Sedimentology and sediment geochemistry of the pelagic Paryab section (Zagros Mountains, Iran): implications for sea level fluctuations and paleoenvironments in the late Paleocene to middle Eocene

AbstractSedimentological and geochemical records are presented for an upper Paleocene to middle Eocene deep-water pelagic succession of the Pabdeh Formation in the Paryab section, Zagros Mountains, NW, Iran. In this study, grain-size statistical parameters, cumulative curves, and bivariate analysis on twenty-five sediment samples were used to decipher depositional processes and paleoenvironments. XRD analysis of the fine-grained silt to clay sediments indicates that quartz, calcite, ankerite/dolomite, and clay minerals such as illite, chlorite, and kaolinite constitute the main minerals within these sediments. Elemental and isotopic chemostratigraphies are used to infer depositional conditions and sea level trends through time. TOC-CaCO3 trends of the samples are used to interpret the type of deposition and sediment accumulation rates, rhythmic bedding, and identification of regressional and transgressional phases. In the studied section, the manganese contents exhibit a declining trend along the lowstand systems tract that terminates in a sea level lowstand and the subsequent start of a transgressive trend. Some geochemical parameters such as Mn values and δ13C contents of sediments along a sequence can be used as potential sea level proxies that are tested in this study. The Paleocene-Eocene Thermal Maximum (PETM) interval of the Pabdeh Formation coincides with increasing Mn contents and Mn/Al ratios. Ti/Al and Si/Al ratios show contrasting trends to Mn values and Mn/Al ratios. Generally, elemental and isotopic results of the Pabdeh Formation confirm the presence of a long-term three-stage sea level cycle in the studied interval that is related to the PETM event. Based on elemental analyses such as Co, Mo, Ni, V, and Cr contents, the Pabdeh Formation sediments were deposited in suboxic to slightly anoxic conditions.

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Contrasting facies patterns between river-dominated and symmetrical wave-dominated delta deposits

Journal of Sedimentary Research ◽

10.2110/jsr.2020.131 ◽

2021 ◽

Vol 91 (3) ◽

pp. 262-295

Author(s):

BRIAN J. WILLIS ◽

TAO SUN ◽

R. BRUCE AINSWORTH

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Preferential Flow ◽

Return Flow ◽

Lateral Migration ◽

Littoral Drift ◽

Delta Front ◽

Reference Case ◽

Depositional Processes ◽

The Impact

Abstract Process-physics-based, coupled hydrodynamic–morphodynamic delta models are constructed to understand preserved facies heterogeneities that can influence subsurface fluid flow. Two deltaic systems are compared that differ only in the presence of waves: one river dominated and the other strongly influenced by longshore currents. To understand an entire preserved deltaic succession, the growth of multiple laterally adjacent delta lobes is modeled to define delta axial to marginal facies trends through an entire regressive–transgressive depositional succession. The goal is to refine a facies model for symmetrical wave-dominated deltas (where littoral drift diverges from the delta lobe apex). Because many factors change depositional processes on deltas, the description of the river-dominated example is included to provide a direct reference case from which to define the impact of waves on preserved facies patterns. Both systems display strong facies trends from delta axis to margin that continued into inter-deltaic areas. River-dominated delta regression preserved a dendritic branching of compensationally stacked bodies. Transgression, initiated by sea-level rise, backfilled the main channel and deposited levees and splays on the submerging delta top. Wave-dominated deltas developed dual clinoforms: a shoreface clinoform built as littoral drift carried sediment away from the river month and onshore, and a subaqueous delta-front clinoform composed of sediment accumulated below wave base. Although littoral drift in both directions away from the delta axis stabilized the position of the river at the shoreline, distributary-channel avulsions and lateral migration of river flows across the subaqueous delta top produced heterogeneities in both sets of clinoform deposits. Separation of shoreface and subaqueous delta-front clinoforms across a subaqueous delta top eroded to wave base produced a discontinuity in progradational vertical successions that appeared gradual in some locations but abrupt in others. Littoral drift flows away from adjacent deltas converged in inter-deltaic areas, producing shallow water longshore bars cut by wave-return-flow channels with associated terminal mouth bars. Transgression initiated by sea-level rise initially led to vertical aggradation of wave-reworked sheet sands on the subaqueous delta top and then retreating shoreface barrier sands as the subaerial delta top flooded. Pseudo inter-well flow tests responded to local heterogeneities in the preserved deposits. As expected, abandoned channels in the river-dominated case defined shoreline-perpendicular preferential flow paths and wave-dominated delta deposits are more locally homogeneous, but scenarios for development of more pronounced shore-parallel heterogeneity patterns for wave-influenced deltas are discussed. The results highlight the need to consider the dual clinoform nature of wave-dominated delta deposition for facies prediction and subsurface interpretation.

