Fluvial Dominated Deltas
Rio Grande - HST 2
Hst 2 is interpreted as a fluvially-dominated delta based on lobate fan-mound geometry, a complex-sigmoid-oblique to oblique tangential seismic pattern, and lithologic information from the Rio Grande area and from age equivalent deposits associated with the Colorado system. The lobate fan-mound geometry is interpreted as being formed by multiple distributaries that are active concurrently and that bifurcate as they prograde across the shelf. The multiple active distributaries also support a fluvial-rather than wave-dominated origin for the delta. The large scale of the deposit (95 km in depositional strike and 60 km in depositional dip) and the bifurcating distributary pattern indicate that the delta is constructed of many sub-lobes. The paleogeographic reconstruction is quite schematic. Individual distributaries cannot be mapped. The locations of the distributary channels on the map are drawn to indicate that they are bifurcating and therefore, creating the observed lobate fan-mound geometry.
core data
seismic data
isopach map
Overview
Main Characteristics
Width (km)
x
Length (km) |
Thickness (ms) |
Shape |
Reflection
Configuration |
Bounding
Surfaces |
Lithology |
Subbottom
Depth (m) |
| 95 x 60 |
~ 100 |
fan
mound |
complex sigmoid-oblique to
oblique tangential
parallel to sub-parallel |
top - 2sb
base - 3mfs |
SP-1, B-2 |
40-200 |
Depositional Interpretation
| Interpretation |
Sediment
Volume (km3) |
Timing (ybp) |
Deposition Rate
per 1000 yrs |
Sea Level |
Eustatic vs
Climatic |
lobate
fluvial-dominated
delta |
112 |
60,700
to
22,000 |
2.89 km3 |
falling |
eustatic |
Sediment Yields
Volume = (4/3)*(Each isochron is divided into a series of spheroids whose volume is then summed (a * b* c, where a,b,c are radii).
| total volume (km3) |
deposition timing |
sediment yield (km3)
per 10000 yrs |
| 111.9 |
38700 |
2.89 |
Comments, questions? Contact us at
gulf@gulf.rice.edu.