Preferential dissolution of the biogenic carbonate polymorph aragonite promotes preservational bias in shelly marine faunas. Whilst field studies have documented the impact of preferential aragonite dissolution on fossil molluscan diversity, its impact on regional and global biodiversity metrics is debated. Epicontinental seas are especially prone to conditions which both promote and inhibit preferential dissolution, which may result in spatially extensive zones with variable preservation. Here we present a multi-faceted evaluation of aragonite dissolution within the late Cretaceous Western Interior Seaway of North America. Occurrence data of molluscs from two time intervals (Cenomanian-Turonian boundary, early Campanian) are plotted on new high-resolution paleogeographies to assess aragonite preservation within the seaway. Fossil occurrences, diversity estimates and sampling probabilities for calcitic and aragonitic fauna were compared in zones defined by depth and distance from the seaway margins. Apparent range sizes, which could be influenced by differential preservation potential of aragonite between separate localities, were also compared. Our results are consistent with exacerbated aragonite dissolution within specific depth zones for both time slices, with aragonitic bivalves additionally showing a statistically significant decrease in range size compared to calcitic fauna within carbonate-dominated Cenomanian-Turonian strata. However, we are unable to conclusively show that aragonite dissolution impacted diversity estimates. Therefore, whilst aragonite dissolution is likely to have affected the preservation of fauna in specific localities, time averaging and instantaneous preservation events preserve regional biodiversity. Our results suggest that the spatial expression of taphonomic biases should be an important consideration for paleontologists working on paleobiogeographic problems.
Supplementary Information 1
Contains information on the following items:
- Time Intervals
- Construction of Paleogeographies
- Regional Overview and Paleobathymetry Evidence
- Fossil Occurrence Dataset
- Multicollinearity Correlation Tables
- Additional Results (Raw occurrences, Sampling Probability, Raw Diversity and SQS)
- Supplementary Figure Captions
- Supplementary Table Captions
Supplementary Information 2
Excel file with the following results, datasets and information: - Cenomanian/Turonian dataset
- Campanian dataset
- Taxonomic Revision
- Raw Occurrences
- Raw Taxonomic Diversity
- SQS Estimates of Diversity
- Spearman's Rank Correlations
- Sampling Probability
- Multiple Logisitic Regression
- Multiple Logisitic Regression II
- Mineralogy and Life Habits
- Mineralogy and Life Habits References
- Cenomanian/Turonian Range Size
- Campanian Range Size
Supplementary Table 1
Spearman’s rank correlations between species level diversity of faunal groups and various sampling proxies for distance-from-paleoshoreline zones within the Cenomanian-Turonian and lower Campanian.
Table_S1.xlsx
Supplementary Figure 1
Additional paleogeographic zoned maps of the WIS used in this study Distance based zones are at 50km intervals A. Paleogeographic map of the Cenomanian-Turonian with distance-from-paleoshoreline zones; B. Paleogeographic map of the early Campanian with distance-from-paleoshoreline zones.
Fig_S1.png
Supplementary Figure 2
Plots of raw occurrences of ammonites, aragonitic and calcitic bivalves, outcrop area and number of collections within depth and distance-from-paleoshoreline zones for the Cenomanian-Turonian and lower Campanian. A. Cenomanian-Turonian occurrences, outcrop area and collections by depth zones, plotted by percentage of total; B. Cenomanian-Turonian occurrences, outcrop area and collections by distance-from-paleoshoreline zones; C. lower Campanian occurrences, outcrop area and collections by depth zones, plotted by percentage of total; D. lower Campanian occurrences, outcrop area and collections by distance-from-paleoshoreline zones.
Fig_S2.png
Supplementary Figure 3
Plots of sampling probabilities for species level occurrences across depth zones, using Method 2 (see main body of text for further information). A. Cenomanian-Turonian; B. lower Campanian.
Fig_S3.png
Supplementary Figure 4
Plots of sampling probabilites for species and generic level results for the Cenomanian-Turonian and lower Campanian across distance-from-paleoshoreline zones, using Method 3 (see main body of text for further information). A. sampling probability for species level occurrences across distance-from-paleoshoreline zones for the Cenomanian-Turonian; B. sampling probability for generic level occurrences across distance-from-paleoshoreline zones for the Cenomanian-Turonian; C. sampling probability for species level occurrences across distance-from-paleoshoreline zones for the lower Campanian; D. sampling probability for generic level occurrences across distance-from-paleoshoreline zones for the lower Campanian.
Fig_S4.png
Supplementary Figure 5
Plots of species level diversity plots for the Cenomanian-Turonian and lower Campanian within depth zones, plotted with number of collections and outcrop area. A. Species diversity and number of collections for the Cenomanian-Turonian; B. Species diversity and number of collections for the lower Campanian; C. Species diversity and outcrop area for the Cenomanian-Turonian; D. Species
diversity and outcrop area for the lower Campanian.
Fig_S5.png
Supplementary Figure 6
Plots of species and generic level diversity plots for the Cenomanian-Turonian and lower Campanian within distance-from-paleoshoreline zones, plotted with number of collections and outcrop area. A. Species diversity and number of collections for the Cenomanian-Turonian; B. Species diversity and number of collections for the lower Campanian; C. Species diversity and outcrop area for the Cenomanian-Turonian; D. Species diversity and outcrop area for the lower Campanian; E. Generic diversity and number of collections for the Cenomanian-Turonian; F. Generic diversity and number of collections for the lower Campanian; G. Generic diversity and outcrop area for the Cenomanian-Turonian; H. Generic diversity and outcrop area for the lower Campanian.
Fig_S6.png
Supplementary Figure 7
Plots of generic level SQS results for distance-from-paleoshoreline zones for the Cenomanian-Turonian and lower Campanian, set at 0.4, 0.5 and 0.6 quorums. A. SQS results for ammonites in the Cenomanian-Turonian; B. SQS results for ammonites in the lower Campanian; C. SQS results for aragonitic bivalves in the Cenomanian-Turonian; D. SQS results for aragonitic bivalves in the lower Campanian; E. SQS results for calcitic bivalves in the Cenomanian-Turonian; F. SQS results for calcitic bivalves in the lower Campanian.
Fig_S7.png