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 (Lower-Middle 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.
The term
Locality map of the study area and measured stratigraphic sections in east-central Iran. (a) Structural units of Iran (modified from Alavi [
Lithostratigraphic columns and 3D depositional model of the siliciclastic tidalites (Top Quartzite) in the East Zarand, NW Kerman. Datum line is base of the Top Quartzite.
Lithostratigraphic columns and 3D depositional model of the carbonate tidalites (Deranjal Formation) in the East Zarand, NW Kerman. Datum line is base of the Deranjal Formation.
Lithostratigraphic columns and 3D depositional model of the mixed tidalites (Padeha Formation) in central Iran. Datum line is base of the Padeha Formation.
The study area is located in the central part of the Central-East Iranian Microcontinent (CEIM; [
This study focuses on the Cambrian and Early-Middle Devonian rocks in the south and north of Tabas Block (Figure
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., [
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. [
This study is based on petrography and facies descriptions from nine stratigraphic sections selected from the Cambrian 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 [
These types of tidalites are identified in the Lower-Middle Cambrian siliciclasts of the Top Quartzite sediments that overlie the fluvial deposits of the Dahu Formation [
The field studies revealed that the Top Quartzite siliciclastic succession can be divided into three lithostratigraphic units. The lower part consists of conglomerate and sandstone. Mudstone and sandstone comprise the middle part of the succession, while the upper part consists mainly of sandstone. The lower and upper parts of the Top Quartzite succession are composed of conglomerate (Gcm, Gms, Gt), sandstone (Sp, St, Sh, Sl, Sr, Sm, Se), and interbedded sandstone-mudstone (Sr(Fl), Sr/Fl) lithofacies (Table
Summery of characteristics of lithofacies (lithofacies codes modified after Miall [
Lithofacies | Code | Description | Petrography | Interpretation | Occurrence |
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Conglomerate | |||||
Clast-supported | Gcm | Massive; granule- to pebble-sized clasts; oligomictic (chert) | Orthoconglomerate | Bedload transport lag deposits in tidal channels | Top Quartzite |
Matrix-supported | Gms | Massive or crudely bedded; granule- to pebble-sized; oligomictic (chert) | Paraconglomerate | Bedload transport lag deposits in tidal channels | Top Quartzite |
Trough cross-bedded | Gt | Granule- to pebble-sized; clasts bed thickness generally 1 to 2 m. | Paraconglomerate | Bedload transport tidal channel deposits | Top Quartzite |
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Sandstone | |||||
Trough cross-bedded | St | Medium sand solitary or grouped; set thickness generally 2–30 cm | Quartzarenite, sometimes litharenite | 3D dunes and interference ripples movement; tidal channels | Top Quartzite |
Planar cross-bedded | Sp | Coarse-fine sand; solitary or grouped; set thickness generally 5–50 cm; herringbone cross-bedding | Quartzarenite, sometimes litharenite | Transverse and linguoid bedforms (ripple or 2D dunes); grouped tabular sets with bipolar-bimodal paleocurrents representing tidal channels | Top Quartzite |
Horizontally bedded |
Sh | Fine sand; set thickness generally 5–100 cm; sometimes with trace fossils | Quartzarenite | Planar bed lower and upper flow in tidal flat | Top Quartzite |
Low-angle (<10) |
Sl | Medium to fine sand; small wedge-shaped sets | Quartzarenite | Oscillation of wave swash and backswash in intertidal | Top Quartzite |
Rippled | Sr | Medium to fine sand wave and interference ripples set thickness generally 2–80 cm | Quartzarenite, sometimes litharenite | Deposition from traction current ripples with low indices (5–7) related to wave-induced currents in tidal flat | Top Quartzite |
Massive | Sm | Medium sand and massive to crudely bedded | Quartzarenite | Gravity and turbulence currents | Top Quartzite |
Scour pits | Se | Coarse-fine sand; base of Sp and Sh lithofacies; set thickness 1–10 cm | Muddy pebble quartzarenite | Scour fills in base of tidal channels | Top Quartzite |
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Interbedded sandstones-mudstone | |||||
Flaser bedded | Sr(Fl) | Lenticular mud interbeds sand | Quartzarenite-siltstone | Alternating strong and weak flows in intertidal | Top Quartzite |
Wavy bedded | Sr/Fl | Rippled sand interbeds mud | Quartzarenite-siltstone | Alternating strong and weak flows in upper intertidal | Top Quartzite |
Lenticular bedded | Fl(Sr) | Rippled sand lenses in mud | Quartzarenite-siltstone | Alternating strong and weak flows in upper intertidal-supratidal | Top Quartzite |
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Mudstone | |||||
Laminated or rippled | Fl | Often silt size 1-2 cm layers; sometimes with ripple and mud cracks | Siltstone; claystone | Deposition from traction current in upper intertidal and supratidal | Top Quartzite |
Laminated marl | Flc | Silt and clay size with carbonates planar laminate and cross-laminated | Silty lime mudstone | Low-energy environments (subtidal lagoon) | Deranjal Fm |
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Carbonate | |||||
Massive | Dim | Carbonate intraclasts; pebble-sized; intraformational | Dolomitic intraclastic grainstone | Debris flow and turbulence currents in tidal channels | Deranjal Fm |