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Continental temperature seasonality from Eocene Warmhouse to Oligocene Coolhouse — A model-data comparison

10.5194/egusphere-egu21-8613 ◽

2021 ◽

Author(s):

Agathe Toumoulin ◽

Yannick Donnadieu ◽

Delphine Tardif ◽

Jean-Baptiste Ladant ◽

Alexis Licht ◽

...

Keyword(s):

Sea Level ◽

Northern Hemisphere ◽

Surface Albedo ◽

Middle Eocene ◽

Late Eocene ◽

Strong Increase ◽

High Latitudes ◽

Sea Level Changes ◽

Annual Range ◽

Temperature Seasonality

At the junction of warmhouse and coolhouse climate phases, the Eocene Oligocene Transition (EOT) is a key moment in the history of the Cenozoic climate. Yet, while it is accompanied by severe extinctions and biodiversity turnovers, terrestrial climate evolution remains poorly resolved. On lands, some fossil and geochemistry records suggest a particularly marked cooling in winter, which would have led to the development of more pronounced seasons (higher Mean Annual Range of Temperatures, MATR) in certain regions of the Northern Hemisphere. This type of climate change should have had consequences on biodiversity and an implication in some of the fauna and flora renewals described at the EOT. However, this season strengthening has been studied only superficially by model studies, and questions remain about the geographical extent of this phenomenon and the associated climatic processes. Although other components of the climate system vary seasonally (e.g., precipitation, wind), we therefore focus on the seasonality of temperatures only.In order to better understand and describe temperature seasonality change patterns from the middle Eocene to the early Oligocene, we use the Earth System Model IPSL-CM5A2 and a set of simulations reconstructing the EOT through three major climate forcings: pCO2 decrease (1120/840 to 560 ppm), the Antarctic ice-sheet (AIS) formation, and the associated sea-level decrease (-70 m).&#160;Our results suggest that seasonality changes across the EOT rely on the combined effects of the different tested mechanisms which result in zonal to regional climate responses. Sea-level changes associated with the earliest stage of the AIS formation may have also contributed to middle to late Eocene MATR reinforcement. We reconstruct strong and heterogeneous patterns of seasonality changes across the EOT. Broad continental areas of increased MATR reflect a strengthening of seasonality (from 4&#176;C to > 10&#176;C increase of the MATR) in agreement with MATR and Coldest Month Mean Temperatures (CMMT) changes indicated by a review of existing proxies. pCO2 decrease induces a zonal pattern with alternating increasing and decreasing seasonality bands. In the northern high-latitudes, it results in sea-ice and surface albedo feedback, driving a strong increase in seasonality (up to 8&#176;C MATR increase). Conversely, the onset of the AIS is responsible for a more constant surface albedo, which leads to a strong decrease in seasonality in the southern mid- to high-latitudes (> 40&#176;S). Finally, continental areas emerged due to the sea level lowering cause the largest increase in seasonality and explain most of the global heterogeneity in MATR changes patterns. The seasonality change patterns we reconstruct are consistent with the variability of the EOT biotic crisis intensity across the Northern Hemisphere.

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Strontium Isotope Stratigraphy at Middle Eocene from the Zagros Mountains of Iran

Sixth Arabian Plate Geology Workshop ◽

10.3997/2214-4609.201602391 ◽

2016 ◽

Author(s):

B. Almasinia ◽

S. Ali Moallemi ◽

F. Fürsich ◽

M. Ahmad Hosseini

Keyword(s):

Middle Eocene ◽

Strontium Isotope ◽

Zagros Mountains ◽

Strontium Isotope Stratigraphy ◽

Isotope Stratigraphy

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Geochronology and Lu-Hf isotopic study of the granodioritic pulse in the Qaradagh batholith (NW Iran)

10.5194/egusphere-egu2020-322 ◽

2020 ◽

Author(s):

Vartan Simmonds ◽

Mohssen Moazzen ◽

Gültekin Topuz ◽

Ali Mohammadi

Keyword(s):

