High-latitude platform carbonate deposition constitutes a climate conundrum at the terminal Mesoproterozoic

Domain: earth_science
Published: 2024-03-06
Editorial outcome: major_revision

Abstract
During the Mesoproterozoic Era, 1600 to 1000 million years ago, global climate was warm with very little evidence of glaciation. Substantial greenhouse warming would have been required to sustain this ice-free state given 5-18% lower solar luminosity. Paleomagnetic data reported here place voluminous ca. 1.2 Ga shallow marine carbonate deposits from India at an unexpectedly high latitude of around 70° from the equator. Previous studies noted high latitudes, but their implication was never considered. Here, we evaluate the temporal-latitudinal distribution of neritic carbonate deposits across the Proterozoic and identify similar deposits from North China that together with those from India are seemingly unique to the late Mesoproterozoic. A uniformitarian interpretation implies that this is cold-water carbonate deposition, but facies similarity with low-latitude neritic deposits rather suggests a hotter climate and elevated polar ocean temperatures of 15–20° or higher. This interpretation represents a climate conundrum that would require much greater greenhouse warming than documented for the Mesoproterozoic.

Introduction
Proterozoic basins from cratonic India are collectively referred to as the ‘Purana’ basins1 and host several unconformity-bound, relatively undeformed and unmetamorphosed sedimentary sequences (Fig. 1a). One such unconformity bound sequence (i.e., Sequence III) is preserved in most of the Purana basins of southern India and consists of shallow-marine sandstone followed by a carbonate ramp succession of limestone and calcareous shale2,3 (Fig. 2). Several terms exist for neritic carbonate deposits based on geometry (i.e., ramps, rimmed shelfs, and open shelfs), but we generically use the term “platform”. Past paleomagnetic studies support the correlation of the Purana platform succession across southern India and indicate that it was deposited at high-latitude3–5, but contradictory results are reported by Goutham et al.6. Together with paleomagnetic data, we discuss the high-latitude, characteristics, and the climatic implications of the Purana platform within the context of known paleolatitude constraints for shallow-marine carbonate deposition since the Proterozoic.

The minimum age limit of the Purana platform is directly constrained by U-Pb zircon crystallization ages from tuffaceous units in the Chhattisgarh and Indravati basins to predate 993±8 million years (Ma) and 1001±7 Ma, respectively7–9, and to postdate 1405±9 Ma in the Chhattisgarh Basin10 (Fig. 2b). An 40Ar/39Ar glauconite age of ca. 1180 Ma provides a minimum constraint for the Purana platform in the Pranhita-Godavari Basin2. Detrital zircon ages of 1158±11 Ma from the Kolhan Group (on the Singhbhum Craton) suggest that it, too, is likely coeval with similar facies in the Pranhita–Godavari Basin11 (Fig. 2b). The timing of the platform’s deposition is even less certain in the Kaladgi, Bhima and Cuddapah basins, but is broadly assigned to the latest Mesoproterozoic to early Neoproterozoic by means of U-Pb ages from detrital zircon grains12,13, 40Ar/39Ar whole rock ages14, 40Ar/39Ar ages and Rb-Sr isochron ages on glauconite3,13, Pb-Pb ages on carbonate13, and the presence of microfossils15 (Fig. 2b).

Within the Cuddapah Basin, the platform is represented by the Kurnool Group, which is preserved in two erosional remnants: the Kurnool and Palnad basins (Fig. 1b). Preservation is more complete in the Kurnool Basin, where the group comprises the Banaganapalle Quartzite, Narji Limestone, Owk Shale, Paniam Quartzite, Koikuntla Limestone and Nandyal Shale from the base upwards (Fig. 2b). The Narji Limestone is mostly micritic with laterally persistent tabular beds of gray limestone with intercalated siliciclastic units and pink limestone near its base. It grades into thinly bedded black limestone and eventually into ochre-coloured shale of the Owk Formation16. Helically coiled Obruchevella microfossils from the Owk Formation suggest a Neoproterozoic to Early Cambrian age15 (Fig. 2b). The Paniam Formation overlying the Narji Limestone yielded a single 913±11 Ma zircon grain12, but the next youngest age population from several grains at 1717±20 Ma is a more conservative maximum depositional age estimate. Paleomagnetic data from the Narji Formation suggest an age of ~1.2 Ga3.

Carbonate accumulation in the ocean today extends as a continuum across low to high latitudes and from shallow marine to pelagic environments. Today, low-latitude warm-water platforms are distinct from high-latitude temperate-to-cold water platforms in terms of biotic constituents17,18. Low-latitude platforms are characterized by a photozoan association of autotrophic carbonate producers such as green calcareous algae, invertebrates with hermatypic coral and precipitates of lime-mud and ooids. Modern cold-water platforms are largely comprised of heterozoan bioclasts with a hermatypic coral, coralline algae and benthic invertebrates, while precipitates like carbonate mud and oolitic grains are poorly documented18. Carbonate mud, which is usually a minor component of high-latitude Phanerozoic carbonate deposits17, are interpreted as the product of skeletal fragment breakdown19. Volumetrically, warm-water neritic environments within ~30° of the equator are the principal settings for carbonate production and preservation during the Phanerozoic20. The divide between modern cold- and warm-water platforms is around seawater temperatures of 20°C21.

Precambrian platforms are generally considered analogous to modern warm-water facies22 and preferential tropical deposition is assumed by palaeogeographers23. This assumption may be false. Precambrian platforms are devoid of bioskeletal grains, coral and bryozoan bioherms, and are instead dominated by stromatolites and participates like lime-mud with a subordinate proportion of ooid grains, but also aragonite fans in the Precambrian, and molar-tooth structures in the later part of the Proterozoic22. Cold-water Precambrian platforms are not well-described and could be difficult to recognize given the modern Metazoan-based definition. They should, however, share those characteristics of modern cold-water facies that are not Metazoan-based. Precambrian high-latitude cold-water carbonate facies are thus likely lower volume deposits compared to tropical counterparts deposited at the same time. In addition, significant reworking (i.e., clastic textures) and minor carbonate mud components are expected, and they are likely to contain interbedded glacial deposits, ice-rafted debris, local hardgrounds, and glendonites17.

Here, we report carbonate deposition at high latitude with paleomagnetic data for the Kurnool Group based on more extensive sampling compared to previous studies (Supplementary Fig. 1). We collected oriented limestone, sandstone, and shale core plugs by standard methods from the Banaganapalle and Narji formations for paleomagnetic and the first rock magnetic analyses for these rocks to better constrain their magnetization and paleolatitudinal setting (see Methods). We compare this with published paleomagnetic results from southern India and constrain carbonate deposition at high latitude around ~1.2 Ga. We further compile paleolatitudes for Proterozoic carbonate platforms from paleomagnetic results listed in the Global Paleomagnetic Database24 and those published recently but not yet incorporated into this database to evaluate the temporal and spatial context of these southern Indian carbonate successions (see Methods). High-latitude (i.e., >50° latitude) neritic carbonate deposition is seemingly unique to the late Mesoproterozoic based on this compilation. Given the facies characteristics, we interpret the high-latitude carbonate deposition as a proxy for polar ocean water temperatures of at least above 15°C (but likely higher than 20°C) and for greenhouse climatic conditions that required higher pCO2 (and other greenhouse gasses) than previously considered for the Mesoproterozoic.

Results
Here we provide a summary of the demagnetization and rock magnetic results. For a more detailed account, see Supplementary Notes.

A small number of samples (mostly from the Palnad Basin) did not respond well to demagnetization and revealed incoherent remanence directions that are excluded from further discussion. With demagnetization below 350°C, our samples are characterized by shallow north-down components (Supplementary Table 1, Supplementary Figs. 2–4). Similarity of these relatively low temperature shallow north-down components with the remanence reported by Goutham et al.6 is noted (Supplementary Fig. 6) and is suspected to represent a record of the modern geomagnetic field. The majority of samples, however, yield steep components during thermal demagnetization to either 420°C or 660°C. These were southeast-up, or northwest-down (Supplementary Table 1, Supplementary Figs. 2–4). Thermomagnetic curves confirm haematite as magnetic carrier of the high-temperature components in pink limestone and magnetite in black and gray limestone (Supplementary Figs. 5 and 7). The identified components are similar to and combined with those from a previous study of the Narji Limestone3 (Fig. 3a). Together the data yield a paleopole at 26.4°N and 66.6°E with A95 = 13.3° (Fig. 3c). Formal evaluation of the reversal test is inconclusive due to the small number of sites that record the southeast-up component. However, a positive fold test illustrated that these steep directions predate ~1.0 Ga deformation3 (Supplementary Notes). In addition, an intraformational conglomerate test imply that the magnetization is primary3 (Supplementary Notes). Our pole is different from the Phanerozoic apparent polar wander path of Gondwana (Supplementary Fig. 8a) and differs from Precambrian key paleomagnetic poles from India at 1465 Ma, 1075 Ma and 770 Ma, which all place India at lower latitudes (Supplementary Fig. 8b). It is, however, similar to the 1192±10 Ma Harohalli alkaline dykes pole25 (HAR in Fig. 3c). The implication is that the age of magnetization and the Purana platform is likely removed from the current maximum (1405±9 Ma) and minimum (1001±7 Ma) age constraints, but closer to 1.2 Ga as also indicated by the ~1180 Ma glauconite age from the Pranhita–Godavari Valley. We tentatively assign the 1192±10 Ma age to our pole but remain cognizant of the wider possible age range.

Limestone of the Purana platform from the Chhattisgarh and Pranhita–Godavari Valley basins and those from the Kaladgi and Bhima basins are also characterized by steep north-down and south-up remanence directions that are stable either above 600°C or up to 420–460°C3,5 (Fig. 3b). Our Kurnool Group pole is similar to poles from these previous studies (K&B and C&PG in Fig. 3c). The pole from the Chhattisgarh and Pranhita–Godavari Valley basins is considered primary based on a record of reversals, a positive regional fold test4, and most importantly, a positive intraformational conglomerate test4. The Kaladgi and Bhima basins also record a reversal, but its age of magnetization is not constrained by field tests5. Our data indicate a paleolatitude of 72°±12° for southern India during Kurnool Group deposition (Fig. 3c), which is comparable to the 72°±13° and 83°±16° obtained from carbonate facies of the Chhattisgarh and Pranhita–Godavari Valley basins and the Kaladgi and Bhima basins4,5. The Purana platform thus developed at least partly at high latitude over much of Peninsular India.