Planar cross-bedded | Dp | Sand-sized grains; herringbone cross-bedding | Dolomitic ooid grainstone to packstone | Tidal channel deposits in intertidal and subtidal | Deranjal Fm |
Rippled | Dr | Wavy and climbing ripples; set thickness 0.1–0.8 m | Dolomitic ooid grainstone to packstone | Tidal channel deposits in intertidal and subtidal | Deranjal Fm |
Laminated | Dl | Set thickness 0.1–2 m; sometimes with sand and mud | Dolomudstone; sandy dolomudstone | Deposited in tidal setting (often upper intertidal to supratidal) | Deranjal Fm |
Stromatolitic | Ds | Set thickness 0.5–3 m; sometimes with sand lenses | Dolomitic boundstone; dolomudstone | Deposited in tidal setting (often intertidal) | Deranjal Fm |
Flaser-wavy bedded | Dr/Dl | Lenticular calcilutite interbeds calcarenite; flaser and wavy bedded | Dolomitic grainstone; dolomudstone | Alternating strong and weak flows in intertidal setting | Deranjal Fm |
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Interbedded sandstones-dolomudstone | |||||
Flaser-wavy bedded | Sr/Dl | Rippled sand interbeds laminated dolomudstone | Quartzarenite-dolomudstone | Alternating strong and weak flows in upper intertidal to supratidal | Padeha Fm |
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Evaporate | |||||
Laminated | El | Set thickness 0.2–1.5 m; enterolithic folding | Gypsum, sometimes anhydrite | Subaerial precipitation in sabkha or supratidal | Padeha Fm |
Laminated or rippled | Efl | Evaporate interbeds mud; sometimes mud crocks, salt casts | Gysiferous mudstone | Subaerial-subaqueous precipitation in sabkha or supratidal | Padeha Fm |
Massive | Efm | Evaporate patch in mud sometimes mud; cracks and rain spots | Gypsum-siltstone | Subaerial-subaqueous precipitation in sabkha or supratidal | Padeha Fm |
Laminated and |
Edl | Evaporate interbeds dolomite | Gypsum-dolomudstone | Subaerial-subaqueous precipitation in sabkha or supratidal | Padeha Fm |
Comparison of sedimentary structures in the siliciclastic, carbonate, and mixed siliciclastic-carbonate tidalites. For more details see text.
Sedimentary structures |
Siliciclastic tidalites (Top Quartzite Unit) | Mixed tidalites (Padeha Formation) | Carbonate tidalites (Deranjal Formation) | Petrofacies | Microfacies |
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Normal graded bedding |
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Qtz and Lit | Grst |
Intraformational clasts |
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Qtz | Intra Grst |
Scour pits |
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Qtz and Lit | Grst |
Wavy ripples |
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Qtz and Lit | Grst-Pkst |
Current ripples |
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Qtz and Lit | Wkst and Dol |
Interference ripples |
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Qtz and Lit |
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Climbing ripples |
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Grst-Wkst |
Trough cross-beds |
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Qtz and Lit | Grst |
Planar cross-beds |
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Qtz and Lit | Grst-Pkst |
Herringbone cross-beds |
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Qtz | Grst-Pkst |
Hummocky cross-beds |
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Qtz |
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Reactivation surfaces |
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Qtz and Lit | Grst |
Flaser bedding |
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Qtz and Stst | Grst-Pkst |
Wavy bedding |
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Qtz and Stst | Grst-Wkst |
Lenticular bedding |
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Stst and Qtz | Dol |
Polygonal mudcracks |
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Stst and Clst |
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V-shaped mudcracks |
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Stst and Clst | Dol |
Syneresis cracks |
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Stst |
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Raindrop imprints |
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Stst and Clst |
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Salt casts |
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Dol |
Pseudomorph calcite |
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Dol |
Entrolithic folding |
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Gyp and Any |
Stromatolite structures |
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Dol and Bdst |
Tepee structures |
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Dol |
Fenestral fabric |
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Dol |
Tracks and trails |
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Qtz and Stst | Grst-Wkst |
Absent (
Comparison of ripple marks in Sr lithofacies. (a) Three types of ripples in the sandstones of Top Quartzite. (1) Double crest wavy ripples. (2) Wavy and current ripples. (3) Interference ripples. (b) Catenary crest of current ripples in the Top Quartzite sandstones. (c) Sinuous-straight crest of wavy ripples in sandstone of Padeha Formation. (d) and (e) Climbing and wavy ripples in the carbonate tidalites of Deranjal Formation.