Middle Eocene ◽

Main Body ◽

Isotopic Study ◽

Quartz Syenite ◽

Magmatic Source ◽

Nw Iran ◽

The North ◽

Magmatic Rocks ◽

Depleted Mantle ◽

Northwest Iran

The Qaradagh batholith in northwest Iran mainly comprises granodioritic rocks, which makes more than 50% of the batholith. This lithology is the first intrusive pulse within this batholith and the oldest Tertiary magmatism in the region, though other younger pulses of granite, diorite, quartz-diorite, syenite, quartz-syenite, monzonite, quartz-monzonite, quartz monzodiorite, monzogranite and gabbro intruded the main body. These magmatic rocks have intruded the Upper Cretaceous and Paleogene sedimentary, volcano-sedimentary and igneous rocks.The Qaradagh batholith hosts vein-type and some local stock-work type Cu&#8211;Au&#8211;Mo mineralization, especially in its central parts, while skarn-type deposits have been formed at its contacts with peripheral carbonate rocks. Its extension towards the north into the neighboring south Armenia (which is part of the South Armenian Block) is known as the Meghri&#8211;Ordubad pluton (MOP), which hosts several large porphyry Cu&#8211;Mo deposits and other precious and base metal mineralizations. U&#8211;Pb geochronology on the zircons separated from the granodioritic unit yielded a weighted 206Pb/238U mean age of 43.81 &#177; 0.18 (MSWD=1.38) and a Pb*/U concordia age of 44.04 &#177; 1.00 Ma (MSWD= 24), which correspond to Middle Eocene.Since the Qaradagh batholith and especially its earliest magmatic phase are considered as the oldest plutonic event of the Cenozoic age in northwest Iran, thus this investigation testifies to the fact that intrusive activities of Tertiary in this region has commenced in Middle Eocene, contrary to the opinion of the majority of authors who believe that plutonism in this region occurred during Oligocene.However, this age is much older than the molybdenite Re&#8211;Os ages of quartz-sulfide veins hosted by granodioritic rocks (25.19 &#177; 0.19 to 31.22 &#177; 0.28 Ma), indicating that mineralization in this batholith is related to another much younger intrusive phase, and even to several phases, as the published ages of molybdenites from various veins and mineralized zones show a large interval. Comparing the obtained age with those from the MOP in southern Armenia indicate that southern part of the MOP is almost coeval with the emplacement of the granodioritic rocks in Qaradagh batholith.The U and Th contents of the zircons range from 17.1 to 1534.0 and from 4.9 to 641.0 ppm, respectively, with Th/U ratios between 0.66 and 5.82 (mean of 1.26), indicating a magmatic source. Meanwhile, the &#949;Hf(t) values of the zircons range from 8.7 to 11.1 with the mean of 9.5, which are plotted between the CHUR and the Depleted Mantle evolution lines, indicating a juvenile and homogeneous magmatic source and the predominance of mantle-derived magmas with limited crustal assimilation.

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High-resolution Stratigraphy of Holocene Lagoon Terraces of Southern Brazil

Quaternary Research ◽

10.1016/j.yqres.2014.08.007 ◽

2015 ◽

Vol 83 (1) ◽

pp. 52-65 ◽

Cited By ~ 1

Author(s):

Natália B. dos Santos ◽

Ernesto L.C. Lavina ◽

Paulo S.G. Paim

Keyword(s):

High Resolution ◽

Sea Level ◽

Radiometric Dating ◽

Sea Level Changes ◽

Relative Sea Level ◽

Base Level ◽

Depositional Processes ◽

Close Relationship ◽

Northern Portion ◽

Depositional Architecture

AbstractThe northern portion of the coastal plain of the Rio Grande do Sul State (southernmost Brazil) comprises an outer sandy barrier that protects a complex lagoon system formed during the Holocene. The terraces of three different lagoons (Gentil, Malvas and Pinguela) formed along their margins record the depositional processes and the relative base level changes over the past 5000 yr. Therefore, our main objective was to characterize and quantify base level fluctuations from the study of these terraces, to correlate them to sea-level changes and to describe the depositional architecture related to the distinct sea-level stages (high-resolution sequence stratigraphy). Satellite images, topographic and GPR profiles, auger holes and radiometric dating were used. The main results indicate a close relationship between relative base level and relative sea-level changes, a stillstand period just after the last transgressive maximum (4840–4650 cal yr BP) and a subsequent overall relative sea-level fall of about 3 m. Both a normal (highstand systems tract) and a forced regression (falling-stage systems tract) controlled the geological record preserved in the terraces. The highstand (older terrace) is characterized by agradational bedding, whereas the falling stage comprises three progradational sets (terraces) bounded by erosive surfaces related to smaller-scale sea-level drops.