Our compilation of paleolatitudes (Supplementary Table 3) reveals only a few studies that fall outside the latitudinal extent of their Phanerozoic counterparts20 (Fig. 4). Nine studies show paleolatitudes greater than 50° and occur either at ~1200–1000 Ma or ~800 Ma. The older grouping is represented by the Purana platform (as discussed above), but also by the Nanfen, Xinxing and Liulaobei formations of the North China craton26–28. In addition, the Jingeryu Formation was recently interpreted as correlative strata of the Nanfen and Xinxing carbonate deposition in the polar region at 1.1 Ga29. Paleolatitudes from the Purana platform and the lower Nanfen Formation and its equivalents are between 59° and 90°. The upper parts of the lower Nanfen Formation and the middle member of the Nanfen Formation yield lower, albeit still high paleolatitudes of 49°–64°. Paleolatitudes between 39° and 85° have previously been reported from the Jingeryu Formation26. The paleomagnetic constraints from the Purana platform are supported by field tests and dual-polarity directions are recorded. The lower part of the Nanfen Formation and its equivalents also record magnetic reversals. The identification of extreme high-latitude carbonate deposition within a broadly similar time frame from two cratonic blocks with a comparable facies change from purplish-pink to gray limestone is suggestive of a shared history, and we reconstruct India and North China as near neighbours during the assembly of Rodinia (Fig. 3c). Such a near-neighbour relationship has been noted before, albeit in a different configutaion30.

The ~800 Ma occurrence of high-latitude carbonates are represented by a unit from South China: the Madiyi Formation31 at 52°±5°. The study is unsupported by field tests, but does record reversals. It further overlaps within uncertainty with the latitudinal extent of Phanerozoic carbonates, thus representing a less convincing argument for extreme high-latitude deposition.

Most Proterozoic platforms conform to modern deposition at <50° latitude (Fig. 4). The absence of platforms at high latitude for much of the Proterozoic, could be the product of a preservation age bias. The likelihood that primary magnetizations are recorded also decreases with age, even if deposits are preserved. As such, our compilation reflects a paucity of data before 1.7 Ga (Fig. 4). The deposition and ultimate preservation of carbonate platforms could also be affected by the supercontinent cycle32. Other biasing factors are the presence of continents near the poles and the area on the globe at high latitude compared to low latitude. If high-latitude neritic carbonates were more commonplace, then they were not preserved. At face value, however, extreme high-latitude platforms are limited to ~1200–1000 Ma. They are not considered cold-water platforms, as the facies document a laterally extensive and distally steepened ramp that is rich in carbonate mud33, devoid of interbedded glacigene deposits and without documented glendonites. The facies are more typical of warm-temperate to warm conditions, and thus likely a proxy for hotter global climatic conditions. We note that an extraordinary climate condition was also recently suggested for the 1.1 Ga high-latitude carbonate platform(s) of North China29.

Methods
Sampling
All samples were collected with the necessary permissions in collaboration with staff of the Geological Studies Unit at the Indian Statistical Institute, Kolkata.

The Kurnool Group of the Cuddapah Basin was sampled for paleomagnetism, rock magnetism, and petrography. The Banaganapalle Formation and the Narji Formation was sampled from both the Kurnool as well as the Palnad basins (Supplementary Fig. 1). Core samples were collected using a portable petrol-powered drill and oriented using both magnetic and sun compasses. Structural orientation of beds was recorded. Small hand samples were also collected from all the localities that were drilled. At two localities it was not possible to drill because of concerns about antagonizing the local community, and oriented block samples that were later plugged using a bench top drill-press were collected instead. No additional hand samples were collected from these localities. One oriented core plug was drilled from each block sample. Oriented cores were cut into ~2 cm long cylindrical specimens with smooth and parallel top and basal surfaces. Selected hand samples, duplicate specimens and cut offs were used to prepare polished thin sections or were used for rock magnetic characterization.

In the Kurnool Basin (Supplementary Fig. 1a) site KBA was sampled from a road cut in immature sandstone and conglomerate of the lower Banaganapalle Formation that dip shallowly to the south. Seven cores were collected here. Site KND, with 10 oriented cores represents pink calcareous shale from the transition between the Banaganapalle and Narji formations. Light purplish gray limestones were collected at sites KNA and KNB (11 and 8 cores, respectively), both in the lower stratigraphic levels of the Narji Formation. Sandstone lenses are interbedded with the limestone at site KNA, where bedding is essentially horizontal. Site KNB near the village of Ambapurum is stratigraphically somewhat below site KNA in light gray to pink ripple-marked limestone. Eight cores were collected from flat bedded light gray limestones at KNC. Twenty cores of planar laminated black limestones (i.e., KNE and KNF) were collected from different parts of a large quarry outside Rama Krishna Purum. In the Palnad Basin (Supplementary Fig. 1b) two sites were sampled within the Banaganapalle Formation (PBA and PBB), and three sites from the Narji Formation (PNA, PNB, and PNC). Site PBA represents fine-grained sandstone and siltstone with well-preserved ripple cross-lamination as well as wave ripple and interference ripple marks. Six oriented block samples were collected here. Five oriented core samples were collected from a course-grained sandstone at site PBB. A dark gray limestone (PNA, 6 cores) and a light gray thinly bedded limestone (PNC, 8 cores) display obvious signs of deformation with a well-developed lineation on bedding planes. There is also abundant stylolitization developed at both localities. At site PNB, a planar bedded dark gray limestone is not obviously affected by deformation, and 5 oriented block samples were collected.

Paleomagnetism
Specimen were magnetically characterized through measurement of the Natural Remanent Magnetization (NRM) using the Superconducting Cryogenic rock magnetometer 2G 760-4K (SQUID) with an automatic sample changer at the University of Johannesburg paleomagnetic laboratory. The components of magnetization that makes up the NRM were identified and quantified through stepwise alternating field and thermal demagnetization. The alternating field (AF) demagnetization utilized coils that are in line with the superconducting rock magnetometer and were used to demagnetize low coercivity magnetic components that were present in the samples. The samples were exposed to AF field strengths of 2.5, 5.0, 7.5, and 10.0 mT. Thermal demagnetization was achieved by heating specimen from 100°C to 680°C at decreasing intervals using a model TD-48SC shielded furnace. Demagnetization generally consisted of 15–20 steps. Remanence components were identified and quantified by means of principal component analyses52 using the software PMag 3.1.053 and PmagPy54. Only components based on three or more demagnetization steps and with a maximum angular deviation (MAD) less than or equal to 15° were considered for further interpretation. Component means were used to calculate VGPs (Virtual geomagnetic poles) and these VGPs were grouped to calculate grand mean poles. All visualizations of calculated and published poles utilized GPlates 2.255.

Selected Narji Formation sample material of this study (i.e., KNE01, PNA02, KND02) and a previous study3 (i.e., KPA07, KPB06) were crushed with an agate mortar and pestle, and 1 g fractions of each sample consisting of a third of the material being >1 mm and the remainder being <0.71 mm were prepared. The changes in magnetic susceptibility (κ) with changes in temperature (T) of these samples were determined in air from 30° to 700°C at a standard heating rate of ~10°C per minute using a MFK1-FA Kappabridge coupled with a CS3 heating apparatus at the Council for Geoscience, Pretoria, South Africa. Data were processed using Cureval (https://www.agico.com/text/software/cureval/cureval.php). Magnetic susceptibility versus temperature (κ-T) curves exhibits distinct characteristics for different magnetic carrier minerals and thus allow for their characterization and the identification of possible phase transitions during thermal demagnetization.