Cross-beds in tidalites. (a) Herringbone cross-bedded in Sp lithofacies of Top Quartzite sandstones. (b), (c), and (d) Herringbone, planar, and ripple cross-beds in carbonate tidalites (Deranjal Formation). (e) Hummocky cross-beds in sandstone layers in Padeha Formation. (f) Reactivation surfaces (arrows) in the sandstone of Padeha Formation.
Field photos of the heterolithic layers in studied tidalites. (a) Flaser bedding (Sr(Fl) lithofacies) in the Padeha Formation. Arrow indicates a mudstone lens. (b) Flaser bedding (Dr/Dl lithofacies) in the carbonate tidalites (Deranjal Formation). Arrow indicates a dolomudstone lens. (c) Wavy bedding in the Top Quartzite. (d) Wavy bedding in the Padeha Formation. (e) and (f) Interbedded sandstone and dolomudstone (Sr/Dl) in the mixed tidalites of Padeha Formation. (g) Lenticular bedding in the supratidal setting of Padeha Formation. Arrow indicates a sandstone lens.
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
Comparison of architectural elements and their interpretation in three tidalite systems.
Architectural element | Code | Lithofacies assemblage | Geometry and relationship | Sedimentary environment |
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(I) | ||||
Channel deposits | CH | Gcm, Gms, Gt, Sp, St, Sr, |
Erosional base; wedge shaped (laterally less than 50 m) | Tidal channels in intertidal and subtidal settings |
Lateral-accretion macroform | LA | Sp, St, Sr, Sl | Erosional base; lense shaped | Meandering (ebb channels), in intertidal setting |
Sandy bedforms | SB | Sp, Sl, Sh, Sr, Sm, Fl, |
Sheet and blanket shaped | Sandy flat in intertidal setting |
Muddy sets | FF | Fl, Fl(Sr), Sp, Sr | Laminated mudstone with sandstone lenses | Supratidal setting |
(II) | ||||
Channel deposits | CH | Dim, Dp, Dr, Dsd, Dsp, |
Erosional base; wedge shaped (70 m up to 100 m) | Tidal channels in intertidal and subtidal settings |
Carbonate bedforms | CB | Dr, Dsd, Dsp, Dl, Dr/Fl, |
Sheet and domal shaped | Intertidal setting |
(III) | ||||
Channel deposits | CH | St, Sp, Sr, Sl, Sh, Se, Ds | Erosional base; wedge shaped |
Tidal channels in intertidal and subtidal settings |
Lateral-accretion macroform | LA | Sp, St, Sr, Sl | Erosional base; lense shaped | Meandering (ebb channels), in intertidal setting |
Sandy bedforms | SB | Sp, Sl, Sh, Sr, Fl, Sr(Fl), Sr/Fl, Ds, Dl | Sheet and platy shaped | Sandy flat in intertidal setting |
Muddy sets | FF | Fl, Fl(Sr), Sp, Sr, Sh, Sr/Dl | Mudstone laminated with sandstone lenses | Supratidal setting |
Evaporate-muddy sets | EF | El, Efl, Efm, Edl | Evaporate layers with laminated mudstone | Upper supratidal and sabkha settings |
(I) Top Quartzite (siliciclastics), (II) Deranjal Formation (carbonates), (III) Padeha Formation (mixed siliciclastic-carbonate).