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Late Weichselian and Holocene Relative Sea-level History of Bröggerhalvöya, Spitsbergen

Quaternary Research ◽

10.1016/0033-5894(87)90048-2 ◽

1987 ◽

Vol 27 (1) ◽

pp. 41-50 ◽

Cited By ~ 77

Author(s):

Steven L. Forman ◽

Daniel H. Mann ◽

Gifford H. Miller

Keyword(s):

Sea Level ◽

Barents Sea ◽

Relative Sea Level ◽

Norwegian Sea ◽

Depositional Processes ◽

Before And After ◽

History Of ◽

Ice Conditions ◽

Late Weichselian ◽

Raised Beaches

AbstractRadiocarbon-dated whalebones from raised beaches record a relative sea-level history for Bröggerhalvöya, western Spitsbergen that suggest a two-step deglaciation on Svalbard at the end of the late Weichselian glaciation. The late Weichselian marine limit was reached at about 13,000 yr B.P. and was followed by relatively slow emergence until about 10,000 yr B.P. either in response to ice unloading in the Barents Sea, initial retreat of local fjord glaciers, or some combination of the two. Rare whale skeletons dating between 13,000 and 10,000 yr B.P. indicate that the Norwegian Sea was at least seasonally ice free during that interval. Deglaciation of Spitsbergen is recorded by the rapid emergence of Bröggerhalvöya after 10,000 yr B.P. This was followed by a transgression during the mid-Holocene, here named the Talavera Transgression, and another in modern times. Raised beach morphologies suggest striking differences in nearshore depositional processes before and after 10,000 yr B.P. that are probably related to changes in the rate of uplift and in sea-ice conditions.

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Facies patterns and depositional processes in two Frasnian mixed siliciclastic-carbonate systems in the Cantabrian Mountains, northwest Spain

Geologos ◽

10.2478/logos-2020-0001 ◽

2020 ◽

Vol 26 (1) ◽

pp. 1-23

Author(s):

Gerard B.S. van Loevezijn ◽

J.G.M. Raven

Keyword(s):

Sea Level ◽

Cantabrian Mountains ◽

Third Order ◽

Relative Sea Level ◽

Sea Level Fluctuations ◽

Depositional Processes ◽

Gravity Flows ◽

Entry Points ◽

Basin Geometry ◽

Order Sequence

AbstractRelative sea level fluctuations during the Frasnian generated two shallow-marine, mixed siliciclastic-carbonate successions in the Devonian Asturo-Leonese Basin. Each system represents a third-order sequence-stratigraphical unit deposited in the same basin during comparable extreme greenhouse conditions without nearby fluvial entry points. Depositional control on the siliciclastic and carbonate distribution was driven by relative sea level fluctuations, basin geometry, availability of sand and the way sediment was distributed by shelf currents. Early Variscan flexural bending of the continental crust changed the basin shape from a shelf with a gradual profile and low dip (early Frasnian) towards a shelf with a steep depositional dip (late Frasnian). Shelf distribution changed from along-shelf transport (early Frasnian) towards offshore-directed gravity flows (late Frasnian). As a consequence, siliciclastic-carbonate distribution changed from a predominance of skeletal carbonate in the proximal shoreface – foreshore area and siliciclastic predominance distally (early Frasnian), to a distribution pattern with proximal shoreface skeletal carbonates, offshore muddy carbonates and a siliciclastic zone in between where gravity flows distributed the siliciclastic sediment down dip (late Frasnian).