Proterozoic carbonate platform paleolatitude compilation
We compiled the temporal variation of paleolatitude for neritic carbonate deposits during the Proterozoic Eon (2500–541 Ma) from published direct and indirect paleomagnetic results as listed in the Global Paleomagnetic Database or GPMD24 and from more recent publications that are not yet incorporated in the GPMD. The GPMD lists numerous entries from data catalogues particularly for units from the former Union of Soviet Socialist Republics and a few from unpublished PhD theses, such entries were not included in our compilation given the difficulty to asses data quality and lack of peer review. Inclusion in our compilation further requires a presumption that the age of magnetization is the same as the rock age and that the studied rock unit contains neritic carbonates. Note that the paleomagnetic data can be obtained directly from neritic carbonates (limestone or dolomite) or from other lithologies that are conformable with carbonate deposits within the same succession. A total of 2569 Proterozoic paleomagnetic studies were listed in the GPMD between 1953 and 2021. Those entries where the age of magnetization is suspected to be different from the rock age (i.e., entries are likely magnetic overprints) were discarded. Particular caution was applied to studies that pre-date 1980, as these pre-date the use of magnetic component characterization by least-squares analysis52. Superseded studies were excluded. Some duplicate entries were kept where studies were published independently but around the same time. We evaluated and report the R score56 for each entry in our compilation to screen in terms of quality. Because the age of rock units are not always updated in the GPDM as new constraints become available, each of the entries had to be reviewed to establish the most recent acceptable constraints. A total of 140 data entries appear in our final compilation (Supplementary Table 3). Where possible, the approximate stratigraphic thickness of carbonate is reported for each of these to provide a proxy for the volume of carbonate deposition.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "First, I would like to thank the editors for the opportunity to read this interesting manuscript. I have\nbeen overcommitted recently, but I could not turn down a manuscript with such an interesting title.\nSecond, I would like to commend the authors on an interesting idea. You will see, below, that I do not\nthink this work is ready for publication, but it is an intriguing idea and one that is innovative and has\nnot been argued before.\nThird, I have made extensive comments in the PDF of the manuscript. Please use these line comments\nduring any revisions that you might make. I will only report the critical elements that lead to a\ndecision of \"not yet publishable\" below:\n(1) The first critical issue is the assertion that high-latitude carbonate deposition requires globally high\ntemperatures. This is really the crux of the manuscript, but the hypothesis is not well supported\n(rather, it is simply asserted).\nThe absence of glacial activity during this time does not require dramatically higher temperatures.\nPolar glaciation also requires the existence of sufficient continental mass as reservoirs for ice (i.e. like\nAntarctica), or sufficient continental mass that restricts active flow of oceanic currents to higher\nlatitudes (i.e. like the northern polar ocean). At times where there is little polar continental mass,\noceans tend to not form ice, and are generally warmer, but need not be drastically so.\n(2) The second critical issue is the assertion that warmer temperatures (see above) is the\nuniformitarian approach. In fact, it is not. On the modern Earth, we have higher-latitude carbonate\nformation (cold water carbonates, to which you refer early in the manuscript). Therefore, the\nuniformitarian approach would be that these high latitude successions are also dominated by cold-\nwater carbonate deposition.\nHowever, to even approach this uniformitarian argument, you need to be able to answer the question\n(and I have no idea what the answer is): what does a cold-water carbonate looks like in the\nPrecambrian? This is a great question, and one I ask students every time I teach about carbonate\nrocks. In the absence of the metazoan organisms that define cold-water carbonate facies today?\nWhat do you look for? At the minimum, you need to make a facies argument that these high latitude\nfacies are fundamentally different in character than similarly aged low-latitude facies.\n(3) Finally, in terms of any of these arguments, you need to address other possibilities. A similar\n\"climate paradox\" has been argued in the past about \"cap carbonate\" facies directly following\nNeoproterozoic low-latitude glacial (snowball Earth) events. This has mostly gone to the wayside in the\nliterature, in favor of either arguing about the timing and number of such events, or arguing unique\ngeochemical conditions that permitted carbonate formation in the aftermath of global glaciation.\nSo, in the end. Do I think that there is something special about these high-latitude carbonate deposits\n– absolutely! Do I think that there is sufficient argument laid out in this manuscript – unfortunately,\nno.\nI would love to read a revised version, however, in the future. You have something here....you just\nneed the right framework for it! Good luck!", "reviewer_2": "This is a well-written and useful manuscript that lays out a new constraint on Mid-Proterozoic climate.\nThe authors report paleomagnetic data that at least purports to show that typical warm-water\ncarbonate platforms were constructed in India at 1.2 Ga when that land mass was north of 70 degrees\nlatitude. If correct, this shows that the polar oceans at that time were at least as warm as during the\nMid-Cretaceous maximum, around 100 Ma. This is a useful target for climate modelers, including this\nreviewer. There is an ongoing debate about the nature of that climate, which should have depended on\ngreenhouse gas concentrations like CO2, CH4, and N2O, but also on O2 because the latter gas would\nhave influenced the concentrations of the last two of these three greenhouse gases.\nI am not going to comment on the observations themselves, as this is best left to other experts in\nthese fields. I hope that the paper is reviewed by a qualified paleomagnetist, as this is a difficult\nsubject that requires expert training. Likewise, the interpretation of what types of carbonate deposits\nformed at what ocean temperatures can be best addressed by a reviewer with a strong\nsedimentology/stratigraphy background. Suffice it to say that to a non-expert in these fields, the study\nseemed carefully done.\nThe section on the ‘Paleoclimate paradox’ is also well-written, but I do have two detailed comments\nthat are listed below. The first concerns possible evidence for glaciation during the Boring Billion. The\nsecond points to a recent 3-D, Mid-Proterozoic climate calculation by some Chinese researchers. The\nlatter project was led by Peng Liu, who spent two years working with me here at Penn State, which is\nwhy I know of this work. It might be useful to include some of these references. This reviewer is\nparticularly interested in whether the evidence for glaciation at 1.8 Ga and 1.1-1.3 Ga should be\nconsidered credible.\nFinally, I was pleased to see that the manuscript is dedicated to Nic Beukes. I met Nic almost 40 years\nago as a member of Bill Schopf’s Precambrian Paleobiology Research Group at UCLA. Nic was a valued\nmember of that team, and he continued to provide valuable advice, and to show other Precambrian\ngeologists around South Africa, for many years after that time. We were all sad to learn of his passing.\nYou may reveal my name to the authors.\nJim Kasting\nPenn State\n----------------------------------------\nDetailed comments:\n1. (l. 183) ‘The Mesoproterozoic has long been considered a warm time based on the absence of\nglaciation(2,8).’\n--Refs. 2 and 8 are to Holland (2006) and Young (2013). This is indeed the currently accepted story.\nBut in writing our 2017 book, Atmospheric Evolution on Inhabited and Lifeless Worlds’, David Catling\nand I discovered references to papers that question this idea, or at least show some of its limitations\n(see Sect. 11.3.1, p. 302-303). More detail follows: i) Two of these papers concern possible glaciation\nin the King Leopold formation in northwestern Australia (G.E. Williams, J. Geol. Soc. 162, 111-124,\n2005; Schmidt and Williams, Precambrian Res. 167, 267-280, 2008). This may be sufficiently removed\nfrom the middle of the ‘Boring Billion’ period to not break up the story too much, as the time span of\nthe Boring Billion is often cited as 1.8-0.8 Ga. Are these papers believable? ii) A third paper concerns\nglaciation in the Vazante group in Brazil, which was previously considered Neoproterozoic in age but\nhas been redated at 1.1-1.3 Ga by N.J. Geboy et al., Precambrian Res. 238, 199-213, 2013). This is\nright during the time in which the high-latitude carbonates in the present paper are reported. Is this\nreport believable and, if so, does it cast doubt on the conclusions reached in this new manuscript?\n2. (Same paragraph) Some additional constraints on Mid-Proterozoic temperatures are provided by 3-\nD climate simulations by P. Liu, Y. Liu, Y. Hu, J. Yang, S. A. Pisarevsky, Warm climate in the “Boring\nBillion” era, Acta Geologica Sinica-English Edition 93, 40–43 (2019). According to their (zero-CH4)\nclimate model results, 3,550 ppmv CO2 at 1.42 Ga would have produced a glacial climate with a mean\nsurface temperature of 10.7 °C, whereas 7,100 ppmv CO2 would have produced a mean surface\ntemperature of 18.6 °C—sufficient to keep the continents (but not the poles) ice free. These\ncalculations account for the fact that solar luminosity at that time was ∼90% of the present value.\nThese two CO2 levels are equivalent to 12-24 PAL, if the Preindustrial Atmospheric Level (PAL) is\nrounded to 300 ppmv. Thus, if these climate calculations are accurate, the new climate constraints\nprovided in the present manuscript would likely require >24 PAL of CO2 and/or additional greenhouse\nwarming by CH4 or N2O.", "reviewer_3": "Review of “Extreme high-latitude platform carbonate deposition …” by de Kock et al. submitted to\nNature Communications\nPrimarily on the basis data on paleopole positions in late Mesoproterozoic, compiled from the literature\nand one new set from India, and, the distribution of carbonate platforms of the time, the authors\nboldly claim that the then poles were not only ice-free but were also warmer than 20°C. On the basis\nof theoretical arguments, they further infer that the atmosphere of the time was charged with super-\ngreenhouse gases.\nBecause I have no training in or insight into paleomagnetism, I am accepting the authors’ results, but\nother reviewers need to assess this main part of the paper. As an outside reader, I suggest that the\nauthors consider stating upfront what the error-bars on paleopoles are (fig. 3C) and what their\nimplications might be. It appears that there is an implicit assumption that paleopole positions of a\ncratonic block determined from a set of dykes must also be those of carbonate deposits in the same\nblock. In the understandable absence of absolute ages of the carbonates (see below), this assumption\nshould also be stated upfront.