An astronomical age-depth model and reconstruction of moisture availability in the sediments of Lake Chalco, central Mexico, using borehole logging data

Understanding the moisture history of low latitudes from the most recent glacial period of the latest Pleistocene to post-glacial warmth in continental tropical regions is hampered by the lack of continuous time series. We conducted downhole spectral gamma (γ) ray and magnetic susceptibility logs over 300 m of lacustrine deposits of Lake Chalco (Mexico City) to reconstruct an age-depth model using an astronomical and correlative approach, and to reconstruct long-term moisture availability. Our results suggest that the Lake Chalco sediments contain several rhythmic alternations with a quasi-cyclic pattern comparable to the Pleistocene benthic stack. This allows us to calculate a time span of about 500,000 years for this sediment deposition. We developed proxies for moisture, detrital input, and salinity, all based on the physical properties of γ-ray spectroscopy and magnetic susceptibility. Our results indicate that Lake Chalco formed during Marine Isotope Stage 13 (MIS13) and the lake level gradually increased over time until the interglacial MIS9. Moisture content is generally higher during interglacials than during glacials. However, two periods, namely MIS6 and MIS4, have higher moisture contents. We developed a model by comparing the obtained moisture proxy with climatic drivers, to understand how different climate systems drove effective moisture availability in the Chalco sub-basin over the past 500,000 years. Carbon dioxide, eccentricity, and precession are all key drivers of the moisture content of Lake Chalco over the past 500,000 years

Diagenetic factors controlling reservoir quality in the Faraghan Formation (Lower Permian), Darang Field, Southern Iran

The role of diagenesis in affecting (reduction or enhancement) reservoir quality in the Faraghan Formation in Darang #1 well was investigated. The Faraghan Formation is mainly composed of sandstone facies along with minor mudstone and siltstone and grades upward into mixed carbonate –siliciclastic facies and then to Dalan Formation carbonates. Depositional environment of this formation comprises various sub-environments of a delta setting in the lower part of the formation which grades upward into a shallow marine clastic environment in the upper part. The processes enhancing reservoir quality include dissolution of carbonate grains and cements and alteration of feldspar grains. Burial history diagram shows that after deposition during Lower Permain, the formation underwent a rapid burial up to 1000 meters below sea level in Upper Permian. Then a slight uplift (about 100 meters) and gradual burial followed up to Mid- Jurassic. Afterwards the formation experienced a series of rapid and moderate uplift from Mid-Jurassic to Tertiary when the formation uplifted to around 2500 meters above sea level. The suitable conditions resulting in dissolution took place in shallow buried sandstones. These conditions occurred two times during burial history: at the early stages of eodiagenesis and during telodiagenesis. The major processes deteriorating reservoir quality include compaction and cementation. Major cement types include carbonate cements (dolomite, siderite), clay cements (kaolinite, sericite, chlorite), silica cement and pyrite cement. The most abundant cement is the carbonate cement especially dolomite. The dolomite cement occurs as intergranular and poikilotopic forms. The most frequent clay cement is sericite which dominates in sitstones and lithicarenites. Silica cement, where present, fills all the pore spaces. The least frequent cement type is pyrite which is found in two forms of poikilotopic and framboidal. Where it is found in the form of poikilotopic cement, it massively fills the pore spaces and deteriorates the porosity and permeability of the sandstones

Atmospheric dust flux in northeastern Gondwana during the peak of the late Paleozoic ice age

The silicate mineral fraction of shallow marine carbonates archives dust contributions to the Central Persian Terranes along the northeastern margin of Gondwana (∼30°S paleolatitude), enabling reconstruction of atmospheric dust loading and circulation for intervals of the late Paleozoic ice age. The Central Persian Terranes hosted cyclic deposition of warm water carbonates from middle Pennsylvanian to earliest Permian time, and our data set includes two ∼28 m sections from the Moscovian and Asselian sampled at 20 cm intervals. Bounding surfaces between successive cycles (high-frequency sequences) are recognized by either abrupt basinward shifts in facies or subtle exposure features; these high-frequency sequences range from 1 m to 5 m thick and are interpreted to record glacioeustatic variations. Time series analysis of the dust fraction through the studied interval supports the hypothesis of orbital forcing for the dust signal. The stratigraphic pattern of the dust flux indicates minimal flux during interglacial highstands (0.19–0.27 g/cm2/kyr) and peak flux during glacial lowstands (3.77–4.57 g/cm2/kyr) after accounting for hiatal time at sequence boundaries. Grain size analysis of the dust for all samples (n = 230) reveals modal sizes (volume-based) of 1–15 µm through the Moscovian interval and 10–75 µm through the Asselian interval. Dust deposition increased during glacial times relative to interglacial times by a factor of 16 to 19. Additionally, the Asselian interval exhibits higher dust flux overall relative to the Moscovian interval, which is interpreted to reflect the more extreme icehouse conditions of the Asselian. Variation in the dust content through the studied sections provides an indicator of temporal changes in atmospheric loading that varied at both glacial–interglacial and higher-frequency (<104 yr) scales. Geochemical data reveal that the Arabian–Nubian Shield and southwestern Pangaea (South America) are the most likely sources of dust deposition in the Central Persian Terranes, with sources shifting during different phases. Increased dust flux during glacials likely reflects multiple factors, including enhanced aridity in the source region, exposure of shelf regions, and potential changes in winds. However, the discrepancy in model reconstructions of the amplitude of glacial–interglacial dust variations indicates that increased production of dust sourced by dynamic glaciation played a large role in enhancing dust flux during glacial phases.Research that contributed to the concepts presented here was funded by the National Science Foundation (EAR-1338331 and EAR-1337463 to G.S. Soreghan, EAR-1543518 to L.A. Hinnov, EAR-1337463 to N.G. Heavens, and EAR-1338440 to the University of Michigan). Supplementary funding was provided by the Eberly Family Chair (University of Oklahoma).Ye