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Statistical modeling of the long-range-dependent structure of barrier island framework geology and surface geomorphology

Earth Surface Dynamics ◽

10.5194/esurf-6-431-2018 ◽

2018 ◽

Vol 6 (2) ◽

pp. 431-450 ◽

Cited By ~ 6

Author(s):

Bradley A. Weymer ◽

Phillipe Wernette ◽

Mark E. Everett ◽

Chris Houser

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Long Range ◽

Moving Average ◽

Quantitative Measure ◽

Barrier Island ◽

Barrier Islands ◽

Wave Number ◽

Statistical Parameters ◽

Padre Island

Abstract. Shorelines exhibit long-range dependence (LRD) and have been shown in some environments to be described in the wave number domain by a power-law characteristic of scale independence. Recent evidence suggests that the geomorphology of barrier islands can, however, exhibit scale dependence as a result of systematic variations in the underlying framework geology. The LRD of framework geology, which influences island geomorphology and its response to storms and sea level rise, has not been previously examined. Electromagnetic induction (EMI) surveys conducted along Padre Island National Seashore (PAIS), Texas, United States, reveal that the EMI apparent conductivity (σa) signal and, by inference, the framework geology exhibits LRD at scales of up to 101 to 102 km. Our study demonstrates the utility of describing EMI σa and lidar spatial series by a fractional autoregressive integrated moving average (ARIMA) process that specifically models LRD. This method offers a robust and compact way of quantifying the geological variations along a barrier island shoreline using three statistical parameters (p, d, q). We discuss how ARIMA models that use a single parameter d provide a quantitative measure for determining free and forced barrier island evolutionary behavior across different scales. Statistical analyses at regional, intermediate, and local scales suggest that the geologic framework within an area of paleo-channels exhibits a first-order control on dune height. The exchange of sediment amongst nearshore, beach, and dune in areas outside this region are scale independent, implying that barrier islands like PAIS exhibit a combination of free and forced behaviors that affect the response of the island to sea level rise.

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Coral meets Milankovitch – or: time-distribution in shallow-marine carbonate sequences

10.5194/egusphere-egu21-1766 ◽

2021 ◽

Author(s):

André Strasser

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Time Distribution ◽

Time Window ◽

Accumulation Rates ◽

Sedimentary Record ◽

Shallow Marine ◽

Subaerial Exposure ◽

Depositional Processes ◽

Marine Carbonate

It is challenging to compare Recent or Holocene accumulation rates of shallow-marine carbonates with accumulation rates interpreted from the fossil sedimentary record. Today, a single coral branch can grow up to 10 cm/year, and vertical accumulation rates may reach 1.4 cm/year if the ecological conditions are favorable for the carbonate-producing organisms and if there is space to accommodate the sediment. However, due to common reworking and transport by waves and currents, and because of potential subaerial exposure, the time-distribution within the sedimentary record is highly irregular.In ancient carbonate sequences, this time-distribution is difficult to evaluate, and a time-resolution as high as possible has to be sought for. Identification of the record of orbital cycles (Milankovitch cycles) is the best way to obtain a relatively narrow time-window, which in the best case corresponds to the 20-kyr precession cycle. During green-house conditions, orbitally-induced climate cycles translated into more or less symmetrical sea-level cycles, which at least partly controlled sediment production and accumulation. This allows for a sequence-stratigraphic subdivision of each individual depositional sequence. Thus, a time-frame is given for the interpretation of facies evolution and sedimentary structures within such a sequence.Based on this hypothesis, two examples are presented, both from the Swiss and French Jura Mountains. A 2-m thick (decompacted) Oxfordian sequence displays carbonate-dominated transgressive deposits followed by marl-dominated highstand deposits. The sequence took 20 kyr to build, but sediment accumulation was episodically interrupted by storm events, and a hardground formed during maximum flooding. The maximum rate of sea-level rise is estimated at 30 cm/kyr (which is ten times slower that today&#8217;s sea-level rise). The second example is of Berriasian age and shows a 45-cm thick bed of beachrock composed of slabs of oolite. The bed overlies tidal-flat deposits and is capped by a 4-cm thick calcrete crust, over which follows a polymictic conglomerate. According to the cyclostratigraphic analysis, this sequence represents 100 kyr. Ooid production and beachrock formation can happen within a few 100 to a few 1000 years, and the formation of the calcrete took a few 1000 years more. The rest of the time available thus is represented by the transgressive surface at the base of the sequence, by subaerial exposure, and especially by the conglomerate composed of different facies that formed, were cemented, and then were reworked during several 20-kyr cycles.The conclusion is that, by careful analysis of ancient shallow-marine carbonate sequences and within a cyclostratigraphic framework, depositional processes may be reconstructed and compared with processes that can be observed and quantified in the Holocene and today, and this at comparable time-scales. Thus, a dynamic and realistic picture of the ancient depositional systems is offered. &#160;

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