\nThe ages and paleopole positions of the igneous rocks are well constrained by using the ~same rock\nunits, for example the Harohalli dykes (zircon; U-Pb), and by using corrections if any. Ages of\ncarbonate platforms discussed in this paper are not as well constrained as the authors rightly state\n(e.g., lines 49-78). The best age-estimates come from the U-Pb ages of zircons and monazites in the\ntuffs near the bottom and the top of some basin in the Bastar craton. Detrital zircon ages from\nsiliciclastic units provide maximum depositional ages; they should not be construed to be close to true\ndepositional ages as the authors state in lines 59-61 (the statement must be corrected). Overall\nhowever, I agree that carbonate deposition occurred around 1.2 Ga in different cratons in India, and\nthat the authors are within permissible limits in their inferences.\nThe authors need to correct the spelling of Chhattisgarh.\nIncidentally, I suppose that the e-compositor will straighten out many space-obliterations in the text\nthat I received.\nAbhijit Basu, Indiana University\nOctober 18, 2023", "reviewer_4": "The manuscript contains some new paleomagnetic data from Mesoproterozoic Indian carbonates and\nan interesting observation about their high paleolatitudes. Unfortunately, the age uncertainties of\nthese data are large, so more studies are required to accept the main suggestion of the manuscript\nabout climatic paradox in late Mesoproterozoic. However, it is suitable as a hypothesis and worth\npublishing after a moderate to major revision.\nCOMMENTS\nUnfortunately the organization of the manuscript is not perfect. It is really hard for readers (and for a\nreviewer) to read three separate texts in parallel (the main one and two supplementary ones), each\nwith separate illustrations and separate, though overlapping reference lists (some references are\npresent in all three lists, having different numbers in each). In addition there is a table S3 with the\nfourth reference list. All these parts are important for an understanding of the authors’ conception,\njustification of their ideas and specific details, so it is quite an effort to jump from one part to another\nall the time. I understand that this problem is partly caused by the strict rules for publications in NC,\nhowever there is a challenge for the reader.\nMain text\nLines 74-78: the ~1.2 Ga age of the Narji Limestone (NL) is poorly justified. Why not ~1.4 Ga, for\nexample - closer to the mean of 913 (above NL) and 1717 (below NL) Ma detrital zircons? More\nexplanations are needed here.\nLines 80-85: be more specific, what is new in you manuscript compare to previous publication [5].\nLines 103-106: did you re-apply the fold and/or conglomerate tests (according to line 20 in\nSupporting information: Methods, you collected more conglomerate samples) with inclusion of new data,\nor just relied on the test results in [5]? If not, I would recommend to do that.\nLine 109: add the table of poles (with ages) for Fig. 3C.\nLine 119-120: “…age is otherwise not well constrained” – this is also applicable to C&PG.\nLine 122: see comment to line 109. Table of poles is needed here.\nLines 127-128: in view of huge age uncertainties, I would add “at least partly”.\nLine 146, 387-396 and Fig. 3C: provide Euler’s rotation parameters please.\nLine 150: see general comment to “Methods”.\nLine 157: instead of “within the tropics” I would say more cautiously “at < 50 degrees latitudes”.\nLine 162: I would say “could also be affected”\nLines 165-166: I propose to rephrase this sentence (it is not only about continents): “The area on the\nglobe on high latitudes is less than area in the low latitudes” – something like this.\nLines 174-176: It would be good to cite Abrajevitch and Van der Voo (EPSL 2010, 293, 164–170).\nThey were the first.\nLine 206: …southern India and North China.\nLine 236: correct reference is: Geol. Mag. 152(4), 728-750. Also – line 221 (in Supporting\nInformation: Results—Paleomagnetism and rockmagnetism); line 184 (in Supporting\nInformation: Proterozoic carbonate platform paleolatitudes (Bibliography))\nFig. 4 and Table S3: why some vertical error bars are asymmetrical? If we suppose the Fisherian\ndistribution for paleomagnetic directions, dp should be the half of this bar.\nSupporting Information: Methods\nGeneral comment: please describe how did you calculate the vertical error bars (+ and -) for the\npaleolatitude. The commonly used method assumes the Fisherian distribution of paleomagnetic\ndirections and consider the minimal axis of the oval of confidence for the pole (dp) as a half of this\nerror bar, as the oval is oriented “perpendicularly” to the arc of great circle connecting the sample\nlocation and paleomagnetic pole. However, in this case the vertical “+” and “-“ in S3 should be the\nsame and vertical error bars in Fig. 4 should be symmetrical.\nFig. S1 caption: sample localities (*Wabo et al., 2021) - according to reference list(s) Wabo et al.,\n2022.\nLine 85 and Table S3: it would be very useful for readers if Table S3 contain a field with RESULTNO\n(reference 8) for the data available in the Online GPMDB. Interested readers then will be able to\nextract much more information about paleomagnetic studies of their interest mentioned in Table S3.\nLines 101-102: some are updated. I propose “… are not always updated…”\nSupporting Information: Results—Paleomagnetism and rockmagnetism\nTable S1 needs captions. Apparently the superscript [2] in the first column means that these entries\nare taken from previous study, which is number 2 in the Reference list to this supporting information,\nbut it is number 5 in the Reference list for the main manuscript, and number 59 in the reference list\nfor the supporting Information: Proterozoic carbonate platform paleolatitudes which is not very\nconvenient to the reader/reviewer. In the table caption it would be good to refer to the tables in the\nstudy [2], e.g. Table 3 for the high-T component.\nLines 131-135: see my comment to lines 103-106 in the main text.\nLines 152-158, Table S1: apparently only the site KBA (sandstone) represents the clastic sediments in\nthis study, others are carbonates. The KBA inclination is much less than inclinations in other sites\n(high-T component). Maybe there is something to do here with inclination compaction correction,\nwhich was found in some clastic rocks? Maybe if you exclude this site, the reversal test became\npositive?\nLines 176-191 and Fig. S8(B): It would be much better to add a table (with ages) of used Indian poles\nin this supporting information.", "reviewer_author_response": "RESPONSE TO REVIEWER COMMENTS\nResponse to comments by Reviewer #1:\nFirst, I would like to thank the editors for the opportunity to read this interesting manuscript. I\nhave been overcommitted recently, but I could not turn down a manuscript with such an\ninteresting title.\nWe thank Reviewer #1 for taking the time to provide a detailed review that raise important\ncriticism of the manuscript.\nSecond, I would like to commend the authors on an interesting idea. You will see, below, that\nI do not think this work is ready for publication, but it is an intriguing idea and one that is\ninnovative and has not been argued before.\nWe are glad that our idea was found to be intriguing and recognized as innovative. In\naddressing the comments and points raised by the reviewer, we produced a more convincing\nargument.\nThird, I have made extensive comments in the PDF of the manuscript. Please use these line\ncomments during any revisions that you might make.\nThe individual comments made in the PDF of the manuscript are addressed in detail after\nreplying to three “critical elements” below.\nI will only report the critical elements that lead to a decision of \"not yet publishable\" below:\n(1) The first critical issue is the assertion that high-latitude carbonate deposition requires\nglobally high temperatures. This is really the crux of the manuscript, but the hypothesis is not\nwell supported (rather, it is simply asserted).\nPoint 1: The high-latitude carbonate deposition presented in the manuscript requires\nglobally higher temperatures, because the facies is distinct from what can be expected from\ncold-water carbonate deposits. James and Lukasik (2010) lists characteristics of carbonate\ndeposits in warm temperate, cool temperate and polar regions. We consider those that do not\ninvolve Metazoan components as valid also for Precambrian deposits:\n Interbedded glacial deposits (polar and cool temperate)\n Ice-rafted debris (polar)\n Minor carbonate mud (polar, cool temperate, and warm temperate)\n Local hardgrounds (cool and warm temperate)\n Glendonites (polar)\n Minor photozoan elements are found in warm temperate settings\nThe carbonates described in the manuscript are voluminous, laterally extensive and generally\nlack reworked clastic carbonate components. They are microbial (with rare spatially limited\ncolumnar and branching stromatolite occurrences) and with a high component of carbonate mud.\nThey are free of interbedded glacial deposits and ice-rafted debris. Glendonites have not been\ndocumented and neither have local hardgrounds been identified in the facies. As such they have\nmore in common with warm water carbonate facies, but we cannot completely rule out a\nwarm temperate setting either. Given the reported polar paleolatitude, the facies implies a\ntemperature of at least 15-20°C, if not higher. As such, climate had to be significantly hotter\nthan today, especially if the effect of a ~10% lower solar luminosity is considered.\n[James, N. P. and Lukasik, J., 2010. Cool- and cold-water neritic carbonates, in James, N. P.\nand Dalrymple, R. W., eds., Facies Models 4. Geological Association of Canada, 271-399.]\nThe absence of glacial activity during this time does not require dramatically higher\ntemperatures. Polar glaciation also requires the existence of sufficient continental mass as\nreservoirs for ice (i.e. like Antarctica), or sufficient continental mass that restricts active flow\nof oceanic currents to higher latitudes (i.e. like the northern polar ocean). At times where there is little polar continental mass, oceans tend to not form ice, and are generally warmer,\nbut need not be drastically so.\nThe Mesoproterozoic was for the greater part free of glaciation, and is generally regarded in\nliterature as a warmer time. It is, however, true that the absence of glacial activity does not\nrequire dramatically higher temperatures, but it is important to be cognizant of the effects of\n~10% lower solar luminosity during this time.\nUnfortunately, continental reconstructions at the moment are not able to provide enough\ngranularity to allow for conclusive statements about ocean currents, but in terms of\ncontinental mass at the poles, we illustrate that southern cratonic India as well as North\nChina likely occupied polar latitude in the same hemisphere at the end of the\nMesoproterozoic. This would have increased the likelihood of glaciation, yet no evidence for\nthis has been forthcoming.\nClimate modelling by Liu et al. (2019) take lower solar luminosity into account and has\nshown that pCO at 12 times PAL would produce a glacial climate. Ice-free continents (but\n2\nnot if they were situated at the poles) would have required 24 times PAL. Ice-free southern\nIndia and North China near the pole thus would have required more than 24 times PAL of\npCO . We therefore think that an ice-free end-Mesoproterozoic probably required\n2\nsignificantly higher temperatures. The carbonate facies of the Purana platform does not\ncontradict this view.