Field photos and photomicrographs of some important sedimentary structures in supratidal setting. (a) Polygonal mud cracks in the Top Quartzite. (b) Mud cracks on the rippled sandstones that show upper intertidal conditions. (c) Large-scale mud cracks in the supratidal deposits (Top Quartzite). (d) V-shaped mud cracks in carbonate tidalites (Deranjal Formation). (e) Shrinkage and polygonal mud cracks in supratidal setting of the Padeha Formation. (f) Syneresis cracks in the Padeha Formation. (g) V-shaped cracks in mudstone petrofacies (Padeha Formation). (h) V-shaped cracks in dolomudstone microfacies (Padeha formation). (i) Raindrop imprints in the muddy sediments of the Padeha Formation. (j) Salt casts or halite casts in the Padeha Formation. (k), Enterolithic folding in the evaporite deposits (Padeha Formation).
The carbonate tidalites are described from the Upper Cambrian carbonate deposits in northwestern Kerman. These carbonate deposits comprise the upper lithostratigraphic unit of the Kuhbanan Formation and can be equivalent to the Deranjal Formation in Tabas area or correlated with the units 2 and 3 of the Mila Formation in the Alborz Mountains [
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
Field photos and photomicrographs of stromatolite and associated sedimentary structures in the carbonate tidalites. (a) Cross section of planar and domal stromatolites in the Deranjal Formation. (b) Domal stromatolite (small scale) in the Deranjal Formation. (c) Boundstone microfacies (stromatolitic) in the Deranjal Formation. (d) Large-scale domal stromatolite. These structures are made up of small-scale stromatolites community. (e) Field photo shows that domal stromatolites are often the last layers of channel deposits. (f) Close-up view of planar stromatolite in the Deranjal Formation. (g) Cross section of domal stromatolite in the Deranjal Formation (close-up view). (h) Photo of stromatolite structures in the Padeha Formation. (i) Tepee structures in the Padeha Formation (without crest fracturing). (j) Tepee structures associated with stromatolite in the Padeha Formation (with crest fracturing (arrow)).
Schematic vertical columns and comparison of channel deposits (CH element) in three tidalite systems.
Filed photos show characteristics of channel deposits in the siliciclastic and mixed tidalites. (a), (b), and (c) Photos show channel deposits in the Top Quartzite and their lithofacies assemblage. Red lines separate fining upward cycles. (d) Photo shows vertical and lateral (67 m) variations in channel deposits in the Padeha Formation. (e) lateral accretion (LA element) in meandering (ebb channels) in the Padeha Formation. (f) Close-up view of a fining and shallowing upward cycle in the mixed tidalites (Padeha Formation). (g) Photo of sandy bedforms element (SB) in the Padeha Formation. (h) Photo of sandy bedforms element (SB) in the Top Quartzite sandstones.
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
Based on the lithological diversity and the presence of different flow regimes in this depositional system, the mixed siliciclastic-carbonate 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., [
The Padeha Formation was first measured and introduced by Ruttner et al. [
Based on the sedimentological analysis, 17 lithofacies and 4 architectural elements (SB, LA, FF, and EF) were recognized in the Padeha Formation and are classified into sandstone, mudstone, interbedded sandstone-mudstone, carbonate, interbedded sandstone-dolomite, and evaporite lithofacies associations (Tables
In the Dahane-Kalot section, the Padeha Formation is 320 m thick. Based on the field observations, three lithostratigraphic units were described. The lower unit of the formation consists of a 97 m thick succession of sandstone-dolomite (Sp, Sr, Sh, Ds, Dl, Sr(Fl), Sr/Fl. Fl(Sr), and Fl lithofacies). The middle unit of the Padeha Formation with 207 m thickness is composed of sandstone-siltstone with Sp, St, Sr, Sl, Sh, Se, Ds, Dl, Sr/Fl. Fl(Sr), and Fl lithofacies. The lithology of the upper unit is dominated by shale-sandstone consisting of a 20 m thick succession of Sh, Se, Sr, Fl(Sr), and Fl lithofacies. The facies analysis revealed that the sediments of the lower and middle units were deposited in intertidal subenvironment, while the identified lithofacies of the upper unit were deposited in supratidal subenvironment.
