subenvironments.
Herringbone cross-beds and reactivation surfaces are the other sedimentary structures in the studied tidalites ( Figure 6). These structures that were observed in Sp and Dp lithofacies were dominant in an intertidal zone and were formed by the movements of ripple marks and waveshaped dunes [40]. Analyses of recent tidal cycles [5] reveal that tidal currents are more important in the formation of tidalites than other currents. The dominant current resulted  in formation of wavy bedforms and subsequent formation of cross-beds. The current from the opposite direction was lower in energy and therefore it could not lead to formation of cross-beds in an opposite direction. It only eroded the sediments from the ripple surface. This process could result in formation of tidal bundles and cross-beds separated by mud drapes. The occurrence of herringbone cross-beds in sandstone lithofacies as well as mud drapes in the upper parts of fining upward cycles reflects deposition of sediments in different depth and tidal current energies in an intertidal subenvironment [2,41,42].
The flaser, wavy, and lenticular beds (Sr/Fl lithofacies association) in heterolithic layers are also the other typical sedimentary structures in tidal flat environments (Figure 7). These structures are more abundant in siliciclastic systems. Such lithofacies resulted from alternative changes in the environmental energy. Based on the energy variations, sandstone-mudstone and sandstone-carbonate lithofacies  were deposited as heterolithic rhythmites. The heterolithic laminas, which occur in tidalites, are known as doublets or couplets [43]. According to Archer and Greb [44], these beds are often formed during semi-and diurnal tidal currents due to changes in tidalite periods. Based on the field analysis of the siliciclasts of the Padeha Formation and the Top Quartzite succession, three Sr(Fl), Sr/Fl, and Fl(Sr) lithofacies were identified. An increase of energy in the environment (deposition of sandstone lithofacies) led to deposition of Sr lithofacies with several ripples morphologies, whereas, finegrained mudstone (Fl lithofacies) precipitated in the trough point of ripples during the decrease of energy. Following the deposition of the mudstones, the environmental energy gradually increased. The alternative changes in the energy level and the elapse time condition result in deposition of interbedded lithofacies comprising flaser, wavy, and lenticular beddings [40,43]. Within the interbedded sandstonemudstone, Sr/Fl with wavy beds is the most abundant interbedded lithofacies observed in the Padeha Formation and the Top Quartzite succession. The thickness of each set ranges from 8 cm to 3 m. This lithofacies association is very dominant in tidal flat [2,4,40,45,46]. Additionally, Sr/Dl lithofacies were identified in the supratidal deposits of the Padeha Formation reflecting interaction of physical and chemical processes in the sedimentary environment ( Figure 7). This led to an input of siliciclastic and formation of sandstone lenses within the dolomudstone microfacies. The flaser beddings were also recognized within the carbonate deposits of the Deranjal Formation and are composed of Dr/Dl lithofacies. Mud cracks and raindrop imprints are the two major sedimentary structures found in tidal flat deposits and are well preserved within the siliciclasts (Figure 8). In the siliciclastic sediments of the Padeha Formation and the Top Quartzite succession, the mud cracks appeared as polygons on the surfaces of fine-grained sandstones and siltstones. Syneresis cracks were also observed in these sediments of the Padeha Formation resulting from salinity changes [47]. Additionally, some V-shaped mud cracks were identified in the carbonates of the Deranjal Formation (Figure 8(d)). Mud cracks are commonly related to the supratidal and upper intertidal zones. Stromatolites and stromatolitic structures are two of the most abundant sedimentary structures within the carbonate settings ( Figure 9). The stromatolites occur in different sizes and morphologies (domal (Dsd) and planar (Dsp)) within the carbonate layers of the Deranjal Formation. Such sedimentary structures are abundant in the tidal flat deposits, particularly in the intertidal zone [5,11].
In the carbonate deposits, tepee structures are also observable. Tepee structures are common in tidalites and are formed as a result of desiccation, cementation and crystal growth, thermal expansion, and contraction of partially lithified sediment in arid tidal flat or high-energy shallow subtidal sediments [11,48]. Due to lithology changes, the tepee structures are more dominant in the mixed siliciclasticcarbonate sediments.

