General comment

Lai and co-authors present an extensive database on geochemical data (major and trace elements, stable isotopes) from deep-time (3.8 Ga to present) marine sediments, i.e. the Deep-Time Marine Sedimentary Element Database (DM-SED). The DM-SED builds upon the Sedimentary Geochemistry and Paleoenvironments Project (SGP) previously presented by Farrel et al. (2021), which is here significantly expanded adding nearly 35,000 new entries, totaling 63,691 entries with 2,412,085 discrete data points. New data supplement spatiotemporal gaps in the SGP and are largely from the Phanerozoic, although substantial new contribution for the Precambrian is provided as well.

I commend Lai et al. for digging out so many new data from the literature. The paper reads well, is clear and concise, and overall sufficient detail is provided in each section. The database is relatively well organized and easy to read. I appreciated that the authors made clear the limitations of their database, which my hamper the use of some listed entries. About this point, my concern is that the lack of any information on the methodology used to obtain the data compiled in DM-SED could discourage some users, given that methodological precision may vary significantly for elements. Therefore, I encourage the authors to integrate this information when available. Alternatively, they could add one or more entries to provide information on the methodology at a later time while keeping the database up to date.

Concluding, I would recommend this database and the companion paper for publication after minor revisions, as they provide a valuable contribution to help geoscientists aiming to improve our knowledge on climate, environments, and biogeochemical cycles from the geological past.

Specific comments

Section 3 – Dataset screening and processing

For completeness, it may be useful to specify the exact coordinate reference system used to express Modern latitude and longitude.

Database file (static copy v. 0.0.1)

I recommend the authors to follow the order listed in lines 127-135 and Table 3. Specifically, I suggest to move isotopic values immediately after carbon element values, and place References and Project details on the far right. I also suggest to avoid abbreviations in the field LithName. If information on the methodology will be provided, it may be included before listing References and Project details.

Technical comments

Line 18: I suggest to replace ‘for studying’ with ‘to study’

Line 25: since the data set focuses only on few isotopes (O, C, S, and N), it may be worth to specify them here or maybe make clear that only stable isotopes are targeted (as opposed to radiogenic ones, for instance)

Line 32: technically speaking I think ‘concentration’ is not correct here because you are referring to a solid. I suggest content, distribution or amount

Line 34: what does ‘its’ refer to? please be more specific

Line 36: replace ‘reconstruct’ with ‘reconstructing’

Line 37: consider ‘perturbations’ instead of ‘changes’; I would also suggest to end the sentence as ‘… thereby revealing mechanisms driving past climate fluctuations’

Line 43: suggested change ‘Oxygen isotopes (d¹⁸O) from fossilized marine organisms’

Lines 84-87: consider simplifying this sentence. A suggestion may be ‘…data on ancient marine sediments, they have shortcomings such as limited spatial coverage, the lack of age data and coarse age resolution, the absence of recent publications, and missing information from original publications.’

Line 87: replace ‘have established’ with ‘propose’

Line 96: replace ‘data’ with ‘portal’ or ‘database’. The same goes for line 312

Lines 105-107: the sentence is not clear in its current form. Please consider rephrasing

Line 115: suggested change ‘ … entries from 433 studies, spanning approximately 3800 Ma and including entries…’

Lines 114-118: the sentence is quite long. It may be better to split it in two after the list of all countries

Line 131: the comma after TOC is probably a mistake and there is a bracket missing here

Line 192: suggested change ‘types of rocks’ or ‘rock types’

Line 193: add ‘the’ before lithostratigraphic

Line 194: maybe you could rephrase as ‘however, for data from marine drilling sites’. What do you mean exactly with ‘there were no corresponding group names’? I this referred to lithological information? please be more precise here

Lines 209-210: ‘And the project includes two parts: new compilation and SGP’ please rephrase this sentence

Line 223-224: suggested change ‘For carbon elements, TOC has the largest record (33,216 entries), followed by Total C (9,201 entries), while C_inorg has the lowest record (7,194 entries).’

Line 232: be more specific here. I suggest ‘Within the Phanerozoic’ in place of ‘From this’

Lines 231-239: it may be good her to provide some temporal references. For instance age intervals for the Phanerozoic and Proterozoic Eons, and for the main Eras mentioned in the text. Alternatively, my suggestion is to include Eons in Figure 4a and Eras in Figure 4b (see below)

Line 285: I think adding a short last sentence on the distribution of data in the Ternary-Quaternary may be useful to increase completeness of the description

Figure 3: is there a specific reason why the list in each table is in reverse order than mentioned in the text (lines 130-135)?

Figure 4: I suggest the authors to indicate here Eons (Fig. 4a) and Eras (Fig. 4b) mentioned in the text to improve clarity. Additionally, abbreviations should be clarified, if not done elsewhere

General comments

This document introduces the “Deep-Time Marine Sedimentary Element Database” (DM-SED), a robust geochemical resource dedicated to deep-time marine sediment records. The database comprises 63,691 entries and an impressive 2,412,085 individual data points, spanning a vast temporal range from ~3800 Ma to the present. Built upon the foundation of the “Sedimentary Geochemistry and Paleoenvironments Project” (SGP) database, DM-SED incorporates newly compiled data from 433 studies. Its primary goal is to support research into Earth’s palaeoenvironments, palaeoclimates, and elemental cycles throughout geological history. The dataset is accessible via Zenodo and the Geobiology data portal. The document further outlines the data sources, criteria for inclusion, metadata associated with proxy measurements, and the spatial and temporal trends within the dataset.