The Padeha Formation in the Sarashk section, with 297 m thickness, is composed of three lithostratigraphic units. The sandstone of the lower unit (149 m thickness) consist of Sr/Fl, Sr(Fl), Se, Sl, Sh, Sr, St, and Sp lithofacies, deposited in intertidal and partially subtidal subenvironments. The sediments of the middle unit (112 m thickness) are dominated by shale-dolomite and sandstone-dolomite with Fl, Efm, El, Se, St, Sr, Dl, Sr/Dl, and Fl(Sr) lithofacies, indicating supratidal and upper intertidal zones. The upper unit with 36 m thickness is composed of white sandstone. The identified lithofacies include Sl, Sr, St, Sp, Fl, and Sr/Fl. These lithofacies were deposited in an intertidal subenvironment (Figure
Generally, the fining upward cycles and the sedimentary structures (Table
The identified tidalites in three depositional systems are compared, based on structural, textural, and architectural elements, through the following sections.
Shanmugam [
He et al. [
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
Herringbone cross-beds and reactivation surfaces are the other sedimentary structures in the studied tidalites (Figure
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
Mud cracks and raindrop imprints are the two major sedimentary structures found in tidal flat deposits and are well preserved within the siliciclasts (Figure
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 [
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.
Ooids, intraclasts, and peloids are the most common grains in the carbonate deposits of the Deranjal Formation. The matrix or the cement is also considered as a useful factor in interpretation of microfacies (e.g., [
Generally, dolomitic mudstone with fenestral fabric, dolomitic pelloidal wackstone-packstone, ooidal-intraclastic packstone, and domal stromatolitic boundstones indicate low-energy conditions of subtidal lagoon (e.g., [
The identified architectural elements within tidal deposition systems are CH. LA, SB, CB, FF, and EF (Table
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 [
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
In the channel deposits of the mixed siliciclastic-carbonate 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
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
Field photos and photomicrograph show the characteristics of channel deposits in the carbonate tidalites (Deranjal Formation). (a) Tidal channel deposits between subtidal lagoon deposits (Flc lithofacies). (b) Domal stromatolites on the channel deposits (arrows). (c) and (d) Close-up view of lithofacies assemblage of channel deposits in the carbonate tidalites. (e) Photomicrograph of tidal channel deposits. Dolomitic ooid grainstone are common at the base of channel deposits and generally changes to, stromatolite toward the top. Arrows show v-shape cracks in stromatolite.
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 [
This element is considered as a part of channel deposits formed by lateral accretion of meandering channels (e.g., [
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 [
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.
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., [
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 siliciclastic-carbonate 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) [
The El, Efm, and Efl lithofacies within the Padeha Formation were deposited in such conditions. According to the classification of sabkhas [
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.
(1) The Lower-Middle Cambrian Top Quartzite is a representative of siliciclastic tidal system. It consists of conglomerate (Gt, Gms, and Gcm), sandstone (Sp, St, Sh, Sl, Sr, Sm, and Se), interbedded sandstone-mudstone (Sr(Fl), Sr/Fl, and Fl(Sr)), and mudstone (Fl) lithofacies. The lithofacies associations were formed in three CH, SB, and FF (CH) elements.
(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.
(3) Tidalites from a mixed siliciclastic-carbonate system were described from the siliciclasts, carbonates, and evaporites of the Padeha Formation (Lower-Middle Devonian). 17 lithofacies were recognized in these deposits and are classified into six facies associations. The lithofacies include sandstone (Sp, St, Sh, Sl, Sr, and Se), mudstone (Fl), interbedded sandstone-mudstone (Sr(Fl), Sr/Fl, and Fl(Sr)), carbonate (Ds and Sl), interbedded sandstone-dolomite (Sr/Dl), and evaporite (El, Efm, Efl, and Edl). The lithofacies associations are subdivided into five CH, LA, SB, FF, and EF elements that were deposited in subtidal-intertidal, intertidal, supratidal, and sabkha environments, respectively.
(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 V-shaped 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 sandstone-mudstone) 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.
This work is a part of a PhD thesis of Hamed Zand-Moghadam, which is supported by the Department of Geology at Ferdowsi University of Mashhad, Iran. The authors would like to acknowledge their logistical and financial support. They are grateful to Dr. Amir Hossin Rahiminejad for editing the paper and Dr. Javad Hasani, Dr. Ahmad Raoufian, and Dr. Ali Aghaei for their contributions to this study, especially during fieldwork.