SOURCE-TO-SINK SEDIMENT BUDGET ANALYSIS OF THE CRETACEOUS FERRON SANDSTONE, UTAH, U.S.A., USING THE FULCRUM APPROACH
Notice bibliographique
Résumé
Abstract This paper matches sediment fluxes, estimated to have passed through an ancient river system, with mapped downstream sediment volumes in a deltaic sink, providing a test of the recently developed fulcrum approach to source-to-sink analysis. This paper uses field measurements (such as channel depth, width, and grain size) to estimate paleodischarge in an ancient trunk channel of the Cretaceous Ferron Sandstone in central Utah. The estimates of instantaneous discharge are then integrated over the geological duration of the river to estimate the total sediment volume delivered to downstream deltaic sinks in an attempt to balance the estimated sediment flux with the mapped deltaic deposits in the sink. The bankfull channel depths, calculated using the scaling relationship between the flow depth and the mean dune height, vary from 3.3 to 5.5 m with an average depth of 4.4 m. The corresponding bankfull channel width estimates vary from 50 to 80 m, with an average value of 65 m, calculated using scaling relationship between channel width and the width of accretion surfaces. Water discharge calculated for these bankfull dimensions vary from 2.7 × 102 m3/s to 8.6 × 102 m3/s, also indicating that these rivers were routinely capable of generating hyperpycnal flows. The instantaneous sediment discharge reaching the fulcrum was calculated using established sediment transport equations. These instantaneous discharge values were first converted to mean annual sediment volume using the bankfull event durations, recurrence intervals, and a factor for the proportion of the total annual sediment load transported during the bankfull period, based on empirical relationships from modern climate analogs, and then projected over the average time duration of individual parasequences in the Ferron Notom clastic wedge, which is approximately 14 kyr. The mass balance across the fulcrum reveals that the average bedload sediment volume derived from the source (about 3 km3) matches with that deposited in the sink within a factor of two. However, underestimation of the bedload volume in the sink suggests sediment escape beyond the limits of currently mapped sink area. Previous models for the Ferron indicate significant SE deflection of sediment due to wave reworking, which may account for the missing sandy sediment. It is also possible that there is an overestimation of time duration for individual valleys, resulting in higher sink-volume estimation and larger source-to-sink mass imbalance. Monte Carlo simulations, based on probabilistic estimation, were used to test the sensitivity of key parameters used in converting bankfull discharge to mean annual discharge. The P10, P50 (median), and P90 values for the average annual bedload volume ( Qmas ) are 9.1 × 104 m3, 1.7 × 105 m3, and 3.7 × 105 m3, respectively. A Qmas value between P50 and P90 yields a source-to-sink balance for bedload volume. The current study establishes a mass balance across the fulcrum with a reduced range of uncertainty for the various parameters used. Uncertainty associated with bankfull channel dimensions has been reduced through inclusion of detailed outcrop data. The uncertainty in estimating average annual sediment volume ( Qmas ) from bankfull events is less than a factor of three. This uncertainty can be further reduced by incorporating a more robust global-discharge dataset from modern analog river systems. Despite many assumptions and uncertainties, our study shows that the fulcrum method appears to be capable of balancing sediment budgets to within at least an order of magnitude in deep-time sedimentary systems.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,004 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,002 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».