\n[Lui, P., Lui, Y., Hu, Y., Yang, J. and Pisarevsky, S., 2019. Warm Climate in the “Boring\nBillion” Era. Acta Geologica Sinica, 93, 40-43.]\n(2) The second critical issue is the assertion that warmer temperatures (see above) is the\nuniformitarian approach. In fact, it is not. On the modern Earth, we have higher-latitude\ncarbonate formation (cold water carbonates, to which you refer early in the manuscript).\nTherefore, the uniformitarian approach would be that these high latitude successions are also\ndominated by cold-water carbonate deposition.\nHowever, to even approach this uniformitarian argument, you need to be able to answer the\nquestion (and I have no idea what the answer is): what does a cold-water carbonate looks like\nin the Precambrian? This is a great question, and one I ask students every time I teach about\ncarbonate rocks. In the absence of the metazoan organisms that define cold-water carbonate\nfacies today?\nWhat do you look for? At the minimum, you need to make a facies argument that these high\nlatitude facies are fundamentally different in character than similarly aged low-latitude facies.\nPoint 2: The reviewer is correct that a uniformitarian approach, in the strict sense, would be\nto regard the high-latitude carbonate succession of the Purana basins as cold-water\ncarbonate deposits. We now acknowledge this view explicitly in the revised manuscript.\nHowever, the Purana carbonate facies is distinct from the facies expected for Precambrian\ncold-water deposition (see the reply at point 1, above). The Purana facies is analogous to\nmodern warm-water carbonate facies, but we also cannot conclusively rule out a warm\ntemperate setting. We thus apply a uniformitarian approach in the loose sense of inferring\nmodern conditions (specifically, water ocean temperature) to the observed ancient facies.\n(3) Finally, in terms of any of these arguments, you need to address other possibilities. A\nsimilar \"climate paradox\" has been argued in the past about \"cap carbonate\" facies directly\nfollowing Neoproterozoic low-latitude glacial (snowball Earth) events. This has mostly gone\nto the wayside in the literature, in favor of either arguing about the timing and number of\nsuch events, or arguing unique geochemical conditions that permitted carbonate formation in\nthe aftermath of global glaciation.\nPoint 3: Given the current poor documentation of cold-water Precambrian carbonate facies,\nwe acknowledge that there is some uncertainty to our interpretation of Purana carbonate\ndeposit. However, based on the facies argument as outlined above in points 1 and 2, we\nconsider polar ocean water temperatures of at least above 15°C, but likely higher than 20°C\na prerequisite. As such the deposits are a proxy for greenhouse climatic conditions that\nrequired higher pCO2 (and other greenhouse gasses) than previously considered for the\nMesoproterozoic.\nWe further acknowledge that, an explanation for our high-latitude carbonate deposits need to\ngo beyond ocean temperature. Other potential controls like carbonate saturation, ocean\ncirculation or continental configuration should be considered in the future. These factors\nrequire a global perspective and level of detail that is not provided just yet by current\ncontinental reconstructions.\nWe also do list several alternative non-actualistic possibilities, and explain why we regard\nthem as unlikely explanations for the late Mesoproterozoic carbonate deposits of southern\nIndia and North China.\nGiven the implications of using the word “paradox” we have opted for a softer expression\nand replaced it with “conundrum” in all instances.\nSo, in the end. Do I think that there is something special about these high-latitude carbonate\ndeposits – absolutely! Do I think that there is sufficient argument laid out in this manuscript –\nunfortunately, no.\nI would love to read a revised version, however, in the future. You have something\nhere....you just need the right framework for it! Good luck!\nWe are excited to note that the significance of the high-latitude carbonate deposits described\nin our manuscript is obvious to the reviewer, and would like to thank him/her once again for\nproviding us with the guidance to present a better argument and framework for our preferred\ninterpretation.\nDetailed comments:\nLine 13: There is no sense in using the phrase \"boring billion\" when: (1) it is clearly used out\nof context, and (2) it is clearly not true. Calling the Mesoproterozoic the \"Dullest time in\nEarth History\" (Buick et al 1995) was in reference to the carbon isotope records of the late\nPaleoproterozoic and early Mesoproterozoic (and shown not to extend into the latter\nMesoproterozoic by Kah et al. in 1999). The phrase \"boring Billion\" was coined by Bob\nHazen, to describe a time interval when the inventory of new minerals was at a minimum. If\nyou are talking about the Mesoproterozoic here, just use Mesoproterozoic.\nAlthough the term “boring billion” is still very much in use today, we agree with the reviewer\nthat this time interval was anything but boring. We also agree that it is not completely\nnecessary to use the term in this manuscript. We have changed it to “Mesoproterozoic”.\nLine 15: “Substantial” instead of “Significant”\nLine 18: “Previous studies noted such high latitudes”\n4-6\nDone.\nLine 22: “high-latitude carbonates represent a paleoclimate paradox”\nDone.\nLine 22: “high-latitude carbonates represent a paleoclimate paradox”\nThis is going to need explained. Why is this paradoxical? Because carbonate deposits are\ntypically tropical (not necessarily -- cf. cold-water carbonate deposits of James et al.)\nSee our reply to the critical elements in points 1-3, above. We discuss cold-water carbonate\ndeposits in some detail, and have highlighted why we think our carbonate facies is more\nlikely to be from warm-temperate to warm water settings. Given the implications of using the\nword “paradox” we have opted for a softer expression and replaced it with “conundrum” in\nall instances.\nLine 23: Carbonate rocks form today in many environments (deep ocean, higher latitudes)\nwhere ocean temperatures are certainly less than 20°C. Carbonate deposits also formed in the\naftermath of snowball earth events (also often called a climate paradox), but to make these a\nparadox, you need to believe that there is not another mechanism that could account for their\ndeposition.\nSee our reply to the critical elements in points 1-3, above. Here we explain why we regard\nthe deposits as out of the ordinary. If our interpretation is correct, they are “paradoxical” in\nthat they require higher atmospheric pCO levels than what is currently excepted for the late\nsofter expression and replaced it with “conundrum” in all instances.\nLine 31: Better to say \"biotic constituents\" because some of the \"abiotic\" constituents (e.g.\ncarbonate mud) are found in high latitudes (cf. O'Connell et al), and extent of cementation\n(which is often said to vary) has not been well-described.\nWe implemented the change of wording to “biotic constituents” as opposed to just\n“constituents”.\nThe identification of carbonate mud in high-latitude settings by O’Connell et al. (2015) is\nnoted and now referred to in the revised manuscript. It is, however, noted that the mud-sized\ncarbonate particles are the product of skeletal fragment breakdown.\nThe question I always ask is....how would one recognize a cold-water carbonate in the\nPrecambrian?\nSee our reply to the critical elements, point 1.\nLine 32: “comprised largely of” instead of “essentially”\nLine 32: “bioclasts” instead of “bioclastics”\nLine 32: “ahermatypic corals”\nDone.\nLine 33: As noted above, this is not necessarily true. [regarding lime-mud]\nWe added the statement: “Carbonate mud, which is usually a minor component of high-\nlatitude Phanerozoic carbonate deposits has been interpreted as the product of skeletal\nfragment breakdown.”\nLine 35: “photosymbiont”\nDone.\nLine 36: “hermatypic corals”\nDone.\nLines 37-39: I know you are making an argument, but this ignores decades of work on cool-\nwater carbonate facies.\nThe statement that warm-water neritic environments are the principal settings for carbonate\nproduction and preservation is based on the analysis by Kiessling et al. (2003). Perhaps it is\nbetter to say that warm-water neritic environments are responsible for most carbonate\nproduction and preservation in terms of volume.\nWork done on cold and cool-water carbonate facies are discussed in some detail.\n[Kiessling, W., Flügel, E. and Golonka, J. A. N., 2003. Patterns of Phanerozoic carbonate\nplatform sedimentation. Lethaia, 36, 195-225.]\nLines 39: “This is also assumed” Please be discrete -- what is assumed? Tropical carboante\ndeposition?\nWe now make it clear that it is the preferential tropical deposition of Precambrian platforms\nthat is assumed by paleogeographers. We note that this may be a false assumption as cold\nwater carbonate facies from the Precambrian are not well documented.\nLine 42-43: Regarding aragonite fans: Also Mesoproterozoic and Neoproterozoic -- could\ncite recent compilations like Cantine et al. (2019) and Kah and Bartley (2021).\nIn an attempt to limit the number of citations (given the constraints imposed by Nature\nCommunications) we rather opted to say that aragonite fans formed during the Precambrian.\nAs such we are inclusive of the Archean as well as the whole of the Proterozoic Era.\nLine 43: What is \"they\" here?\nIn the revision we make it clear that we are referring to Precambrian carbonate platforms.\nLine 45: “pattens” was replaced with “patterns”\nLine 50: Comma added after India\nLine 54: “A succession of” was added before “carbonate and shale”\nLine 54: “facies” instead of “carbonates”\nLine 60: Comma added before and after “too”\nLine 62: What is \"it\" here? The Purana platform cover in the Kaladgi, Bhima, and Cuddapah\nbasins?\nThe statement was revised to clarify that thetiming of the platform’s depositionin the\nKaladgi, Bhima and Cuddapah basins is the subject here.\nLine 70-73: Just thinking ahead. At present, this is not enough of a description to place this\ninto any sort of platform context.\nWe agree that the description on its own is not enough to place the units within a platform\ncontext, but this has been done by the detailed sedimentological work of previous studies on\nwhich we rely. It is also only after the Kurnool Group is considered in the context of its\ncorrelation to the other Purana basin successions that the large lateral extent and\nvoluminous nature of the platform becomes apparent. In addition, further description and\ndetails are provided in Figure 2 and its caption. These carbonates were mostly deposited\nbelow wave base and are bedded lime mudstones with spatially limited columnar and\nbranching stromatolite occurrences, calcareous shales, and locally developed lime-clast\ndebris-flow conglomerates and calciturbidites in distally steepened settings. The facies is\ninterpreted as being deposited in a carbonate ramp environment.\nIn order to avoid confusion regarding terminology we provide the following statement in the\nintroduction: “Several terms exist for neritic carbonate deposits based on geometry (i.e.,\nramps, rimmed and open shelfs), but we generically use the term “platform”.\nLine 76: “minimum” was replaced with “maximum”\nLine 85-88: We are pleased that the reviewer likes our compilation of Precambrian\ncarbonate platform paleolatitudes.