We appreciate Inman's (2008) interest in our study of latest Pleistocene to Holocene submarine-fan growth in the southeastern Gulf of Santa Catalina and San Diego Trough (Covault et al., 2007). His Comment includes important references regarding intricacies of air-sea-land interactions that influence the development of submarine-fan architecture offshore Southern California (e.g., Inman et al., 1976; Inman, 1983; Masters, 2006). Inman's estimates of the sediment flux from rivers and bluffs into the Oceanside littoral cell during historical times are particularly interesting. However, as noted by Inman, the vast difference in time scales between the historical rates (i.e., twentieth century) and our Quaternary rate of La Jolla fan growth precludes meaningful comparison. This was recognized by Inman (1983, p. 22) in an assessment of paleocoastlines in the vicinity of La Jolla, California: “...the budget of sediment for a given littoral cell may be quite different from one decade, century or millennium to another, making the budget of sediments that is of interest to coastal dynamicists, planners and engineers quite different in time span, magnitude, and to some extent in the kind of source, transport path, and sink, than would be of interest to geomorphologists and archaeologists.” Broader, more inclusive studies reached the same conclusion. Sadler (1981) compiled nearly 25,000 sedimentation rates and demonstrated a systematic trend of falling mean rate with increasing time span of measured interval. Sadler (1981) and Gardner et al. (1987) attributed this trend to unsteady and nonuniform geologic processes (i.e., processes that are variable in frequency and magnitude through time and in space). This is especially preva lent in deepwater depositional environments as a result of the episodic nature of sediment gravity-flow initiation and processes (for a review, see Normark and Piper, 1991). Deepwater sedimentation rates averaged over increasingly longer intervals incorporate longer intervals of inactivity (e.g., hemipelagic suspension settling; i.e., “background” sedimentation), thus producing an apparently slower rate (Gardner et al., 1987). For this reason, we avoided directly comparing rates of historical sediment flux into the Oceanside littoral cell and Quaternary La Jolla fan growth, which span three orders of magnitude with respect to duration.
The work of Inman and others was revolutionary and particularly pertinent to historical air-sea-land interactions in the staging area and coastal zone that influence the development of submarine-fan architecture offshore Southern California (e.g., Inman et al., 1976; Inman, 1983). However, the purpose of our paper was to present a general model of submarine-fan growth offshore Southern California during latest Pleistocene and Holocene sea-level fluctuations, and to discuss those results within the context of commonly cited stratigraphic concepts, rather than elaborate on the intricacies of Southern California air-sea-land inter actions, including characteristics of Holocene Oceanside littoral cell evolution and historical littoral cell sediment budget.