  We present deep photometry of the Carina dwarf Spheroidal galaxy in the B,V
filters from CTIO/MOSAIC, out to and beyond the tidal radius. The accurately
calibrated photometry is combined with spectroscopic metallicity distributions
of Red Giant Branch stars to determine the detailed star formation and chemical
evolution history. The star formation history confirms the episodic formation
history of Carina and quantifies the duration and strength of each episode in
great detail, as a function radius from the centre. Two main episodes of star
formation occurred at old (>8 Gyr) and intermediate (2-8 Gyr) ages, both
enriching stars starting from low metallicities ([Fe/H]<-2 dex). By dividing
the SFH into two components, we determine that 60pm9 percent of the total
number of stars formed within the intermediate age episode. Furthermore, within
the tidal radius (0.48 degrees or 888 pc) a total mass in stars of 1.07pm0.08
x10^6 M_sun was formed, giving Carina a stellar mass-to-light ratio of
1.8pm0.8. Combining the detailed star formation history with spectroscopic
observations of RGB stars, we are able to determine the detailed
age-metallicity relation of each episode and the timescale of alpha-element
evolution of Carina from individual stars. The oldest episode displays a tight
age-metallicity relation over 6 Gyr with steadily declining alpha-element
abundances and a possible alpha-element knee at [Fe/H]~ -2.5 dex. The
intermediate age sequence displays a more complex age-metallicity relation
starting from low metallicity and a sequence in alpha-element abundances with a
slope much steeper than observed in the old episode, starting from [Fe/H]=-1.8
dex and [Mg/Fe]~0.4 dex and declining to Mg-poor values ([Mg/Fe]<-0.5 dex).
This indicates clearly that both episodes of star formation formed from gas
with different abundance patterns, inconsistent with simple evolution in an
isolated system.