Textural Lines of Evidence.
In addition to sedimentary structures, textural feature is also one of the main factors in identification of tidal flat sediments. The texture of siliciclastic rocks consists of size, shape, and fabric of the grains. In the studied siliciclastic deposits, grain size ranges from pebble to silt size. Well-rounded pebbles were only observed within the sediments of the Top Quartzite succession reflecting dominance of wave currents and tidal currents during transportation and sedimentation. Recent tidal deposits have high compositional and textural maturity similar to the studied sandstones.
The most abundant petrofacies within the Top Quartzite and Padeha Formation are mature to supermature quartzarenite with a few chertarenite. The textural inversion and bimodality in some petrofacies reflect the effects of sedimentary currents (e.g., waves and wind) in the tidal flat zone. The importance of textural features is also obvious in the carbonate rocks. In addition to parameters such as the roundness and sorting of carbonate grains, the types of grains are also the other important factors in identification of carbonate tidalites.

Architectural Elements.
The identified architectural elements within tidal deposition systems are CH. LA, SB, CB, FF, and EF (Table 3); that will be discussed next.

Channel Deposits (CH).
The CH is one of the major elements that are common in three tidal systems. Tidal channels contain a wide range of bedforms with different sizes, forming with bidirectional currents in shallow marine environments to sandy barriers [53]. Tidal channels are usually present in intertidal and subtidal zone and commonly have dendritic network. Several factors, such as physical and hydrodynamic process, controll the morphology and distribution of tidal channels (e.g., [54]). The channel-filling sediments are commonly showing shallowing upward cycles.
Abundance of bidirectional structure such as planar and herringbone cross-beds and ripple marks as well as the presence of channel lag (at the base) along with thin sandstone layers and the lines of evidence of exposure (e.g., mud cracks and raindrop imprints) in an upward direction reflects tidal channel deposits [42,46,53].
In the siliciclastic depositional systems, fining upward of sediments shows either a decrease of energy or a shallowing upward trend in the sedimentary environment. Within the Top Quartzite succession, the basal parts of the channel deposits are composed of chert pebbles or coarse-grained sandstones changing into fine-grained sandstone or siltstone in an upward direction (Figures 10(a) and 11(a)-11(c)). In the shallowing upward cycles of siliciclastic systems, from the base to the top, a sedimentary succession typically consists of the following lithofacies: (Gcm, Gt, Gp)-(St, Sp)-(Sl, Sh, Sr)-(Sr(Fl), Sr/Fl, and Fl(Sr))-(Fl). In the Top Quartzite siliciclasts, this succession was deposited either as an incomplete or a complete (Figures 11(a)-11(c)) and extends laterally about 10-30 m with 3 to 10 m in thickness.
In the channel deposits of the mixed siliciclasticcarbonate succession of the Padeha Formation, the base part is erosional and is composed of medium to coarse-grained sandstones that subsequently change into dolomites and stromatolitic limestone at the top (Figures 10(b)  The thickness of the element in the tidal carbonate system of the Deranjal Formation is less than in other depositional systems. Typically, the basal parts of the deposits are mostly composed of dolomitic ooidal-intraclast grainstone microfacies with erosional base that changes to dolomitic ooidal packstone and grainstone with ripple lamination toward the top (Figures 10(c) and 12). Following this shallowing upward trend, the dolomitic stromatolitic boundstone with a few dolomudstone beds was deposited. These lithofacies are mainly intercalated with alternations of subtidal lagoon carbonate mudstones (marls). The CH element in these deposits typically consists of (Dim)-(Dr, Dp)-(Dsd, Dsp, Dr/Dl)-(Dl) lithofacies with vertical thickness of 1-3 m and lateral extension of 30-100 m. The Dim lithofacies is composed of rounded, poorly sorted limestone clasts that are deposited by debris flows in tidal or storm channels in tidal flats. These lithofacies are common on Cambrian and Ordovician carbonate platforms (e.g., [55,56]).
The comparison of the CH element in these three depositional systems shows that the channel deposits in the siliciclastic systems have the least lateral extension with the maximum vertical thickness. Hughes [53] discussed that tidal channels can exist in different depths and hydrodynamic conditions that directly control the CH element. The channels in the deeper environments are more extended and preserved than the shallow channels. The facies and environmental analysis of the Deranjal Formation indicate that such channels were mostly extended in barrier and subtidal lagoon and 18 ISRN Geology therefore, the depth of the environment could control the distribution of channel element in the sediments than the deposits of the Top Quartzite and the Padeha Formation.