\nLine 97-98: The steep primary magnetizations were indeed surprising.\nLine 106-109: How different? Is there evidence of a very large shift in pole location between\n1400 and 1075?\nA large shift in pole location is what is observed between 1400 and 1075 Ma (Fig. S.8B). At\nboth these instances southern India was located at a lower or equatorial latitude,\nrespectively.\nDoes the character of carbonate change during this time?\nThere are no carbonate units in the Purana succession that are ~1.4 Ga in age. Limestone\ndeposited near the upper part of Kurnool Group is likely around ~1.0 Ga, but not\nconstrained by any paleomagnetic data. The carbonate facies here and in the other Purana\nbasins (i.e., upper parts of the Raipur Group, Indravati Group and the Pranhita-Godavari\nValley Basin) are dominated by pink-reddish calcareous shale.\nLine 120-124: OK, but you previously said that the pole was very different in character from\nIndian poles at 1465, 1075, and 770.\nThe implication is that the age of magnetization and the Purana platform is likely removed\nfrom the current maximum (1405 ± 9 Ma) and minimum (1001 ± 7 Ma) age constraints, but\ncloser to 1.2 Ga as also indicated by the ~1180 Ma glauconite age from the Pranhita-\nGodavari Valley. We thus tentatively assign the 1192 ± 10 Ma age of the Harohalli alkaline\ndyke pole to our pole. This age is, however, subject to debate and we remain cognizant of the\nwider age range when considering the Purana platform’s paleomagnetic constraints.\nLine 126: Is this your work, or is there a citation missing here?\nWe have added references for the paleolatitude of the Chhattisgarh and Pranhita-Godavari\nValley basins and the Kaladgi and Bhima basins.\nLine 126: “carbonates” was changed to “carbonate facies”\nLine 143-146: OK. This is not a lot to go on for the interpretation, but North China has\nalways been a bit of a problem.\nA change from purplish-pink to grey limestone is seen in both the Purana platform as well as\nthe North China platform. This, together with the paleomagnetic correlation and near\ncoevality of the two successions is suggestive of a shared history.\nLine 147: If this is plural, please cite more than one paper.\nWe revised the text to now read: “Such a near-neighbour relationship has been noted before,\nalbeit in a different configuration”\nLine 157-160: Whereas this is true, the more pressing issue is our ability to determine what a\ncold-water carbonate would look like in the Precambrian....this has not really been discussed\nat all, yet.\nSee our reply to critical elements, point 1. Cold-water carbonates and what they might look\nlike in the Precambrian is now discussed in the revision.\nLine 161-163: Whereas this is true, these are broadly epicontinental successions within rift\nbasins, so this argument does not really apply.\nThis was also commented on by Reviewer #4. We have revised and shortened the text to read:\n“deposition … could also be affected by the supercontinent cycle”.\nLine 167-168: OK, so I am mostly through the manuscript before you really come down and\ntell your audience what is going on....and it is this: You assert that these high-latitude\ncarbonate platforms indicate a much hotter earth.\nThis “punchline” is now stated already in the abstract, while also mentioning other possible\ninterpretations. In the discussionwe clarify why we think these facies are not representative\nof the cold-water realm, but rather a warm-temperate to warm-water realm. See our reply to\ncritical elements.\nUnfortunately, you have not given the reader any argument for this possibility. Only an\nunsupported assertion.\nWe have now articulated our argument more clearly and support it with a facies argument.\nLines 156-169: Much of these arguments are pro-forma and not very interesting. Could be\ncondensed.\nThe section was condensed.\nFigure 3C: OK, I am a bit behind on new reconstructions from Paleomag, but this is even a\nvery different reconstruction than that given in the Chinese work that is cited here for the\nhigh latitudes of the North China platform.\nIn the text we note that “we reconstruct India and North China as near neighbours during the\nassembly of Rodinia. Such a near-neighbour relationship has been noted before, albeit in a\ndifferent configuration” to that proposed by Zhao et al. (2018).\nPaleomagnetic reconstruction of continental blocks are non-unique with many degrees of\nfreedom, particularly if continental blocks are restored at a specific time (i.e., closest\napproach reconstruction method) as opposed to over a longer time interval (i.e., apparent\npolar wander path matching reconstruction method).\nOur reconstruction of North China relative to the better constrained core of Rodinia (i.e.,\nLaurentia, Siberia, and Baltica) follows Zhang et al. (2021) and is also illustrated by Evans\n(2021):\nZhang et al. (2021)\nREDACTED\nEvans (2021):\nREDACTED\n[Zhang, S., Chang, L., Zhao, H., Ding, J., Xian, H., Li, H., Wu, H. and Yang, T., 2021. The\nPrecambrian drift history and paleogeography of the Chinese cratons, in Pesonen, L. J.,\nSalminen, J., Elming, S. Å., Evans, D. A. D. and Veikkolainen, T., eds., Ancient\nSupercontinents and the Paleogeography of Earth. Elsevier, 333-376.]\n[Evans, D. A. D., 2021. Meso-Neoproterozoic Rodinia supercycle, in Pesonen, L. J.,\nSalminen, J., Elming, S. Å., Evans, D. A. D. and Veikkolainen, T., eds., Ancient\nSupercontinents and the Paleogeography of Earth. Elsevier, 549-576.]\nResponse to comments by Reviewer #2:\nThis is a well-written and useful manuscript that lays out a new constraint on Mid-\nProterozoic climate. The authors report paleomagnetic data that at least purports to show that\ntypical warm-water carbonate platforms were constructed in India at 1.2 Ga when that land\nmass was north of 70 degrees latitude. If correct, this shows that the polar oceans at that time\nwere at least as warm as during the Mid-Cretaceous maximum, around 100 Ma. This is a\nuseful target for climate modelers, including this reviewer. There is an ongoing debate about\nthe nature of that climate, which should have depended on greenhouse gas concentrations like\nCO2, CH4, and N2O, but also on O2 because the latter gas would have influenced the\nconcentrations of the last two of these three greenhouse gases.\nI am not going to comment on the observations themselves, as this is best left to other experts\nin these fields. I hope that the paper is reviewed by a qualified paleomagnetist, as this is a\ndifficult subject that requires expert training. Likewise, the interpretation of what types of\ncarbonate deposits formed at what ocean temperatures can be best addressed by a reviewer\nwith a strong sedimentology/stratigraphy background. Suffice it to say that to a non-expert in\nthese fields, the study seemed carefully done.\nReviewer #1 commented on the carbonate sedimentology, while Reviewer #3 commented on\nthe stratigraphy. Reviewer #4 commented on aspects of the paleomagnetism.\nThe section on the ‘Paleoclimate paradox’ is also well-written, but I do have two detailed\ncomments that are listed below. The first concerns possible evidence for glaciation during the\nBoring Billion. The second points to a recent 3-D, Mid-Proterozoic climate calculation by\nsome Chinese researchers. The latter project was led by Peng Liu, who spent two years\nworking with me here at Penn State, which is why I know of this work. It might be useful to\ninclude some of these references. This reviewer is particularly interested in whether the\nevidence for glaciation at 1.8 Ga and 1.1-1.3 Ga should be considered credible.\nSee responses to the detailed comments below.\nFinally, I was pleased to see that the manuscript is dedicated to Nic Beukes. I met Nic almost\n40 years ago as a member of Bill Schopf’s Precambrian Paleobiology Research Group at\nUCLA. Nic was a valued member of that team, and he continued to provide valuable advice,\nand to show other Precambrian geologists around South Africa, for many years after that\ntime. We were all sad to learn of his passing. You may reveal my name to the authors.\nJim Kasting\nPenn State\n----------------------------------------\nWe thank Prof Kasting for his positive review of the manuscript and for his constructive\ndetailed comments below. We addressed these in our revision.\nDetailed comments:\n1. (l. 183) ‘The Mesoproterozoic has long been considered a warm time based on the absence\nof glaciation(2,8).’\n--Refs. 2 and 8 are to Holland (2006) and Young (2013). This is indeed the currently accepted\nstory. But in writing our 2017 book, Atmospheric Evolution on Inhabited and Lifeless\nWorlds’, David Catling and I discovered references to papers that question this idea, or at\nleast show some of its limitations (see Sect. 11.3.1, p. 302-303). More detail follows: i) Two\nof these papers concern possible glaciation in the King Leopold formation in northwestern\nAustralia (G.E. Williams, J. Geol. Soc. 162, 111-124, 2005; Schmidt and Williams,\nPrecambrian Res. 167, 267-280, 2008). This may be sufficiently removed from the middle of\nthe ‘Boring Billion’ period to not break up the story too much, as the time span of the Boring\nBillion is often cited as 1.8-0.8 Ga. Are these papers believable? ii) A third paper concerns\nglaciation in the Vazante group in Brazil, which was previously considered Neoproterozoic in\nage but has been redated at 1.1-1.3 Ga by N.J. Geboy et al., Precambrian Res. 238, 199-213,\n2013). This is right during the time in which the high-latitude carbonates in the present paper\nare reported. Is this report believable and, if so, does it cast doubt on the conclusions reached\nin this new manuscript?\nWe note the reviewer’s concern regarding the statement that the Mesoproterozoic is\nconsidered warm based on the absence of glaciation. The statement was revised to read:\n“The Mesoproterozoic has long been considered a warm time based on the general absence\nof glaciation at a time of lower solar luminosity”. This statement now accommodates the\nisolated reports of possible glaciation mentioned by the reviewer. The 1.0-1.1 Ga possible\nglacial unit occurrences are also now listed in the revised manuscript. The 1.8 Ga King\nLeopold glaciation is far removed from the time interval that is the focus of this manuscript\nbut is indicated on Figure 4. The purported 1.0-1.1 Ga Vazante Group glacial record is\ncomplicated in that the São Fransisco craton was probably located at low latitude at the time\nin question (See figure below from Trindade et al., 2021) and adds to the climatic conundrum.\nREDACTED\n[Trindade, R. I. F., D’Agrella-Filho, M. S., Antonio, P. Y. J. and Teixeira, W., 2021. The\nPrecambrian drift history and paleogeography of Congo-São Francisco craton, in Pesonen,\nL. J., Salminen, J., Elming, S. Å., Evans, D. A. D. and Veikkolainen, T., eds., Ancient\nSupercontinents and the Paleogeography of Earth. Elsevier. Amsterdam, Netherlands, 445-\n464.]