The sedimentology of the Lower Permian Dandot Formation: a component of the Gondwana deglaciation sequence of the Salt Range, Pakistan

The Dandot Formation is a part of the Lower Permian, dominantly continental, Gondwanan Nilawahan Group in the Salt Range, Pakistan. The formation conformably overlies the glacio-fluvial Tobra Formation and has a sharp conformable contact with the overlying fluvio-continental Warchha Sandstone. Sedimentary analyses show that the Dandot Formation consists of 1: bioturbated sandstone lithofacies (L1), 2: dark green mudstone/shale lithofacies (L2), 3: flaser bedded sandstone lithofacies (L3), 4: rippled sandstone lithofacies (L4), 5: cross-bedded sandstone lithofacies (L5), and 6: planar sandstone lithofacies (L6). These can be grouped into shoreface, inner shelf, and tidal flat and estuarine facies associations, deposited in shallow marine to intertidal environments. The upper part of the Tobra Formation at the Choa-Khewra road section, where it conformably underlies the Dandot Formation, contains palynomorphs assignable to the earliest Permian 2141B Biozone. In south Oman, the 2141B Biozone is closely associated with the Rahab Shale Member, a widespread shale unit which is considered to represent part of a Permian deglaciation sequence which culminates in the marine beds of the Lower Gharif Member, interpreted as due to post glacial marine transgression. Thus, the Tobra Formation and the overlying marine Dandot Formation may form part of a similar deglaciation sequence

Modes of Pangean lake level cyclicity driven by astronomical climate pacing modulated by continental position and p CO2

Orbital cyclicity is a fundamental pacemaker of Earth’s climate system. The Newark–Hartford Basin (NHB) lake sediment record of eastern North America contains compelling geologic expressions of this cyclicity, reflecting variations of climatic conditions in tropical Pangea during the Late Triassic and earliest Jurassic (~233 to 199 Ma). Climate modeling enables a deeper mechanistic understanding of Earth system modulation during this unique greenhouse and supercontinent period. We link major features of the NHB record to the combined climatic effects of orbital forcing, paleogeographic changes, and atmospheric p CO 2 variations. An ensemble of transient, orbitally driven climate simulations is assessed for nine time slices, three atmospheric p CO 2 values, and two paleogeographic reconstructions. Climatic transitions from tropical humid to more seasonal and ultimately semiarid are associated with tectonic drift of the NHB from ~ 5 ° N to 20 ° N . The modeled orbital modulation of the precipitation–evaporation balance is most pronounced during the 220 to 200 Ma interval, whereas it is limited by weak seasonality and increasing aridity before and after this interval. Lower p CO 2 at around 205 Ma contributes to drier climates and could have led to the observed damping of sediment cyclicity. Eccentricity-modulated precession dominates the orbitally driven climate response in the NHB region. High obliquity further amplifies summer precipitation through the seasonal shifts in the tropical rainfall belt. Regions with other proxy records are also assessed, providing guidance toward an integrated picture of global astronomical climate forcing in the Late Triassic and ultimately of other periods in Earth history

A periglacial palaeoenvionment in the Upper Carboniferous-Lower Permian Tobra Formation of the Salt Range, Pakistan

The Upper Carboniferous–Lower Permian (Upper Pennsylvanian–Asselian) Tobra Formation is exposed in the Salt and Trans Indus ranges of Pakistan. The formation exhibits an alluvial plain (alluvial fan–piedmont alluvial plain) fades association in the Salt Range and Khisor Range. In addition, a stream flow facies association is restricted to the eastern Salt Range. The alluvial plain facies association is comprised of clast-supported massive conglomerate (Gmc), diamictite (Dm) facies, and massive sandstone (Sm) lithofacies whereas the stream flow-dominated alluvial plain facies association includes fine-grained sandstone and siltstone (Fss), fining upwards pebbly sandstone (Sf), and massive mudstone (Fm) lithofacies. The lack of glacial signatures (particularly glacial grooves and striations) in the deposits in the Tobra Formation, which are, in contrast, present in their time-equivalent and palaeogeographically nearby strata of the Arabian peninsula, e.g. the Al Khlata Formation of Oman and Unayzah B member of the Saudi Arabia, suggests a pro- to periglacial, i.e. glaciofluvial depositional setting for the Tobra Formation. The sedimentology of the Tobra Formation attests that the Salt Range, Pakistan, occupied a palaeogeographic position just beyond the maximum glacial extent during Upper Pennsylvanian–Asselian time

Data from Climate Model Simulations for Triassic-Jurassic Orbital Climate Cycles

The data is generated using the Earth System Model CLIMBER-X which simulates climate globally on a 5&deg;x5&deg; horizontal grid. Its coupled atmosphere, ocean, sea-ice and land surface have been used in this study.,In &quot;Astronomical Forcing, Continental Drift and CO2 Paced Pangaean Lake Level Cycles&quot; we study the effect of cyclic orbital parameter changes on Late Triassic to Early Jurassic paleoclimates. For this, in total 36 transient climate simulations are performed with reconstructed paleogeographies for 9 time slices in 5 Myr steps (230 to 190 million years ago) at 3 different atmospheric pCO2 values, each driven by a simplified orbital forcing over a 250,000 yr period. The data presented here is the model output on which the results of the main article are based. (The majority of further output data is not included due to its large size, but it can be made available upon request.) Also included are different model configuration files and the scripts to generate the included figures (using the Python programming language in a Jupyter Notebook). The model output data is provided in different NetCDF files, see README for detailed description.</span