Report on ICDP Deep Dust workshops: probing continental climate of the late Paleozoic icehouse–greenhouse transition and beyond

Chamberlin and Salisbury's assessment of the Permian a century ago captured the essence of the period: it is an interval of extremes yet one sufficiently recent to have affected a biosphere with near-modern complexity. The events of the Permian - the orogenic episodes, massive biospheric turnovers, both icehouse and greenhouse antitheses, and Mars-analog lithofacies - boggle the imagination and present us with great opportunities to explore Earth system behavior. The ICDP-funded workshops dubbed "Deep Dust," held in Oklahoma (USA) in March 2019 (67 participants from nine countries) and Paris (France) in January 2020 (33 participants from eight countries), focused on clarifying the scientific drivers and key sites for coring continuous sections of Permian continental (loess, lacustrine, and associated) strata that preserve high-resolution records. Combined, the two workshops hosted a total of 91 participants representing 14 countries, with broad expertise. Discussions at Deep Dust 1.0 (USA) focused on the primary research questions of paleoclimate, paleoenvironments, and paleoecology of icehouse collapse and the run-up to the Great Dying and both the modern and Permian deep microbial biosphere. Auxiliary science topics included tectonics, induced seismicity, geothermal energy, and planetary science. Deep Dust 1.0 also addressed site selection as well as scientific approaches, logistical challenges, and broader impacts and included a mid-workshop field trip to view the Permian of Oklahoma. Deep Dust 2.0 focused specifically on honing the European target. The Anadarko Basin (Oklahoma) and Paris Basin (France) represent the most promising initial targets to capture complete or near-complete stratigraphic coverage through continental successions that serve as reference points for western and eastern equatorial Pangaea. © 2020 Copernicus GmbH. All rights reserved

Report on ICDP Deep Dust workshops: probing continental climate of the late Paleozoic icehouse–greenhouse transition and beyond

Chamberlin and Salisbury's assessment of the Permian a century ago captured the essence of the period: it is an interval of extremes yet one sufficiently recent to have affected a biosphere with near-modern complexity. The events of the Permian - the orogenic episodes, massive biospheric turnovers, both icehouse and greenhouse antitheses, and Mars-analog lithofacies - boggle the imagination and present us with great opportunities to explore Earth system behavior. The ICDP-funded workshops dubbed "Deep Dust," held in Oklahoma (USA) in March 2019 (67 participants from nine countries) and Paris (France) in January 2020 (33 participants from eight countries), focused on clarifying the scientific drivers and key sites for coring continuous sections of Permian continental (loess, lacustrine, and associated) strata that preserve high-resolution records. Combined, the two workshops hosted a total of 91 participants representing 14 countries, with broad expertise. Discussions at Deep Dust 1.0 (USA) focused on the primary research questions of paleoclimate, paleoenvironments, and paleoecology of icehouse collapse and the run-up to the Great Dying and both the modern and Permian deep microbial biosphere. Auxiliary science topics included tectonics, induced seismicity, geothermal energy, and planetary science. Deep Dust 1.0 also addressed site selection as well as scientific approaches, logistical challenges, and broader impacts and included a mid-workshop field trip to view the Permian of Oklahoma. Deep Dust 2.0 focused specifically on honing the European target. The Anadarko Basin (Oklahoma) and Paris Basin (France) represent the most promising initial targets to capture complete or near-complete stratigraphic coverage through continental successions that serve as reference points for western and eastern equatorial Pangaea.This research has been supported by the ICDP (DeepDust2019 grant).Ye

Lower Carboniferous shallow marine sequences from the Central Alborz Basin, Iran (north-eastern margin of Gondwana): sedimentology, biostratigraphy and rock– magnetic studies