The strengths of that paper are:

• The DM-SED database features an extensive dataset comprising 63,691 entries and 2,412,085 individual data points. Spanning a broad temporal range from 3800 Ma to the present, it serves as a valuable resource for the study of deep-time marine sediments.
• The database includes data from various continents and oceans, providing a global perspective on marine sedimentary geochemistry. 
• The database incorporates extensive metadata, including location, age, stratigraphy, and geochemical values, ensuring improved usability, traceability, and contextual understanding of the data.
• The DM-SED expands on the SGP database and incorporates data from additional reputable sources, increasing its scope, reliability.
• More importantly, the authors plan to keep improving and updating the dataset to ensure it stays accurate and useful for future studies.

Some (minor and mainly acknowledged by the authors) weaknesses of this paper are:

• The criteria for age determination are not entirely uniform, relying on fossil zones and lithostratigraphic unit information, which can lead to coarse age resolutions for some samples. 
• There may be significant differences in methodological precision between older and newer literature, potentially affecting data consistency. ​
• The spatial and temporal distribution of the data is not uniform, with a higher concentration of data from certain regions and time periods, which may bias the results of studies using the database.
• There are many more exotic isotopes that could be useful to add to the DM-SED. These are increasingly being used by the geochemistry community.
• More importantly, the database lacks detailed information about the methods used for element analysis. This may impact the reproducibility and comparability of the data.

To sum up, this paper must be accepted pending minor corrections. Since it presents a valuable and comprehensive database for deep-time marine sedimentary geochemistry, with significant strengths in data compilation, global coverage. However, it also has some weaknesses related to age determination variability, data quantity for certain elements, and potential methodological inconsistencies. ​ Addressing these weaknesses in future updates could further enhance the database's utility and reliability. ​

Detailed comments:

 Lines 62-92.

The authors may also include the NOAA and MMS Marine Minerals Geochemical Database. This database contains geochemical analyses and auxiliary information on present-day marine deposits, primarily ferromanganese nodules and crusts, as well as some data on heavy minerals and phosphorites. It is maintained by the National Centers for Environmental Information (NCEI).

They also may include GEOTRACES, which provides hydrographical and marine geochemical data acquired over the past decade. The data covers the global ocean, with a focus on trace elements and their isotopes, aiding in the study of marine biogeochemical cycles.

Lines 131-132

There are many more exotic isotopes that could be useful to add to the DM-SED, such as:

δ98/95Mo (Molybdenum isotopes) which indicates redox conditions, particularly euxinia (anoxic and sulfidic conditions) in marine environments.

δ238/235U (Uranium isotopes), which tracks redox conditions and changes in seawater chemistry.

δ44/40Ca (Calcium isotopes), which tracks carbonate precipitation and dissolution, diagenesis, and biological activity.

δ30Si (Silicon isotopes), which Indicates biogenic silica production and nutrient cycling.

δ114/110Cd (Cadmium isotopes) which reflects nutrient utilization and past productivity in surface waters.

δ54/52Cr (Chromium isotopes) Tracks redox-sensitive processes and oxidative weathering.

87Sr/86Sr (Strontium isotopes) which reflects changes in seawater composition due to continental weathering and hydrothermal activity.

143Nd/144Nd (Neodymium isotopes) which tracks water mass mixing and provenance of sediments.

187Os/188Os (Osmium isotopes) which indicates continental weathering rates and extraterrestrial inputs.

Δ47 Clumped Isotopes must be also added since they provide direct estimates of past temperatures independent of seawater δ18O.

Line 144-212,

Data set screening I don’t know if it is too difficult, but it would be good to roughly indicate the methods which has been used.

Line 189

For sure that GTS 2020 remains highly accurate for most applications, but it’s essential to stay informed of incremental updates in absolute ages and boundary definitions, especially for precise or controversial stratigraphic intervals. International Chronostratigraphic Chart (ICS) online for the latest updates (ICS website).

Line 191

 “dolomite”, the authors may use dolostone and not dolomite, which is a mineral and not a lithology sensu stricto

Line 192

This classification is a bit too large. It would be possible to be more precise ?

Calcareous Rock

Marls (35-60 % of carbonate)

Sand

Clay

Line 196:

The authors may include the tidal flats into the inner shelf subdivision.

Line 197:

Ok, but there are also many data set coming from shallow settings.

Line 231-241 and figure 4:

 The number of entries for the 100-113 Ma interval (Albian) is surprisingly high compared to the 100-90 Ma interval (Cenomanian), which includes the OA2 event, one of the best studied intervals of the Cretaceous. The low number of Paleogene entries is also striking, especially for the Lower Paleogene, which includes several hyperthermals (including the PETM) that are among the most studied events of the Phanerozoic.

In Figure 4a, it would be good to include eons. Furthermore, it is not sure that the potential readers are familiar enough with the Proterozoic periods to understand the abbreviations used (e.g. Ec (Ectasien)). There is also a problem of scale in figure 4b: the rectangle corresponding to the Albian is almost twice as wide as that of the Aptian, but their duration is almost the same, around 12 million years. It would be clearer for the reader if the eras were also shown in Figure 4b.

Lines 249:

That sentence is difficult to understand. The Quaternary period includes the Pleistocene and Holocene stage.

Lines 257:

 As said above, to my knowledge the OA2 is clearly more studied than the OA1b.

275:

are mainly located in the deep ocean,