\n2. (Same paragraph) Some additional constraints on Mid-Proterozoic temperatures are\nprovided by 3-D climate simulations by P. Liu, Y. Liu, Y. Hu, J. Yang, S. A. Pisarevsky,\nWarm climate in the “Boring Billion” era, Acta Geologica Sinica-English Edition 93, 40–43\n(2019). According to their (zero-CH4) climate model results, 3,550 ppmv CO2 at 1.42 Ga\nwould have produced a glacial climate with a mean surface temperature of 10.7 °C, whereas\n7,100 ppmv CO2 would have produced a mean surface temperature of 18.6 °C—sufficient to\nkeep the continents (but not the poles) ice free. These calculations account for the fact that\nsolar luminosity at that time was 90% of the present value. These two CO2 levels are\nequivalent to 12-24 PAL, if the Preindustrial Atmospheric Level (PAL) is rounded to 300\nppmv. Thus, if these climate calcu∼lations are accurate, the new climate constraints\nprovided in the present manuscript would likely require >24 PAL of CO2 and/or additional greenhouse\nwarming by CH4 or N2O.\nWe thank the reviewer for bringing our attention to the interesting climate model of Liu et al.\n(2019). The results of these simulations have now been worked into the revised manuscript.\nReviewer #3 (Remarks to the Author):\nReview of “Extreme high-latitude platform carbonate deposition …” by de Kock et al.\nsubmitted to Nature Communications\nPrimarily on the basis data on paleopole positions in late Mesoproterozoic, compiled from the\nliterature and one new set from India, and, the distribution of carbonate platforms of the time,\nthe authors boldly claim that the then poles were not only ice-free but were also warmer than\n20°C. On the basis of theoretical arguments, they further infer that the atmosphere of the time\nwas charged with super-greenhouse gases.\nWe would like to thank Reviewer #3 for reviewing the manuscript and for the valuable\nconstructive criticism. We have addressed all the issues raised.\nIt is noted that we follow previous studies that claim generally ice-free conditions during\nmuch of the Mesoproterozoic. Our illustration of the occurrence of laterally extensive and\nthick carbonate deposition at very high latitude without documented glendonite occurrences\nor interbedded glacial sedimentary units supports the idea that at least one of the poles was\nunglaciated and that indeed the Earth was probably experiencing greenhouse climatic\nconditions. It is further noted that we revised the use of the wording “super greenhouse” to\nsimply “greenhouse” in our revision as it has been brought to our attention that “super\ngreenhouse” has a very specific meaning in climate science. “Super greenhouse conditions”\nimply a positive feedback of greenhouse warming due to connections between increases in\ntemperature and water vapor. This is not the meaning that we intend to convey.\nBecause I have no training in or insight into paleomagnetism, I am accepting the authors’\nresults, but other reviewers need to assess this main part of the paper.\nReviewer #4 commented on aspects of the paleomagnetism.\nAs an outside reader, I suggest that the authors consider stating upfront what the error-bars on\npaleopoles are (fig. 3C) and what their implications might be.\nAlthough we are not completely sure what the reviewer’s expectation is here, we do explain\nin the text that the poles imply a paleolatitude of 72° ±12° for the Kurnool Group deposition,\nwhich is comparable to the 72° ±13° and 83° ±16° obtained from the Chhattisgarh and\nPranhita-Godavari Valley basins and the Kaladgi and Bhima basins. The implications of this\nare discussed in the manuscript.\nIt appears that there is an implicit assumption that paleopole positions of a cratonic block\ndetermined from a set of dykes must also be those of carbonate deposits in the same block. In\nthe understandable absence of absolute ages of the carbonates (see below), this assumption\nshould also be stated upfront.\nWe have added two sentences at the end of the section concerning the age of the pole for the\ncarbonates in the light of the comparison with known paleopoles. The comparison implies\nthat the age of magnetization and the Purana platform is likely removed from the current\nmaximum (1405 ± 9 Ma) and minimum (1001 ± 7 Ma) age constraints, but closer to 1.2 Ga\nas also indicated by the ~1180 Ma glauconite age from the Pranhita-Godavari Valley. We\nthus tentatively assign the 1192 ± 10 Ma age of the Harohalli alkaline dyke pole to our pole.\nThis age is, however, subject to debate and we remain cognizant of the possibe wider age\nrange when considering the Purana platform’s paleomagnetic constraints.\nThe ages and paleopole positions of the igneous rocks are well constrained by using the\n~same rock units, for example the Harohalli dykes (zircon; U-Pb), and by using corrections if\nany. Ages of carbonate platforms discussed in this paper are not as well constrained as the\nauthors rightly state (e.g., lines 49-78). The best age-estimates come from the U-Pb ages of\nzircons and monazites in the tuffs near the bottom and the top of some basin in the Bastar\ncraton.\nThis is clearly articulated in the text: “The minimum age limit of the platform is directly\nconstrained by U-Pb zircon crystallization ages from tuffaceous units in the Chhattisgarh\nand Indravati basins to predate 993 ± 8 million year (Ma) and 1001 ± 7 Ma repectively, and\nto post-date 1405 ± 9 Ma in the Chhattisgarh Basin. The timing of the platform’s deposition\nis less certain in the Kaladgi, Bhima and Cuddapah basins, but is broadly assigned to the\nlatest Mesoproterozoic to early Neoproterozoic …”.\nDetrital zircon ages from siliciclastic units provide maximum depositional ages; they should\nnot be construed to be close to true depositional ages as the authors state in lines 59-61 (the\nstatement must be corrected).\nThis comment applies to constraints on the age of the Kolhan Group The statement\nconcerning detrital zircon ages for the Kolhan Group was revised.\nOverall however, I agree that carbonate deposition occurred around 1.2 Ga in different\ncratons in India, and that the authors are within permissible limits in their inferences.\nWe are happy to note the reviewer’s agreement that the carbonate deposition occurred\naround 1.2 Ga.\nThe authors need to correct the spelling of Chhattisgarh.\nThe spelling of Chhattisgarh was corrected in all instances.\nIncidentally, I suppose that the e-compositor will straighten out many space-obliterations in\nthe text that I received.\nThis is unfortunate. It is noted that space-obliterations were not visible in the approved pdf of\nthe initial submission. This issue was not commented on by the other three reviewers.\nPerhaps it is due to a display issue or software version related.\nDetailed comments:\nLine 55: “upper” was replaced with “minimum”\nLine 82: What are the rock types?\nCore plug rock types are now listed.\nLine 100: I am not familiar with the conventions in sedimentary paleomagnetic studies.\nHence I ask for my education - Are the hematite and magnetite crystals co-precipitates with\nthe carbonates, or, diagenetic, or detrital?\nThe positive intraformational conglomerate tests indicate that the magnetization carried by\nhematite and magnetite was recorded at the time of carbonate deposition. The exact nature of\nthe magnetic minerals (i.e, co-precipitates vs. detrital, or even very early diagenetic) is not\nconstrained.\nAnd, are \"intraformational conglomerate tests\" universally accepted?\nThe conglomerate test is widely used in palaeomagnetism to date components of natural\nremanent magnetization with respect to deposition of conglomerates. A positive\nconglomerate test from an intraformational conglomerate provides very strong evidence for a\nprimary magnetization (Butler, 1992).\n[Butler, R. F., 1992. Paleomagnetism: magnetic domains to geologic terranes. Blackwell\nScientific Publishers, Boston, 319pp.]\nLines 127-128: It would be fair if the authors draw attention to the uncertainties in the\npaleopole positions. Most can be considered \"high latitude\" even at extremes of the \"error\ncircles\".\nWe replaced “extreme high latitude” with “high latitude”\nLine 133: This is the crux. While Kiessling et al. (2003) summarize the data on Phanerozoic\ncarbonate platforms, acceptance of >50 deg deposits require robust proof. Only reviewers\nwith expertise in paleomagnetism can assess the data; not me.\nReviewer #4 accessed the paleomagnetic data in detail, and accepts that the units were\ndeposited at more than 50° from the equator.\nLine 180: Sounds reasonable. GW's hypothesis has not caught on. DADE prevails.\nWe note the reviewer’s general agreement with the statement that high-obliquity and non-\naxial dipole geomagnetic fields are unlikely during the late Mesoproterozoic.\nLine 188: This is a good argument. Regardless of their latitudinal positions, late\nMesoproterozoic carbonates are abundant. Atmospheric and sea water conditions must have\nconspired to aid such deposition.\nWe note the reviewer’s agreement with the argument.\nLines 209-210 Suggest \"likely higher than\" … at authors' discretion.\nDone.\nReviewer #4 (Remarks to the Author):\nThe manuscript contains some new paleomagnetic data from Mesoproterozoic Indian\ncarbonates and an interesting observation about their high paleolatitudes. Unfortunately, the\nage uncertainties of these data are large, so more studies are required to accept the main\nsuggestion of the manuscript about climatic paradox in late Mesoproterozoic. However, it is\nsuitable as a hypothesis and worth publishing after a moderate to major revision.\nWe thank the reviewer for his detailed report on the manuscript and for the valuable\nconstructive comments. The age uncertainties are indeed large and the limitations of this is\nclearly articulated in the manuscript. We agree with the reviewer that more studies are\nneeded. We hope that acceptance of our manuscript will result in more attention being given\nto these interesting units from southern India. We, however, do not agree with the reviewer\nthat the climatic implications of high-latitude non-cold-water carbonate deposition are\nnecessarily negatively affected by the current age constraints. These implications remain no\nmatter what the absolute age of the carbonate deposition is within the possible age range\nbetween 1.4 and 1.0 Ga. We are therefore pleased to note that the reviewer considers our\nhypothesis worth publishing.\nCOMMENTS\nUnfortunately the organization of the manuscript is not perfect. It is really hard for readers\n(and for a reviewer) to read three separate texts in parallel (the main one and two\nsupplementary ones), each with separate illustrations and separate, though overlapping\nreference lists (some references are present in all three lists, having different numbers in\neach). In addition there is a table S3 with the fourth reference list. All these parts are\nimportant for an understanding of the authors’ conception, justification of their ideas and\nspecific details, so it is quite an effort to jump from one part to another all the time. I\nunderstand that this problem is partly caused by the strict rules for publications in NC,\nhowever there is a challenge for the reader.\nThe organization of the manuscript is indeed largely dictated by the strict rules for\npublication in Nature from which the manuscript was transferred. The Supplementary\nInformation was now reorganized into a single PDF document as per formatting instructions\nof Nature Communications and many of the issues raised by Reviewer #4 are resolved\nthrough this. We do, however, believe that the dataset, its interpretation, and discussion can\nbe followed by the general reader without issue (e.g., reviewer 1-3 did not find issues with the\norganization). The supplementary information is mostly of interest to paleomagnetic\nspecialists, and should not pose a challenge to the wider readership.