Lateral-Accretion Bedforms (LA).
This element is considered as a part of channel deposits formed by lateral accretion of meandering channels (e.g., [40,57]). Sudden movements of channels result in the establishment of fining and shallowing upward cycles with more limited lateral movements than CH element (Figure 11(e)). The LA element is common in the siliciclastic tidalites and none was identified in the carbonate tidalites.

Sandy Bedforms (SB).
The SB element is linear in plane view and asymmetrical in cross section. They are parallel to the main flow of tidal currents. Sand on these sedimentary bodies ranges in size from very fine to very coarse grained depending on availability, and sorting in the bedforms developed on the sand bodies includes wavy and current ripples and dune [4]. The Sp, Sh, Sm, and Sr lithofacies are the dominant constituents of this type of element ( Table 3). The Gp and Gt lithofacies are also the other types of lithofacies in the siliciclastic sediments of the Top Quartzite. In the mixed siliciclastic-carbonate system (the Padeha Formation), thin layers of D1 and Ds lithofacies and also sandstone lithofacies are composed of the SB element (Figures 11(g) and 11(h)). The SB element is not observed in the carbonate tidalites. According to the identified lithofacies, the SB element is often formed in tidal flats or intertidal zone due to high sedimentation rate of sand-sized grains. Intertidal sand body systems have been accumulated in areas with relatively strong bottom tidal current velocities, subjecting the seabed with a high rate of sand transport by bedload processes of deposition [4].

Carbonate Bedforms (CB).
In the carbonate deposits of the Deranjal Formation consisting mainly of boundstone and dolomudstone microfacies, Ds and Dl are the major constituents of this type of element. However, thin layers of mudstone were deposited between the lithofacies as mud drapes. Based on the sedimentation rate of the carbonate materials in the mixed siliciclastic-carbonate depositional system, the CB element could be present. Scattered CB element was identified in the lower part of the Padeha Formation at the type section. The identified lithofacies associations in the CB revealed that this element was formed in an intertidal and the lower parts of a supratidal subenvironment.

Fine-Grained Beds (FF).
This element is composed of fine-grained mudstones with dominant Fl as well as Sr and Sp lithofacies. The structural characteristics and the stratigraphic position of the facies associations reflect deposition of these lithofacies in a low-energy supratidal zone. The FF element was clearly recognized within the Top Quartzite and the Padeha Formation. The sandstone lithofacies were mainly deposited during the flood and input of flooding channels to a supratidal subenvironment (e.g., [49]). The flooding channel deposits are 20 cm to 1 m thick and have a limited lateral extension. Although the FF element can also be formed in carbonate tidal environments (e.g., [11]), no traces of such element were found in the carbonates of the Deranjal Formation.

