| 24 Jun 2026
A peat-depth database for Canada (PDD-Can-1)
Abstract. Canadian peatlands hold an estimated ~25 % of the world's peatland carbon (C) stock. However, a more accurate calculation of C stock requires high-quality empirical datasets to refine numerical techniques, perform validation steps, and calculate the resulting uncertainties in prediction. Here, we present two databases (i) a compilation of 88,763 survey points of basal peat-depth across Canada, extracted from 844 publications (government reports, environmental impact assessments and scholarly journals), and (ii) a compilation of 436,923 survey points containing no peat. Many of these peat-depth survey points were digitized here for the first time. We showcase the peat-depth data by presenting a timeline of peat studies over the past ~100 years and discuss the motivation behind much of this peatland work across the country. Measurements of peat-depth across Canada range from 0–1200 cm and from relatively shallow wetlands in the Arctic tundra to deep fens and bogs in the southern temperate forests. Importantly, our compilation includes peat-depth measurements from regional soil or surficial material surveys, largely from environmental impact assessments. These datasets tend toward shallower peats in the range of 50–100 cm, and therefore represent transition areas, regions of shallow peat and/or forested peatlands that were not previously widely documented. There are five data-quality considerations: (i) some data have low precision geographic (latitude and longitude) coordinates; (ii) across the database, there are apparent issues with rounding, vague methodology and unclear definition of the mineral-peat interface; (iii) some peat-depth data were measured 100+ years ago, so there may be mismatches between the present-day condition of the peatland and the original measurements; (iv) there are notable spatial gaps and biases across Canada, including few data from the Hudson Bay Lowlands, overall sparse coverage north of ~55° and a patchwork of peat-depth data that is sometimes abruptly truncated at provincial/territorial borders; (v) we do not include a classification of peat-depth data into fens or bogs because this information is lacking in the original data or was unreliable. We finish by discussing potential uses for these databases along with future improvements. The databases are available at https://doi.org/10.5281/zenodo.17409850 (Dalton et al., 2025).
Having read Dalton et al’s paper, I would like to draw attention to a number of items they have misconstrued, confused, or omitted. I do not, however, dispute their main point that the shothole drillers’ log-derived muskeg depths can be suspect.
First, the seismic shothole drillers’ log database was a project iteratively compiled and published over several years of effort trawling through Industry’s archives (see discussion in Smith (2015)). Dalton et al. have used the version 2 database (Smith and Lesk-Winfield 2010a – GSC Open File 6049) which contained approximately 275,000 records, and not the final database compilation (Smith, 2011 – GSC Open File 6833) which contained ~344,000 records; although they cite both publications, they appear to only use the actual data from OF 6049.
The use of these records to decipher regional extents and thicknesses of muskeg is also something that I had already published – based on the same version 2 database that they used – Smith and Lesk-Winfield 2010b – GSC Open File 6410, so, Dalton et al.’s “application” of the shothole data in this example is not original (our number of “muskeg” records queried from the version 2 database differ only slightly – 13,140 in OF 6410 and 13,014 for Dalton et al. (there’s some “complexed” term records they have missed) . Note, in this OF 6410 publication, I had also included the records from S. Smith et al. (2005) (digital borehole geotechnical database), which Dalton et al. has also I presume discovered and included. I too share Dalton et al’s profound sense that these geotechnical borehole records are far more accurate, and indeed I had suggested and used these as reliable “anchor” points to ground regional interpretations of the shothole records (although there are also limitations to the geotechnical records (and more broadly of hand auger/probe records with refusal at base of active layers) that also need to be understood).
Derivative publications based on the lithostratigraphic shothole drillers’ log data were created and published for 13 different thematic/subject areas at various stages of the database compilations – muskeg thickness included, although if you understand the nature of the data and its collection, it’s probably one of the more suspect records. Indeed, in OF 6410 I made the following comments in the Discussion:
"As with all other aspects of the shothole database, caution is required when interpreting this data. The most obvious constraint is that muskeg presence and/or thickness was not consistently recorded by drillers, or in all areas. Muskeg is clearly more extensive than the distribution of points illustrated here conveys. The data presented here should instead be used to deduce generalized regional trends, principally as they pertain to thickness. More specific inferences can be made where a proposed development coincides directly with actual “muskeg” records. Users seeking further information on peatlands along the Mackenzie corridor are directed to Aylsworth and Kettles (2000; and references therein)."
