Geological Processes and Evolution

Abstract

Abstract. Geological mapping and establishment of stratigraphic relationships provides an overview of geological processes operating on Mars and how they have varied in time and space. Impact craters and basins shaped the crust in earliest history and as their importance declined, evidence of extensive regional volcanism emerged during the Late Noachian. Regional volcanism characterized the Early Hesperian and subsequent to that time, volcanism was largely centered at Tharsis and Elysium, continuing until the recent geological past. The Tharsis region appears to have been largely constructed by the Late Noachian, and represents a series of tectonic and volcanic centers. Globally distributed structural features representing contraction characterize the middle Hesperian. Water-related processes involve the formation of valley networks in the Late Noachian and into the Hesperian, an ice sheet at the south pole in the middle Hesperian, and outflow channels and possible standing bodies of water in the northern lowlands in the Late Hesperian and into the Amazonian. A significant part of the present water budget occurs in the present geologically young polar layered terrains. In order to establish more firmly rates of processes, we stress the need to improve the calibration of the absolute timescale, which today is based on crater count systems with substantial uncertainties, along with a sampling of rocks of unknown provenance. Sample return from carefully chosen stratigraphic units could calibrate the existing timescale and vastly improve our knowledge of Martian evolution.

The thermal evolution of Mars as constrained by paleo-heat flows

“…The use of a wet diabase law is appropriate for a basaltic martian crust and is consistent with extensive evidence for water-related geological activity in early Mars (e.g., Head et al, 2001;Dohm et al, 2009b); moreover, the water amount needed to "wet" the diabase is certainly modest (lower than 1%; see Caristan, 1982). The ductile strength of the mantle lithosphere is calculated for dry and wet olivine dislocation creep rheologies, which give upper and lower limits, respectively, to the surface heat flow.…”

Ancient heat flow and crustal thickness at Warrego rise, Thaumasia highlands, Mars: Implications for a stratified crust

“…For creep parameters of the martian crust, we use the constants for the flow law of diabase: A = 0.0612 MPa Àn s À1 , n = 3.05 and Q = 276 kJ mol À1 (Caristan, 1982). The use of a wet diabase for the martian crust is consistent with extensive evidence for water-related geological activity during early Mars (e.g., Scott et al, 1995;Head et al, 2001;Fairén et al, 2003).…”

Ancient heat flow, crustal thickness, and lithospheric mantle rheology in the Amenthes region, Mars

“…For creep parameters of the Martian crust we use the constants for the flow law of diabase: A = 0.0612 MPa − n s − 1 , n = 3.05 and Q = 276 kJ mol − 1 (Caristan, 1982). The use of a "standard" wet diabase for the Martian crust is consistent with extensive evidence for water-related geological activity during the Late Noachian and Early Hesperian (e.g., Head et al, 2001). Otherwise, a dry crustal rheology is hardly consistent with the comparison among the evolution of effective elastic thickness of the lithosphere and the thermal history models for Mars (Guest and Smrekar, 2007;Grott and Breuer, 2007).…”