Geology Biostratigraphy First Appearance Datum Calculator
Observed first taxon occurrence bracket on caller increasing depositional coordinate; lower-coverage censoring explicit, not global evolutionary FAD. Caller independently establishes matching units, evidence, method edition and applicability; output is not compliance, diagnosis, work-safety approval, geological identity or validated hazard prediction.
Description
A first observed fossil occurrence brackets detection within a sampled section rather than proving the organism's evolutionary origin.
A first observed fossil occurrence brackets detection within a sampled section rather than proving the organism's evolutionary origin.1
If the first sampled level already contains the taxon, the lower extent of the occurrence is censored by coverage. Use this tool to calculate biostratigraphy first appearance datum from the supplied measurements and assumptions.
When to use Geology Biostratigraphy First Appearance Datum Calculator
Use this tool to calculate biostratigraphy first appearance datum from the supplied measurements and assumptions. Establish the measurement units, sampled interval, calibration or model edition and geological assumptions before entering data.
How to use Geology Biostratigraphy First Appearance Datum Calculator and understand its results
- Establish the measurement units, sampled interval, calibration or model edition and geological assumptions before entering data.
- Enter sampleDepthsM, taxonPresenceFlags, using the field meanings and rules below, then run the tool.
- Read firstObservedDepthM, previousAbsentDepthM, lowerCoverageCensored. Interpret the fields using their units, signs and evidence conventions below.
- If input validation fails, correct the reported field and run again. Before applying the result, check reference scope, model assumptions and any missing evidence or placeholder values.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| sampleDepthsM | Sample depths m | list of number | Required |
| taxonPresenceFlags | Taxon presence flags; binary 0/1 under the definitions below | list of number | Required |
Enter strictly increasing sampled depths and aligned binary presence flags with at least one presence. Select the first flag 1; return its depth and the preceding sampled absent depth. If it is the first sample, lowerCoverageCensored is true and previousAbsentDepthM repeats that first depth as a placeholder, not an observed absence.
i=first index with presence_i=1; firstDepth=depth_i; previousDepth=depth_max(0,i−1); censored=(i=0) Use the exact units, boundary rules, ordering and missing-evidence conventions above.
| Output field | Meaning | Value type |
|---|---|---|
| firstObservedDepthM | First Observed Depth M; follow the units, sign, ordering and evidence convention stated above | number |
| previousAbsentDepthM | Preceding absent sampled depth, or first-depth placeholder when coverage is censored | number |
| lowerCoverageCensored | True when the first submitted sample already contains the taxon | boolean |
{
"input": {
"sampleDepthsM": [
0,
1,
2,
3
],
"taxonPresenceFlags": [
0,
0,
1,
1
]
},
"output": {
"firstObservedDepthM": 2,
"previousAbsentDepthM": 1,
"lowerCoverageCensored": false
}
}Limitations and assumptions
If the first sampled level already contains the taxon, the lower extent of the occurrence is censored by coverage. Interpretation depends on the units, sampling scope and exact model described above.
All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse evidence arrays fail validation; the specific bounds and alignment requirements are stated above. Extremely large inputs or outputs can also be rejected. An input error is distinct from a successful result reporting false, no matches or missing evidence.
Alternative or Complementary methods
Use Geology Varve Thickness Calculator for this related task: A varve is an independently identified annual sedimentary layer or layer pair under the adopted counting convention.
Use Geology Biostratigraphy Zone Thickness Calculator when its separate inputs and assumptions fit the question: A biozone thickness can be bounded when both its base and top have independent coordinate intervals.
References
Similar or alternative tools
- Geology Varve Thickness Calculator
A varve is an independently identified annual sedimentary layer or layer pair under the adopted counting convention.
- Geology Biostratigraphy Zone Thickness Calculator
A biozone thickness can be bounded when both its base and top have independent coordinate intervals.