Note, my comments published in OF 6410 clearly identify a major contention I have with how Dalton et al. have used this data. Quite simply, you cannot use the “null” hypothesis with the shothole data – i.e., just because a driller did not record the presence of a particular unit (in this case, surface muskeg presence), you cannot ascribe a non-presence to that data point. What you can do at a minimum I would argue (with a reasonable sense of confidence), is use the records that do identify muskeg as a simple record of “presence,” separate from any considerations or concerns of unit thickness. This requires a re-querying of the database (already done in OF 6410…but please consider using instead the final database in OF 6833) to include complexed drillers logs where “muskeg” is identified in combination with other lithostratigraphic records (e.g. 0-10 m, muskeg, clay, rocks), but its individual thickness is not identified – for OF 6410, this includes an additional 8331 records (identified in the publication as a separate GIS layer).
Dalton et al use the word “haphazard” to describe the data collection – I have chosen to use “inconsistent” to better describe what can be discerned from this data collection…and specifically the caution I have urged users to employ with this data. To correct Dalton et al., the lithostratigraphic materials and the drill logs were created by drillers, NOT geologists, and there is no way to go back and interrogate seismic or petroleum companies as to what instructions were given to drillers for guiding lithostratigraphic logging – this was never something I’d ever encountered that was written down. There are about 5 different formats (with several different variations) that drill log records were written up/recorded through the 50 or so years of records in the shothole database. Different companies may well have instructed their drillers to note particular items, perhaps, including muskeg, however there is no way to know this from the archival records.
Dalton et al. also identify the “stepped” nature (modal depth) of reported unit thicknesses – something I had also recognized and discussed in the shothole publications. They are quite correct, but for this, a greater appreciation of how these shotholes were drilled, and how the data was recorded is needed. The principal reason these shotholes were drilled was to seat explosive charges, preferably in bedrock, for petroleum seismic exploration. Because it mattered in terms of static interferences and seismic propagation, it was most critical for the drillers to note whether the charge was seated in bedrock, and at what depth that occurred (this then was something more accurately recorded), and then if not in bedrock, what the nature of the overlying sediments were (lithologies and depths). Any other lithostratigraphic attributes that the drillers recorded over and above that is considered baseline geoscience “gravy”. Some of this may well have been collected to assist in development/access considerations (i.e. muskeg thickness was problematic for any contemplated summer petroleum well drilling operations; seismic shothole drilling was always conducted in the winter months), but any conversations I had with petroleum or exploration companies wouldn’t support this – indeed, this kind of use/insight for the shothole data was almost wholly unrecognized previously. Shothole drilling rigs (albeit the records would reflect changes in technology used over a 50-year time period) typically used air-rotary drills with 5- to 10-foot-long auger flights (1.5 to 3 m). It can be surmised that some drillers may have been “homogenizing” lithostratigraphic records in accordance with individual auger flights, or pairs of flights …i.e. “in the upper 5 feet, it was mostly muskeg, but maybe a foot or so of clay and rocks, so I’m going to write down 0-5’ muskeg.” This is not always the case, and indeed you can interrogate the records to see where individual drillers along a particular seismic line have much more precisely broken-down depths by the foot (i.e. not correlating to drill stem intervals of 5’, 10’, 15’ or 1.5, 3, 4.5 m etc.); any hope for reporting precision beyond the foot or half metre is simply not realistic to the drilling and recording practices employed. This is, however, one way I have previously queried out records I am more confident in, while regarding others as more generalized, or regarded as “maximum thickness” estimates – look for records with specific depths that don’t match drill-stem length intervals. You can also look where there are crossing/proximal seismic lines from different years reporting very much the same thing – adds weight to their reliability.
Can drillers’ logs be completely wrong or misleading …absolutely! I similarly regard the exceptional muskeg thickness records (>10 m…indeed probably anything >5 m) as highly dubious. Can’t provide the explanation for these, other than to go back and re-interrogate the original archival record to see if there was a transcription error (tested at <0.5% for the overall database during pre-publication QA/QC).
So…can the shothole drillers’ log muskeg thickness records be used – perhaps with some greater caution and data interrogation, and probably best when anchored by what are considered more “reliable” records (e.g. geotechnical borehole data). Can they be used to identify trends in muskeg thickness across a broader region – probably. At a minimum, drillers’ log records citing the presence of muskeg, can be used to simply identify presence …at that specific shotpoint…but CANNOT be used in the null sense. If you choose to use the data for simple presence…then consider also that there is a separate shothole drillers’ log compilation for Banks Island that also includes muskeg records (Smith and Farineau 2015 – GSC Open File 7322).
Regards,
Rod Smith
Smith 2015 http://dx.doi.org/10.1016/j.grj.2015.01.005
Smith and Farineau 2015 http://dx.doi.org/10.4095/296215
Smith 2011 http://dx.doi.org/10.4095/288754
Smith and Lesk-Winfield 2010a http://dx.doi.org/10.4095/261497
Smith and Lesk-Winfield 2010b http://dx.doi.org/10.4095/261784