The Lower Carboniferous Mobarak Formation records the development of a carbonate platform on the southern Paleo-Tethyan passive margin. This pervasive carbonate factory was deposited following the opening of the Paleo-Tethys Ocean into the Alborz Basin along the northern margin of Gondwana. The depositional facies range from the most proximal to the most distal and include coastal environments, inner ramp peritidal facies, peloidal to crinoidal shoals, storm to fair-weather influenced mid-ramps, proximal to distal shell beds and low energy outer ramps. Storms clearly played a dominant role in the distribution of skeletal and non-skeletal shoals on the carbonate ramp. Sedimentological analyses complemented with foraminiferal biostratigraphy reveal four events which are interpreted to represent the principal factors controlling carbonate platform evolution in the Alborz Basin during the Lower Carboniferous: 1) A transgression linked to global temperature rise in the Early Tournaisian (Middle Hastarain) resulted in the formation of thick-bedded argillaceous limestones. 2) the Hastarian–Ivorian boundary glaciation phase, 3) Upper Ivorian–Lower Viséan? tectonic block faulting. 4) the Viséan- Serpukhovian glaciation phase. The three foraminiferal assemblages encountered in the Tournaisian interval of the Mobarak Formation are restricted to specific periods within the Ivorian. The occurrence of specific foraminiferal taxa in Alborz is tightly governed by transgressions and migration of North Paleo–Tethyan biotic elements as response to the thermal period. We also combined proxies for ambient paleothermometry in addition to the indications for arid conditions and arid conditions and the presence of foraminiferal taxa with a North Paleo-Tethyan affinity in the Lower Carboniferous Mobarak Formation to suggest a paleo-position for the Alborz Basin at lower latitudes than approximately 45 –50 southern paleolatitude reported thus far. Magnetic susceptibility ( in ) was measured and compared with facies from the same sample. There is a clear link between in and facies, and the average in values are higher for distal facies than for proximal ones. The in profile of Lower Carboniferous carbonate sequence reflects stratigraphic variations in response to relative sea level changes and detrital input. In the context of the sequence stratigraphic framework, the average in values for lowstand and transgressive system tracts deposits are higher than for the highstand system tracts deposits. The clear link between in and facies points to at least partly preserved primary in signal, related to detrital inputs. In respect to the hysteresis measurements the in signal is mainly carried by low coercivity ferromagnetic minerals such as magnetite, with a mixture of relatively coarse grains (detrital fraction) and ultra-fine grains (probably formed during diagenesis)

Tournaisian and Visean (Lower Carboniferous) of the Alborz Mountains (Iran).

peer reviewe

Sedimentology and magnetic susceptibility of Mobarak Formation (Lower Carboniferous in central and eastern Albroz Mountains, North of Iran)

peer reviewe

Mixed Middle Jurassic sedimentation from North East of Iran: sedimentological model and carbonate production versus detrital inputs influence

peer reviewe

Delta and deep basin Jurassic deposits from Iran: relationship between magnetic susceptibility and facies

This study concerns, the Kashafrud Formation from Kopet Dagh Basin in its type section, which corresponds to the first Jurassic sedimentary cycle in Iran,. Sedimentary studies were carried out to propose a paleoenvironmental model of the sedimentary succession. Furthermore, magnetic susceptibility (MS) measurements were performed and compared with sedimentological evolution. The MS curve evolution is related to the abundance of magnetic minerals, which itself is related to lithogenic supplies which could be related mostly to sea level and climatic changes. Theoretically, a regression will lead to a more important proportion of landmass exposed and so to an increase of detritic minerals in the sedimentary system and so to an increasing MS. A transgression will decrease MS (Ellwood et al., 2000). Palaeoenvironments of this Jurassic succession from base to top are: flood dominated delta, deep basin deposits, silisiclastic and mixed silisiclastic and carbonate shoreface deposits. Comparison between facies evolution and MS curve shows that the facies which are deposited in delta and shoreface zones have low MS values; on the contrary basinal deposits are presenting high MS values. The facies deposited in mixed silisiclastic and carbonate shoreface have lowest MS values. So it appears that the deeper basinal deposits have the highest MS values and the shallower deltaic and shorelines facies have the lowest MS values, in opposition with theoretical background. This could be related to water agitation and sedimentation rate during deposition. In the deltaic and shoreface environments, a high water agitation could prevent the detritic particles to settle and a high sedimentary rate could dilute the magnetic minerals (see Da Silva et al., 2009). It actually seams that the carbonate production in the upper parts of the studied interval has led to a dramatic decrease in MS values. This study clearly shows the significant role of MS in environmental analysis, and the importance of a strong sedimentological background. Ellwood, B.B., Crick, R.E., El Hassani, A., Benoist, S.L. & Young, R.H., 2000. Magnetosusceptibility event and cyclostratigraphy method applied to marine rocks: detrital input versus carbonate productivity. Geology, 28: 1135-1138. Da Silva, A.-C., Mabille, C. & Boulvain, F., 2009. Influence of sedimentary setting on the use of magnetic susceptibility: examples from the Devonian of Belgium. Sedimentology, 56: 1292-1306