\nMain text\nLines 74-78: the ~1.2 Ga age of the Narji Limestone (NL) is poorly justified. Why not ~1.4\nGa, for example - closer to the mean of 913 (above NL) and 1717 (below NL) Ma detrital\nzircons? More explanations are needed here.\nThe interpretation of the ages mentioned by the reviewer are not correct. The 913 Ma and\ndeveloped above the Narji Formation. The Paniam Formation yielded a single 913 ± 11 Ma\nzircon grain, but the next youngest age population from several grains at 1717 ± 20 Ma is a\nmore conservative maximum depositional age estimate for the Paniam Formation. The age\nconstraints thus at best suggest that the Narji Formation is older than 913 Ma.\nOur ~1.2 Ga age assignment of the Narji Limestone is justified by means of a comparison to\nwell-established Precambrian paleomagnetic poles from India. The implication of this\ncomparison is that the age of magnetization and the Purana platform (and thus the Narji\nLimestone) is likely well removed from the current maximum (1405 ± 9 Ma) and minimum\n(1001 ± 7 Ma) age constraints, but closer to 1.2 Ga. This is based on its pole similarity to\nthat of the Chhattisgarh and Pranhita-Godavari Valley basins as well as the 1192 ± 10 Ma\nHarohalli alkaline dykes pole. The latter age is now tentatively assigned to the poles of the\nPurana platform, while remaining cognizant of the possible wider age range. This is now\nexplicitly stated in the text.\nLines 80-85: be more specific, what is new in you manuscript compare to previous\npublication [5].\nIt is now made clear that our data is based on more extensive sampling of the Kurnool Group\ncompared to previous work [5]. Our sampling includes new sites and wider stratigraphic\ncoverage of the Kurnool Basin and, importantly, also include results from strata of the\nPalnad Basin, which was not sampled before. In addition, we present the first rock-magnetic\nresults for the Kurnool Group. This is clearly stated in the revised text.\nLines 103-106: did you re-apply the fold and/or conglomerate tests (according to line 20 in\nSupporting information: Methods, you collected more conglomerate samples) with inclusion\nof new data, or just relied on the test results in [5]? If not, I would recommend to do that.\nWe did not re-apply the fold and conglomerate tests, but did indeed rely on the results of\nthese tests in [5]. These tests are considered robust. Our new data also cannot be directly\napplied to these tests for a re-evaluation. The reason for this is that the fold structure used\nfor the fold test [5] was a small scale and localized anticlinal structure. The test was\nconducted at the site level using sample data. Regionally the strata display minimal\ndeformation with dips of less than 10°.\nLine 109: add the table of poles (with ages) for Fig. 3C.\nA table of poles used in comparison in Fig. 3C is now provided in the supplementary\ninformation (Table S2).\nLines 119-120: “…age is otherwise not well constrained” – this is also applicable to C&PG.\nWe have changed the wording to: “but its age of magnetization is not constrained by field\ntests”. The intention here is to highlight the difference between the K&B basins and the\nKurnool Group and the C&PG basins, where the age of magnetizations for the Kurnool\nGroup and the C&PG basins are illustrated to be primary based on intraformational\nconglomerate tests and a fold test.\nLine 122: see comment to line 109. Table of poles is needed here.\nA table of poles used in comparison in Fig. 3C is now provided in the supplementary\ninformation (Table S2).\nLines 127-128: in view of huge age uncertainties, I would add “at least partly”.\nDone.\nLines 146, 387-396 and Fig. 3C: provide Euler’s rotation parameters please.\nEuler rotation parameters are provided in the caption.\nLine 150: see general comment to “Methods”.\nSee responses below.\nLine 157: instead of “within the tropics” I would say more cautiously “at < 50 degrees\nlatitudes”.\nDone.\nLine 162: I would say “could also be affected”\nDone.\nLines 165-166: I propose to rephrase this sentence (it is not only about continents): “The area\non the globe on high latitudes is less than area in the low latitudes” – something like this.\nThe paragraph was shortened based on the comments of Reviewer 1. The statement now\nreads: “Other biasing factors are the presence of continents near the poles and the area on\nthe globe at high latitude compared to low latitude.”\nLines 174-176: It would be good to cite Abrajevitch and Van der Voo (EPSL 2010, 293, 164–\n170). They were the first.\nDone.\nLine 206: …southern India and North China.\nDone.\nLine 236: correct reference is: Geol. Mag. 152(4), 728-750. Also – line 221 (in Supporting\nInformation: Results—Paleomagnetism and rockmagnetism); line 184 (in Supporting\nInformation: Proterozoic carbonate platform paleolatitudes (Bibliography))\nThe reference was corrected in all instances.\nFig. 4 and Table S3: why some vertical error bars are asymmetrical? If we suppose the\nFisherian distribution for paleomagnetic directions, dp should be the half of this bar.\nWe thank the reviewer for highlighting the issue with the vertical error bars. The vertical\nerror bars should be symmetrical and not asymmetrical. They are now represented as ±dp\n(the minimal axis of the oval of confidence for the virtual geomagnetic pole) or as ±A (the\n95\nradius of the circle of confidence for the paleomagnetic pole). The text, Figure 4, and Table\nS3 have been corrected accordingly.\nSupporting Information: Methods\nGeneral comment: please describe how did you calculate the vertical error bars (+ and -) for\nthe paleolatitude. The commonly used method assumes the Fisherian distribution of\npaleomagnetic directions and consider the minimal axis of the oval of confidence for the pole\n(dp) as a half of this error bar, as the oval is oriented “perpendicularly” to the arc of great\ncircle connecting the sample location and paleomagnetic pole. However, in this case the\nvertical “+” and “-“ in S3 should be the same and vertical error bars in Fig. 4 should be\nsymmetrical.\nWe thank the reviewer for highlighting the issue with the vertical error bars. The vertical\nerror bars should be symmetrical and not asymmetrical. They are now represented as ±dp\n(the minimal axis of the oval of confidence for the pole) or as ±A (the radius of the circle of\n95\nconfidence for the paleomagnetic pole). The text, Figure 4, and Table S3 have been corrected\naccordingly.\nFig. S1 caption: sample localities (*Wabo et al., 2021) - according to reference list(s) Wabo\net al., 2022.\nThe reference in the figure legend was corrected to Wabo et al., 2022.\nLine 85 and Table S3: it would be very useful for readers if Table S3 contain a field with\nRESULTNO (reference 8) for the data available in the Online GPMDB. Interested readers\nthen will be able to extract much more information about paleomagnetic studies of their\ninterest mentioned in Table S3.\nWe thank the reviewer for this suggestion. We agree that inclusion of the Online GPMD\nresult numbers would indeed be useful. Table S3 was updated to include a column listing\nGPMD result numbers.\nLines 101-102: some are updated. I propose “… are not always updated…”\nDone.\nSupporting Information: Results—Paleomagnetism and rockmagnetism\nTable S1 needs captions. Apparently the superscript [2] in the first column means that these\nentries are taken from previous study, which is number 2 in the Reference list to this\nsupporting information, but it is number 5 in the Reference list for the main manuscript, and\nnumber 59 in the reference list for the supporting Information: Proterozoic carbonate\nplatform paleolatitudes which is not very convenient to the reader/reviewer. In the table\ncaption it would be good to refer to the tables in the study [2], e.g. Table 3 for the high-T\ncomponent.\nCaptions have been added to Table S1.\nLines 131-135: see my comment to lines 103-106 in the main text.\nWe did not re-apply the fold and conglomerate tests, but did indeed rely on the results of\nthese tests in [5]. These tests are considered robust. Our new data also cannot be directly\napplied to these tests for a re-evaluation. The reason for this is that the fold structure used\nfor the fold test [5] was a small scale and localized anticlinal structure. The test was\nconducted at the site level using sample data. Regionally the strata display minimal\ndeformation with dips of less than 10°.\nLines 152-158, Table S1: apparently only the site KBA (sandstone) represents the clastic\nsediments in this study, others are carbonates. The KBA inclination is much less than\ninclinations in other sites (high-T component). Maybe there is something to do here with\ninclination compaction correction, which was found in some clastic rocks? Maybe if you\nexclude this site, the reversal test became positive?\nSite KBA is indeed the only one from clastic sedimentary units, and its inclination is lower\nthan those of the carbonate samples. It is possible that these inclinations are the product of\ninclination flattening due to compaction. However, exclusion of site KBA does not result in a\npositive reversal test, nor does it significantly change the high-temperature component mean.\nIn the interest of transparency, we prefer to keep the result.\nLines 176-191 and Fig. S8(B): It would be much better to add a table (with ages) of used\nIndian poles in this supporting information.\nWe have added Table S2 listing Indian and North China poles (with their ages) used for\ncomparison and reconstruction.\nREVIEWERS' COMMENTS\nReviewer #1 (Remarks to the Author):\nThis is the second time that I have read this manuscript (once in its first submission, and now after\nrevision). First, I want to thank the authors on their careful and considered revision and response to\nthe initial reviewers. When reading a revision, I am always careful to read the response to reviewers\nto see that the authors have accommodated, or explained, all criticism.\nIn this case, I can clearly say that the primary criticisms have been adequately covered in the\nrevision.\nAt this point, the only real drawback to the manuscript is driven by the short format of the work. The\nauthors, however, have extensive supplementary information to round this out.\nAs before, I find this manuscript intriguing, and am pleased to now recommend it for publication.\nCheers,\nLinda Kah\nReviewer #2 (Remarks to the Author):\nThe authors have done a good job of responding to my (minimal) comments on their original\nsubmission. But I am admittedly not an expert on these types of indirect indications of climate. I defer\nto the other reviewers, all of whom seem to have a better grip on the arguments than I do.\nReviewer #3 (Remarks to the Author):\nReview of “High-latitude platform carbonate deposition…” (revised) by de Kock et al. submitted to\nNature Communications\nThis revised version of the manuscript adequately addresses all of my comments except the one on\npaleomagnetism, which will be reviewer #4’s call.\nI am happy to note that the authors have toned down their extremism in using adjectives and\nadverbs, such as replacing “paradox” with “conundrum” and “very high latitude” with “high latitude”.\nYes, I am comfortable with this version.\nAbhijit Basu, Indiana University\nJanuary 17, 2024\nReviewer #4 (Remarks to the Author):\nThe corrections made by the authors are satisfactory. They properly addressed the issues I rose in my\nprevious reviews. The corrections to remarks of other reviewers are also"}, "author_response": ""}]

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