Evaporite-Mud Rocks Beds (EF).
The EF element consists of an assemblage of evaporite lithofacies. Generally, evaporites can be formed in all three depositional systems but are only recognized in the Padeha Formation. An arid climate and an idealized coastal morphology, to deposition of evaporite in sabkha or salina. Such environmental conditions were prevailing during the formation of the mixed siliciclasticcarbonate tidalites of the Padeha Formation, and El, Efl, Efm, and Edl lithofacies were formed the EF framework in a coastal sabkhas. Sedimentary structures such as mud cracks, raindrop imprints, and wavy ripples as well as the presence of primary fine-grained dolomites show that the facies associations were formed in a continental-coastal environment (subaerial precipitation). In this model, evaporite deposits are formed in the sediments above the tidal flat zones or sabkha environment. Low energy in this area caused deposition of fine-grained clay-sized deposits. If conditions are ready for precipitation of evaporite deposits, gypsum and anhydrite are precipitated from the pore waters in vadose and upper phreatic zones with respect to capillary properties between fine-grained sediment (mudstone) [47,58].
The El, Efm, and Efl lithofacies within the Padeha Formation were deposited in such conditions. According to the classification of sabkhas [59,60] and the lithofacies characteristics, the evaporite facies of the Padeha Formation were formed in marine or coastal sabkhas. These sabkhas were present either in dry or arid climates between land and sea, but the source of brine is often from the sea. Thus, the lithofacies of these environments consist of evaporite deposits, particularly gypsum and in some cases anhydrite with evaporitic dolomite and siliciclastic facies [47,61]. Depositions of primary dolomite are carried out prior to or simultaneously with the process of forming evaporite minerals. Dolomites were formed when the ratio of Mg/Ca was rising in the environment. Deposition of gypsum caused the concentration of calcium ions to decrease, therefore, providing conditions for the formation and deposition of dolomite. This process is the most important factor in formation of Edl facies in the studied settings. These lithofacies have a wide stratigraphic distribution in the Padeha Formation at the type section. Efm and El are the only lithofacies identified in the Sarashk section. The limited extension of evaporite facies in the Kerman area reflects sedimentation in a salina flat.

Conclusions
Based on facies analysis and comparison of tidalites in siliciclastic, carbonate, and mixed siliciclastic-carbonate systems in the Cambrian and Devonian of central Iran, the following results have been obtained.
(2) The Upper Cambrian carbonate deposits (equivalent to the Deranjal Formation) are interpreted as carbonate tidalites. Six lithofacies (Dim, Dp, Dr, Ds, Dl, and Dr/Dl) were identified in these deposits. The lithofacies consist mainly of ooidal-interclastic grainstone and packstone, boundstone and dolomudstone. The sediments were dolomitized with well-preserved original texture. The sedimentological analysis led to recognition of two CH and CB elements that were deposited in intertidal and subtidal lagoon. The supratidal lithofacies have a limited stratigraphic extension.
(4) The lithofacies analysis of the three studied tidalites reveals that the mixed siliciclastic-carbonate systems contain the most diverse sedimentary structures. Instead, in the siliciclastic depositional systems, the sedimentary structures are present in larger scales. The most significant texture and sedimentary structures of the tidalites, which are the same in the three depositional systems but different in abundance, include wavy, current, and interference ripples, herringbone cross-beds, reactivation surfaces, flaser, wavy, and lenticular bedding, mud cracks, and raindrop imprints, but are well preserved within the siliciclastic sediments. In the carbonate tidalites stromatolitic and tepee structures, small-scale Vshaped mud cracks, fenestral fabrics, and pseudomorph calcite are more abundant.
(5) The architectural elements revealed that the channel element (CH) is the most important element in the tidalites and is observed in the shallowing upward cycles. In the siliciclastic sediments, the channel element is composed of fining upward (conglomerate-sandstone to sandstonemudstone) cycles. In the carbonate tidalites, this element is representative of vertical changes of dolomitic ooidal and interclastic grainstones to packstone and stromatolitic boundstones. Finally, the CH element in siliciclastic tidalites has the greatest vertical thickness and the least lateral extension than in other systems. Instead, channel deposits in carbonate tidalites have the least vertical thickness and the greatest lateral extension.